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chris455
01-28-2004, 10:58 PM
OK was watching a show tonight on HC about US planes of WWII. Said the Mustangs radiator design acted like a miniature jet engine, giving 30 mph boost to the Mustangs top speed.

Now, when I was a kid, my uncle used to tell me that in WWII the groundcrews would sometimes apply a special wax job to the P-51. Took a long time to do, and would give the Mustang a whopping 10 MPH boost in speed. This was considered well worth the effort.

So, a 30 mph boost must have been a God send.
Is this modelled in FB?
And before anyone asks NO I DON'T beleive everything I see on TV- so, if you have word that this is BS, fill us in http://ubbxforums.ubi.com/images/smiley/16x16_smiley-wink.gif
S!

http://members.cox.net/miataman1/P47.jpg

chris455
01-28-2004, 10:58 PM
OK was watching a show tonight on HC about US planes of WWII. Said the Mustangs radiator design acted like a miniature jet engine, giving 30 mph boost to the Mustangs top speed.

Now, when I was a kid, my uncle used to tell me that in WWII the groundcrews would sometimes apply a special wax job to the P-51. Took a long time to do, and would give the Mustang a whopping 10 MPH boost in speed. This was considered well worth the effort.

So, a 30 mph boost must have been a God send.
Is this modelled in FB?
And before anyone asks NO I DON'T beleive everything I see on TV- so, if you have word that this is BS, fill us in http://ubbxforums.ubi.com/images/smiley/16x16_smiley-wink.gif
S!

http://members.cox.net/miataman1/P47.jpg

biggs222
01-28-2004, 11:16 PM
there was a big topic about this very subject a while back by Skychimp i think, i think it was proven false or they decided that it was true but it didnt give it 30mph boost or somethign like that, but yeah waxing planes helps the speed a bit, less air friction, also leavign the plane bare metal made it lighter and faster but only by a little.

http://www.stenbergaa.com/stenberg/wong-friendlyord.jpg

HarryVoyager
01-29-2004, 12:32 AM
It is a genuine effect, but it primarily served to counter the drag the radiator generated. I do believe it was responcible for a significnat part ofthe aircraft's top speed at altitude, however.

Harry Voyager

PZ_D_352FG
01-29-2004, 01:19 AM
"Edgar Schmued (cheif design engineer on the P-51) and Edward Horkey calculated that an aerodynamic duct formed at the entry and exit of the radiator could provide up to 300 lbs of thrust by utilizing ram air to eject the warmed airflow and thus overcome the drag offered to the fuselage by the duct itself."

Mustang: Story of the P-51 fighter
Gruenhagen
Arco Publishing; 1969
ISBN:0-668-03912-4

FA_Whisky
01-29-2004, 01:37 AM
"the radiator could provide up to 300 lbs of thrust by utilizing ram air to eject the warmed airflow and thus overcome the drag offered to the fuselage by the duct itself."

There you have it and it only works when the plane is already flying at high speed. The radiator design did not give thrust(like a jet engine) but, it lowered drag considerably. And yet, this could make the plane 30mkh faster than when the radiator would be closed. btw, this is not modeled and that migh be one of the reasons that you cannot sustain(or reach, you need to dive alittle) top speed.

WUAF_Badsight
01-29-2004, 01:43 AM
yes the Radiator actually produced Thrust

the thrust produced negated the drag of the radiator & contributed to pushing the plane

DaBallz
01-29-2004, 03:47 AM
This feature is a key to the success of the P-51
as a race plane. Opening the radiator when the engine
reached operating temprature increased top speed
where on a Spit or a Bf-109 it was like a speed brake.
The design negated the coolant system drag normally
associated with piston engined fighters.

I don't think it's properly modeled in FB, but it's
as close as oleg will allow.

Keep in mind this is a Russian flight sim.
russian aircraft will continue to dominate.

Da

FA_Whisky
01-29-2004, 05:51 AM
"yes the Radiator actually produced Thrust

the thrust produced negated the drag of the radiator & contributed to pushing the plane"

So, if you heat up the engine and thus the coolant opening your radiator would make the plane drive along the runway withou the prop turning. Neet for taxiing...

tenmmike
01-29-2004, 05:54 AM
http://www.icon.co.za/~pauljnr/radsta.jpg

http://images.ar15.com/forums/smiles/anim_50cal.gif U.S INFANTRY 1984-1991

BerkshireHunt
01-29-2004, 06:23 AM
.[QUOTE]Originally posted by DaBallz:
This feature is a key to the success of the P-51
as a race plane. Opening the radiator when the engine
reached operating temprature increased top speed
where on a Spit or a Bf-109 it was like a speed brake.
The design negated the coolant system drag normally
associated with piston engined fighters.

The effect you are talking about was investigated in Britain in the 1930s and various radiator designs incorporating specially shaped ducts were patented by a Mr Meredith. The idea was to ensure that under some conditions of flight radiator drag was cancelled out by thrust, the hot radiator and its duct acting in a way similar to the combustion chamber of a gas turbine, pressurising, heating and accelerating a gas (though the pressure ratios in no way compare to those of a gas turbine).
Lee Atwood of North American claimed in the 1990s that the British did not use this innovation and left it to his company to exploit in the design of the P51's radiator duct (the so called 'Meredith Effect'). He told an amusing anecdote at a meeting attended by a friend of mine regarding this. Apparently, he met Willi Messerschmitt after the war who told him that the Germans couldn't figure out why the Mustang was so fast (in relation to its installed power) - they had stripped it down to the last nut and bolt but hadn't thought the shape of the radiator duct significant.
I can believe this coming from Messerschmitt as the 109's radiator ducts had a positive effect on drag under all conditions of flight (Oryx has more details)- they were semi- recessed but their internal duct shape was not set up to produce a Meredith effect.
But it is wrong to say that only the P51 benefitted from this research. Morgan and Shacklady's book on the Spitfire includes many development drawings concerning its radiator design and it is clear that Supermarine brought in Mr Meredith as a consultant to perfect the radiator duct design of the prototype Spitfire. I don't know if this was carried through to later Spitfires with two radiators but I would be surprised if this were not so.
I'm also curious as to whether Dornier was aware of this principle as Arthur Bentley's drawings of the internal ducting of the Do335's rear engine radiator duct shows that it was remarkably similar to the P51's even to the extent of having an underbelly scoop. The same could also be said of the LaGG 3.
You can't really judge by external appearances as it's the internal duct shape that is crucially important to this effect, but nevertheless, it's possible that it was more widely exploited by designers than is commonly realised by aviation buffs. It is known that Supermarine and Heinkel shared information as commercial companies before the war and von Ohain had read Whittle's patents regarding gas turbines in the 1930s. Once an idea was published by patent it was effectively available to any researcher who wanted it and it would have been foolish not to have kept abreast of aviation developments in other countries. So I think there's a better than even chance that other designers used the same principle- it's just become part of North American's mythology that only the P51 used it. Where is the proof of this claim?

LeadSpitter_
01-29-2004, 06:39 AM
Also yeager and anderson said you would takeoff with the 85 centertank drain it to 45 gal so it was equal balance, then switch to wing tanks, if not the 85 would make the plane real twitchy to fly.

http://www.geocities.com/leadspittersig/LSIG.txt
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Chadburn
01-29-2004, 07:04 AM
I posted this in another thread, but here it is again regarding Oleg's take on the P51 radiator design:

"posted 04-11-03 09:54
RE: The Mustang, its radiator and speed.

1. Finally we plan to have it Auto. In real life the temperature of the coolant determided by thermostat, Like on many other aircraft (Bf109F-G-K, Yak-3, Yak-9 late, etc).

2. The drag is present anyway for the closed radiator in P-51D. But in this position the construction of radiator cowling with laminar flow around it really has small drag that allow to get greater speed of the plane itself in comparison with usual radiator cowl placed in that aerodynamically 100% _optimal_ area (like say on Yak-3 or on Yak-9U, that has it in the same place, but hasn't laminar airflow in the place beween radiator airintake and fuselage. Germans also tried to place there after great experimantal works, but it was too late...You may see it on experimental FWs and Bfs). But when it begins to open - drag will increases anyway. So you are worng in your opinion. I know where you took that info But this isn't professional aerodynamical magazine, be sure. There was just private opinion. The only thing there is correct that the design of radiator cowling was really best comapring to other planes.


SkyChimp wrote:
- Just in case its modelled this way, the P-51's
- radiator air outlet shutter should be automatic. In
- real life, the temperature of the coolant determined
- how much the flap opened. Otherwise, there was a
- switch in the cockpit with "auto", "open", "closed"
- and "off." "Auto" was the usual setting.
-
- And when the P-51's radiator opens (the flap opens
- up), the Mustang should not loose speed. In fact,
- the Mustang's radiator design created thrust.
-
- If the Mustang is loosing speed with an open
- radiator, it should not.
-
- Regards,
-
- SkyChimp"

http://home.cogeco.ca/~jkinley/FB_JG27.jpg

tenmmike
01-29-2004, 07:34 AM
i remember a account of a p-51 pilot as he chased a me-262 ...this is how i remeber it to the best of my memory ......i saw a german jet pass by my below and to the right..i knew the german plane was fast so i went to full throtle and started to dive i closed the radiator i keep the radiator closed as i dived untill i could smell the ethylene glycol boiling ...i was closing but i dared not stay at the condition for long the water temp was above max..i was forced to open the radiator and at that time i was behind him but still a distance away ..i fired a long burst at the german but no effect was noticed ....i retured to base and reported the incident in my debrief..................take that for what its worth

http://images.ar15.com/forums/smiles/anim_50cal.gif U.S INFANTRY 1984-1991

Blutarski2004
01-29-2004, 08:40 AM
[QUOTE]Originally posted by tenmmike:
i remember a account of a p-51 pilot as he chased a me-262 ...this is how i remeber it to the best of my memory ......i saw a german jet pass by my below and to the right..i knew the german plane was fast so i went to full throtle and started to dive i closed the radiator i keep the radiator closed as i dived untill i could smell the ethylene glycol boiling ...i was closing but i dared not stay at the condition for long the water temp was above max..i was forced to open the radiator and at that time i was behind him but still a distance away ..i fired a long burst at the german but no effect was noticed ....i retured to base and reported the incident in my debrief..................take that for what its worth


..... This account is not necessarily inconsistent with the above discussion. It might be that the lowest possible drag configuration was still with radiator shut, but that the Meredith-effect radiator design drastically reduced the degree of additional drag when the radiator was open.

If I understand Oleg's remarks correctly, I must disagree. Laminar flow inlet design and Meredith-effect internal radiator design are different animals, each making their own unique contributions to the drag equation.

BLUTARSKI

chris455
01-29-2004, 09:54 AM
Thanks for the responses guys.
Seems to be two schools of thought here:

The "decreased drag school" which beleives that the radiator design allowed for efficient cooling while eliminating 90% of the drag associated with aconventional radiator and:

The "Increased thrust school" which beleives that the warm air expelled by the special radiator design actually added to the planes top speed.

I'm pretty sure I can see now what school the P-51 in FB was designed by http://ubbxforums.ubi.com/images/smiley/16x16_smiley-surprised.gif

Oh well, it still pretty much kicks arse in the game I think.
Thanks again for all the great info guys-
S!

http://members.cox.net/miataman1/P47.jpg

Blutarski2004
01-29-2004, 10:10 AM
[QUOTE]Originally posted by chris455:
Thanks for the responses guys.
Seems to be two schools of thought here:

The "decreased drag school" which beleives that the radiator design allowed for efficient cooling while eliminating 90% of the drag associated with aconventional radiator and:

The "Increased thrust school" which beleives that the warm air expelled by the special radiator design actually added to the planes top speed.

..... Both schools are correct, if allowances for certain imprecisions of language are made. There was indeed thrust exiting the radiator when open. This thrust counter-balanced most of the drag which was produced by the radiator. The design of the cooler intake also offered reduced overall drag compared to other colling inlet approaches.

BLUTARSKI

lbhskier37
01-29-2004, 10:36 AM
Looking at Tenmikes picture, I think that is the most plausible explanation. The effect should produce a little thrust, but the radiator still has to breakup the incoming airstream into a turbulent flow which causes a lot of drag. Full closed should be the fastest condition on the plane becuase it is the closest the plane gets to having a good laminar flow around it, but opening it causes a lot of turbulence in part of the airstream. I would definitly agree with Oleg that this design is much better than others, but opening the radiator isnt going to make the plane faster, if that were the case why would you ever close it?

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horseback
01-29-2004, 12:37 PM
I seem to recall a study the RAF did regarding features that increased aircraft speed. They found that closely fitted cowlings (undented) and fairings could add something like 10 mph each to an aircraft's top end.

They took a Spit Mk V (if I remember correctly) at random off a frontline squadron, put new (clean standard, not modified) cowl and wing root fairings on it, replaced the exhausts with the individual pipes pointing straight back, changed the plugs, repainted it, waxed it, cleaned off the tail wheel strut (part of the standard ritual before going on a combat mission involved the 'anointing' of the tailwheel before entering the cockpit), replaced the original two cannon fairing over the wing cannon breech with the narrower single cannon breech fairing, among other things.

They performed each step one at a time, carefully measuring top speed and the time required to reach it before and after each step.

Overall, the Spit's top speed increased by something like 40 mph over it's initial test, and something like 15-20 mph over the rated top speed. Waxing alone added 8-10 mph, and I believe the individual exhausts' jet effect increased top speed by another 8-10 mph as well.

My point is, that the extra thrust provided by the radiator would be hard to measure and prove without a lot of other extra work. Individual aircraft in varying states of very condition would get different results, and the extra thrust might put a nonstandard demand on the radiator coding required to model (how much additional thrust with radiator in postion 1?). I imagine Oleg just examined the problem and said to hell with it, let's just average it out and treat the open radiator the same as the others.

Cheers

horseback

"Here's your new Mustangs, boys. You can learn to fly'em on the way to the target. Cheers!" -LTCOL Don Blakeslee, 4th FG CO, February 27th, 1944

tagert
01-29-2004, 01:56 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by chris455:
Thanks for the responses guys.
Seems to be two schools of thought here:

The "decreased drag school" which beleives that the radiator design allowed for efficient cooling while eliminating 90% of the drag associated with aconventional radiator and:

The "Increased thrust school" which beleives that the warm air expelled by the special radiator design actually added to the planes top speed.

I'm pretty sure I can see now what school the P-51 in FB was designed by http://ubbxforums.ubi.com/images/smiley/16x16_smiley-surprised.gif

Oh well, it still pretty much kicks arse in the game I think.
Thanks again for all the great info guys-
S!<HR></BLOCKQUOTE>I think Blutarski2004 hit on it, I wish skychimp would post that thing he found, in that he too initally thought the max speed of the P51 was with the radiator open, taking advantage of the extra thrust.. But he found something that actually said the max speed was obtained with it closed... Thus, it sounds like the thrust with it opened help CANCEL out SOME OF THE DRAG due to it being OPEN.. but NOT ALL OF IT! Or put another way, the THRUST produced 300, but the drag was 400, end result 100 drag... which is better than 400 drag!!

TAGERT

DaBallz
01-29-2004, 04:05 PM
In the 1950's the USAF entertained the thought of
nuclear powered planes. It was and is a workable
idea. The idea was passed up because of the danger
posed by a nuclear plane crashing on land, especially
in an populated area.

The concept is similar to the P-51 radiator
concept.
A reactor using a liquid metal for the carrying
the heat, pumped liquid Sodium to a heat exchanger
in a turbo jet engine. In place of the combustion
chamber in the jet was the heat exchanger.
Both GE and P&W built prototypes, one of them
actually ran a prototype engine.

A B-36 was modified to carry a nuclear reactor
and did in fact fly with the reactor running.

The reactor NEVER did power the plane.

My point is that heat alone can in fact be used
to power an aircraft. Various sources give
widely varying descriptions of the effecency
of the P-51's colling system, but the best source
is the pilots that flew and raced them. There
was little or no peanalty in the radiator
being opened.

The reverse is true for all other piston engined
planes I have heard of.
I remember the story of a B-24 that was forced down
because the cowl flaps stuck full open after takeoff.

Radial engined planes suffered greatly from cooling
drag. After WWII Republic built the XF-12 rainbow
recon plane. It was the fastest 4 engined piston
powered plane ever.
The story is that it was 4 square, 4 engines,
40,000' and 400mph cruise!
Republic solved the problem, too late.

http://avia.russian.ee/air/usa/republic_xf-12.html

It obviously had to run with its cooling air
flowing at near 100%.

Da

Chadburn
01-29-2004, 04:59 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by tagert:


The "decreased drag school" which beleives that the radiator design allowed for efficient cooling while eliminating 90% of the drag associated with aconventional radiator and:

The "Increased thrust school" which beleives that the warm air expelled by the special radiator design actually added to the planes top speed.

QUOTE]I think Blutarski2004 hit on it, I wish skychimp would post that thing he found, in that he too initally thought the max speed of the P51 was with the radiator open, taking advantage of the extra thrust.. But he found something that actually said the max speed was obtained with it closed... Thus, it sounds like the thrust with it opened help CANCEL out SOME OF THE DRAG due to it being OPEN.. but NOT ALL OF IT! Or put another way, the THRUST produced 300, but the drag was 400, end result 100 drag... which is better than 400 drag!!

TAGERT<HR></BLOCKQUOTE>

Here's what SC said:

"Oleg:

I extend to you my humblest apologies. I now think you were right about the P-51D. I now too believe the radiator air exit shutter was closed when it achieved it's top speed of 437 mph.

I argued that the P-51D could not have possibly accelerated to 437 mph on combat power with the radiator air exit shutter closed without over-heating. As you know, the P-51D achieved 437 mph at a little under 25,000 feet. And if the Mustang was running on true combat power at that altitude, I would maintain my position. But it really wasn't running at true combat power at 25,000 feet. In reality, it was simply running at full throttle.

Combat Power in the P-51D was defined as a manifold pressure of 67" of mercury. And 67" of mercury can be maintained by the P-51D up to about 19,000 feet. At that point, manifold pressure begins to drop off dramatically. At 25,000 feet, manifold pressure is down to about 45" hg."

http://home.cogeco.ca/~jkinley/FB_JG27.jpg

tenmmike
01-29-2004, 06:10 PM
allright i just picked up the book MUSTANG DESIGNER edgar schmued and the p-51....he talks about all sorts of things about the radiator ..several pages worth all combined including the discovery of the thrust which they had not expected.........he talks about all sorts of things having to do with the radiator all the problems etc lots about problems with the inlet but not once does he mention the outlit !!!!! LOL .................this is a excallent book get it if ya get the chance ..all sorts neat stuff of what the man himself was thinking at the time

http://images.ar15.com/forums/smiles/anim_50cal.gif U.S INFANTRY 1984-1991

SkyChimp
01-29-2004, 06:11 PM
JG, the reason I changed my mind was because the radiator shutter on the P-51 is never fully closed. Even in it's most closed position, it still has an opening that allows thrust to be expelled.

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

Triscadec
01-29-2004, 06:37 PM
"...but yeah waxing planes helps the speed a bit, less air friction..."

This is a common misconception. The air that is located just above the surface of the aircraft is for all intents and purposes stagnant(sp). Waxing the plane has no effect at this level. Also, if you were to take a look at the bare metal highly magnified, and then polished it and magnified that, you would see that they are both equally "rough".

A few years ago, an aerodynamics professor did a little test with a Mooney. Him and his class waited for a relatively stable weather day. They then did a flight test with the Mooney and gathered performance data. Then the whole class converged on the plane washing and waxing it in under an hour, to keep the weather variables at a minimum. Another flight was undertaken in the waxed plane. The result was no signifigant increase in speed. The only positive result was that the airplane looked nice.

T

TheGozr
01-29-2004, 06:46 PM
Thrust?

DO you mean Ram air compression in the chambers?
It work in motorcycles it gives more HP's when reaching a certain speed.

Tested and proved..

-GOZR
"TheMotorheads" All for One and One for All (http://www.french.themotorhead.com/themotorhead_fighters/)

tagert
01-29-2004, 06:49 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by SkyChimp:
JG, the reason I changed my mind was because the radiator shutter on the P-51 is _never_ fully closed. Even in it's most closed position, it still has an opening that allows thrust to be expelled.

_Regards,_
_SkyChimp_
<HR></BLOCKQUOTE>Ahhhhhhhh good point!

TAGERT

HomeboyWu
01-29-2004, 07:39 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by TheGozr:
Thrust?

DO you mean Ram air compression in the chambers?
It work in motorcycles it gives more HP's when reaching a certain speed.

Tested and proved..

-GOZR
http://www.french.themotorhead.com/themotorhead_fighters/ <HR></BLOCKQUOTE>

No no no...

That thrust comes from hot exhaust air expanding, cooling and accelerating itself upon exit.

bombing_man
01-29-2004, 10:15 PM
doesn't apply to p51 but saw a history channel special on jet engines and thos coils under b17 engines were the earliest jet engins according to it

bombing_man
01-29-2004, 10:17 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by bombing_man:
doesn't apply to p51 but saw a history channel special on jet engines and thos coils under b17 engines were the earliest jet engins according to it<HR></BLOCKQUOTE>not "true" jet engines though. But the air was compresed and ignited like in a jet engine. think p51s had them. http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif

chris455
01-29-2004, 10:19 PM
Called Turbosuperchargers. Not "jet engines" in the literal sense, as you know, but share some of the same principles of operation.

http://members.cox.net/miataman1/P47.jpg

DaBallz
01-30-2004, 04:22 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by chris455:
Called Turbosuperchargers. Not "jet engines" in the literal sense, as you know, but share some of the same principles of operation.

http://members.cox.net/miataman1/P47.jpg <HR></BLOCKQUOTE>

Turbo's are little more than jet engines with
a piston engine in place of the combustion chambers.

Turbo's were developed first then Jets were developed
from them.


Those B-17's used a primative turbocharger that
lacked a bonnet over the turbine section.
Although they were very reliable the turbines
would over heat when a bonnet was used.
During the late 30's bonneted turbo's were developed
but were not retrofitted to the B-17, B-24 or
even the B-29 (two per engine). The P-38 used
an un bonneted turbo behind and on top each engine.

Da

MatuDa_
01-30-2004, 04:49 AM
As far as this boost issue with the radiator goes, you cannot produce anything comparable to jet propulsion with a radiator. The fact that air density falls as it expands cancels even the theoretical chance of this. (weight remains the same, only area grows so..)

The way radiator helps in the 'tang is managing the airflow to cause better combined aerodynamics in the cooling system and negate drag caused by the scoop by "injecting" air into the area that would otherwise have lower air pressure and "suck" the plane back.

In other words it counters some of the drag caused by the radiator, not all. Radiators do not produce thrust http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif

Aaron_GT
01-30-2004, 06:04 AM
"doesn't apply to p51 but saw a history channel special on jet engines and thos coils under b17 engines were the earliest jet engins according to it"

I thought that honour went to the Hungarian(?)
plane in 1910 that used a form of jet engine,
which was latter adapted by the Italians in
the late 1930s. Not a true jet, but I don't
think turbosuperchargest count as true jet
engines either!

JG14_Josf
01-30-2004, 09:14 AM
Virtualpilots 109myths web page/#radi-fuselage and drag (http://www.virtualpilots.fi/hist/109myths/#radi)

- After the re-design that occurred with the Friedrich, the Me 109 fully employed the Meredith effect. It's radiator had boundary layer separation with separate discharge, a continously adjustable intake and a continously adjustable outlet that was automatically regulated to create thrust. That's the same degree of sophistication as found on the Mustang. The thermodynamic effect of the engine cooling was well-known in the 1920s and 1930s and in fact had been first pointed out by Hugo Junkers in 1915 when he acquired a patent for the "Düsenkühler" ('jet radiator'). Thermodynamics probably were the most advanced science in the late 19th/early 20th century due to their tremendous economical value in a society that based its wealth primarily on steam engines. The "Meredith" effect probably was painfully obvious to Junkers, who included it right in the first aircraft he ever built.

LEBillfish
02-01-2004, 08:50 AM
From: Charles.K.Scott@dartmouth.edu (Charles K. Scott)
Newsgroups: rec.aviation.military
Subject: Mustang, was it's wing really laminar flow? Very long
Date: 5 Feb 1997 14:13:04 GMT

Was the Mustang's laminar flow wing laminar or not?

That is a question asked often in several groups and recently, after
finishing "Pursue and Destroy" by Leonard "Kit" Carson, I believe I
have found a definitive answer.

Mr. Carson's credentials are that 1. He flew the Mustang in combat. 2.
He was an engineer who understood aerodynamics. 3. He was a test pilot
for a while after W.W.II. He goes into extreme technical detail while
telling about the Mustang and his career flying it.

Carson begins his analysis of the Mustang and it's laminar flow wing
back in the late 20's and early 30's when NACA, the National Advisory
Committee for Aerodynamics began it's research on airfoils, airflow,
and other aspects of flying. The airplane companies were in no
position to do this research because they did not have the money to
develop and build wind tunnels. He described airfoil research prior to
NACA as piecemeal, with many airfoils being developed by the OTLAR
method (Oh That Looks About Right, my words, not his)

It was during the thirties that NACA established the relationship
between turbulent flow and drag. Their measurements indicated that the
3/32 inch rivets heads and lap joints on the typical metal airliner
"dissipated" 182 horsepower. On one airplane they were measuring, they
found that a coat of paint cost the airplane 91 horsepower over the
same airplane with bare aluminum. They learned that mere dust, fine
sand or a piece of scotch tape "would cause the smooth laminar layer
next to the wing surface to jump over To a turbulent, high drag
condition."

Then, in 1938, in a wind tunnel designed to smooth out the airflow
through the tunnel (designed by Jacobs and Dryden, prior to this wind
tunnel, flow through the tunnel was too turbulent to test laminar
theories) a new type of airfoil was tested that set new and incredible
drag coefficients compared to any airfoil previously tested. It
recorded a drag coefficient of .003 "which was about half of the lowest
ever recorded before for an airfoil of similar thickness."

Further tests conducted in England "demonstrated that laminar flow and
a reduction of drag could be obtained for a considerable distance over
a smooth full scale wing."

This was in the wind tunnel, however, and it turned out that an
enormous gulf existed between test aircraft and the wind tunnel and
combat aircraft.

The following reasons were given by Carson explaining why in real life
laminar flow simply did not occur on the P-51's wing.

1. The effects of propeller Slipstream. Airflow within the arc of the
prop is very turbulent, "the whole fuselage and inboard section of the
wing next to the fuselage operate in that turbulent stream. Tests in
the Langley wind tunnel revealed that airflow within the arc of the
prop (the prop was 11 feet in diameter which meant that turbulent air
was encountered all the way out to within 13 inches of the inner gun
position) was "90 to 95 percent turbulent" (in other words non laminar)

2. Vibration: "Engine and propeller vibrations transmitted through the
structure will induce transition to turbulence." Tests indicated that
laminar flow on twin engine aircraft was greater with one engine
feathered than with both running. Engineers surmised that the lack of
engine/prop vibration on the dead engine side promoted laminar flow.
Honest, that's what the book said. Of course with both props turning,
more of the wing would be bathed in the prop slipstream which as has
been mentioned above, trips laminar flow to turbulent.

3. Airfoil surface condition: "Mud, dirt, ice and frost will induce the
transition to turbulent conditions." "Fuel truck hoses, ammo belts,
tools, guns and large feet in GI. shoes found the way to the tops of
wings" the scrapes and dents this servicing caused had negative effects
on laminar flow.

4. Manufacturing tolerances: "The Mustang was the smoothest airplane
around in 1940, but there is a practical limit in construction. We're
talking about surface roughness or waviness of .01 inches which will
cause transition to turbulence." (remember the afore mentioned dust
and scotch tape which was observed to trip airflow to turbulent). Some
aerodynamicists have stated that true laminar flow did not occur
outside the wind tunnel until the advent of Burt Rutan's Vary E-Z in
the early 70's with it's incredibly smooth fiberglass over carved foam
wing and aft mounted engine which of course kept the wing ahead of the
prop slipstream.

5. Wing Surface Distortion in Flight: Flight brings flight loads which
can and did distort the wing and cause ripples in the wing surface
which were fully capable of tripping the laminar flow to turbulent.

Carson went on to state: "The Mustang wing was a high lift
configuration, as well as low drag. . . the Mustang in squadron service
was not laminar to the same extent as the wind tunnel development
models. Not one day in the past 34 years (the book was written in 74)
has it performed in that manner for any or all of the reasons just
given."

So if it wasn't the laminar flow wing that gave it it's high speed and
extensive range, what was it?

The most prominent speed secret was the dramatic reduction of cooling
drag. Placing the airscoop on the belly just in front of the rear edge
of the wing removed it as far as was practicable from the turbulence of
the prop and placed it in a high pressure zone which augmented air
inflow. Tests in the wind tunnel with the initial flush mounted scoop
were disappointing. There was so much turbulence that cooling was
inadequate and some doubted that the belly scoop would work. The
breakthrough was to space the scoop away from the surface of the belly
out of the turbulent boundary layer of the fuselage. Further testing
showed that spacing it further out would increase cooling but at a cost
to overall drag. Various wind tunnel tests established the spacing at
the current distance which represents the best compromise between
spacing out from the turbulent flow of the fuselage, drag and airflow.

With the flow into the scoop now smooth and relatively nonturbulent,
the duct leading to the radiator/oil cooler/intercooler was carefully
shaped to slow the air down (the duct shape moves from narrow to wide,
in other words a plenum chamber) enough from the high external speeds
to speeds through the heat exchangers that allowed the flow to extract
maximum heat from the coolant. As the air passed through the radiators
and became heated, it expanded. The duct shape aft of the radiator
forced this heated and expanded air into a narrow passage which gave it
considerable thrust as it exited the exhaust port. The exhaust port
incorporated a movable hinged door that opened automatically depending
on engine temperature to augment the airflow. The thrust realised from
this "jet" of heated air was first postulated by a British
aerodynamicist in 1935. The realization of thrust from suitably
shaped air coolant passages is named after him and called the "Meredith
Effect". Some have said that at certain altitudes and at a particular
power setting the Meredith effect was strong enough to actually
overcome all cooling drag; this is not regarded as being accurate by
most aerodynamicists. It greatly contributed to overall efficiency of
the cooling system but never equaled or overcame cooling drag.

Combine the low overall drag of the Mustang with significantly greater
internal fuel tankage than either the Spitfire, Messerschmitt or
Focke-Wulf 190 and you can easily see how it could fly so far. Add the
two 105 gal external wing tanks and the Mustang was fully capable of
flying to any target the heavy bombers could attack in the ETO. Kit
Carson mentioned that he flew more than 35 missions during which he was
in the cockpit for more than 5 hours.

Finally, Carson was interested to find, while reading flight test
reports in research for his book, that the quoted top speed for the
P-51B was less than what was attained during test flying. The
information is as follows:

Report: NA-5798
Title: "Flight Test Performance for the P-51B-1
Date: January, 1944
Test Weight: 8,460 lbs
High Speed: 453 mph true airspeed at 28,800 feet at 67" HG and 1298 HP,
war emergency power, high blower, critical altitude.

The quoted top speed for the B model Mustang is 440 mph.

I can only speculate that it is likely the test airplane used in the
above mentioned flight was a well maintained and unblemished Mustang.
It's probable that the actual combat aircraft would not be able to
quite equal that performance. Never the less, Carson notes this
information and concludes with the following:

"It's easy to see why many pilots preferred the P-51B, including
myself, even if it did have only 4 guns and the "birdcage" canopy. If
you can't hit'em with 4 guns, two more aren't' going to make your aim
any better."

Corky Scott

tagert
02-01-2004, 09:11 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by LEBillfish:
From: Charles.K.Scott@dartmouth.edu (Charles K. Scott)
Newsgroups: rec.aviation.military
Subject: Mustang, was it's wing really laminar flow? Very long
Date: 5 Feb 1997 14:13:04 GMT<HR></BLOCKQUOTE>Very cool post Corky, thank you! It's a keeper!

TAGERT

VW-IceFire
02-01-2004, 09:26 AM
I must say...I still find the Mustang to be the fastest non-jet aircraft we have in the game at the moment. Unlike the La-7 (which accelerates well but has a tough time sustaining maximum speed)...once its up to speed it seems to glide along at that speed till you change your direction.

Gotta love the Mustang one way or another.

http://home.cogeco.ca/~cczerneda/sigs/temp_sig1.jpg
The New IL2 Database is Coming Soon!

SkyChimp
02-01-2004, 10:52 AM
The jury is still out on whether the exit shutter was open, closed or somewhere in between at max speed. I still tend to believe it was somewhat open (not all the way)at max level speed. I have the British flight manual for the P-51B/C which indicates that the shutter opens automatically, and that it opens to some degree at just a little above minimum operating temperature.

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

LEBillfish
02-01-2004, 12:12 PM
Corky Scott was the Author, not I lol....

Found this doing a search for Laminar flow (had an idea for boat hulls and sails)....Anywho, also found this bit on the P51 / P38 vs. Japanese fighters...

From: cdb100620@aol.com (CDB100620)
Subject: Re: P-51 bob weights and rudder tabs
Date: 16 Sep 1997
Newsgroups: soc.history.war.world-war-ii

The Merlin P-51 had a lot of teething problems, but, for some reason, they
are largely overlooked. It had problems with the canopy frosting over,
with jamming guns, with the engine cooling system and the engine
itself--and with shedding the tail. In fact, the plane had so many
problems initially that Col. Don Blakeslee, CO of the 4FG, called it "an
experimental aircraft" and expressed doubts that it could be successful.
The P-38 had gone through its teething troubles the previous fall and with
the introduction into ETO combat of the J model well-pleased its pilots.
FGs getting the P-51 were unhappy and pilots grumbled that they would
rather have the Lockheed. It was not uncommon to have almost 30 percent of
P-51 sorties aborted for mechanical reasons during the winter and spring of
1944 (typical abort rate for all causes for all USAAF aircraft was 8 percent).
When the D model became available in quantity in the summer, cases of the
aircraft losing its tail surfaces in flight began to be reported. Flight
restrictions were placed on the aircraft and the tail surfaces were beefed
up. Wing failures were also reported due to control stick force reversal
in high-speed dives. The bobweight was added to the elevator control
system to fix this problem. But for the aircraft to be even marginally
stable, the fuselage fuel tank had to be less than half full.
The Mustang still had problems a year later when the 7AF began B-29 escort
missions to Japan. Incidences were reported of tail surface failures in
dogfights. In one instance in April, 1945, a P-51D got into a dogfight with
a Mitsubishi Raiden. During the violent maneuvering, the Mustang first
shed its tail control surfaces and then its wings were torn off. The
pilot, 2Lt. James Beattie, did not get out. The Raiden apparently suffered
no damage from the severe loads placed on it during the dogfight.

All that said, the Merlin Mustang was a very effective fighter, but its
greatest successes came in the ETO, where its high abort rate would not
result in equally high pilot fatalities. Over the vast reaches of the
Pacific, the P-38 was the fighter of choice. Mustangs suffered their
greatest operational loss of the war on an escort mission to Japan when 27
out of a force of 148 went down. Most of the losse were weather-related
(always a greater danger than the enemy in those days) rather than
mechanical failures, but the Mustang seemed dogged by bad luck and had
little success battling Japanese fighters over the home islands. The
contrast with its sweeping victories over the Luftwaffe is striking.
P-38 pilots relate the story of an apparently new-in-theater pilot who
called over the radio, "Mayday! I've been hit and am losing coolant. What
should I do." To which a P-38 pilot replied, "Calm down. Just feather the
prop and trim for single-engine flight and you'll get home okay." There is
a long pause, and then the first pilot says, "Feather it, hell! I'm in a P-51."
Mustang pilots in the PTO sang a ditty that went:

"Don't give me a P-51.
It was all right for fighting the Hun,
But if fighting the Jap you try,
You'll run out of sky.
Don't give me a P-51."

(The reference to "running out of sky" refers to the great amount of
altitude lost in dogfighting the maneverable Japanese fighters.)

In contrast, they sang about the Lightning:

"The P-38 is some machine,
The answer to a flyer's dream.
She'll dive, loop and climb
And turn on a dime.
To every pilot, she's the queen."

It's interesting that these two ditties imply that pilots thought the
P-38 was more maneuverable than the P-51. It could be that they simply
trusted the Lockheed not to come apart during violent maneuvers, and were
leery of pushing the North American fighter. It's even more interesting
that in the MTO and the ETO, apparently, P-38 pilots were a little afraid
of their mounts and hesitated to dogfight Luftwaffe fighters. Go figure.

jenikovtaw
02-01-2004, 12:26 PM
I thought spitfire had something like that as well, not sure though.

chris455
02-01-2004, 12:51 PM
There is alot in this post that I would have to take with several grains of salt.

Nothing against you lilfish, of course, but I take it this is simply the unsupported writings of a subscriber to a newsgroup?
If so, it makes a little more sense.
The "ditties" to me are especially suspect. They don't sound genuine. Especially the unabashed praise of the P-38. Now, I know for a fact that lots of Lightning pilots (especially in the PTO) loved their planes, but the ditty about "she's the queen" is a bit much. If it had been about the Lightning's tendancy to freeze it's pilots arse off, it would be more beleivable.THAT'S the kind of stuff soldiers write about http://ubbxforums.ubi.com/images/smiley/16x16_smiley-wink.gif
Here's another thing:

"Don't give me a P-51.
It was all right for fighting the Hun,
But if fighting the Jap you try,
You'll run out of sky.
Don't give me a P-51."

(The reference to "running out of sky" refers to the great amount of
altitude lost in dogfighting the maneverable Japanese fighters.)"

Fact: as early as 1942 it was doctrine that you never tried to turnfight the Zero (or any Japanese plane for that matter) in ANY U.S. fighter. No U.S. aviator in 1944-45 would not have known this, and could even be subject to disciplinary action in most units for even trying. So why the line about "running out of sky again?

Another:
"The P-38 had gone through its teething troubles the previous fall and with
the introduction into ETO combat of the J model well-pleased its pilots.
FGs getting the P-51 were unhappy and pilots grumbled that they would
rather have the Lockheed".

The only "grumbling" I am familiar with along these lines (P-38 vs P-51) is the persistent complaints among P-38 pilots in the ETO about lack of an adequate cockpit heater- a problem the Mustang didn't have. This problem was never adequately solved (not that Lockeed didn't try). I am unaware of any prevalent sentiment among Mustang units that they would "rather have a Lockheed". This is the first time I have heard of this, but there are many here with much more knowledge than I. It would be interesting to see what others have read or hear about these comparisons.

Again Lilfish, absolutely nothing personal meant here. You've given us somr interesting points to ponder- I'm sure others will want to add their information.
S!

http://members.cox.net/miataman1/P47.jpg

DaBallz
02-01-2004, 04:22 PM
I have read a bunch of P-51 combat accounts
from the ETO, they can be quite hair raising.

The PTO P-51 combat accounts are by comparison
boring. The speed advantage was to large it
seems to have become like strafing planes in flight.

A P-51D or P-51K had a 80-100mph advantage over
the A5M2 or A6M5 Zero at most altitudes.

The climb of the Zero was of little use
against a plane that could run away from you
and climb at the same time.
The higher performance Japanese fighters were
rare and had serious quality issues.

I seem to remember one USAAC P-51 pilot destroyed 7 Japanese fighters in one mission (confirmed).

Da

MiloMorai
02-01-2004, 04:32 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by DaBallz:

I seem to remember one USAAC P-51 pilot destroyed 7 Japanese fighters in one mission (confirmed).

Da<HR></BLOCKQUOTE>

SHOMO, WILLIAM A.

Rank and organization: Major, U.S. Army Air Corps, 82d Tactical Reconnaissance Squadron.

Place and date: Over Luzon, Philippine Islands, 11 January 1 945.

Entered service at: Westmoreland County, Pa.

Birth: Jeannette, Pa.

G.O. No.: 25, 7 April 1945.

Citation: For conspicuous gallantry and intrepidity at the risk of his life above and beyond the call of duty. Maj. Shomo was lead pilot of a flight of 2 fighter planes charged with an armed photographic and strafing mission against the Aparri and Laoag airdromes. While en route to the objective, he observed an enemy twin engine bomber, protected by 12 fighters, flying about 2,500 feet above him and in the opposite direction Although the odds were 13 to 2, Maj. Shomo immediately ordered an attack. Accompanied by his wingman he closed on the enemy formation in a climbing turn and scored hits on the leading plane of the third element, which exploded in midair. Maj. Shomo then attacked the second element from the left side of the formation and shot another fighter down in flames. When the enemy formed for Counterattack, Maj. Shomo moved to the other side of the formation and hit a third fighter which exploded and fell. Diving below the bomber he put a burst into its underside and it crashed and burned. Pulling up from this pass he encountered a fifth plane firing head on and destroyed it. He next dived upon the first element and shot down the lead plane; then diving to 300 feet in pursuit of another fighter he caught it with his initial burst and it crashed in flames. During this action his wingman had shot down 3 planes, while the 3 remaining enemy fighters had fled into a cloudbank and escaped. Maj. Shomo's extraordinary gallantry and intrepidity in attacking such a far superior force and destroying 7 enemy aircraft in one action is unparalleled in the southwest Pacific area.

http://www.distantcousin.com/military/medalofhonor/wwii/4/053.html



Long live the Horse Clans.

LEBillfish
02-01-2004, 06:48 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>It's interesting that these two ditties imply that pilots thought the
P-38 was more maneuverable than the P-51. It could be that they simply
trusted the Lockheed not to come apart during violent maneuvers, and were
leery of pushing the North American fighter. It's even more interesting
that in the MTO and the ETO, apparently, P-38 pilots were a little afraid
of their mounts and hesitated to dogfight Luftwaffe fighters. Go figure.<HR></BLOCKQUOTE>


I'd call that the grain of salt http://ubbxforums.ubi.com/infopop/emoticons/icon_wink.gif .

EPP-Gibbs
02-01-2004, 07:07 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by jenikovtaw:
I thought spitfire had something like that as well, not sure though.<HR></BLOCKQUOTE>

It did. The Spitfire was given Meredith effect radiators at prototype stage, ie 1935. The thrust overcame most, but not all, of the drag produced by the radiator, the same as it did five years later in the Mustang.

If I had all the money I'd spent on drink..I'd spend it on drink!

EPP-Gibbs
02-01-2004, 07:13 PM
The Spitfire successor, the Spiteful, was given laminar flow wings but after extensive flight testing, no advantage was found over the Spitfire's elliptical normal section wings. Mind you, the Spit wing was very good.

The resons given were the same as those by Carson, in that Laminar flow is a nice theoretical and experimental condition that simply doesn't occur in the reality that is an actual combat aircraft, complete with lumps, bumps, vibration, propwash, buffet, *****, dents, and dirt.

If I had all the money I'd spent on drink..I'd spend it on drink!

chris455
02-01-2004, 07:28 PM
PS LEBillfish-
Sorry I referred to you as "Lillfish" earlier.
I guess my 45-something eyes are playing tricks on me http://ubbxforums.ubi.com/infopop/emoticons/icon_eek.gif

http://members.cox.net/miataman1/P47.jpg

DaBallz
02-02-2004, 03:53 PM
There was a Spitfire fitted with Laminar flow wings
for testing, the results were promising.
The fuselage was stock and as a result
the full porential of the wings could not be realised.
Milo can fill in the details as I lent my book
of Spitfires out years ago and can not give a reference.

The Spiteful was indeed a lot faster than a Griffon engined Spit.
In excess of 470mph I believe. Not bad for a failure?

One more point, when Rolls Royce decided to develop
the ultimate piston fighter they chose P-51
wings and tail with a centrally mounted
Griffon engine a'la P-39. Time ran out for
pistons and the plane was never assembled.
The parts had however been manufactured
and the P-51 victim had been aquired.

Da

By the way, i have seen claims for 500mph
at altitude for a Spiteful, but I have my doubts.

BM357_Raven
02-02-2004, 07:14 PM
So let's say I am at 20,000 ft and I wanna accelerate the fastest.

In terms of the radiator, where should I set it to acheive the max speed in the shortest amount of time?

Should I gradually 'close it down' and if so at what speed to I goto the next stage?

Is it a problem that the key command opens it incrementally as opposed to closes it... so to close it you have to toggle past an more 'open' stage first. Does this have any affect in terms of drag or otherwise? Am I slowing myslef down by trying to close the radiator in stages (because when I want to go to 2 from 6 I have to first go past full open).

I am truly looking to become wiser in this matter so straighten me out if I am on the wrong track here. Thanks!

S~

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BM357_Raven
02-02-2004, 09:56 PM
Here's another way of posing the same question for clarity:

In the P-51, if I am accelerating from 200 to 400 mph let's say, what should my setting should I be as I hit 200 and subsequently as I hit 250, 300, 350, etc.?

Also, as alt. changes and outside pressures change, how should I monitor my Tach and Manifold Pressure in the sense of achieving maximum acceleration?

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JR_Greenhorn
02-02-2004, 10:16 PM
Another question:
Does anyone think that the owner of a restored P-51D could provide any expertise on these matters?
I can think of a couple I could ask, but it the questions would be pointless and a waste of the pilot's valuable time if they don't push those planes that hard anymore.