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Ruy Horta
03-20-2004, 11:36 AM
First let me say that I am very happy with AEP, although I was disappointed to find a/c like the I-185 not to be modeled as promised - gathered they will be added in an "extra" patch. Not bad for Euro 21,50 incl. discount, not bad at all!

http://ubbxforums.ubi.com/images/smiley/11.gif

Back to the topic though, although if it has been mentione before, please disregard and accept my apology.

Although I tend to fly Luftwaffe a/c, its also fun to try out the other types, both on- and off-line.

Today I was flying a Spit Mk Vb 1942 when I went into a diving contest with a 109F-4. At first all things happened as I expected, he pulled away and the distance widened. I did not want to abuse the crate, so I even flattened the dive although still at full throttle. But while the distance seemed to be stable, or even close a little, I started to buffet and started loosing parts until I lost my left wing.

NP, I should think...

But come to think of it, compared to a 109F-4 the Spit would have had a stronger wing AND a higher critical Mach number.

So why this result?

All things being equal, either he would have had more problems, and have been damaged critically or I would closed in on the second stage of the dive and the flattening out part.

(lost my wing while flying fast but almost horizonal, pulling little G-s as I was careful).

My record does not warrant any bias towards the Spitfire http://ubbxforums.ubi.com/images/smiley/35.gif

Ruy Horta

Ruy Horta
03-20-2004, 11:36 AM
First let me say that I am very happy with AEP, although I was disappointed to find a/c like the I-185 not to be modeled as promised - gathered they will be added in an "extra" patch. Not bad for Euro 21,50 incl. discount, not bad at all!

http://ubbxforums.ubi.com/images/smiley/11.gif

Back to the topic though, although if it has been mentione before, please disregard and accept my apology.

Although I tend to fly Luftwaffe a/c, its also fun to try out the other types, both on- and off-line.

Today I was flying a Spit Mk Vb 1942 when I went into a diving contest with a 109F-4. At first all things happened as I expected, he pulled away and the distance widened. I did not want to abuse the crate, so I even flattened the dive although still at full throttle. But while the distance seemed to be stable, or even close a little, I started to buffet and started loosing parts until I lost my left wing.

NP, I should think...

But come to think of it, compared to a 109F-4 the Spit would have had a stronger wing AND a higher critical Mach number.

So why this result?

All things being equal, either he would have had more problems, and have been damaged critically or I would closed in on the second stage of the dive and the flattening out part.

(lost my wing while flying fast but almost horizonal, pulling little G-s as I was careful).

My record does not warrant any bias towards the Spitfire http://ubbxforums.ubi.com/images/smiley/35.gif

Ruy Horta

LEXX_Luthor
03-20-2004, 11:41 AM
I don't see a problem I always thought Fb109s outdive everybody else until USA came and crashed the party.

__________________
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:
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Close this book forever and don't open anymore!" ~Oleg_Maddox http://ubbxforums.ubi.com/images/smiley/16x16_smiley-surprised.gif

Ruy Horta
03-20-2004, 11:46 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by LEXX_Luthor:
I don't see a problem I always thought Fb109s outdive everybody else until USA came and crashed the party.<HR></BLOCKQUOTE>

Please learn to read better:

1. I did say that the dive looked good at the initial stage - as in 109F pulling away.

2. What I did not suspect was catastrophic damage to the Spit - due to wing with greater strength and HIGHER critical Mach number than the 109F.

To freshen the mind there are plenty of combat reports of critical damage to 109Fs in power dives, few on Spits.

Again, I am not biased towards the Spitfire...

But this was an unexpected outcome.

So I am not discussing the initial advantage of the 109 in a dive.

Ruy Horta

p1ngu666
03-20-2004, 02:56 PM
spit wing would do mach1.2, if u could get it there
was used for m52 test program btw http://ubbxforums.ubi.com/infopop/emoticons/icon_wink.gif

http://www.pingu666.modded.me.uk/mysig3.jpg

Arm_slinger
03-20-2004, 04:57 PM
Bugger pingu you beat me to that little fact http://ubbxforums.ubi.com/infopop/emoticons/icon_frown.gif http://ubbxforums.ubi.com/infopop/emoticons/icon_mad.gif http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif http://ubbxforums.ubi.com/images/smiley/93.gif

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Sim lover?, want something new? Then look at "Target for Tonight the definitive night bombing simulation ever, featuring the RAF's Bomber Command.

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HellToupee
03-20-2004, 05:18 PM
the spit comes apart around you at a little over 600ias, kinda weird.

http://lamppost.mine.nu/ahclan/files/sigs/spitwhiners1.jpg

nixon-fiend.
03-21-2004, 05:58 AM
It should be noted that the spitfire holds the record of highest speed ever attained by a prop plane..

mach 0.92 in a dive at RAE farnborough in april 1944..

Granted, this was a mk.XI, not a mk.V - but the airframe is similar so I would expect a mk.V spit to hold out a little longer in a dive.

SkyChimp
03-21-2004, 07:11 AM
.92 mach. As Hop would say, I've seen that bandied around here, without any real proof to date. My understanding is that this .92 figure was corrected to something like .90 later. Not sure why it had to be "corrected." The highest verified dive speed I've seen was .89 by the Spit, in a document Neil Stirling posted at the defunct AllAboutWarfare site.

And while the Spitfire could clearly reach high dive speeds - eventually - (probably any clean later WWII fighter could) I've never heard that the dive ability of the Spitfire gave it any tactical advantage over the Bf-109, which from what I've read, always held a dive ability advantage over the Spitfire.

Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

[This message was edited by SkyChimp on Sun March 21 2004 at 06:51 AM.]

CTO88
03-21-2004, 07:27 AM
mach 0.92 is for late spits, like spit 14 and 21 with late war clipped wings.

spit vB has a huge wing. it's clear that makes lot of drag and wingforces at highspeed.

hop2002
03-21-2004, 08:20 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>.92 mach. As Hop would say, I've seen that bandied around here, without any real proof to date. My understanding is that this .92 figure was corrected to something like .90 later. Not sure why it had to be "corrected." The highest verified dive speed I've seen was .89 by the Spit, in a document Neil Stirling posted at the defunct AllAboutWarfare site.
<HR></BLOCKQUOTE>

The highest verified I've seen is .89. Possibly .92 refers to the dive Martindale's plane crashed on, and from what I've read elsewhere several pilots were killed during these high speed dives, so it might refer to some other test.

But .89 is documented.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>And while the Spitfire could clearly reach high dive speeds - eventually - (probably any clean later WWII fighter could) I've never heard that the dive ability of the Spitfire gave it any tactical advantage over the Bf-109, which from what I've read, always held a dive ability advantage over the Spitfire.<HR></BLOCKQUOTE>

Well, Rhorta is talking about high speeds, not dive acceleration. Ie, a sustained dive, in which it seems the Spit in AEP has to pull out before the 109 otherwise it will suffer damage. The opposite is true.

The Spit should be able to continue the dive to higher speeds than any of the other prop fighters, not lose it's wings before they do.

Dive acceleration should not favour the Spit, and most late war fighters should pull away from it initially, and againg accoding Ruy, the 109 did initially pull away.

karost
03-21-2004, 08:58 AM
Hi... I don't have any knowledge about a/c engineering but refer to L/W book , Hit and run( drive) are standard tactic of L/W at begining time of WWII. so if spit5 can capture 109 in drive, so this tactic shout be a forgotten tactic.. http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif or may be I worng...

In game, there have some tactic for save dirve in 109 , just use manual pit at 60 then drive when speed reach over 700 km/h then cut power to zero and dump pit to 10 or 0 (this will apply to be a pit air break) and opend radiator 8 , this will keep me not lose wing ... http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif

so.. it is good news for me that "hit and run" tactic can apply in game same as history http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif

S.

WWMaxGunz
03-21-2004, 09:11 AM
Spit V wing the same as the much later Spits? Anyone real sure about that?

Wings built for high climb and turn rates at moderate to lower speeds I for one would not expect to handle high speeds well. It's because the low speed high lift wing has to be fatter and curve the air more. The air over the wing travels faster than the plane does. If the wing is fatter then the air over the wing will reach compression that much sooner and the ailerons will get buzzing from shock waves, the elevators as well esp if they're not well above the shock disturbed air from the wings...
So it's critical just what wing cross section and how wide the wings are. Did they or did they not thin the wings out as the war progressed in the press for higher speeds? I've read that the Spits got bigger and heavier as the war went on so why think the wings stayed the same profile?


Neal

butch2k
03-21-2004, 09:23 AM
With a 109F-4 dive speed of 750km/h was tolerated at low alt without any special caution, 800 km/h could be reached but pull-out had to be slow.

F19_Ob
03-21-2004, 09:53 AM
Actually the spit had a very vulnerable ving and even later in the war many spitfires got damaged and or lost its wings in heavy g maneuvers, seemingly in dives.
One pilot in a tv interview once saw hundreds of gathered crashed spitfires lost due to accidents and broken wings. the same pilot liked the hurricane alot since it was virtually impossible to pull anything off it.

Although spitfires was almost as fast in dives as the 109 it was a dangeruos situation.the early 109pilots also had hard times since the stick got so heavy in fast dives but they soon learned to use a combination of trim and applying elevator to cope with the situation.


Remember also one report about an 109f who lost its wing in a hard turn. But the wingman who witnessed this thinks his mate might have taken some hits in an earlier engagement, so the cause of this is uncertain.

In the litterature there is frequent statements or stories where spitfires loses their wings due to high G dives and pulls, but very rare when it comes to bf109's.
One finnish pilot even stated that he had reached a speed of close to 900 km in a dive and recovered by applying elevator trim slowly.


http://ubbxforums.ubi.com/images/smiley/16x16_smiley-wink.gif

Aaron_GT
03-21-2004, 10:31 AM
WWMaxGunz,

The Spitfire had a
relatively thin wing cross
section. For example note
the need for cannon bulges
not required on the
Hurricane

There are construction
differences between the
wing on the Vb wing (b
wing) and the c and e
wings. The later changes
included different internal
bay/cell structure and
strengthened gear
attachments. It's not
impossible that the Vb
wing (basically a Spit I
wing) might be weaker than
the later wings.

AFAIK even at only 0.89
mach, the Spit still holds
the max _verified_ mach for
a prop plane.

SkyChimp
03-21-2004, 10:32 AM
I've been able to get the Spit to 856 km/h tas at about 3000m. At that point the right wing came off.

I'm not sure that it's correct to say that the Spit should reach a higher dive speed than any other prop job in the game. It's the highest published number I've seen, but it's alos the only test I've seen conducted in that manner it was.

I've never seen a dive test of the Mustang or a Thunderbolt conducted in the same manner that Spit test that produced the .89 speed. All I've seen or heard of are vertical dive tests. Diving at a rather shallow angles, as did that Spit, and diving vertically, as did the Mustang and Thunderbolt, are quite different. And If I recall correctly, both the Thunderbolt and Mustang were equal or better aerodynamically.


Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

Willey
03-21-2004, 11:04 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by butch2k:
With a 109F-4 dive speed of 750km/h was tolerated at low alt without any special caution, 800 km/h could be reached but pull-out had to be slow.<HR></BLOCKQUOTE>

LOL try that in FB... 750 and your plane starts disintegrating. Also I'm not able to reach the 850 IAS the Finns could dive with thier G-2/G-6es. Between 750 and 800 IAS I'm loosing parts already.

SkyChimp
03-21-2004, 11:27 AM
These dives began at 10,000m at 50% throttle. This what I came up with:

http://members.cox.net/us.fighters/p51b.jpg

http://members.cox.net/us.fighters/p47d.jpg

http://members.cox.net/us.fighters/spit.jpg

http://members.cox.net/us.fighters/bf109g2.jpg

Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

BlackHawkLeader
03-21-2004, 12:33 PM
The Spit was a better turn fighter, than the 109 so perhaps the physics of the Wing work against the Spit in a dive.
After all the Zero was probably the best turn fighter of all, yet its wing area caused problems in a higher speed dive.

Perhaps an attempt by 1C to model real life physics in the game who knows?

S!

hop2002
03-21-2004, 12:33 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>So it's critical just what wing cross section and how wide the wings are. Did they or did they not thin the wings out as the war progressed in the press for higher speeds? I've read that the Spits got bigger and heavier as the war went on so why think the wings stayed the same profile?
<HR></BLOCKQUOTE>

The profile remained the same, certainly up to the F 21, and I think even the 20 series had the same profile.

The thickness was 13% root, 9% tip for all Spits (with the possible exception of the 21, 22 and 24)

Of course, clipped or extended wings might change the tip ratio, but only the tip, they were simply bolted on outboard of the ailerons.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I've been able to get the Spit to 856 km/h tas at about 3000m. At that point the right wing came off.<HR></BLOCKQUOTE>

The limit at that alt (and up to about 6,000m) was around that, so that's not far off. The advantage in critical mach for the Spit wing only really manifests itself at higher altitudes (iirc, allowed limit was higher than the P-51 from 15,000ft up)

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I've never seen a dive test of the Mustang or a Thunderbolt conducted in the same manner that Spit test that produced the .89 speed. All I've seen or heard of are vertical dive tests. Diving at a rather shallow angles, as did that Spit, and diving vertically, as did the Mustang and Thunderbolt, are quite different.<HR></BLOCKQUOTE>

The RAE tested the Mustang in a similar manner, although as it was a Mustang I the dive started from much lower altitude.

The docs Neil Sterling came up with show Naca tested the P-47 in a similar manner, again from a lower height, and with a steeper initial dive, but still the dive angle only went up to 67 degrees, the RAE went up to 47 degrees with the Spit.

I presume the reason for taking the Spit higher is that it needed longer to accelerate up to the same speed as the P-47/51.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>And If I recall correctly, both the Thunderbolt and Mustang were equal or better aerodynamically.
<HR></BLOCKQUOTE>

Not at very high speeds.

The P-51 (A, but I don't think there were major changes to the wing section) had an earlier onset of mach divergent drag, as did the P-47.

The RAE report gives the Cd at mach 0.8 as 0.048 for the P-47 (from Naca tests), 0.037 for the P-51, 0.028 for the Spit.

This is the most critical point. It shows why the Spitfire could be dived to higher speeds, it entered compression at higher speeds, and because the drag rise occured at higher speeds, it had much lower drag at these high speeds than the other aircraft.

At mach 0.89, the Spit drag had risen to 0.052.

The P-47 reached 0.052 at mach 0.82, and by mach 0.86 (the fastest speed reached) drag had risen to 0.078.

The first page of the report sums up the results:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>All three aeroplanes show the characteristic rise in drag coefficient at mach numbers above about mach 0.7. Spitfire is superior to Mustang or Thunderbolt, presumably because it's wing is only 13% thick at the root, compared to 16% for the Mustang and Thunderbolt<HR></BLOCKQUOTE>

Ruy Horta
03-21-2004, 12:37 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by hop2002:
Well, Rhorta is talking about high speeds, not dive acceleration. Ie, a sustained dive, in which it seems the Spit in AEP has to pull out before the 109 otherwise it will suffer damage. The opposite is true.

Dive acceleration should not favour the Spit, and most late war fighters should pull away from it initially, and againg accoding Ruy, the 109 did initially pull away.<HR></BLOCKQUOTE>

Thanks Hop, you understood what I tried to explain. We are discussing comperative performance. It could be that both or one of the models is wrong, but events did not agree with reports and annecdotes.

The Spit could risk damage to the elevator if pulled out to hard, if my mem. serves me right (Quill/Henshaw) the 109F was notorious for having a weak tail and perhaps weak wing. The tail is well known, it got strengthened first externally and later internally. The wing is a matter of dispute, I agree, although there is evidence from RAF reports and (fair ammount)of annecdotal reference.

1. This is not a post about overmodeled 109s
2. This is not a whine about undermodeled Spits.

My aim is to proof or disproof my observation, to establish if its in accordance with a/c specs and reports or that somethings is not right.

PS. The 109 is perhaps my favorite fighter of WW2, so bias is not an issue. http://ubbxforums.ubi.com/images/smiley/784.gif

Ruy Horta

Ruy Horta
03-21-2004, 12:45 PM
Also...my aim is peaceful, I don't want this to turn in a flamefest. I hope we can stick with numbers and reports http://ubbxforums.ubi.com/images/smiley/11.gif

Ruy Horta

SkyChimp
03-21-2004, 01:56 PM
Hop:

I didn't save that report when Neil posted it, could you post it or send it to me?

Let's leave the Mustang I out for a moment, it wasn't really as clean aerodynamically as the Merlin Mustangs due to its higher drag radiator inlet.

I suppose the difficulty I have with it all is that the Spit had a relatively high Cd0 compared to the P-51 and P-47. The Spit IX had an engine, IIRC, that was equivalent to the V-1650-3 that was in the P-51B. Yet the P-51B, despite being significantly heavier, was around 40mph faster in level flight than the Spit. And the use of the dive as an evasion tactic is something I rarely see in the same sentence as Spitfire. Undoubtedly, this was due to the Mustang being much cleaner.

I know you've said in the past this was due to the Spitfire's thinner wing, but that wing also had high drag radiator inlets, open wheel wells, big guns sticking out. So despite having a wing profile that resisted an increase in drag longer, the Spitfire seemed to have a lot of various protuberences that should not be so resistent - especially the radiator inlets.

I don't think there would be any point in comparing the Mustang's and Spitfire's fuselage.

It seems as if the British found the magic bullet with the Spitfire's wing. It almost makes me wonder why the British went to a wing that was a lot closer to that of the Mustang than the Spitfire when they produced the Spiteful.

I don't think that a mere 3% difference in wing root thickness tells the whole story.


BTW, the NACA Terminal Dive Speed report, that shows a dive speed of mach .86 (@ 20,000 feet) is available on the net. That test, as summarized in various books, was not a test conducted at a shallow dive angle, it was a vertical dive test.

Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

HellToupee
03-21-2004, 02:05 PM
fact is spit v breaks up too soon, the XI wich is very similar went faster than anyother ww2 prop and lived http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif.

http://lamppost.mine.nu/ahclan/files/sigs/spitwhiners1.jpg

SkyChimp
03-21-2004, 02:17 PM
Here's an interesting newsgroup thread I found:

http://yarchive.net/air/spitfire.html

Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

hop2002
03-21-2004, 03:28 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I didn't save that report when Neil posted it, could you post it or send it to me?
<HR></BLOCKQUOTE>
I don't think I've got the full thing, most of it went way over my head, I've got the bit's I could understand saved and will post them in this reply. I'll have a look for the rest, my HDD is rather chaotic and they might be here somewhere, but I'm not certain if I ever had the full thing.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I suppose the difficulty I have with it all is that the Spit had a relatively high Cd0 compared to the P-51 and P-47. The Spit IX had an engine, IIRC, that was equivalent to the V-1650-3 that was in the P-51B. Yet the P-51B, despite being significantly heavier, was around 40mph faster in level flight than the Spit.<HR></BLOCKQUOTE>

There was no equivalent of the V-1650-3 fitted to a Spit.

The Merlin 61, which iirc had similar critical alt to the -3, had a smaller supercharger diameter and lower allowable manifold pressure (15 lbs, instead of the 18 lbs used on the -3)

The Merlin 61 was the first production two stage Merlin, and had major differences from the rest of the 60/70 series engines on which the 1650 -3 and -7 were based.

IMHO, 40 mph is overstating the difference.

The Spit Lf IX, which had a Merlin 66 almost identical to the 1650-7, had a speed at sea level of 335 mph. A new P-51D, tested by the A&AEE had a max at sea level at 18 lbs boost of 354 mph, which seems low for a Mustang, but even so is only 19 mph faster that the Spit IX with similar power.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I know you've said in the past this was due to the Spitfire's thinner wing, but that wing also had high drag radiator inlets, open wheel wells, big guns sticking out. So despite having a wing profile that resisted an increase in drag longer, the Spitfire seemed to have a lot of various protuberences that should not be so resistent - especially the radiator inlets.
<HR></BLOCKQUOTE>

Drag due to exceeding critical mach is not like other drag. It's not caused by simple air pressure against a moving surface.

When the entire wing area starts generating a large rise in drag, it's going to swamp everything else.

Here's the table from the test (the most important part, I think)
http://www.onpoi.net/ah/pics/users/282_1079907714_sd16.jpg

As you can see, normal drag increases very quickly as critical mach is reached.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>It seems as if the British found the magic bullet with the Spitfire's wing. It almost makes me wonder why the British went to a wing that was a lot closer to that of the Mustang than the Spitfire when they produced the Spiteful. <HR></BLOCKQUOTE>

The Spiteful wing wasn't similar to the Mustang's. It was smaller than either the Spit's or Mustang's, at 210 sq/ft, it was designed for laminar flow like the Mutang's, but not to the same section, and it had a thickness at the root of 13% (same as the Spit, Mustang was 16%) and only 8% at the tip (thinner than the Spit's, much thinner than the Mustang's)

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I don't think that a mere 3% difference in wing root thickness tells the whole story.<HR></BLOCKQUOTE>

A difference between a wing 16% thick and one 13% thick is a difference between the two wings of about 25%.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>BTW, the NACA Terminal Dive Speed report, that shows a dive speed of mach .86 (@ 20,000 feet) is available on the net. That test, as summarized in various books, was not a test conducted at a shallow dive angle, it was a vertical dive test.
<HR></BLOCKQUOTE>

Perhaps different tests? Here's the one included in the Spit report:

http://www.onpoi.net/ah/pics/users/282_1079907691_sd12.jpg

The other pages I have are the front page:

http://www.onpoi.net/ah/pics/users/282_1079907443_sd1.jpg

and the results of a Spit dive to .89

http://www.onpoi.net/ah/pics/users/282_1079907664_sd11.jpg

All the images were originally posted by Neil Sterling, here or on other groups.

[This message was edited by hop2002 on Sun March 21 2004 at 02:52 PM.]

WWMaxGunz
03-21-2004, 03:33 PM
Mach .89 or even .86 is great for any prop plane.

Late 80's corp jets rated about .78 mach or at least that's what the Flight Safety books and instructors had to say. .78 is damned fast.

Maybe the VB model shakes at the speeds it does because it lacks the weight of later Spits? Yes, I say maybe. Wish "The Man" would come say why but maybe why will be out with the patch. Maybe one or two weeks unless more needs to be done? A year ago I remember waiting two weeks for... ummmm, it was a while and I think we did better than if 1.1 had been a rush job. Even still, AEP is what I wanted and I don't mind the wait for things this good. Not perfect but very good!


Neal

Abbuzze
03-21-2004, 04:15 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by butch2k:
With a 109F-4 dive speed of 750km/h was tolerated at low alt without any special caution, 800 km/h could be reached but pull-out had to be slow.<HR></BLOCKQUOTE>

Are you sure about this Butch? the slow pull out I mean.

Pls take a look at this from the

http://109lair.hobbyvista.com/index1024.htm


http://109lair.hobbyvista.com/techref/structures/tails/109.05e43_report/05e43-p10.htm

Both flightpaths show the behavier of a 109F with 109 G wings and the late G Tail
the left flightpath show a recover of the dive with the help of the trim, cause with the wrong trimset the pilot was not able to pull out. With the use of the trim it was necessary to push the stick foreward to get no blackout!
The right flightpath show a recover of a dive with a correct trimst and just using the stick.
Both paths are very similar, so with the correct trim it was possible to pull such hard to get close to a blackout, so even in a 109 the limiting factor was the pilot, not the plane... even if the controllforces made this uncomfortable...

JG53 PikAs Abbuzze
I./Gruppe

http://www.jg53-pikas.de/

http://mitglied.lycos.de/p123/Ani_pikasbanner_langsam.gif

SkyChimp
03-21-2004, 05:31 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I don't think I've got the full thing, most of it went way over my head, I've got the bit's I could understand saved and will post them in this reply. I'll have a look for the rest, my HDD is rather chaotic and they might be here somewhere, but I'm not certain if I ever had the full thing.<HR></BLOCKQUOTE>

OK, thanks.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>There was no equivalent of the V-1650-3 fitted to a Spit.

The Merlin 61, which iirc had similar critical alt to the -3, had a smaller supercharger diameter and lower allowable manifold pressure (15 lbs, instead of the 18 lbs used on the -3)...<HR></BLOCKQUOTE>

OK, I thought the V-1650-3 equivalent was fitted to the IX. The U.S. Navy found the P-51B to have a top TAS of 450 mph. Nevertheless, the comparsion to the P-51D still works. The P-51D was heavier still compared to the IX.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
Drag due to exceeding critical mach is not like other drag. It's not caused by simple air pressure against a moving surface.

When the entire wing area starts generating a large rise in drag, it's going to swamp everything else.

Here's the table from the test (the most important part, I think)<HR></BLOCKQUOTE>

I'm not sure what a "radiator spoiler" is. I've never heard that term before and can't find it on any of the drawings or exploded diagrams I have of any P-51. Is that the radiator outlet exit shutter? Maybe it's unique to the Allison Mustang which did not have the laminar flow radiator inlet of the Merlin Mustangs.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> The Spiteful wing wasn't similar to the Mustang's. It was smaller than either the Spit's or Mustang's, at 210 sq/ft, it was designed for laminar flow like the Mutang's, but not to the same section, and it had a thickness at the root of 13% (same as the Spit, Mustang was 16%) and only 8% at the tip (thinner than the Spit's, much thinner than the Mustang's)<HR></BLOCKQUOTE>

For what it's worth, another case-in-point can be made here. The Spiteful with its Griffon engine and very thin wings (but still retaining the less efficient wing mounted radiator inlets) was less performant in top speed (slightly) than the penultimate P-51H (which also had revised wings and a cleaner fuselage over the P-51D) but which was heavier and less powerful than the Spiteful. The P-51H had a critical mach of .80 versus .74 for the P-51D.

===

Back to the charts. If I'm reading this right, the Spitfire reached it's highest Mach number right around the same height at which the Thunderbolt entered into its dive. What could the Thunderbolt have done from nearly 40,000 feet?

The P-47 entered its dive at somewhere above 27,700 feet (30,000 feet?), reached 19,000 feet in 22 seconds, at an angle of 65.4 degrees, where it was traveling at mach .861 and a true air speed of 608 mph. It looks like that the Thunderbolt pilot deployed flaps (and probably throttled back) right after mach .861 was reached.

The Spitfire entered its dive at 39,690 feet, in 36.4 seconds dove to 28,820 feet where it was diving at an angle of 46.2 degrees, and traveling at mach .891 and a true air speed of 606 mph.

I'm not sure what it all proves. The Spitfire reached a higher mach, but not a higher true air speed (well, 609 versus 608). The Spitfire started higher and took longer to reach its top mach speed, at a shallower angle. I'm not so sure that the P-47 would not have been capable of that if it had been tested in a similar manner. And from the accounts I've seen, test pilots agree the P-51 was better in extended dives than the P-47.

The divergence chart is also peculiar. The curve for the Mustang, presumably that Mustang I, is actually better than what the NACA found for the P-51B, which was a little less draggy than the Mustang I (Allison P-51) due to its more refined radiator inlet.

Here's what the NACA found with the P-51B:
http://members.cox.net/us.fighters/p51bdrag.jpg


Interesting.

Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

DIRTY-MAC
03-21-2004, 06:48 PM
I think it more of
wich pilot dares to push his aircraft
to the highest speed before it will break.
I think many pilot in WWII dived a H#ll of a lot faster than "the airframe could take"
and wasnt there something about
the Havker Tempest
being the best of the allies fighters at achieving speeds "close" to that of the sound withought to much inconvinience for the pilot.

hop2002
03-21-2004, 06:52 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I'm not sure what a "radiator spoiler" is. I've never heard that term before and can't find it on any of the drawings or exploded diagrams I have of any P-51. Is that the radiator outlet exit shutter? Maybe it's unique to the Allison Mustang which did not have the laminar flow radiator inlet of the Merlin Mustangs.
<HR></BLOCKQUOTE>

I suspect it's a plate that can blank off the radiator inlet. Wether it was just used for these tests, was standard on the P-51A, or was fitted because of the overcooling problems the Allison Mustangs experienced in Britain, I don't know.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>For what it's worth, another case-in-point can be made here. The Spiteful with its Griffon engine and very thin wings (but still retaining the less efficient wing mounted radiator inlets) was less performant in top speed (slightly) than the penultimate P-51H <HR></BLOCKQUOTE>

I don't know about slower, the Spiteful did 494 mph in tests.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>(which also had revised wings and a cleaner fuselage over the P-51D) but which was heavier and less powerful than the Spiteful. <HR></BLOCKQUOTE>

The weight difference was tiny, about 300 lbs according to what I've seen. Weight makes little difference to level speed, anyway.

I'm not sure how many conclusions it's to draw from the Spiteful, it was a prototype, and an especially troublesome one at that. They were constantly changing engines, retrimming, etc. Even the prop, a 6 bladed contra prop, was known to reduce top speed, but of course eliminated torque.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The P-51H had a critical mach of .80 versus .74 for the P-51D.
<HR></BLOCKQUOTE>

Thinner wings on the P-51H, which explains the improvement in critical mach.
I wouldn't mind seeing some dive test results for that.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Back to the charts. If I'm reading this right, the Spitfire reached it's highest Mach number right around the same height at which the Thunderbolt entered into its dive. What could the Thunderbolt have done from nearly 40,000 feet?
<HR></BLOCKQUOTE>

Nothing different to what it did at the lower altitudes. Look at that drag coefficient. You're looking at approx 0.08 cd to reach the same speed the Spit did. The Spit at mach 0.89 had a cd of .0519, which translated at approx 29,000ft in to 4,720 lbs of drag. The P-47 was bigger as well as heavier, and with a cd of about 0.08, what's the drag going to be in pounds?

CD doesn't change with altitude, even though absolute drag does.

Anyway, they did similar tests post war at Curtiss, with Herb Fischer as the pilot.

See the dive chart at http://home.att.net/~Historyzone/DiveChart.html

If I'm reading that chart right, the dive was started at over 35,000ft, and max speed of 0.79 mach was reached at 28,000ft, and held to about 23,000ft.

Note the report included by the RAE says that when the cd had reached 0.07, the Thunderbold needed 7 deg of elevator to maintain level flight, which it says the pilot couldn't do. What happens if you push it more? The plane goes into an outside loop at over 600 mph, which I don't think is going to be survivable.

There's a reason they fitted those dive flaps to the P-47.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I'm not sure what it all proves. The Spitfire reached a higher mach, but not a higher true air speed (well, 609 versus 608). The Spitfire started higher and took longer to reach its top mach speed, at a shallower angle. I'm not so sure that the P-47 would not have been capable of that if it had been tested in a similar manner.<HR></BLOCKQUOTE>

I've never seen anything to suggest the P-47 did reach the same speed, though. Ignoring the cd of 0.08 or so it would need, and the problem of going out of control so that neither the pilot or trim could hold it steady, and not have it steepen the dive, the P-47 never did reach the same speeds. Probably for those very reasons.

The fact remains, the Spitfire seems to have had a higher critical mach, and experienced less drag at very highs speeds. There's not only the experimental evidence, it's what is predicted by aerodynamic theory.

Theory says thinner wings = higher critical mach. I've never seen anything to contradict that, it's accepted fact.

The Spitfire had thinner wings, tests showed it had a higher critical mach.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>And from the accounts I've seen, test pilots agree the P-51 was better in extended dives than the P-47.
<HR></BLOCKQUOTE>

The RAE report seems to say the same.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The divergence chart is also peculiar. The curve for the Mustang, presumably that Mustang I, is actually better than what the NACA found for the P-51B, which was a little less draggy than the Mustang I (Allison P-51) due to its more refined radiator inlet.
<HR></BLOCKQUOTE>

Which brings us back to the radiator spoiler. If it blocked off most, if not all the radiator inlet, then that's to be expected, isn't it?

I found this from Eric Brown:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>"A Mustang III Ser No KH 505 was allocated to the RAE for high speed research, and this showed up some unpleasant compressibility effects, and indeed the aircraft was eventually lost in failing to recover fro a high mach number dive, killing the Canadian pilot, S/Ldr. E.B.Gale.
In such dives compressibility effects set in at M=0.71 with a slight vibration of the aircraft and buffeting of the controls, accompanied by a slight nose down pitching moment. These symptoms increased in intensity up to M=0.75 which was the limit imposed for service use. Above M=0.75 a porposing motion started and increased in intensity together with the other effects up to M=0.8, when nose down pitch became so strong that it required a two handed pull force for recovery." <HR></BLOCKQUOTE>

Mustang III is a P-51B or C.

WWMaxGunz
03-21-2004, 09:28 PM
Thin wings just ain't about %'s. You still have to know how wide the wings were to apply the %'s to.

Why I wonder is because it's often stated that the FW190's did not turn well becausea weight and having thin wings. Now I'm pretty sure the FW's have higher wingloading than the Spits, don't they?

There's things said about surface areas and wetted areas that I have not seen here either. Hard to make full discussion on limited factors or am I just totally wrong?


Neal

SkyChimp
03-21-2004, 09:43 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
I suspect it's a plate that can blank off the radiator inlet. Wether it was just used for these tests, was standard on the P-51A, or was fitted because of the overcooling problems the Allison Mustangs experienced in Britain, I don't know.<HR></BLOCKQUOTE>

Neither do I, it's a term I've never heard.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I don't know about slower, the Spiteful did 494 mph in tests.<HR></BLOCKQUOTE>

The only Spiteful that went that fast was the F XVI RB518 with a 3-speed Griffon 101. There was only one built. The "production" Spiteful, the F XIV, had a top speed of 483mph.

If we are going to speak in terms of one-off aircraft, the P-51G Mustang went 495 mph.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The weight difference was tiny, about 300 lbs according to what I've seen. Weight makes little difference to level speed, anyway.

I'm not sure how many conclusions it's to draw from the Spiteful, it was a prototype, and an especially troublesome one at that. They were constantly changing engines, retrimming, etc. Even the prop, a 6 bladed contra prop, was known to reduce top speed, but of course eliminated torque.<HR></BLOCKQUOTE>

The P-51H weighed a few hundred pounds more, and had a few hundred less horsepower.

While only a handful of Spitefuls were produced, this comparison, nevertheless, illustrates the benefits of a clean airframe.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
Thinner wings on the P-51H, which explains the improvement in critical mach.
I wouldn't mind seeing some dive test results for that.<HR></BLOCKQUOTE>

The H didn't have thinner wings. The H deleted the wing filets, but didn't change thickness. The improved drag situation came mainly from a revised fuselage. The radiator housing remained deeper further back eliminating a lot of turbulance.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Nothing different to what it did at the lower altitudes. Look at that drag coefficient. You're looking at approx 0.08 cd to reach the same speed the Spit did. The Spit at mach 0.89 had a cd of .0519, which translated at approx 29,000ft in to 4,720 lbs of drag. The P-47 was bigger as well as heavier, and with a cd of about 0.08, what's the drag going to be in pounds?

CD doesn't change with altitude, even though absolute drag does.

Anyway, they did similar tests post war at Curtiss, with Herb Fischer as the pilot.

See the dive chart at http://home.att.net/~Historyzone/DiveChart.html

If I'm reading that chart right, the dive was started at over 35,000ft, and max speed of 0.79 mach was reached at 28,000ft, and held to about 23,000ft.

Note the report included by the RAE says that when the cd had reached 0.07, the Thunderbold needed 7 deg of elevator to maintain level flight, which it says the pilot couldn't do. What happens if you push it more? The plane goes into an outside loop at over 600 mph, which I don't think is going to be survivable.

There's a reason they fitted those dive flaps to the P-47.<HR></BLOCKQUOTE>

Nothing different than it did at lower altitudes. Do you mean mach .861 or 608 mph TAS? Because if 608 mph TAS could be achieved at higher altitudes, then mach .891 is certainly achievable.

For your conclusion to be correct, then it would have to be that there was no way for the P-47 to obtain 608 mph TAS at 28,000 feet. I don't know if that's a correct assumption or not.

Are you relying on the suggestions that drag would have been too great to achieve mach .891 because at that speed Cd would have been around .08, and that level flight could not be maintained above a Cd of .07 due to elevator forces?

And as for 7 degrees of negative elevator being require to maintain level flight, it's intertesting that the chart shows anywhere from +1.1 to -3.7 being used to maintain a relatively constant 66 degree dive angle. In that range, Cd is as high as .0690.

It looks as if the Spitfire used about 4.6 degrees of elevator to maintain a constant 33-35 degree dive angle. It appears that the pilot let up on the elevators starting at mach .880 as the elevator angle goes from 3.3 to .8, and dive angle suddenly increases by about 13 degrees to 46 degrees.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
I've never seen anything to suggest the P-47 did reach the same speed, though. Ignoring the cd of 0.08 or so it would need, and the problem of going out of control so that neither the pilot or trim could hold it steady, and not have it steepen the dive, the P-47 never did reach the same speeds. Probably for those very reasons.

The fact remains, the Spitfire seems to have had a higher critical mach, and experienced less drag at very highs speeds. There's not only the experimental evidence, it's what is predicted by aerodynamic theory.

Theory says thinner wings = higher critical mach. I've never seen anything to contradict that, it's accepted fact.

The Spitfire had thinner wings, tests showed it had a higher critical mach.
<HR></BLOCKQUOTE>

Maybe. But I've never seen anything to suggest the Thunderbolt, or the Mustang for that matter, was tested in the same fashion or altitude as the Spitfire.

And it's simply not a matter of "thinner wings = higher critical mach." That's a true statement if you reduce wing thickness while all other things stay the same, otherwise the Spitfire would be faster than today's jetliners. Scale changes perspective.

BTW, while the Spitfire had thinner wings of conventional profile, the Mustang had laminar flow wings - which are more efficient at high speed than conventional profiles. I know you've said in the past that laminar wings are more efficient than conventional wings of the same thickness. Then by inference isn't it correct to say that thicker laminar wings are "at-least" as efficient as some thinner conventional wings?

Nevertheless, the Spitfire may indeed have had a higher critical mach according that those charts. But it didn't attain signficantly higher True Air Speeds.

I just don't believe the thinner wings is the full answer here.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
Which brings us back to the radiator spoiler. If it blocked off most, if not all the radiator inlet, then that's to be expected, isn't it?
<HR></BLOCKQUOTE>

It's not determined that's what it is.

What is clear is this: the P-51B was less draggy than the P-51A (essentially the Mustang I) mainly due to the fact that the B model had a laminar flow radiator inlet that was outside the boundry layer. There's no question that the B model was more aerodynamically efficient than the P-51A, or there would have been no reason to make the aerodynamic changes that occurred with the B model. The changes to the radiator inlet between the A and B model were almost solely for aerodynamic purposes.

The P-51B, in model form, was wind-tunnel tested by the NACA. That test produced the results in the chart I posted. The model afforded the best aerodynamic cleanliness possible. What I find interesting is that a somehow the Britsh were able to achieve better results with a draggier, real, Mustang I.

Look (NACA findings in red):

http://members.cox.net/us.fighters/overlay.jpg

The British chart suggests the Mustang I resisted drag build-up better than the B, something I've only seen in that chart. Additionally, it suggests the P-47 was less draggy at high speed than either the P-51A or the P-51B, something else I've never seen except in that chart.

People see what they want. You see a chart that offers irrefutable evidence that the Spitfire had the lowest Cd of any prop plane at high speed.

I see a chart that is at odds with NACA findings; which shows much better numbers for a real Mustang I than the cleanest NACA P-51B model achieved; which shows the P-47 better at very high speeds than the Mustang which is at odds with both US pilots and RAE (and despite the fact that the P-47 had conventional wings of the same thickness as the P-51's laminar wings); and (if my observations are the least bit correct concerning the questionable Mustang and Thunderbolt drag lines) consequently brings into -at least some- question the accuracy of the Spitfire numbers.

Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

[This message was edited by SkyChimp on Sun March 21 2004 at 08:53 PM.]

Kurfurst__
03-22-2004, 05:41 AM
Here`s the english comparision of 109F-2 and Spit VB. The 109 was found superior in a dive for practical purposes. It should be noted that the test machine was a belly landed one, that already sustained damage to the engine and airframe, as mentioned in the report, and was in "poor condition". Despite that, they managed to dive it to 420 mph IAS later on during the test w/o troubles.

The F-2 had about 200 HP less, and was somewhat lighter than the F-4.

http://www.x-plane.org/users/isegrim/FvsF/109F-2_diveAFDU.jpg

A similiar story emerges from just about every Spit vs. 109 dive tests I have seen, ie., a later test of a MkIX LF vs. a 109G-6 with gunpods :

"Dive
19.........Comparitive dives between the two aircraft have shown that the Me.109 can leave the Spitfire without any difficulty. "

The later trials vs. Mk XIV shows the 109G being in advantage up to 380mph IAS, then the Mk XIV pulling ahead. I doubt this would be because the "better high speed drag" of the MkXIV, rather than the much higher maximum speed which meant the engine was still accelerating the plane whereas the gondola equipped G-6 already reached it. The MkXIV was hardly a clean a/c anyway.

Regarding airframe strenght, in AEP, the 109F is weaker than the 109Gs, and the Spits broke up earlier. I think this is about correct.The subsequent 109G had reinforced wing structure, the wing cover, the main spar and the wing ribs were all reinforced to take the wing stores that were typical on this series, ie. gondolas, which is probably why the 109G also last longer in dives than the 109F in the game.

The Spits were known to have numerous structural failures, wings being lost in dives, loops on all models, I have also read they lost wings over Normandy in 1944 when wing mounted bombs failed to drop and they tried to pull out.. I am not sure about the exact reason, I think it was the lack of stiffness of wing and resulting vibration - aileron reversal speed was very low on the Spit compared to other fighters - but it was a constant existing problem. IIRC around 1941 with the MkVs there was also a problem with loosing whole tail units (some similiarity with the 109F), which forced them grounded until a fix was found. The wing failirues however never ceased to exist, and these are as said well documented.

The 109F also had tail problems, with the new engine critical vibration from the engine was a problem. This was fixed by adding external stiffeneres, later changed to internal ones. But I have never heard of any actual Bf 109 wing failure, the only source for these are usually gossip in British sources, nothing actual.. I believe this was invented during the Battle of Britain to boost the pilot`s morale. If there would be actual cases in numbers, you bet it would be well known and throughly documented.

I wouldn`t put much faith in the alleged ".89 Mach" dive of that unarmed Spit recon version (it was rather different than fighter variants). It`s some kind of a religous belief of Spit dweebs, despite the fact that it was the only a single dive (out of some 20), whereas dozens of others dives even with the same plane never reached such speed again, rather they resulted in structural failures. The method they used to get the airspeed was a simple pitot, which is by no standards is an accurate mean of measuring high mach numbers. But whatever, those who want to believe it will remain believers no matter what. Just a sidenote.

In brief, I think it`s quite well modelled in AEP, the 109s can take advantage in dives and zoom climbs, in which they are and were superior to Spits. Most likely Rhorta`s adversary simple took advantage of that, I use to do that vs. early Soviet planes, go into a dive and stabilize speed around 800 IAS.. if he is foolish enough to follow he will disingtegrate. Or sometimes its me who gets blackout and finish the engagement as a pencake on the ground, my last sight being just getting my vision back 15m above the ground. http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif You may have gone over to the limit, rhorta in applying Gs, its easy to do that in the Spit because of the light elevator forces permit excessive Gs to be applied that might overstress the structure.

[This message was edited by Kurfurst__ on Mon March 22 2004 at 05:38 AM.]

dahdah
03-22-2004, 07:22 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Here`s the english comparision of 109F-2 and Spit VB. The 109 was found superior in a dive for practical purposes. It should be noted that the test machine was a belly landed one, that already sustained damage to the engine and airframe, as mentioned in the report, and was in "poor condition"<HR></BLOCKQUOTE>

All German a/c flown by the LW were in perfect condition? http://ubbxforums.ubi.com/infopop/emoticons/icon_eek.gif http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gifhttp://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif


What was the difference between the Spit IX and Spit XI?

If the Spit XIV was was not a 'clean' a/c then what would you call the G-6 then with two huge bulges on the fuselage as well as bulges on the wing? Many G-6 even had a big stick for the antenna.

Like to see a 109 with a 500lb bomb under the wing pull out of a 60 degree dive and keep their wing attached.

I see in this post by Kurfurst, someone who hates the Spitfire.

[This message was edited by dahdah on Mon March 22 2004 at 06:32 AM.]

BerkshireHunt
03-22-2004, 08:56 AM
[QUOTE]Originally posted by Kurfurst__:
The Spits were known to have numerous structural failures, wings being lost in dives, loops on all models, I have also read they lost wings over Normandy in 1944 when wing mounted bombs failed to drop and they tried to pull out.. I am not sure about the exact reason, I think it was the lack of stiffness of wing and resulting vibration -
--------------------
Isegrim,
You are only able to post this because you have the Morgan and Shacklady book which includes a list of all known structural failures experienced by the Spitfire. A similar book does not exist for the 109 so you are able to adopt the stance that structural failures 'rarely' occurred with this machine. But 'absence of evidence' is not 'evidence of absence'.
In fact, there is some evidence relating to 109 structural failures from Messerschmitt test pilot Heinrich Beauvais:
"In the early days of the 109 many bent wings were brought to Rechlin. Then after a time, no more arrived. Had the troops learned? Or had everyone got used to bending wings? I do not know. Later during the war the damage increased again. There would never be a totally safe way of avoiding overstressing the aircraft, either through strengthening the airframe or by improving the flight controls and wing loading. It all boiled down to a compromise of strength, sturdiness and flight performance ie purely tactical requirements."
A very balanced view.

Test pilot Lukas Schmid says he received an official report marked 'Confidential' which stated, "the troops have recorded more than 20 accidents with the 109G within the last two months. All had been preceded by dives from high altitudes." After investigation it was found that pilots had tried to use the elevator trim wheel to pull out of high speed dives (because the elevator was so heavy) with the result that the rear fuselage /tailplane broke off. Recommended procedures had not been followed- and the same was true for most of the recorded Spitfire failures. Service pilots will exceed limits in life or death situations.

Wolfgang Spate remembers that: "In at least three cases I had to return home with damage to the wings of my 109 due to my own fault in having failed to observe the G limits in air combat."
-------------------------

I have never heard of any actual Bf 109 wing failure..

Yes you have- but you are professionally deaf where the 109 is concerned. It is a matter of historic record that Wilhelm Balthasar was killed when both wings fell off his 109F in combat. He presumably exceeded the G limit.
In fact, Willi Messerschmitt wrote to Ernst Udet in June 1941: "The deformation and breaking of the wings of the 109 can be put down to the fact that we cannot calculate the load distribution on the wings at high speeds".

-------------------------
I wouldn`t put much faith in the alleged ".89 Mach" dive of that unarmed Spit recon version (it was rather different than fighter variants). It`s some kind of a religous belief of Spit dweebs.

No, it's a documented fact. And you offer just an opinion.

Ruy Horta
03-22-2004, 11:07 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>In brief, I think it`s quite well modelled in AEP, the 109s can take advantage in dives and zoom climbs, in which they are and were superior to Spits. Most likely Rhorta`s adversary simple took advantage of that, I use to do that vs. early Soviet planes, go into a dive and stabilize speed around 800 IAS.. if he is foolish enough to follow he will disingtegrate. Or sometimes its me who gets blackout and finish the engagement as a pencake on the ground, my last sight being just getting my vision back 15m above the ground. http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif You may have gone over to the limit, rhorta in applying Gs, its easy to do that in the Spit because of the light elevator forces permit excessive Gs to be applied that might overstress the structure.<HR></BLOCKQUOTE>

Interesting that a large part of my original observation was ignored.

1. I did state that the initial advantage of the 109F-4 was in accordance to expectation.
2. That although I did not check IAS, I did flatten out the dive gently.
3. I lost my wing flying all but horizontal, while the 109 was also level.
4. The latter had to pull up harder in order to level out at more or less the same time, since he was diving more steeply.

Now I am not comparing Spits with P-47s and P-51s or even Spitefulls, so these comparisons are not very useful.

We are comparing the Spit Mk V with a b-type wing and a "generic" Bf 109 F-4.

Annecdotal evidence does not support Spitfires taking care not to break up in dives vs 109s. Although they might have had a tactical disadvantage wrt to speed, its not one of structural weakness. OTOH there was certainly a time when the 109F suffered from structural failures during pull ups in combat. This is well known, and should be acknowledged even by those who are attracted by the 109.

Reports also indicate that although the initial advantage lay with the 109, it was mainly initial. As long as the Spit type didn't suffer from neg-G engine cutouts, the types were well matched. (Lets not forget that the choice of JOINING an enemy who's diving out of combat also means to give away ones tactical advantage of height - not wise if combat is still heated, this for those who mentioned the entry of the USA as an end to the diving tactics as a means of escape.)

So we are basically left with a couple of options:

1. The 109F-4 is stronger than the Spit MkV, AEP is correct

2. The 109F-4 is overmodeled in terms of structural strength, AEP is incorrect...

3. The Spit MkV is undermodeled in terms of structural strength, AEP is incorrect...

SO AGAIN, the question is NOT one of initial advantage in a dive, or a higher diving speed, but one of structural integrity.

Annecdotal evidence points against the current modeling of AEP, leaving points 2 and 3. Since sims are all about COMPERATIVE modeling either is will spoil the outcome.

Of course this is not a unique situation in the IL2 series, there are more such issues when it comes to structural modeling (or failing to include structural weaknesses/strengths of certain types).

Ruy Horta

[This message was edited by rhorta on Mon March 22 2004 at 10:16 AM.]

Ugly_Kid
03-22-2004, 11:49 AM
The divespeeds reached by Spit or Thunderbolt were not necessarily a drag issue but rather a question of stability and control.

Mustang: "As the dive Mach number was increased the compressibility effects became more violent, but the aircraft was still controllable. At Mach .83 the shaking and buffeting was of the aircraft was so strong that it was decided to explore no further. THe airplane had suffered considerable structural damage and was written off."

P-47´: "At this altitude the limit dive speed corresponded to 601 mph TAS (true speed) and a Mach number of 0.82. At this speed the P-47 was well into compressibilty with a drag coefficient of at least two and a half times the value at moderate speeds. A pilot described a long almost vertical high speed dive by two early P-47B versions into compressibility. He said they could not pull out because the stick would not move and chopping throttle did not help. Only when they got into warmer air at a lower altitude were they able to recover."

So the final factor would be strength, stability and control for Spitfire. Strength is more an issue of IAS (indicated airspeed) and somewhere an issue of Mach effects (in a stable dive). Stability and control in this case is mainly a Mach effect (compressability, shockwave formations).

Initially and for a long long dive all the other fighters will out dive Spitfire. Somewhere the limit will be pilot's and Spitfire being faster feat might be possible only under certain conditions. Note hops' table. The dive commences from 12 km! and the high Mach number is reached already at 9 km! then it's time to slow down. So practically at lower alt starting from maybe 8km there is no high speed dive trick anymore...

[This message was edited by Ugly_Kid on Mon March 22 2004 at 02:00 PM.]

robban75
03-22-2004, 11:55 AM
Planes breaking apart in FB has nothing to do with the planes structural strength. It's just the way this sim models how planes otherwise would lawndart at insanely high speeds due to elevators losing their authority.
Planes didn't lose their wings during 0 G vertical dives in RL. Pilots that survived these killer dives, wasn't able to pull out of the dive until the came in to the denser air at the lower altitudes in which the drag of the aircraft automatically slowed it down to speeds when the elevators became effective again. German planes actually had a great advantage in these terminal dives because they were fitted with an all moving trimmable tailplane. Meaning, at least to me that a 109 or a 190 could pull out of a dive at speeds that most other planes weren't able to. Care had to be taken using this trim, more so in the 109 than the 190.

And please, in no way am I trying to put down the Spitfire. It's probably my second most favourite WW2 fighter. Just thought I'd add the above.http://ubbxforums.ubi.com/images/smiley/16x16_smiley-happy.gif

http://members.chello.se/unni/D-9.JPG

When it comes to aircombat, I'd rather be lucky than good any day!

Kurfurst__
03-22-2004, 01:01 PM
Originally posted by BerkshireHunt:

"A very balanced view."

Hardly. It`s the usual stuff from Hop2002, mixing facts and his own fiction. But he also admits Morgan and Shacklady lists a LARGE number of Spitfire wign failures. Fact, but every time I hear that stuff about the exceptionally strong Spit airframe. Facts are different.

He claims there no similiar comparision for the 109 exists. This is simply not true, there are the work of Matti Salonen, containing TEN THOUSENDS of indidvidual LW aircraft fates are KNOWN. Werknummers and fates are also well known even the latest K-4...Just because someone on a BB who would want to make the Spit`s record to look better would want to forget about all those studies or more likely never ever heard about them hardly makes his statemetn true. Wheter Hop knows about these research work has no relavance to the facts shown in them. This work is available to all 109 researchers - why none of them dedicates pages to those "frequent" wing failures of the 109, hmm? Perhaps because it`s a good old english myth developed in the darkest hours of the RAF to boost the morale of fighter pilots who began to flee from engagement against 109s?

Fact is still that there are known problems with the Spitfire structural integrity in dives and pullups, and not with the 109. You may or may not like this fact, but its stil a fact. Shooting from the hip the sentence "but yeah, the 109s had a lot of wing failures, altough it`s never documented, there is no source towards that" hardly proves anything but the poster`s bias vs the 109.

Then from pure fiction we travel to the world of rewritten quotes, such as :

**
Test pilot Lukas Schmid says he received an official report marked 'Confidential' which stated, "the troops have recorded more than 20 accidents with the 109G within the last two months. All had been preceded by dives from high altitudes."
**

Well the source must be the Otto/Radinger book, which Hop doesn`t even possess, just seen a scan of a page of it and re-written the story to fit his own taste. I cannot find 109Gs mentioned there, neither Schmidt mentionning receiving "confidental reports". The story is again built up from small fragments, and modified to fit the agenda.


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Wolfgang Spate remembers that: "In at least three cases I had to return home with damage to the wings of my 109 due to my own fault in having failed to observe the G limits in air combat." <HR></BLOCKQUOTE>

So if I read that correctly, Spate exceeded the allowed the limits, and wings didn`t break even despite that ? Sorry, but wasn`t the point to prove the Spit should break up later than the 109 in a dive ? Spate`s did not do that.


"I have never heard of any actual Bf 109 wing failure..

Yes you have- but you are professionally deaf where the 109 is concerned."

Accusations and insults lead to bans on these boards. Keep that in mind.

"It is a matter of historic record that Wilhelm Balthasar was killed when both wings fell off his 109F in combat.He presumably exceeded the G limit."

Hmm, allowed G limit was 6.5 at maximum takeoff weight, a rather avarage value, altough it was designed with plenty of safety factor, as usual in aircraft industry.

Balthasar was flying a brand new F-4 in June 1941 when the aircraft just arrived to the unit. He was attacked by Spitfires in the unarmed plane, was fired at, probably hit as well, when he made a hard evasive turn and a wign failure happened. Make up you own mind, but to me, a brand new plane, untested in service, with the pilot going over the imposed limits - and it broke in a single case?Not to mention Balthasar`s accident lead to the structure being strenghtened, just in case, making the event of failure even less likely.. Again, where`s the proof in that it happened "often"? To prove that, you would have to find a dozen case of 109 structural failures. Not a single one, with a plane that wasn`t yet ironed out. The point is, there is no such bad record existing for the 109, but there`s one such bad record for the Spit. So pray, why should one believe the way it is in AEP is wrong ?


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>In fact, Willi Messerschmitt wrote to Ernst Udet in June 1941: "The deformation and breaking of the wings of the 109 can be put down to the fact that we cannot calculate the load distribution on the wings at high speeds". <HR></BLOCKQUOTE>

This was written at the exact same time Balthasar had his accident after overstressing the airframe. As a matter of fact Balthasar took off in the plane originally to test it`s limits for the other pilots, when he was attacked by Spits.
You are in fact bringing up the same - single - case mutliple times. But it won`t make it two cases, still.


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>No, it's a documented fact. And you offer just an opinion.<HR></BLOCKQUOTE>

Did you say documented, Berkshirehunt ? The last time you I seen that word from you, which was interestingly another case of 109 bashing, you got the following reply from Oleg :

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
-----------------------------------
Originally posted by BerkshireHunt:
Yes, and while we're about it what about the 109's heavy elevator on dive recovery?... It's well documented, I believe.
-----------------------------------

Oleg Maddox

Yes it well documented in trials. True aircpeed is 980 km/h - no problem to recover. Force on the stick less than 40 kg (without use of trim)
From the trals in Rechlin. I have all the data for this..
And it is the very similar force on a stick like for the best easy flying planes of WWII.... Any other questions? <HR></BLOCKQUOTE>


But let`s just see the facts about that Spit dive. The plane is an unarmed, high altitude recond version of the Spitfire, with modified wing design. It did about 20 or more dives, never achieving .89 Mach in all but 1 case. And even that case, the way of measuring speed was nothing more than using a pitot, not radar or anything reliable. It`s simply a fact that an 1940 vintage pitot DOES not give accurate numbers at high Mach numbers for a miriad of reasons. And it`s also known the same plane with the alleged .89 Mach claim later suffered from a catashrophic failure in a dive, and dozens of other Spits suffered the same way in high speed dives. The Spitfire didn`t have a special design for high speed either, the radiators, wing bulges and excessively steep windscreen ALL disroving this theory (interesting to note that UNARMED variant they did those tests with have neither these featerus, except of course the radiators).
Considering all this, I would say to believe the .89 Mach claim is a matter of mere belief. Believe it if you want, I have no trouble with that. As for me, I say it`s a HYPE.


Here are some anecdotal testimonies :

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
"- Are the stories true, that the 109 had weak wings and would loose them easily?
He has never heard of a 109 loosing its wings from his experience or others. The wings could withstand 12 g's and since most pilots could only handle at most 9 g's there was never a problem. He was never worried about loosing a wing in any form of combat."
- Franz Stigler, German fighter ace. 28 victories
<HR></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
My flight chased 12 109s south of Vienna. They climbed and we followed, unable to close on them. At 38,000 feet I fired a long burst at one of them from at least a 1000 yards, and saw some strikes. It rolled over and dived and I followed but soon reached compressibility with severe buffeting of the tail and loss of elevator control. I slowed my plane and regained control, but the 109 got away.
On two other occasions ME 109s got away from me because the P 51d could not stay with them in a high-speed dive. At 525-550 mph the plane would start to porpoise uncontrollably and had to be slowed to regain control. The P 51 was redlined at 505 mph, meaning that this speed should not be exceeded. But when chasing 109s or 190s in a dive from 25-26,000 it often was exceeded, if you wanted to keep up with those enemy planes. The P 51b, and c, could stay with those planes in a dive. The P 51d had a thicker wing and a bubble canopy which changed the airflow and brought on compressibility at lower speeds."
- Robert C.Curtis, American P-51 pilot.
<HR></BLOCKQUOTE>


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
Me 109 G:
"The maximum speed not to be exceeded was 750kmh. Once I was flying above Helsinki as I received a report of Russkies in the South. There was a big Cumulus cloud on my way there but I decided to fly right through. I centered the controls and then something extraordinary happened. I must have involuntarily entered into half-roll and dive. The planes had individual handling characteristics; even though I held the turning indicator in the middle, the plane kept going faster and faster, I pulled the stick, yet the plane went into an ever steeper dive.
In the same time she started rotating, and I came out of the cloud with less than one kilometer of altitude. I started pulling the stick, nothing happened, I checked the speed, it was about 850kmh. I tried to recover the plane but the stick was as if locked and nothing happened. I broke into a sweat of agony: now I am going into the sea and cannot help it. I pulled with both hands, groaning and by and by she started recovering, she recovered more, I pulled and pulled, but the surface of the sea approached, I thought I was going to crash. I kept pulling until I saw that I had survived. The distance between me and the sea may have been five meters. I pulled up and found myself on the coast of Estonia.
If I in that situation had used the vertical trim the wings would have been broken off. A minimal trim movement has a strong effect on wings when the speed limit has been exceded. I had 100kmh overspeed! It was out of all limits.
The Messerschmitt's wings were fastened with two bolts. When I saw the construction I had thought that they are strong enough but in this case I was thinking, when are they going to break
- What about the phenomenon called "buffeting" or vibration, was there any?
No, I did not encounter it even in the 850kmh speed."
- Ky¶sti Karhila, Finnish fighter ace. 32 victories. <HR></BLOCKQUOTE>

etc. One can find a dozen stories about 109s entering VERY high speeds, well in excess of their official limits, without structural failure. Basically the claim is here the 109s structure was weak, and prone to failures in pullups, or at least, more prone that the Spits. Prove it. There`s no serious evidence to that. There`s evidence to great structural strenght under load, one can qoute Finn, US, Hungarian pilots describing 109s doing very high speed dives.

Kurfurst__
03-22-2004, 01:24 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by rhorta:
Annecdotal evidence does not support Spitfires taking care not to break up in dives vs 109s. <HR></BLOCKQUOTE>

Please expand on that. There`s evidence that Spits broke up in pullups during dives during the whole war. There`s evidence they had tailplane troubles. There`s evidence they suffered from wing torsion at high speed more than any other modern fighter.
It`s also a fact that the Spit`s elevator was light, and the pilot could apply such G forces easily that would rip the plane apart easily, whereas the 109`s pilot was usually unable to do that, because the high stickforces present. It`s also an aerodynamical fact that the Spitfire had poor longitudal stability - this also aggrevates problems with structural integrity in dives. The Spit`s wing is also a very large area one, and during pullups, there`s a lot more force applied to it than to a smaller surfaced wing... Rhorta, there`s a lot of evidence, and reason to believe the Spit`s structure should not and did not show especially high strenght in dives.


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
OTOH there was certainly a time when the 109F suffered from structural failures during pull ups in combat. This is well known, and should be acknowledged even by those who are attracted by the 109.<HR></BLOCKQUOTE>

Rhorta, there was time the early 109F suffered from engine vibrations and it caused tailplane failures, and this was fixed (and it`s also true for the Spit MkV).
There was time where pilot`s EXCEEDED the given limits and it led to crashes - it should on all planes. There was time when they had problem with the elevator trimmer`s grease, which froze at high altitude at cruise speeds, making recovery hard if not impossible in long dives from high altitudes; this was fixed with a new type of grease soon, too, and wasn`t a structural shortcoming either.

But I never heard of actual 109F structural failures during pull ups in combat. There`s literally OVERWHELMING amount of anecdotal evidence that dives were probably the most favoured tactic of 109 pilots for escape. They seem to trust the structural strenght of the aircraft. Despite that you say it`s "well known". Please enlighten me with the details.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Reports also indicate that although the initial advantage lay with the 109, it was mainly initial. As long as the Spit type didn't suffer from neg-G engine cutouts, the types were well matched. <HR></BLOCKQUOTE>

Please rhorta... what reports ? Every report, even that of AFDU notes the 109s outdives the Spits...Period. Show me a report where a current model Spit outdives the 109 from the same timeframe, on whatever dive range. There`s NO evidence, just guesses.


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> So we are basically left with a couple of options:

1. The 109F-4 is stronger than the Spit MkV, AEP is correct
2. The 109F-4 is overmodeled in terms of structural strength, AEP is incorrect...
3. The Spit MkV is undermodeled in terms of structural strength, AEP is incorrect...

SO AGAIN, the question is NOT one of initial advantage in a dive, or a higher diving speed, but one of structural integrity.<HR></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Annecdotal evidence points against the current modeling of AEP, leaving points 2 and 3.<HR></BLOCKQUOTE>

That`s a sweeping statement, Rhorta. What was the anecdotal evidence that disproves the statement "109F-4 is stronger than the Mk VB in dives", exactly? Is there any dive tests, or telling of a pilot who stated a 109F broke up before him in a dive while he returned to base safely in a Spitfire ? No.

CTO88
03-22-2004, 01:30 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by butch2k:
With a 109F2 dive speed of 750km/h was tolerated at low alt without any special caution, 800 km/h could be reached but pull-out had to be slow.<HR></BLOCKQUOTE>

according to testpilots 109f4 had 750km/h ne = never exceed!. but front units report that 109f2 even broke at slightly slower speeds. 800km/h are a very risky number.
so the germans tested the 109f's in highspeed and reached mach 0,8 906km/h. but this was a special checked version, sometimes at highspeeds 109f's gear was pull out by airforces and destroyed the plane. the reason was the too light construction of the 109 which sometimes let gear disform due hard landings. so the gear procuces additional drag.
so for a normal series version 750km/h should be the correct speed. after that there is no safety for any damage and 109f can be serious damaged.

hop2002
03-22-2004, 02:56 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Thin wings just ain't about %'s. You still have to know how wide the wings were to apply the %'s to.
<HR></BLOCKQUOTE>

No, only the % counts. Absolute thickness doesn't matter, only the thickness/chord ratio.


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The only Spiteful that went that fast was the F XVI RB518 with a 3-speed Griffon 101. There was only one built. The "production" Spiteful, the F XIV, had a top speed of 483mph.<HR></BLOCKQUOTE>

I wouldn't call any Spiteful production, and I believe the only performance figures are estimates. Spitfire the History gives an estimate of 481 mph at 18lbs boost, which would be something around 2000 hp or less, I believe the P-51H had 2200 hp+

I really think this is getting off track, though, the Spiteful has very little to tell us about etiher the Spitfire or Mustang.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The P-51H weighed a few hundred pounds more, and had a few hundred less horsepower<HR></BLOCKQUOTE>

I'm not even sure the H weighed more. The H weighed 9500 lbs normal loaded according to Joe Baugher's site. Spitfire the History gives the weight of the Spitefeul as 9,950 lbs takeoff.

AS to HP, the Griffon 69 developed 2350 hp or so, but that was at 1,250 ft. Again according to Baugher, the P-51H had 2218 hp at 10,200 ft, and 1900 hp at 19,000ft. I'd be suprised if the Griffon was developing more than that at high alt.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>While only a handful of Spitefuls were produced, this comparison, nevertheless, illustrates the benefits of a clean airframe.
<HR></BLOCKQUOTE>

Reading Spitfire the History, they were busy attaching external reinforcing strips, spoilers on the wing, even gluing balsa wood strips to the upper surface of the wing on the Spiteful. I really think we'd need to see proper tests of the Spiteful to draw any conclusions, and I don't think they were done.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The H didn't have thinner wings. The H deleted the wing filets, but didn't change thickness<HR></BLOCKQUOTE>

They certainly used a different wing profile, changing from Naca 45-100 to Naca 66 - 15.5

The P-51 B and H, ignoring the wing filet, had 16.2% at the root. The H had 15.5% at the root. David Lednicer, in "A CFD Evaluation of Three Prominent World War II
Fighter Aircraft," Aeronautical Journal of the Royal Aeronautical Society, June/July 1995 (it's mentioned by the author in the thread from Yarchve you linked to above) says the same, 15.5% root for the 51H.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Nothing different than it did at lower altitudes. Do you mean mach .861 or 608 mph TAS? Because if 608 mph TAS could be achieved at higher altitudes, then mach .891 is certainly achievable.
<HR></BLOCKQUOTE>

That's the whole point. 608 TAS is achievable at lower altitudes, so if it wasn't for the sound barrier, it would be achievable at higher altitudes as well.

But the massive drag rise is caused not by a rise in tas, or even IAS, but by a rise in mach number. It's the mach number that's the limiting factor.

Drag caused by approaching and exceeding critical mach is different.

If 609 TAS could be achieved at 35,000 ft, the P-47 would be supersonic.

The limit to speed at high altitude isn't IAS, it's mach.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>For your conclusion to be correct, then it would have to be that there was no way for the P-47 to obtain 608 mph TAS at 28,000 feet. I don't know if that's a correct assumption or not.
<HR></BLOCKQUOTE>

No, the TAS, or IAS achieved has nothing to do with the maximum mach achieved. The TAS is roughly the same for the 3, but the higher you can sustain the same TAS, the higher your mach limit.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Are you relying on the suggestions that drag would have been too great to achieve mach .891 because at that speed Cd would have been around .08, and that level flight could not be maintained above a Cd of .07 due to elevator forces?
<HR></BLOCKQUOTE>

Yes.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>And as for 7 degrees of negative elevator being require to maintain level flight, it's intertesting that the chart shows anywhere from +1.1 to -3.7 being used to maintain a relatively constant 66 degree dive angle. In that range, Cd is as high as .0690.
<HR></BLOCKQUOTE>

Presumably the chart is not counting trim. Note the angle is changing rather quickly, and constantly, for it to be counting trim, and the text is pretty explicit:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>In the worst case, that of the Thunderbolt at M = 0.86, over 7 deg of change of elevator angle must be applied to restore trim, it is not possible for the pilot to do so, and the aeroplane must go out of control until a lower altitude and smaller mach number are reached<HR></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>It looks as if the Spitfire used about 4.6 degrees of elevator to maintain a constant 33-35 degree dive angle. It appears that the pilot let up on the elevators starting at mach .880 as the elevator angle goes from 3.3 to .8, and dive angle suddenly increases by about 13 degrees to 46 degrees.<HR></BLOCKQUOTE>

Note that the text explicitly states the P-47 rrequired more trim, so either the Spit is without trim and the Thunderbolt with, or both are with trim, but less trim in the Spit.

Note as well that the positive elevator angles are pushing the nose down, negative angles pulling up.

It looks like the P-47 is actually out of control before the flaps are deployed.

At 24 seconds, the elevator is being pulled back, but there is actually an acceleration of -0.7 g, which is pretty high for negative G. The flaps are then deployed, and a positive G pullout begins.

That leaves 2 questions. Would the P-47 have survived without the flaps, and would the pilot have pushed it that much without the flaps? Once tuck under begins, you have to hope that the effect of denser air on mach speed increases faster than your speed due to the ever increasing angle of dive.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>And it's simply not a matter of "thinner wings = higher critical mach." That's a true statement if you reduce wing thickness while all other things stay the same, otherwise the Spitfire would be faster than today's jetliners. Scale changes perspective.<HR></BLOCKQUOTE>

Not faster, but a higher critical mach.

Obviously thickness is not the only thing that matters, the other important thing for critical mach is sweep, and modern airliners have quite a lot of sweep.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>BTW, while the Spitfire had thinner wings of conventional profile, the Mustang had laminar flow wings - which are more efficient at high speed than conventional profiles. I know you've said in the past that laminar wings are more efficient than conventional wings of the same thickness. Then by inference isn't it correct to say that thicker laminar wings are "at-least" as efficient as some thinner conventional wings?
<HR></BLOCKQUOTE>

I don't know how much of an effect laminar flow wings have on transonic drag. Certainly they are more efficient at normal airspeeds.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Nevertheless, the Spitfire may indeed have had a higher critical mach according that those charts. But it didn't attain signficantly higher True Air Speeds.
<HR></BLOCKQUOTE>

No, but it can attain significantly higher true airspeeds at any particular altitude (over about 20,000ft).

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>What is clear is this: the P-51B was less draggy than the P-51A (essentially the Mustang I) mainly due to the fact that the B model had a laminar flow radiator inlet that was outside the boundry layer. There's no question that the B model was more aerodynamically efficient than the P-51A, or there would have been no reason to make the aerodynamic changes that occurred with the B model. The changes to the radiator inlet between the A and B model were almost solely for aerodynamic purposes.
<HR></BLOCKQUOTE>

The changes were no doubt made because of their effects at normal speeds. That doesn't neccessarily mean they had as much effect on transonic drag.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The P-51B, in model form, was wind-tunnel tested by the NACA. That test produced the results in the chart I posted. The model afforded the best aerodynamic cleanliness possible. What I find interesting is that a somehow the Britsh were able to achieve better results with a draggier, real, Mustang I.

Look (NACA findings in red):
<HR></BLOCKQUOTE>

The Naca findings seem to compare closely with the admittedly limited range for the P-51 with radiator spoiler lowered.

Look at the red line. The P-51B clearly has lower drag at normal speeds, but it reaches critical mach earlier. Transonic drag is not the same, it's not a function of the same forces that cause normal drag.

From that Naca test of the P-51B:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>the minimum drag of the airplane was affected by the presence of dust on the surface of the airplane, and that, as would be expected, the dustier the surface the higher the minimum drag of the airplane

It is noteworthy that the mach number of drag divergence and the variation of drag coefficient with mach number above the mach number of drag divergence are essentially unaffected by the presence of dust on the airplane<HR></BLOCKQUOTE>

The dust increased normal drag, but didn't affect the onset, or the extent, of drag divegence.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>which shows the P-47 better at very high speeds than the Mustang which is at odds with both US pilots and RAE (and despite the fact that the P-47 had conventional wings of the same thickness as the P-51's laminar wings);<HR></BLOCKQUOTE>

Hold on. The P-47 data in that report is from NACA, as is the P-51B data you are providing.

The RAE tested the Spitfire and Mustang. The Spitfire was best, but the Mustang came in clearly better than the P-47 data the US had provided.

The only odd result is the NACA P-51B, which shows it to be worse (much, much worse) than the P-47 data which also came from the US.

If this is a fault in RAE measuring, it doesn't explain why they still found the Spit better than the Mustang, or why the NACA results showed the P-51B to be much worse than the P-47 results also provided by the US (I am assuming the P-47 comes from NACA, but it does say it comes from the US)

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>and (if my observations are the least bit correct concerning the questionable Mustang and Thunderbolt drag lines) consequently brings into -at least some- question the accuracy of the Spitfire numbers.
<HR></BLOCKQUOTE>

It certainly brings in to question the P-51B numbers.

Firstly, the two US tests, of the P-47 and P-51B, show the P-51B to be much worse than the P-47.

Secondly, the P-51B data doesn't fit with other tests. The US test of the P-47 shows a maximum of mach 0.86. Look at the drag factor the P-51B would be at to match the US P-47 data. I'm running at 1280x1024, and it still looks to me like it's going to run off the top of my monitor.

Thirdly, I've got the following quote from AHT on my drive. I can't swear to the accuracy, but I think it's correct:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
"In July 1944 Wright Field test pilots explored the high speed dive characteristics of a Merlin powered Mustang. A series of dive tests were made starting from about 35,000 ft. in a test airplane equipped with a mach meter. The idea was to explore the effects of compressibility such as buffeting, vibration, control force changes, and so on. Initial dives showed the onset of the problem to occur at just under mach .75. Additional dives were made, usiung three test pilots, which carried the aircraft sucessively to mach .77, then .79, and up to mach .81, and finally to mach .83 (605 mph) As the dive mach number was increased the compressibility effects became more violent, but the aircraft wsa still controllable, and it was possible to fly it out of the problem when desired, at mach .83 the shaking and buffeting of the aircraft was so strong that it was decided to explore no further. The airplane had suffered considerable structural damage and was written off." <HR></BLOCKQUOTE>

Wright Field claim to have got 0.83 from the Mustang. According to the red line from NACA, that would be a drag coefficient of 0.09, way higher than even the Thunderbolt.

The only test that doesn't fit with the others is the NACA P-51B, and note that it didn't have a prop fitted, and was only dived to a max of 0.755 on one occasion, all the other tests were slower. Anything over 7.55 on that graph is extrapolation.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>But I have never heard of any actual Bf 109 wing failure, the only source for these are usually gossip in British sources, nothing actual.. <HR></BLOCKQUOTE>

I have.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
Technical Instructions of the Generalluftzeugmeister:

Reference Bf 109 - wing breakages. Owing to continually recurring accidents caused by wing breakages in Bf 109 aircraft attention is drawn to the following:

The maximum permissible indicated air speeds in the different heights are not being observed and are being widely exceeded. On the basis of evidence which is now available the speed limitations ordered by the teleprint message GL/6 No. 2428/41 of 10.6.41 are cancelled and replaced by the following data:

<pre class="ip-ubbcode-code-pre">
Altitude Speed Previous limit
Up to 3KM 750 km/h (466mph) 466 mph
At 5 km 700 km/h (435mph) 425 mph
At 7 km 575 km/h (357mph) 382 mph
At 9 km 450 km/h (280mph) 341 mph
At 11 km 400 km/h (248mph) 304 mph
</pre>

These limitations are valid for the time being for all building series including the Bf 109 G.

Yawing in a dive leads to high one-sided wing stresses which, under certain circumstances, the wing tip cannot support. When a yawing condition is detected the dive is to be broken off without exercising force. In a flying condition of yawing and turning at the same time correction must be made with the rudder and not with the ailerons.

snip a few regarding undercarriage unlocking in flight.

The ailerons are not to be painted with the yellow recognition paint as this changes their characteristics unfavourably.<HR></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>whereas dozens of others dives even with the same plane never reached such speed again,<HR></BLOCKQUOTE>

Source?

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The method they used to get the airspeed was a simple pitot, which is by no standards is an accurate mean of measuring high mach numbers.<HR></BLOCKQUOTE>

No, they actually removed the pitot, and replaced it with a new pitot on the wing tip, calibrated up to mach 0.9 by the NPL. They used a 14" trailing pitot comb, linked altimeters, and cameras to record the instruments every second.

hop2002
03-22-2004, 03:05 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Interesting that a large part of my original observation was ignored.

1. I did state that the initial advantage of the 109F-4 was in accordance to expectation.
2. That although I did not check IAS, I did flatten out the dive gently.
3. I lost my wing flying all but horizontal, while the 109 was also level.
4. The latter had to pull up harder in order to level out at more or less the same time, since he was diving more steeply.
<HR></BLOCKQUOTE>

I think the problem is many don't seem willing or able to seperate dive acceleration from dive speed, or dive limits.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Planes breaking apart in FB has nothing to do with the planes structural strength. It's just the way this sim models how planes otherwise would lawndart at insanely high speeds due to elevators losing their authority.
<HR></BLOCKQUOTE>

If this is the case then the Spitfire should still have a clear advantage.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Planes didn't lose their wings during 0 G vertical dives in RL.<HR></BLOCKQUOTE>

Not quite 0g, because a 0g dive is hard to maintain. When speed builds up enough, mach tuck makes the plane nose down more, and an outside loop can begin. Your chances of surving at that point are not that good.

Look at the figures for the Spitfire. It had over 4700 lbs of drag on it, and was travelling at over 600 mph. WW2 fighters couldn't withstand much more than that. Many pilots were killed researching high speed flight, more when their planes simply failed at high speed in combat.

The US developed dive recovery flaps for two of it's fighters that suffered most, the P-47 and P-38.

SkyChimp
03-22-2004, 08:49 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
I wouldn't call any Spiteful production, and I believe the only performance figures are estimates. Spitfire the History gives an estimate of 481 mph at 18lbs boost, which would be something around 2000 hp or less, I believe the P-51H had 2200 hp+

I really think this is getting off track, though, the Spiteful has very little to tell us about etiher the Spitfire or Mustang.
<HR></BLOCKQUOTE>

Well, I wouldn't call it "production" either, hence the quotations and my comment that only a handful were produced.

And while it may be off track, the comparison proves the benefits of the clean airframe. It's a valid comparison even if the H and Spiteful weighed the same and had the same horsepower. The H had thicker wings, yet it was faster.

I'll leave this one alone, now.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
They certainly used a different wing profile, changing from Naca 45-100 to Naca 66 - 15.5

The P-51 B and H, ignoring the wing filet, had 16.2% at the root. The H had 15.5% at the root. David Lednicer, in "A CFD Evaluation of Three Prominent World War II
Fighter Aircraft," Aeronautical Journal of the Royal Aeronautical Society, June/July 1995 (it's mentioned by the author in the thread from Yarchve you linked to above) says the same, 15.5% root for the 51H.
<HR></BLOCKQUOTE>

Hop, of course there is some difference. But the differences were minimal. And change, no matter how minute, qualifies as a "different" profile.

The wings can't be exactly the same after the deletion of the wing filet. But they are close enough that the difference in root thickness is almost inconsequential.

The D model had an airfoil thickness ratio of 0.165 at center line to .115 at tip. The H had was .155 at centerline to .115 at tip.

The D model had a sweep back at leading edge of 3 degrees 35' 32", the H was 3 degrees 39' 33".

The D had a mean aerodynamic chord of 70.6 inches, the H 80.17.

So yes, there was a little bit of a difference since the wing on the H was ever so slightly broader than the D.

The point I made about the H was that it had thicker wings than the Spiteful, yet was faster.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
That's the whole point. 608 TAS is achievable at lower altitudes, so if it wasn't for the sound barrier, it would be achievable at higher altitudes as well.

But the massive drag rise is caused not by a rise in tas, or even IAS, but by a rise in mach number. It's the mach number that's the limiting factor.

Drag caused by approaching and exceeding critical mach is different.

If 609 TAS could be achieved at 35,000 ft, the P-47 would be supersonic.

The limit to speed at high altitude isn't IAS, it's mach.
<HR></BLOCKQUOTE>

Of course it was achievable at lower altitudes - that's where it was tested and proven. That doesn't answer the question as to whether it was achievable at higher altitudes. You assume that it wasn't. But it was never tested from 40,000 feet like the Spitfire was, at a shallower angle like the Sptifire was, and without the urgency of having to pull out lest the pilot float back up to the heavens on his own wings, like the Sptifire was. The tests are dissimilar.

And I'm quite aware that Mach is the limiting factor. And I'm not sure where I said it might be possible for the Thunderbolt to reach 608 mph TAS at 35,000 feet - I reread my post and could not find it. I did say possibly 28,000 feet though, and that, according to the chart you posted, is around mach .89.

You make the assumption that the drag rise for the Thunderbolt was enough to keep it from reaching similar speead as the Spitfire if dived from the same heights and in the same manner. I say there is no way to say that with certainty since the Thunderbolt was no tested in a similar manner.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
No, the TAS, or IAS achieved has nothing to do with the maximum mach achieved. The TAS is roughly the same for the 3, but the higher you can sustain the same TAS, the higher your mach limit.
<HR></BLOCKQUOTE>

You miss my point. I'm not talking about mach in that statement. Mach and TAS are incidental to each other depending on altitude.

What I am trying to say is that you assume there was no way for the Thunderbolt to reach 608 mph TAS at 28,000 feet (which, incidentally, is Mach .89).



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
quote:
--------------------------------------------------------------------------------
Are you relying on the suggestions that drag would have been too great to achieve mach .891 because at that speed Cd would have been around .08, and that level flight could not be maintained above a Cd of .07 due to elevator forces?

--------------------------------------------------------------------------------

Yes.
<HR></BLOCKQUOTE>

It seems to me that elevator control would be much more critical in a near vertical dive (like the Thunderbolt's) than it is in a more shallow dive (like the Sptifire's) due to the fact that pull out would have to done harder, sooner.

What's clear about the Spitfire test is that from mach .84 to mach .891 the elevator angle was lessening - from 4.4 degrees to .8. Before mach .84 is reached, the Sptifire is diving at a relatively constant 33.5 degrees or so. But in the transition from mach .84 to mach .891, the dive angle goes from 33 degrees to 46 degrees. The plane is starting to take a nose dive from mach .84 to mach .891. At mach .84, either the pilot is letting up on the elevators and letting the plane do what it would, or he is beginning to lose control. Further the pilot decelerates to mach .864, but does not start to get his elevators back until he decelerates to mach .841 - the mach at which he began to lose them. To me it's either a gimmick to get a higher speed, or the pilot is starting to lose control beginning at mach .84. I think it's the latter.

The Thunderbolt performed a much more level dive all the way to its highest mach of .861. At mach .847 the plane was diving at a 65.4 degrees. At mach .861, it highest mach, it was still diving at a 65.4 degrees. As the pilot slowed to mach .857 the plane was still at an angle of 66.1. During this time, presumably, the pilot was experiencing high elevator forces. Yet he was obviously able to maintain control as evidenced by the constant dive angle.

This tells me that the Thunderbolt was still controlable at mach .861. But the pilot of the Spitefire was beginning to lose control at mach .84.

If that's not the case, and the Sptifire pilot deliberately "let go" of the stick which allowed the plane to take control of itself and increase it's speed, then why would that gimmick not also work for the Thuunderbolt?



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
It looks like the P-47 is actually out of control before the flaps are deployed.
<HR></BLOCKQUOTE>

Doesn't look like that to me at all - quite the opposite.

As stated, the Thunderbolt maintained a level dive up to mach .861, remaining level as speed came back down. (And when I say "level" I mean a constant dive angle). The Spitfire could not keep its dive angle constant past mach .84. At that speed, it's begining to take a nose dive. And the pilot does not begin to recover from that ever-increasing nose dive until speed is brought back down to mach .84.

Again, the Thunderbolt appears to be controllable at a higher mach than the Spitfire. At mach .861 the Thunderbolt may have been hard to pull out, but its also not pitching down like the Sptifire is. At mach .861 the Thunderbolt could maintain a constant dive angle, the Spitfire couldn't.



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
That leaves 2 questions. Would the P-47 have survived without the flaps, and would the pilot have pushed it that much without the flaps? Once tuck under begins, you have to hope that the effect of denser air on mach speed increases faster than your speed due to the ever increasing angle of dive.
<HR></BLOCKQUOTE>

Why wouldn't it? The chart clearly shows that Mach was beginning to drop before flaps were deployed.

And I'm not sure if you think the "flaps" in that chart refer to dive-laps or conventional flaps. Since that test most likely refers to the NACA test of the P-47C-1,then it' conventional flaps, not dive flap as the C-1 didn't have dive flaps.



It's getting late. More tomorrow.

Despite Isegrim's appearence, we'll try to keep our debate civilized. Thanks.

Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

WWMaxGunz
03-23-2004, 01:36 AM
Kurfurst is Isegrim? Well whoever, he's been pretty good about posting reasonably. Why bait the guy? What did he say so wrong in this thread?


Neal

Kurfurst__
03-23-2004, 05:30 AM
I think we should concentrate on the subject rather than reading through the offtopic discussion of Chimp and Hop about interesting, but irrelevant question, often peppered with Chimp`s insulting, derogratory comments.

Rather we should return to the original subject.

This post was made by another poster in another forum years ago. There Hop 2002 argued about it some 16 pages long, if I recall correctly.

"This is just a partial list of structural failures and dive-related accidents involving RAF Spitfires. The following is from SPITFIRE: THE HISTORY, Eric Morgan & Edward Shacklady. Most of the data on the chart is quoted from the aircraft construction lists, although some information is found in the text sections of the book and this is noted by page number.

---------------------------------------
Mar 39...Mk I....K9838...Structural failure in dive.
Jan 41...Mk I....N3191...Both wings broke off in dive.
Jul 41...Mk I....X4354...Port wing broke off in dive.
Aug 41...Mk I....X4381...Starboard wing broke off in dive.
Mar 41...Mk I....X4421...Both wings broke off in dive pullout.
Jul 41...Mk I....X4662...Stbd wing broke off in dive pullout.
Jun 41...Mk I....X4680...Wings/tail broke off in dive pullout.
Nov 42...Mk I....X4621...Failed to recover from dive.
Apr 43...Mk II...P7352...Broke up in dive.
Sep 41...Mk II...P7522...Both wings broke off in dive.
Jun 43...Mk V....BL531...Both wings broke off in dive.
Feb 42...Mk V....AA876...Disintegrated in dive.
Jul 43...Mk V....BL389...Pilot thrown from aircraft in dive.
Jan 43...Mk IX...BS251...Structural failure in dive.
May 43...Mk IX...BS385...Structural failure in dive.
Aug 43...Mk IX...BS441...Disintegrated in dive.
Oct 46...Mk IX...PL387...Disintegrated in dive.
Jan 48...Mk XVI..SL724...Crashed after recovery from dive.
Sep 48...Mk XVI..TD119...Crashed after recovery from dive.
--------------------------------------
Aug 42...Mk I....N3284...Broke up in flight.
Aug 41...Mk I....N3286...Broke up in flight.
Sep 40...Mk I....P9546...Structural failure in flight.
May 42...Mk I....P9309...Lost wing in flight.
Apr 43...Mk I....X4234...Lost wing in spin.
Sep 42...Mk I....P9322...Broke up in flight.
Aug 43...Mk I....R6706...Aileron failure which led to crash.
Jan 43...Mk I....X4854...Starboard wing broke off in flight.
Nov 40...Mk II...P7593...Stbd wing and tail broke off in flight.
Dec 41...Mk II...P8183...Port wing broke off in flight.
Jun 42...Mk II...P8644...Starboard wing broke off in flight.
May 41...Mk II...N8245...Structural failure in flight.
Feb 44...Mk II...P7911...Flap failure which led to crash.
Sep 42...Mk V....AD555...Flap failure which led to crash.
Mar 44...Mk V....BL303...Flap failure which led to crash.
Dec 41...Mk V....BL407...Structural failure suspected.
Jun 42...Mk V....AB172...Structural failure in flight.
Mar 43...Mk V....AA970...Structural failure in flight.
Jun 43...Mk V....BL290...Port wing broke off in flight.
May 43...Mk V....BR627...Port wing failed in spin.
Oct 41...Mk IV...AA801...Structural failure in flight.
Feb 43...Mk IX...BS404...Structural failure in spin.
Feb 45...Mk IX...MH349...Wing failed during aerobatics.(pg.318)
Sep 46...Mk IX...MJ843...Port wing, tailplane broke off in loop.
---------------------------------------
Apr 43...Mk V....EP335...Wings, fuselage, tail, damaged in dive.(pg.63)
Jul 42...Mk VI...AB200...Wings buckled in dive at 450mph IAS.
Apr 44...Mk IX...MA308...Wings severely buckled around cannons.(pg.63)
Feb 44...Mk XI...EN409...Many wing rivets failed in dive.(pg.389)
Apr 44...Mk XI...EN409...Prop/gear broke off at 427mph IAS.(pg.389,399)
Nov 44...Mk IX...MH692...Tail section damaged in dive.(pg.318)

In addition, the construction lists identified a few Spitfires that broke up in bad weather, but I did not include those.

WING and TAILPLANE FAILURES
In July 1941, Spitfire Mk I - X4268 was used to investigate wing failures by taking measurements of internal pressure on the wings. In June 1942, Spitfire Mk II - P7251 was used to investigate tailplane failures, by taking measurements of tailplane deflection in high speed dives. Eventually it was judged that the port and starboard tailplane tips were at slightly different angles in a dive and this caused an excessive degree of twist in the airframe. That could be overcome to some extent by applying full left rudder, although using full right rudder made the problem much worse. The summary says that the terminal velocity of the Spitfire was about 560mph TAS.

In July 1942, there was a meeting at the MAP to discuss the chronic aileron problems with the Spitfire. After six years of flight testing this aircraft, surprisingly little progress had been made at improving the aileron response at high speeds.That includes the results of replacing fabric ailerons with metal ones, and associated attempts to add inertia weights to the elevator system. Pilots involved in the aileron testing noted that as speed increased, the rate of aileron upfloat increased suddenly and disproportionately. Squadron Leader Raynhan of the Accidents Branch asserted that the most significant fact emerging from recent Spitfire accidents was that no change in the type of failure had been brought about by the introduction of the inertia device or by readjusting the center of gravity, which he believed pointed to aileron instability. Also, there had been evidence of ailerons flying right up at a very early stage of the accident in certain instances, and failures of the aileron circuit which could not be explained by the wings breaking off the aircraft in flight.

When the tail unit failed on a Spitfire, it often sheared off at fuselage frame No. 19. In 1942, an official at RAE Farnborough noted that out of 36 Spitfire accidents, the tail unit had broken off in flight during 24 of these mishaps.By 1944, the Spitfire was often used in the fighter-bomber role and it was reported that the engine mounting U frames had frequently buckled in dive pullouts. About 35 Spitfires from Biggin Hill Wing were found to have this fault.

After the Spitfire Mk V had been in service for some time, alarm had been raised over several accidents where the aircraft simply dived straight into the ground for no apparent reason. The Accidents Branch investigated this matter and later determined that firing the 20mm cannons could damage the oxygen regulating apparatus, so that thereafter the rate of supply could not be varied and could lead to the pilot losing consciousness."


Make up your own mind which aircraft should break up first in a dive...


But also take some time to think about the following example as a demonstration.

There are two different aircraft.
For simplicity, we take that both structures are exactly the same strenght.

"A" aircraft has very large wing surface compared to "B" aircraft by 40%.
Both are single spar designs, which means the distribution of force is not as even as on two spar designs. The result is wing flex under load in the areas that fell far away from the spar design. This problem is aggrevated with the increase of wing area, and subsequently the distance between the load carrying spar and rear wing areas.

"A" aircraft mounts it`s spar near the leading edge, with a torsion box design in the leading edge. "A" aircraft`s wing is thin, the spar is not located in the thickest section. The spar is atteched to the U fram of the engine by bolts in one axis. As "A" aircraft groups it`s weapons in the wings, it was neccesary to cut holes for the cannons, and machinguns, plus their accessories through the entire lenght of the main spar. "A" aircraft is know to suffer from wing twist from reports to a very great extent, reducing it`s roll rate by 65% at 400mph. "A" aircraft`s undercarriage is connected to the wing, they transmit the stress during landings and takeoff to the wings and main spar directly, causing wear over time.
"A" aircraft is capable of carrying a total of 500 lbs under it`s wings, however, there are restriction with it, air combat, violent manouvers must be avoided, dives steeper than 60 degree should not be used. During pullups many accidents happened with this addition weight present during pullups, resulting in lost wings. 1000 lbs can be carried, with restrictions that half of this weight must be jettisoned before landing, and takeoff/landing should only be made from smooth, well prepeared runways.

"B" aircraft mounts it`s spar in the middle wing section, where the wing is the thickest (and already thicker in profile than as "A" aircraft), the single main spar is also supported made up by a box spar design in the whole wing, made up by the ribs and the cover plates of the wing. Since on "B" aircraft does not mount any weapons in the wings, the whole spar can be made from a single solid, "I-profile" forged steel piece of rather massive appearace, without a series of holes compromising structral strenght. The spar is connected to the fusalge by two bolts at the centre closing 90 degree angle with each other, plus a third that fastens the leading edge with the fusalage. "B" aircraft proved to be a surprise for foreign engineers, as it`s ability to resitst wing twist was good, comparable to larger two spar designs. "B" aircraft`s undercarriage has no connection with the wing, it is attached to the fusalage on the engine bearer frame, and does not transmit stress to the wings. "B" aircraft carried 1100 lbs load during the war on a regular basis, without restriction of airfield type or need to jettison weights before landing. "B" aircraft participated in air combat, applying heavy G loads, violent evasive manouvers and vertical dives followed by pullups with 500 lbs external weight attached to the wings.

Then these two types follow each other in a dive. The two race next to each other, at the same airspeed, and attempt a pullout at the same time. The applied air pressure is equal, as the airspeed is also equal. "A" will face 40% more force applied to it`s wings during the high Angle of Attack applied during the pullout, because of have larger area. Also because of the larger area, wing twist will be more pronounced on "A" aircraft. Moreover, "A" aircraft has light elevator, which allows to pilot to pull out quicker, which means the force is applied more abrubtly on "A" aircraft, and could be many times under higher G loads. "B" aircraft`s pilot, because of the high stickforces, under any circumstances, can only apply elevator gradually.

Which aeroplane is more likely to suffer catastropich wing failure first ?

dahdah
03-23-2004, 08:48 AM
Yet, MA308 did an outside loop and survived. 35 other Spitfires from BH that did high G manuevers survived. http://ubbxforums.ubi.com/infopop/emoticons/icon_eek.gif

EN560 was stressed to +10Gs when its structured failed.

Another was lost when the pilot lost his oxygen(passed out). http://ubbxforums.ubi.com/infopop/emoticons/icon_rolleyes.gif

MH349, a 2 year old a/c and MJ843, a 3 year old a/c, that had seen combat. What damaged had it received and had been repaired or what abuse had it been put to before?

"Feb 44...Mk XI...EN409...Many wing rivets failed in dive.(pg.389)
Apr 44...Mk XI...EN409...Prop/gear broke off at 427mph IAS.(pg.389,399)"

Yes a test a/c that was abussed from the pre production run of Spitfire IXs. Yet the pilot landed the a/c from the high Mach dive. This was part of the testing that had the Spitfire reaching M .89.

I like the way you only give part of the history Kurfurst to support your agenda.

We all know that only 2 cannons were fitted because the Spitfire IXs u/c and tires could not support the added weight. http://ubbxforums.ubi.com/infopop/emoticons/icon_rolleyes.gif

Kurfurst__
03-23-2004, 08:53 AM
Found that in my archieves. It`s exactly the situation Rhorta was talking about :

"This is from the book "We defended you, Sofia" by Stoyan Stoyanov(N1 Ace of Bulgarian Air Force). After he managed to fend off a few P-38s attacking a fellow, he was in a difficult situation himself.

"I pushed the stick and immediatelly felt the consequences of the Centripetal forces. My stomach pushed hard at my lungs. I lost sight for a moment but my brain was working and I continued pushing as if for an inverted looping while at the same time rolling so I could level out in a normal position. In that manner I dove for more than 6000 meters and low above the terrain I "broke" the plane in level flight. My speed was more than 700kmh and without decreasing it I kept on level. I turned around a few times but there was nobody on my tail."

Ruy Horta
03-23-2004, 08:53 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Which aeroplane is more likely to suffer catastropich wing failure first ?<HR></BLOCKQUOTE>

Isegrim,

Data is only compatible if all things are equal. In this case we have the (almost) the FULL history of Spitfire failures, while we cannot represent the same case for the 109 for the simple fact that 90-95% of Luftwaffe files were destroyed.

So you are actually substituting a full record with a "record" that's only covered by at best 10%.

I am a "Luftwaffe enthusiast" but in this case you are presenting a skewed picture as being all inclusive and finally conclusive, which it is absolutely not.

Of course I agree that the 109 held some tactical advantage in a dive versus the Spitfire, some since much of this is based on the negative G-issue and initial acceleration.

Yak's were reported to have structural problems as well, which even Yakovlev mentions in his biography.

How many a/c are these compaired to the full production run?

But lets assume that the Spit should break-up faster. Does that mean that the current modeling of when this happens in AEP, for both types is correct?

Maybe the Spit breaks up too soon and the 109F too late, maybe the comperative difference should simply be smaller?

What is the Vne for the Bf109F-4 and MkVb respectively?

That's a number to start with...

Ruy Horta

Ruy Horta
03-23-2004, 09:00 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
"I pushed the stick and immediatelly felt the consequences of the Centripetal forces. My stomach pushed hard at my lungs. I lost sight for a moment but my brain was working and I continued pushing as if for an inverted looping while at the same time rolling so I could level out in a normal position. In that manner I dove for more than 6000 meters and low above the terrain I "broke" the plane in level flight. My speed was more than 700kmh and without decreasing it I kept on level. I turned around a few times but there was nobody on my tail."<HR></BLOCKQUOTE>

I am confused about what exactly you are trying to demonstrate with this quote.

The ability of a 109G (?) to clear itself by diving out of harm's way, or the fact that he "broke" his a/c flying level (after pulling out) at 700 kph?

Ruy Horta

Kurfurst__
03-23-2004, 09:09 AM
Rhorta, "to broke" here refers to the pullout.

The memoir proves the thing the guy did in his 109 was indeed possible in real life.

blabla0001
03-23-2004, 09:49 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Kurfurst__:
Rhorta, "to broke" here refers to the pullout.

The memoir proves the thing the guy did in his 109 was indeed possible in real life.<HR></BLOCKQUOTE>

But 700km/h is not 984km/h you can reach with a F4 now.

Well ok, it starts to loose control surfaces at that speed so let's say 965km/h.

A bit overdone if you ask me.

JG14_Josf
03-23-2004, 09:57 AM
virtualpilots/109myths/dives (http://www.virtualpilots.fi/hist/109myths/#dives)

Kurfurst__
03-23-2004, 10:37 AM
"But 700km/h is not 984km/h you can reach with a F4 now. Well ok, it starts to loose control surfaces at that speed so let's say 965km/h."

http://members.cox.net/us.fighters/bf109g2.jpg

The 984 kph figure in Skychimps picture shows a G-2`s "break-up" velocity in TAS, not an F-4. I did testing of this a long time ago, the F series break up definiately earlier than the G series aircraft. And this is how it should be, Gs were tougher, their wing structure was beefed up considerably compared to the F.

984 is also a TAS figure, and TAS having little relavance, I would bet that at higher altitudes even higher TAS speeds could be reached. IAS and Mach number are the important one. Also I think Il-2 calculates TAS in bit faulty way, probably not taking into account either compressibility or Mach effect...

The trouble is, the Vne numbers neither give much clue, as these were specified by different methods by the different manufacturers and nations, and would not directly tell WHEN exactly the plane would break up. If say two different planes from different companies/countries have the very same Vne number, still it could be one of them was cautious, and the plane would fell apart only if the VNE is exceeded by 200 km/h, the other provided only a small margin of error and 50 km/h exceeding of the limit would yield fatal consequences. But as I said, in a general and relative manner, I think the current modelling is about OK and similiar to the real life experiences.

Ruy Horta
03-23-2004, 11:15 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Cappadocian_317:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Kurfurst__:
Rhorta, "to broke" here refers to the pullout.

The memoir proves the thing the guy did in his 109 was indeed possible in real life.<HR></BLOCKQUOTE>

But 700km/h is not 984km/h you can reach with a F4 now.

Well ok, it starts to loose control surfaces at that speed so let's say 965km/h.

A bit overdone if you ask me.<HR></BLOCKQUOTE>

If the 109F-4 were only diving at c. 700kph I would even be more surprised if my MkV broke up while flying a less steep dive.

according to the Mk IX manual the flight limitations are:

Diving without ext. stores, corresponding to Mach. No. of .85:

mph (kph) IAS

Between

SL and 20.000ft - 450 (724.05)
20 and 25.000ft - 430 (691.87)
25 and 30.000ft - 390 (627.51)
30 and 35.000ft - 340 (547.06)

with single 500lbs bomb this would be reduced between SL and 20.000 by 10 to 40 mph IAS, depending on the type of bomb. or a minimum of 420 (643 kph).

Someone might have better dive figures, but at least these are MkIX figures from a manual, that means fairly conservative. Unfortunately the MkV manual does not include such a table.

Now how do these table figures compare?

Not to max test values, but conservative (manual) recommendation for the pilots.

If the Bf 109G pilot's manual specifically mentions a max diving speed of 750kph (unfortunately without the extra alt. detail, but the same as the max number for the F-model) we must accept that the max. dive values are fairly close:

724 vs 750kph IAS respectively for the Mk IX and Bf 109G-2.

(we should assume that these figures have a failsafe of at least 10% if not more)

A difference of only 26 kph would not indicate such a great difference in strength as to dictate a tactical restriction on the Spitfire. This coincides with the accepted view of the two a/c being closely matched, and that the 109s dive advantage was mainly one of initial acceleration (and earlier the neg-G cut out).

The presentation of a couple of dozen catastrophic structural failures is meaningless without an equal representation of figures of the 109. I might even go as far that without any other comperative figures (other fighters of the era) you cannot even tell if this Spit data is significantly high or low.

If we conclude that the current STRUCTURAL strength of the 109F is according to specs, its very probable that the Spifire is currently too weak. Again - STRUCTURAL strength being at issue, not diving speed or acceleration.

Ruy Horta

[This message was edited by rhorta on Tue March 23 2004 at 10:23 AM.]

SkyChimp
03-23-2004, 04:48 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
I think we should concentrate on the subject rather than reading through the offtopic discussion of Chimp and Hop about interesting, but irrelevant question, often peppered with Chimp`s insulting, derogratory comments.
<HR></BLOCKQUOTE>

You're right. It was uncalled for. And I apologize for it.

Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

SkyChimp
03-23-2004, 05:46 PM
I don't agree with Isegrim much. But I'm tending to think he's possibly onto something now that I've had the opportunity to really look at the chart Hop posted.

What seems apparent to me is that these so-called Terminal Dive Speed Tests, be they American, British or German, aren't really trying to determine the absolute maximum a plane can fly. In order to determine a true Terminal Dive Speed, the plane MUST be flown to destruction. I don't see any way around it. Until it is, it seems to me that that there is some area between the highest speed obtained and the highest speed obtainable. Hop has said in the past, and I agree, that, give enough altitude,a plane will eventually dive to destruction. I haven't seen a test yet where that has happened - though I'm sure it's happened. So, it seems a true Terminal Dive Speed has not been recorded in one of these tests we've seen.

What I think we are looking at are tests that take the planes to the highest controllable speed, and maybe a bit further with the Thunderbolt and Spitfire.

Isegrim wrote something interesting. I hadn't paid too much attention to it in the past:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
WING and TAILPLANE FAILURES
In July 1941, Spitfire Mk I - X4268 was used to investigate wing failures by taking measurements of internal pressure on the wings. In June 1942, Spitfire Mk II - P7251 was used to investigate tailplane failures, by taking measurements of tailplane deflection in high speed dives. Eventually it was judged that the port and starboard tailplane tips were at slightly different angles in a dive and this caused an excessive degree of twist in the airframe. That could be overcome to some extent by applying full left rudder, although using full right rudder made the problem much worse. The summary says that the terminal velocity of the Spitfire was about 560mph TAS.
<HR></BLOCKQUOTE>

560 mph TAS? OK.

It's interesting, perhaps coincidentally, that the chart posted by Hop indicates that, in this instance, 560 mph TAS was the speed at which the pilot lost authority over the elevators (if that's what's happening). 559 mph TAS, 560 mph TAS. Not much difference. Take a look.

http://members.cox.net/us.fighters/spitfigs.jpg

At 560 mph (incidentally mach .84), the elevators were still at 4.4 degrees (roughly where they had been since the dive began). Once 560 mph TAS is exceeded, the elevator angle is lessening, and the dive angle is increasing. The pilot can't hold the elevators, or at least that's the way it appears.

At 609 mph TAS (incidentally mach .891), there was only a .3 degree elevator angle. The pilot does not appear to be able to get 4.4 degrees of elevator back again unitl speed fell below 574 mph TAS (incidentally Mach .82).

Now, maybe I'm all wet with this elevator thing. If I'm wrong, maybe Hop can explain it to me.

====

One more thing that I'd like to comment on is the wing failure on the Spitfires. My personal opinion is that few failed simply as a result "going too fast." More than likely they failed as a result of high-G pullouts. Maybe this accounts for the reason that the Spitfire test Hop posted was conducted at a gentle 33 degrees and such a high altitude. For nearly 5,000 feet, the dive angle hardly changes. It appears elevator controllability is lost above mach .84 and the plane takes a much more radical pitch down, but the dive angle is still not so great that a low-G pullout can't be made. The plane is certainly at a high enough altitude. I mean, look at the chart. The Spitfire barely breaks 2 Gs in its pull out.

The Thunderbolt, on the other hand, was not known for losing its wings in higher-G pullouts like the Spitfire and Mustang were. In fact, I have never heard a story of this happening with the Thunderbolt (although it may have). It was dived at a much greater angle, and the pullout was made at substantially higher Gs (up to 4.8) than the Spitfire was. (Admittedly, the elevators were heavy during the portion of the dive where mach was greatest, but dive angle was maintained.)

I think the Spitfire was tested this way because it was the safest way to do it.

Just my 2 cents, and admittedly I may be wrong.

One last thing. The capabilities of a plane to fly well past it's critical mach with all the danger inherent in doing so seems completely academic. It is not a practical combat capability, and was probably deadly to the average combat pilot. Makes for interesting conversation and I'm learning something here. Thanks, Hop.

Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

[This message was edited by SkyChimp on Tue March 23 2004 at 08:26 PM.]

faustnik
03-23-2004, 05:54 PM
Wow! That test against the Hawk is a surprise! Maybe the Spit elevators were not as good as I thought. http://ubbxforums.ubi.com/images/smiley/16x16_smiley-surprised.gif

That would make the 109 elevator really bad at high speed. http://ubbxforums.ubi.com/images/smiley/16x16_smiley-indifferent.gif

http://pages.sbcglobal.net/mdegnan/_images/FaustSig
www.7Jg77.com (http://www.7jg77.com)
CWoS FB forum. More Cheese, Less Whine. (http://www.acompletewasteofspace.com/forum/viewforum.php?f=25)

HellToupee
03-23-2004, 05:59 PM
spitfire mk1 had fabric coverd control surfaces which balloned at high speed.

http://lamppost.mine.nu/ahclan/files/sigs/spitwhiners1.jpg

SkyChimp
03-23-2004, 06:04 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by HellToupee:
spitfire mk1 had fabric coverd control surfaces which balloned at high speed.

http://lamppost.mine.nu/ahclan/files/sigs/spitwhiners1.jpg <HR></BLOCKQUOTE>

Yes, you're correct. Disregard that portion of my post. I've deleted it. That had to do with ailerons, no elevators. My bad.


Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

[This message was edited by SkyChimp on Tue March 23 2004 at 07:19 PM.]

HellToupee
03-23-2004, 06:12 PM
"Spitfire pilots would escape from 109s by diving towards the ground and pulling up at the last moment knowing that the German would find it much harder to pull back on the stick to escape destruction. The Spitfire was capable of being pulled out of a dive with such high "g" forces that the pilot would black out (for only a second or so), meaning the aircraft itself was the limiting factor."

this being the mk1, tho it is the mkV that is being discussed.

http://lamppost.mine.nu/ahclan/files/sigs/spitwhiners1.jpg

SkyChimp
03-23-2004, 06:20 PM
Just about any fighter could pull Gs sufficient to black-out the pilot.

Regards,
SkyChimp
http://members.cox.net/us.fighters/skychimp.jpg

Ugly_Kid
03-23-2004, 10:57 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by SkyChimp:
It's interesting, perhaps coincidentally, that the chart posted by Hop indicates that, in this instance, 560 mph TAS was the speed at which the pilot lost authority over the elevators (if that's what's happening). 559 mph TAS, 560 mph TAS. Not much difference. Take a look.
<HR></BLOCKQUOTE>

That's of little help. TAS means very little here. In the incompressible subsonic flight the aerodynamic pressure/forces would differ largely at different altitudes. The EAS on the other hand would roughly give a sort of universal figure that works for all alts. What comes on top of this in high speed flight (compressible subsonic flow) are the corrections of the aerodynamic coefficients. Now giving such a limit in TAS is of not much use.

For example:
At SL, for example 560 mph TAS means roughly Ma=0.73. This means drag coefficient would be theoretically about 47% higher than in incompressible flow.

Now at 33000 ft the Ma=0.835 and drag coefficient would be theoretically 82% higher BUT air density drops to 66% of the SL value. Resulting raise in the drag force is only 22% compared with 47% from the SL.

As a side note steeper or shallower dive probably makes but a psychological difference. The issue is controllability and spit seems to loose this later than the others. This did not make spit a competitive diver, however. It had one of the worst accelerations through the dive, initially and in the end. It seems very much possible that it can reach higher Mach numbers than the others but with the limitation that this stunt has to be performed in such a high alt that the aerodynamic forces are smaller. Now the same Mach number might have been still flyable (controllability) for spit at lower alt but not necessarily sustainable (strength). This said it seems to be wrong (since we don't account for manufacturing imperfections) that spit blows up at dives earlier. I do not know if the code makes corrections to compressability (others than loss of controls on P-38 or so). With this I mean aerodynamic coefficients and the penalty at higher Mach numbers. This would mean, yes no breakup, but the dive acceleration would drop down even more at higher Mach area. As for the topic F-4 was able to outdive Spit and so it does in the sim, with or without blow ups. If the sim does not correct for Mach effects it would outdive it with even higher margin with them. This is perhaps just the games limitations and it's way of telling/compensating the fact that you can't catch Bf with Spit at dives, if you try exploiting this limit of the game engine you will explode. On the other side of the coin P-47 and P-51 do not get unflyable at high Mach dives, Jug does not break at all and P-51 also at some insane speed. This way they will outdive everything in the end. Not historical way but compensated in another way from the gameplay point of view.

Ruy Horta
03-24-2004, 02:55 AM
It took a while but I finally found some report material that I found usefull.

Dive trials in Oct. 1940 with some good Spitfire Mk I observations.

One notable entry:

(Unit)
54 Sqdn.

(ASI)
Highest speed recorded
520 mph in a dive from 35.000 to 10.000ft

(Lateral Control)
Aileron control becomes very heavy

(Fore & Aft Control)
Elevator control remains reasonably good

(Rudder Control)
Rudder control disappears at an earlt stage of the dive

(Remarks)
Aircraft drops a wing and invariably turns (usually left). Rudder bias control is usually required in the recover.

This is an extreme example, sincemost observational entries were around 450 mph ASI.

Point is that this document is completely focused on the loss of control, especially lateral at high speeds (in part because of the fabric covered ailerons). It also points to the elevator as being still effective (indeed we know it to be overeffective).

The loss of lateral control would certainly be a tactical disadvantage, combined with slow accelaration and at that time neg-G engine cut out (all good reasons for a 109 to bug out in a dive).

However the extreme case of 520mph IAS (836 kph) would indicate that our Spitfire MkV should be (AT LEAST?) able to reach this speed in a dive without break up (all things being bright an beautiful in IL2 world - no weak ducklings being present).

If according to the previous post "breaking up" is a substitute for proper modeling, than we should see many a/c breaking up in IL2/FB/AEP - right? However in AEP we see many a/c being able to do maneuvers that would rip their RL counterparts to pieces, yet we should accept this possible "balancing" handicap for the Spit?

Ironic how I am spending my time discussing the Spitfire...

EDIT:

Since I wrote this I decided to return to the game. My thoughts have since then changed somewhat.

Perhaps the problem is / was twofold.

1. Online is always a tricky observation, in terms of what you see can be influenced by the connection of both players.

2. In terms of critical speed the MkV and F-model are some 100kph IAS apart. The MkVs magic number appears to be 900-950 the F-model 1000-1050.

3. The figures of 900-950kph IAS for the Spit are higher than 836 kph, and the never exceed valued in the MkIX manual, period, and that's one basic fact.

4. The WAY critical damage happens may be the deciding factor. The Spitfire breaks up pretty fast, once you get an indication of damage, all things happen in quick succession. Aileron - wing...catastrophic

However the 109 appears to have more leeway, there the tendency is loss of controls. This I found also the case for the Yak light fighter (I toook this a/c as a control, since the Yak also had a history of structural "weakness" - interestingly the 1B could manage +900 the Yak-3 +1000).

So the Spit is as things appear to be, not significantly weaker in terms of critical dive speed, but has a slightly less forgiving "failure model". This combined with the "optical illusion" caused by netlag etc, can be deadly in following an enemy in a high speed dive, especially types with a higher critical diving speed (the 109 has a roughly 10% advantage here, about twice as much as the never exceed speeds would suggest).

Ruy Horta

[This message was edited by rhorta on Wed March 24 2004 at 02:58 AM.]