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zugfuhrer
01-01-2007, 02:24 PM
An aircraft with a small, highly loaded wing may have superior instantaneous turn performance, but poor sustained turn performance, it reacts quickly to control input, but its ability to sustain a tight turn is limited.

Aircraft with low wing loading tend to have superior sustained turn performance.

A lightly loaded wing will tend to have greater mass and inertia and create greater induced drag.

Interesting and logical. The 190/109 is suposed to react faster than the Spit/Hurricane and have superior instantaneous turn performance, but Spit/Hurri are superior in sustained turning.

Kurfurst__
01-01-2007, 02:46 PM
Originally posted by zugfuhrer:
An aircraft with a small, highly loaded wing may have superior instantaneous turn performance, but poor sustained turn performance, it reacts quickly to control input, but its ability to sustain a tight turn is limited.

Yak3, Yak9? Those were the best turning monoplanes of the war, with rather towards the highish wingloading. The Yak-3 definietely matches the 'small, highly loaded wing' description, being only around 14 m2 big. I can't think of any smaller wings ATM, yet the plane was one of the best sustained turners.

Sustained turn rate is about equaling drag with thrust. You can achieve good results with either a lot of thrust, or with low drag. Increasing thrust has a major effect on sustained turn ability, wingloading doesn't - bigger wings also came with bigger parasite-drag, and while their CDi coefficients may look good, it's still just a coefficient that in the end will be multiplied with the bigger wing area to get the absolute amount of drag.

Liftloading OTOH has a profound effect in turn radius, which is rather closely connected to stall speed/liftloading.

Wingloading itself is also not very important in itself, as many profiles can exist for the same wing area, giving very different lift characteristics, simply to put, different LIFTing force for similiar area wings with different profiles.<div class="ev_tpc_signature">

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Nyugodjon Békében - May he rest in Peace.

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"The Me 109 was exceptional in turning combat. If there is a fighter plane built for turning combat , it has to be the Messer! Speedy, maneuverable (especially in the vertical) and extremely dynamic."
- Major Kozhemyako, Soviet fighter pilot of the VVS

Ignored Posters : AKA_Tagert, Wurkeri, Gibbage, LStarosta, Sergio_101.

WWMaxGunz
01-01-2007, 05:52 PM
Originally posted by zugfuhrer:
An aircraft with a small, highly loaded wing may have superior instantaneous turn performance, but poor sustained turn performance, it reacts quickly to control input, but its ability to sustain a tight turn is limited.

May have........


Aircraft with low wing loading tend to have superior sustained turn performance.

Tend to...........


A lightly loaded wing will tend to have greater mass and inertia and create greater induced drag.

Tend to, and WTH you get this and what you think the weight of a wing really tells?
Oh, I see below it is the gathering of maybes to try and make some kind of proof/agenda.


Interesting and logical.

Very poor and loose excuse for logic really. Old wives tale kind of tale-stringing.


The 190/109 is suposed to react faster than the Spit/Hurricane and have superior instantaneous turn performance, but Spit/Hurri are superior in sustained turning.

You taking lessons from Josf perhaps? Or just drinking too much beer?
I notice how you introduce non-facts as definite realities.

Here is a modern pilot's term about instantaneous turn: Energy For Angles.

Tully__
01-02-2007, 02:49 AM
Originally posted by Kurfurst__:
Yak3, Yak9? Those were the best turning monoplanes of the war, with rather towards the highish wingloading. The Yak-3 definietely matches the 'small, highly loaded wing' description, being only around 14 m2 big. I can't think of any smaller wings ATM, yet the plane was one of the best sustained turners.
Wing loading is about wing area & weight, not just wing area.

Spitfire Vb @ max takeoff: 133kg/m^2
@ empty: 102kg/m^2

Yak3 @ max takeoff: 181kg/m^2
@ empty: 142kg/m2

Bf109G-6 @ max takeoff: 207kg/m^2
@ empty: 137kg/m^2

Considerably better than the 109 over most of the load range, considerably worse than an earlyish Spit (numbers courtesy of Wikipedia and don't argue, I was only looking for ballpark figures anyway).

For sustained turn power loading is as important as or more important than wing loading. If you don't have to power to combat the induced drag incurred in a tight turn, it can't be sustained (without losing altitude).<div class="ev_tpc_signature">

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Wurkeri
01-02-2007, 03:05 AM
Originally posted by zugfuhrer:
An aircraft with a small, highly loaded wing may have superior instantaneous turn performance, but poor sustained turn performance, it reacts quickly to control input, but its ability to sustain a tight turn is limited.


Generally, reaction to the control input is not related to the wing loading. And the same physics limit sustained as well as instantaneous turn.

Kurfurst__
01-02-2007, 03:58 AM
Don't rely on Wikipedia too much. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

207 kg/22 would be something like 3322 kg takeoff weight for the G-6, which is a bit much, as it weighted 3100 kg at takeoff (193kg/m2). I'd prefer the G-2, as the Russians measured that for turn as well, so the figures are at about compatible.

The G-2 weighted 3037 kg at takeoff, which gives 189 kg/m2, which is almos the same as the Yak-3, which again turns significantly better. The clue is of course that while the Yak has about the same power at low lever as the 109G-2, it is considerably lighter, and as you pointed out, power loading is an important aspect of sustaining the turn.

The Yak-3 was brought up because some appearantly believe that The Big Wing gives insurmountable advantage in the drag in turn, while small winged aircraft is greatly disadvantaged because of the mountaining induced drag.

The Yak-3 case is a good reality check for these.<div class="ev_tpc_signature">

http://newsimg.bbc.co.uk/media/images/42333000/jpg/_42333631_puskasbudapest_ap203b.jpg
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Nyugodjon Békében - May he rest in Peace.

http://kurfurst.allaboutwarfare.com/
Kurfürst - Your Resource for Messerschmitt Bf 109 Performance!

"The Me 109 was exceptional in turning combat. If there is a fighter plane built for turning combat , it has to be the Messer! Speedy, maneuverable (especially in the vertical) and extremely dynamic."
- Major Kozhemyako, Soviet fighter pilot of the VVS

Ignored Posters : AKA_Tagert, Wurkeri, Gibbage, LStarosta, Sergio_101.

Wurkeri
01-02-2007, 06:33 AM
Well, the Yak-3 case is really a good reality check; long time ago there was a discussion about the Yak-3 VVS values in the SimHQ:

http://www.simhq.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=98;t=004876;p=1

The claimed turn time 17s for the Yak-3 appear to be for the prototype while for the production plane the time is claimed to be 21s.

http://wunderwaffe.narod.ru/Magazine/AirWar/33/28.htm

So, which one to believe?

Kurfurst__
01-02-2007, 08:03 AM
Figures of a respectable organisations like Rechlin and TsaGi over some with wishful thinking.

http://i38.photobucket.com/albums/e133/Kurfurst/yak3turn_germantrials.jpg

These crafty Germans, they must have snatched away a ruskie prototype for evaluation !<div class="ev_tpc_signature">

http://newsimg.bbc.co.uk/media/images/42333000/jpg/_42333631_puskasbudapest_ap203b.jpg
In memoriam Puskás Ferenc,2 April 1927 - 17 November 2006.
Nyugodjon Békében - May he rest in Peace.

http://kurfurst.allaboutwarfare.com/
Kurfürst - Your Resource for Messerschmitt Bf 109 Performance!

"The Me 109 was exceptional in turning combat. If there is a fighter plane built for turning combat , it has to be the Messer! Speedy, maneuverable (especially in the vertical) and extremely dynamic."
- Major Kozhemyako, Soviet fighter pilot of the VVS

Ignored Posters : AKA_Tagert, Wurkeri, Gibbage, LStarosta, Sergio_101.

zugfuhrer
01-02-2007, 10:48 AM
The source is
http://en.wikipedia.org/wiki/Wing_loading
what j**k has written this?

Wurkeri
01-02-2007, 11:17 AM
Originally posted by Kurfurst__:
These crafty Germans, they must have snatched away a ruskie prototype for evaluation !

Ah, now there is even more data to choose.

DarkWingDuck...
01-02-2007, 11:35 AM
lightly loaded wing will tend to have greater mass and inertia and create greater induced drag.

Butnot always so, a lightly loaded wing can support an aircrafts weight at a low angle of attack, whereas a highly loaded one would need greater Angle of attack at the same speed to lift the same weight induced drag goes up with AOA<div class="ev_tpc_signature">

QUACK

zugfuhrer
01-02-2007, 11:40 AM
D.W.D I think that the auther meant that a large wing has more mass than a small one.
It not always so but the idea of a big wing generate more lifting power cause this.

Kettenhunde
01-02-2007, 03:02 PM
Ah, now there is even more data to choose.


I think you meant to say:

Oh ****!! It is not the prototype and once again I am busted manipulating data.<div class="ev_tpc_signature">

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WWMaxGunz
01-02-2007, 03:16 PM
I would expect the 109 to *maybe* get better instantaneous turn at cost in speed due to the
slats allowing more AOA but perhaps I have that wrong by not counting so much else.

Crumpp, would a comparison of landing speeds be a good indicator of wing efficiency in the
wasteful change of direction?

Kurfurst__
01-02-2007, 03:24 PM
I'd figure instantenous turn rate has probably mor e to do with stability of the aircraft in the pitch axis, and, Centre of Gravity (inertia and all). But that's just a vogue guess, I believe it would not harm to define what is 'instantenous turn performance' in the first place. It's not as nearly as self-explaining as a sustained one.<div class="ev_tpc_signature">

http://newsimg.bbc.co.uk/media/images/42333000/jpg/_42333631_puskasbudapest_ap203b.jpg
In memoriam Puskás Ferenc,2 April 1927 - 17 November 2006.
Nyugodjon Békében - May he rest in Peace.

http://kurfurst.allaboutwarfare.com/
Kurfürst - Your Resource for Messerschmitt Bf 109 Performance!

"The Me 109 was exceptional in turning combat. If there is a fighter plane built for turning combat , it has to be the Messer! Speedy, maneuverable (especially in the vertical) and extremely dynamic."
- Major Kozhemyako, Soviet fighter pilot of the VVS

Ignored Posters : AKA_Tagert, Wurkeri, Gibbage, LStarosta, Sergio_101.

Wurkeri
01-02-2007, 03:48 PM
Originally posted by Kettenhunde:
[
I think you meant to say:

Oh ****!! It is not the prototype and once again I am busted manipulating data.

Hm... so are you saying that I'm manipulating something if I point out that there is many kind of values for the Yak-3?

The situation is pretty much same as in the Fw 190 thread; there is wide variety of data to choose and people tend to choose the one which supports his/her sayings.

JtD
01-02-2007, 04:01 PM
Is the full Yak-3 Rechlin test available somewhere?

Kurfurst__
01-02-2007, 04:01 PM
You can (did) make a valid confession describing that preference on your own behalf, but not others.<div class="ev_tpc_signature">

http://newsimg.bbc.co.uk/media/images/42333000/jpg/_42333631_puskasbudapest_ap203b.jpg
In memoriam Puskás Ferenc,2 April 1927 - 17 November 2006.
Nyugodjon Békében - May he rest in Peace.

http://kurfurst.allaboutwarfare.com/
Kurfürst - Your Resource for Messerschmitt Bf 109 Performance!

"The Me 109 was exceptional in turning combat. If there is a fighter plane built for turning combat , it has to be the Messer! Speedy, maneuverable (especially in the vertical) and extremely dynamic."
- Major Kozhemyako, Soviet fighter pilot of the VVS

Ignored Posters : AKA_Tagert, Wurkeri, Gibbage, LStarosta, Sergio_101.

WWMaxGunz
01-02-2007, 05:18 PM
Originally posted by Kurfurst__:
I'd figure instantenous turn rate has probably mor e to do with stability of the aircraft in the pitch axis, and, Centre of Gravity (inertia and all). But that's just a vogue guess, I believe it would not harm to define what is 'instantenous turn performance' in the first place. It's not as nearly as self-explaining as a sustained one.

The books and sites I see that show the doghouse charts and explain the curves give it as a
kind of lift in the attitude the plane is at rather than how quickly the plane can get to
the proper attitude (AC attitude, not people attitude as you know but others read also).
So the charts start with a V-n diagram, with lift limit and structural limit at speeds and
G's. In the Shaw book it is very close to the start of the Appendix chapter named Turn
Performance.

With more elevator and lighter stability for sure you can change the conditions quicker.
The chart has more use as 'you are here, this is the cost, that is the possible' meaning
to me.

I know that you are not first language english so this is not a cut but only information.
Where you spelled vogue, the word you want is vague which means like not definite where
vogue is a fashion term I am sure you do not mean. Please, any time pick on my German
when I am dumb enough to try use it! Your english is far better than many people's that
live and went to school here in the US.

Kettenhunde
01-02-2007, 06:10 PM
Crumpp, would a comparison of landing speeds be a good indicator of wing efficiency in the wasteful change of direction?

Not really because the aircraft is all dirtied up with flaps and gear at landing. Aircraft can have some really wild differences in stall speed and low speed behavior in this condition.

Here is the standard definition of instantaneous turn ability:

http://www.onpoi.net/ah/pics/users/503_1167785399_instantturndefinition.jpg

All the best,

Crumpp<div class="ev_tpc_signature">

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WWMaxGunz
01-03-2007, 12:54 PM
Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Crumpp, would a comparison of landing speeds be a good indicator of wing efficiency in the wasteful change of direction?

Not really because the aircraft is all dirtied up with flaps and gear at landing. Aircraft can have some really wild differences in stall speed and low speed behavior in this condition.

Here is the standard definition of instantaneous turn ability:

http://www.onpoi.net/ah/pics/users/503_1167785399_instantturndefinition.jpg

All the best,

Crumpp </div></BLOCKQUOTE>

Good thing I asked.

I see one problem with instantaneous turn performance is that 1 second into it you have a
much less instantaneous turn unless you have extra energy to spend like height to lose.

Well not a problem unless one tries to apply instantaneous turn as if it were constant
again unless there is height to lose. Two planes spiralling down at max G's, that would
be one where it could apply at least until one was able to make the hard turn while losing
less height long enough for the other to get below and in front... maybe?

I have seen one guy post about 109 that he was chasing in a hard turn and he says suddenly
the 109 just looped right over his cockpit onto his tail in just a couple of seconds.
After much looking at I arrived at a far different picture. The 109 did pull hard inside
of him from in front but doing so it bled speed like mad. So it is inside the turn and
slower, yes it will be seen as flying above his cockpit but no the 109 did not loop clear
around in any couple seconds. I asked for a track really just to see if the nose of the
109 ever pointed backwards relative to his motion which in the time given, nuh-uh. No
track of course.
So the 109 in that case, in my view, used instantaneous turn and the associated drag in a
very positive way and was in a couple seconds able to relax his extra hard turn as the in
this case P-51 shot out under him (below his floor) and waxed the P-51 before that pilot
knew what happened!

PBNA-Boosher
01-03-2007, 02:16 PM
Yak-3 the best turning monoplane of the war? What happened to the Ki-27? A6M? Ki-43?<div class="ev_tpc_signature">

http://img181.imageshack.us/img181/8237/booshersig2ry6.jpg

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Wurkeri
01-05-2007, 03:01 AM
I did some spreadsheet calculations (basicly similar as Cube in that SimHQ thread) to check the 16-17s turn times for Yak-3. The parameters were mostly same as used by Cube (taken from Tsagi book etc.) but I started from flying weight 2600kg and assumed 85% prop efficiency, e factor 0,8 and 70kp exhaust thrust. These resulted 20,5s turn time at 371km/h (true speed) so the results were close the results by Cube and VVS for production plane.

Then I started to check what was needed to to reach 16-17s turn time at 360-380km/h (seem to be indicated). Reducing weight (as supposed by Cube) to 2400kg resulted 18,4s turn time so something else was also needed.

Some VK-105 engines of the Yak-9 were rated for 1360hp and using this output and increasing the exhaust thrust to 80kp (increasing the top speed to 613km/h at 1000m), turn time dropped to 17,7s at 384km/h so a bit even more was needed.

The Clmax value 1 used by Cube sounded low (despite apparently coming from good source) and the calculations gave rather high speeds for best turn so I increased the Clmax to 1,1. These changes resulted finaly desired 16,9s turn time at 365km/h.

So it seems that 16-17s turn times were possible for the Yak-3 assuming lightly loaded condition and rather high rating of the engine.

Kettenhunde
01-05-2007, 06:09 AM
assumed 85% prop efficiency, e factor 0,8 and 70kp exhaust thrust.

Just a caution note for the readers. It is also very easy to change the outcome to support your favorite game shape.

Be careful making sweeping judgments on absolute aircraft performance from SWAG like this. While it much better than just guessing there are some rather large factors which are not accurately covered just in these properties.

1. Propeller efficiency is not thrust nor is this likely to be an accurate assessment of the propellers actual efficiency. Propellers are tuned for an engine and produce peak efficiency under the conditions they were tuned for on that aircraft. This is referred too as the "climb" or "cruise" propeller in GA.

2. Wing efficiency is extremely easy to manipulate for a given factor no matter what the physical shape. It easy to make a rectangle be just as efficient as an ellipse with no washout for any given portion of the envelope the designer wants.

3. Exhaust thrust changes considerably over the envelope. It's contribution is tied to altitude and velocity.

SWAG's such as this are nice but they hardly replace tested performance data. If they did then there would be no need for flight testing or wind tunnels!

All the best,

Crumpp<div class="ev_tpc_signature">

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Kettenhunde
01-05-2007, 06:26 AM
The Clmax value 1 used by Cube sounded low (despite apparently coming from good source) and the calculations gave rather high speeds for best turn so I increased the Clmax to 1,1.

Thrust can increase lift rather dramatically, Gripen.

http://www.onpoi.net/ah/pics/users/503_1154714942_effectofthrust.jpg

Increasing thrust directly effects the load factor limit an aircraft can sustain and indirectly effects the lift limit on high powered propeller aircraft.

http://www.onpoi.net/ah/pics/users/503_1156852270_emdiagram.jpg

The propeller literally energizes the boundry layer of the wing delaying the onset of the stall:

http://www.onpoi.net/ah/pics/users/503_1156852124_thrustonlift.jpg

Of course this related to velocity as you can tell from Tc.

Here is a comparision of a rectangle to an ellipse with no washout for efficiency:

http://www.onpoi.net/ah/pics/users/503_1156863229_induceddrag.jpg <div class="ev_tpc_signature">

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Wurkeri
01-05-2007, 06:31 AM
Originally posted by Kettenhunde:
Just a caution note for the readers. It is also very easy to change the outcome to support your favourite gameshape.

Well, the parameters and methods of the calculations are open for everyone to check them out, same can't be said about some other data presented in this thread. Anyone can open a spreadsheet and test what effect would different parameters give.

The purpose was simply to the check possible reasons why the claimed prototype and LW results differ so much from the VVS series aircraft results. My results seem to support Cube's conclusions but feel free to present your calculation results if those are much different (show the parameters and methods so anyone can check them out as well).

Wurkeri
01-05-2007, 06:38 AM
Originally posted by Kettenhunde:
Thrust can increase lift rather dramatically, Gripen.


Well, the problem here is that higher Cl values would result much lower speed than claimed 360-380km/h (appear to be indicated) for the best turn so Cube's parameters can't be much off. I choosed 10% increase but the field is open for your calculations.

Kettenhunde
01-05-2007, 06:49 AM
(appear to be indicated)

Do you have data for difference in local air velocity and the freestream velocity?<div class="ev_tpc_signature">

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Kettenhunde
01-05-2007, 06:52 AM
show the parameters and methods so anyone can check them out as well)


That would be a welcome change for you to present your methodology in some of your conclusions in the past.

You could probably tone down your always defensive attitude some as nobody has attacked you as well.

Please point out any mistake in fact of my postings in this thread!

All the best,

Crumpp<div class="ev_tpc_signature">

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Kettenhunde
01-05-2007, 06:54 AM
The purpose was simply to the check possible reasons why the claimed prototype and LW results differ so much from the VVS series aircraft results.


Certainly, Gripen...you made a SWAG which is just fine. I simply pointed out why your conclusion is just a SWAG and not an absolute.

If it was an absolute then we wouldn't need test pilots or wind tunnels!

I would change the CLmax you are using in your calcs to a little higher value. As you can see there is a rather large variation in measured CLmax.

Do you have good 1G level stall speed to get in the ballpark and some engine data at the altitude the test was conducted?

I would be very happy to provide an analysis but lets agree on the conditions of flight first.

It will keep it from being a "he said, she said" affair. Perhaps Kurfurst will be kind enough to provide the details as he knows them on altitude, aircraft conditions, weight, etc..<div class="ev_tpc_signature">

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Of some, parts of this aircraft are the only traces which remain.

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Wurkeri
01-05-2007, 07:01 AM
Originally posted by Kettenhunde:
Do you have data for difference in local air velocity and the freestream velocity?

The quote says "Geräteanzeige" ie appears to be indicated, no other data available.


That would be a welcome change for you to present your methodology in some of your conclusions in the past.

IIRC I have pretty much allways claimed the sources as well as the methods. Same can't be said about some others.

Anyway, in this case everything should be open for everyone so the field is open for your calculations.

Wurkeri
01-05-2007, 07:06 AM
Originally posted by Kettenhunde:
I would be very happy to provide an analysis but lets agree on the conditions of flight first.


Well, all the needed parameters to check out the calculations are given above or in the SimHQ thread.

Kettenhunde
01-05-2007, 07:16 AM
Maybe your methodology is different?

My aeronautics professor insisted we use True Air Speed in ft/sec or the equivilent metric units.

I guess it is fine to directly convert as long as we keep in mind it is one more error in our analysis. It is not exact but close, most likely 10 percent error or less.

For a general SWAG we could use it but I certainly would not draw absolute conclusions from any result.

All the best,

Crumpp<div class="ev_tpc_signature">

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Kettenhunde
01-05-2007, 07:19 AM
Well, all the needed parameters to check out the calculations are given above or in the SimHQ thread.


The same thread that concluded the values could only be from a prototype Yak 3?<div class="ev_tpc_signature">

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Of some, parts of this aircraft are the only traces which remain.

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Wurkeri
01-05-2007, 07:21 AM
Originally posted by Kettenhunde:
Maybe your methodology is different?


I have no idea what you are trying to argue?

The methods are presented by Cube and similar approach can be found from several sources like Perkins&Hage and many others.

PikeBishop
01-05-2007, 07:59 AM
Dear all,
I must admit I quite enjoy reading discussions of this type and manner because every time I come to the conclusion that as WWII progressed the new designs appearing from each nation slowly utilized all the small advantages until there came a point when most front line aircraft had similar weights and dimensions and even power/weight ratio's, because all the wind tunnel experiments that went on in each country pointed to similar conclusions to a greater or lesser extent. Of course as soon as the jet engine appeared then it was a whole new ballgame. Early on
all combatants in WWII strived to build the 'perfect' machine with the best characteristics but with emphasis on a different aspect of combat, such as the American view of good speed and heavy load carrying ability compared to the Japanese view of good manoeuvering ability.
But in the end everything moved in a similar direction with very little to choose between types.
Best regards,
SLP

WWMaxGunz
01-05-2007, 10:18 AM
That might fit with pilot quotes that said the top planes were all pretty close in speed.

Xiolablu3
01-05-2007, 11:21 AM
Originally posted by Wurkeri:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kettenhunde:
Maybe your methodology is different?


I have no idea what you are trying to argue?

The methods are presented by Cube and similar approach can be found from several sources like Perkins&Hage and many others. </div></BLOCKQUOTE>


I dont think hes trying to argue Wurkeri, just to discuss.


Please carry on, this is interesting for people who didnt know this stuff.<div class="ev_tpc_signature">

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msalama
01-05-2007, 11:27 AM
Please carry on, this is interesting for people who didnt know this stuff.

+1

Following w/ interest too!<div class="ev_tpc_signature">

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

Hippies FTW!

Wurkeri
01-05-2007, 02:04 PM
Originally posted by Xiolablu3:
I dont think hes trying to argue Wurkeri, just to discuss.


These are very basic calculations and Cube did fine work showing the methods from the ground up in the SimHQ thread. So why should I explain the whole thing here again?

Basicly I tested first that my spreadsheet gave similar results as Cube's calculations and VVS test for a production Yak-3. Then I just altered the parameters (weight, output and Cl) to match claimed turn performance because those parameters seem to be the most obivious to cause the difference (there is endless list of other possibilities). There really is nothing special on these; anyone can make similar spreadsheet according to SimHQ thread and test different parameters.

As an example the alternative way to match turn time would had been increasing the Clmax to 1,5 but that would have resulted speed 296km/h (true) for 16,8s at 2600kg so that does not match. Yet another way would have been decreasing the drag and weight but that would have required something like 20% reduction for both etc...

Xiolablu3
01-05-2007, 03:30 PM
Originally posted by msalama:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Please carry on, this is interesting for people who didnt know this stuff.

+1

Following w/ interest too! </div></BLOCKQUOTE>


I am trying, but I dont understand it all. I genenrally pick a bit of it up tho, if I read a lot!<div class="ev_tpc_signature">

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Kettenhunde
01-05-2007, 07:58 PM
I don't see what is so fantastical.

Using a CLmax of 1.5 which I believe given the effects of thrust is perfectly reasonable, I show the turn characteristics of the Yak 3:

Vs1 = 103 mph
o = 71.5 degrees
Nz = 3.15
Gross weight 2984Kg's

Turn time for 360 equals 17.63s or 20.4 deg/sec

Radius = 757 ft

Using Gordan and Khazanov's data on the Yak 3.

Seems pretty doable to me at gross weight.

All the best,

Crumpp<div class="ev_tpc_signature">

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WWMaxGunz
01-05-2007, 08:28 PM
Effect of wash over wings has got to be pretty tricky since angle of the wash will change
with speed of the plane, yes?

Kettenhunde
01-05-2007, 09:10 PM
Effect of wash over wings has got to be pretty tricky since angle of the wash will change
with speed of the plane, yes?

Actually the propeller slipstream path itself is effected by throttle position more than velocity.

As velocity increases however the efficiency of the propeller begins to decrease. That is why it's effect increases inversely with velocity. So the faster your velocity, the less force the slipstrean is able to exert on the aircraft to energize the boundry layer.

Remember too that once the turn is estabilished the relative wind aligns with the motion of the aircraft.

A CLmax of 1.5 is reasonable for a mid velocity Tc.

All the best,

Crumpp<div class="ev_tpc_signature">

Support the White 1 Foundation!

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Of some, parts of this aircraft are the only traces which remain.

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NonWonderDog
01-05-2007, 09:13 PM
Not so much the propeller wash, but the downwash around the wing will change with speed, but that's far more precise than you're realistically going to get without a lot more information. You'd have to be able to compute the circulation distribution all along the wing in order to get the induced angle of attack.

You'd also have to account for the variation of stall angle of attack with Reynolds number and Mach number if you wanted an exact answer, and that's beyond what you can do with pen and paper. Stall angle of attack will increase a little bit with Reynolds number (and thus with speed) by some extremely complex relationship, and will decrease a bit with Mach number by the approximate factor sqrt(1-M^2) as long as the flow is everywhere subsonic.

If you're really dedicated, this tool < http://web.mit.edu/drela/Public/web/avl/ > will do most everything you'd need to get some realistic approximations. I don't have the time to set everything up just to fuel debate here, but there it is. Just trading SWAGs doesn't get us very far, if you want my opinion.


Eh, I should read threads more carefully. That tool won't do anything with propwash. I saw "wash" in Max's response and immediately though downwash and horseshoe vortices.

Kettenhunde
01-05-2007, 09:25 PM
Yep, but that's far more precise than you're realistically going to get without a lot more information.


Hi Nonwonderdog,

Before we get into a silly argument allow me to clarify my statement.

The path of the slipstream is not effected as much by velocity as it throttle position in a constant speed propeller. In a CSP the pitch angle changes with velocity taking larger "bites" out of the air so the path remains fairly constant.

In a fix pitch propeller it will change more dramatically with velocity.

All the best,

Crumpp<div class="ev_tpc_signature">

Support the White 1 Foundation!

The White 1 Foundation was started to facilitate the museum quality conservation, display, study, restoration, and operation of the Focke Wulf FW 190 F8, known by its WWII call sign, White 1. In doing so, we are preserving parts of World history in a living memorial to all people who lost their lives in the war. We are preserving an integral part of great aerial battles which once filled the skies.

Of some, parts of this aircraft are the only traces which remain.

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Kettenhunde
01-05-2007, 09:35 PM
Just trading SWAGs doesn't get us very far, if you want my opinion.


It does not get us far IMHO either. That was my whole point in raising the questions I did with Gripen.

As we have progressed with our restoration of "White 1" I have come to realize that the designers during WWII very much knew what they were doing. Facts are they knew much more about their designs than we do.

Seems rather silly IMHO to come back 60 years later and try to claim they were idiots based on SWAG's with incomplete information. Especially when we try to pass those SWAG's off as absolute judgements.

All the best,

Crumpp<div class="ev_tpc_signature">

Support the White 1 Foundation!

The White 1 Foundation was started to facilitate the museum quality conservation, display, study, restoration, and operation of the Focke Wulf FW 190 F8, known by its WWII call sign, White 1. In doing so, we are preserving parts of World history in a living memorial to all people who lost their lives in the war. We are preserving an integral part of great aerial battles which once filled the skies.

Of some, parts of this aircraft are the only traces which remain.

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Wurkeri
01-06-2007, 01:12 AM
Originally posted by Kettenhunde:
I don't see what is so fantastical.

Using a CLmax of 1.5 which I believe given the effects of thrust is perfectly reasonable, I show the turn characteristics of the Yak 3:

Vs1 = 103 mph
o = 71.5 degrees
Nz = 3.15
Gross weight 2984Kg's

Turn time for 360 equals 17.63s or 20.4 deg/sec

Radius = 757 ft

Using Gordan and Khazanov's data on the Yak 3.

Seems pretty doable to me at gross weight.

Hm... The weight of the production Yak-3 (1944) with the VK-105PF as given by Cube is 2692kg so I wonder which Yak-3 you are talking about?

Could you list the following values at best sustained turn rate to check your calculation:

Prop efficiency
Value of the e
output of the engine (hp/ps, exhaust thrust)
Max speed at 1000m

If I use the weight and the Cl you listed, keeping the other parameters constant, I got 19,5s turn at 298km/h (true), the turn radius being 257m (843ft). Note that I allready calculated above the effect of Clmax 1,5 but as noted, it results speed value well below claimed.

So apparently you are using quite bit different parameters than me and Cube. And due to higher Clmax the speed from your calculations 296km/h (true) is also quite bit below the claimed 360-380km/h (apparently indicated). So I can only conclude your values do not match particularly well.

(edited: input error in the check calculation)

majnos64
01-06-2007, 02:17 AM
Originally posted by Kurfurst__:
Yak3, Yak9? Those were the best turning monoplanes of the war, with rather towards the highish wingloading. The Yak-3 definietely matches the 'small, highly loaded wing' description, being only around 14 m2 big. I can't think of any smaller wings ATM, yet the plane was one of the best sustained turners.


Agreed Yak1,3,7,9 were very good turn planes. But as all russian planes they had wing loading 180kg/m2 according to CAGI(TsAGI in english) which said it is the best wing loading for fighters. And if you look at La-5/7 it has the same wing loading because of this theory. Whereas british/american planes has 200-250 kg/m2 P-47 285kg/m2 P-51 200kg/m2. Germans had around 220-260kg/m2. All said is said is about late war situation.

All I wanted to say is that Russians had the lowest late war wing loading that's why they had best turn rate.

To the factors which do have influence on turn rate that is pretty difficult issue. Wing loading has the biggest influence. But also wing profile(lift/drag ratio), engine power, propeller efficiency, weight distribution and so.<div class="ev_tpc_signature">

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Kettenhunde
01-06-2007, 04:46 AM
VK-105PF


Yak 3 Vk-107A....

My altitude is at 100 feet.......<div class="ev_tpc_signature">

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Wurkeri
01-06-2007, 06:32 AM
Originally posted by Kettenhunde:
Yak 3 Vk-107A....

My altitude is at 100 feet.......

Thanks for the input but the others have been talking about the VK-105 powered Yak-3. Should have been clear if you have actually read Cube's postings in the SimHQ thread as well as mine above. The altitude for the VVS test was 1000m.

JG14_Josf
01-06-2007, 02:00 PM
An aircraft with a small, highly loaded wing may have superior instantaneous turn performance, but poor sustained turn performance, it reacts quickly to control input, but its ability to sustain a tight turn is limited.

Aircraft with low wing loading tend to have superior sustained turn performance.

A lightly loaded wing will tend to have greater mass and inertia and create greater induced drag.

Interesting and logical. The 190/109 is suposed to react faster than the Spit/Hurricane and have superior instantaneous turn performance, but Spit/Hurri are superior in sustained turning.

BUMP^

Does anyone have an accurate number for Maximum turn rate for any WWII fighter plane?

When speaking of ?turn performance? it may be a good idea to distinguish between ?sustained? level flight and all the other possible considerations including ?instantaneous? turn rate.

For example:

A 6 g turn can be ?sustained? so long as the earth doesn?t get in the way, the wings remain functioning, the pilot remains conscious; even when the engine isn?t running, and the pilot?s arms can keep on pulling on the stick.

Combat pilots appear to understand the limitations of level sustained turn performance.

Example:


The MiG pilot fired several rounds, and my wingman broke without telling me. I couldn?t believe what I was seeing. Now the first two MiGs are coming around to cut off my wingman. I checked my fuel gauge and said to myself, "Oh man, this is one thing I don?t need." I came back down, sandwiching the two MiGs between my wingman and myself. I could see the number three and four MiGs trying to cut me off, trying to come in behind me. This fight had started about 23,000 feet; we still had lots of altitude. I told him, "Put your nose down and keep four "G?s" on that thing and we?ll be okay. So he did, he was pulling it around and going down, the MiGs were trying to get on him, and finally I got in position on the number two man, and I hit him. Sparks flew and pieces of his tail came off. He broke off right away, then the leader broke off, and the two of them left. I called my wingman and said, "Okay, you?re clear, roll it out, heading such and such and keep going. Climb to 32,000 feet and you?ll be okay." He did that and got home fine.



Sustained turn performance (http://www.acepilots.com/korea_blesse2.html)

Having a 4 g or 6 g instantaneous turn rate (sustained for as long as things hold together) is OK to see, measure, talk about, utilize, and understand or whatever. Having a fetish for level sustained turn performance is OK too.

Kettenhunde
01-06-2007, 03:43 PM
hanks for the input but the others have been talking about the VK-105 powered Yak-3.


Point begin Gripen you were very quick to "poo poo" the German test without knowing a single thing about the conditions it was conducted.

One of the largest factors is a weight correction. No aircraft will remain at take off weight nor does its weight remain stable. It is constantly burning fuel and losing weight. If the weight the turning times were measured at is not used or the turning time corrected for the test weight then your calcs will not be representative of the aircraft's actual performance in the air.

The actual flight test is much more believable than half baked SWAG's.

Lastly, if you do not know the difference in the in the local air velocity and the free stream velocity of the aircraft then you are guessing. That can be a significant amount of speed either way.


The altitude for the VVS test was 1000m.

Pressure altitude, density altitude, true altitude, indicated altitude, or absolute Altitude?

The differences can be rather large and is the number one reason we read about small planes flying into mountain sides.

All the best,

Crumpp

Wurkeri
01-06-2007, 04:53 PM
Originally posted by Kettenhunde:
Point begin Gripen you were very quick to "poo poo" the German test without knowing a single thing about the conditions it was conducted.


Thanks for the input again. There is no conditions claimed but the plane as well as the claimed performance is known so the rest is just very simple calculations to check out what is needed to reach that performance at certain conditions despite what ever conditions the test was made. Sorry if that makes you unhappy.



One of the largest factors is a weight correction. No aircraft will remain at take off weight nor does it's weight remain stable.


Well, unlike some others, I corrected weight twice, first from 2692kg to 2600kg and then to 2400kg to check out the effect.



The test is much more believable than half baked SWAG's.


I can't follow your argument here; I just calculated what was needed to reach that claimed performance.

BTW claimed value (21s) for the production Yak-3 is supposed to be tested as well.



Lastly, if you do not know the difference in the in the local airvelocity and the freestream velocity of the aircraft then you are guessing. That can be a significant amount of speed either way.


The pitot tube of the Yak-3 seem to be located near wing tip so there should be no large problems with airspeed readings. The speed seem to be given as indicated, if there is error that would make claimed performance even more difficult to reach. 360-380km/h indicated is roughly 380-400km/h true at 1000m.

So infact calculations are probably in the optimistic side because it's unlikely that tests were done close to sea level due to safety reasons.



Pressure altitude, density altitude, true altitude, indicated altitude, or absolute Altitude?


These all can be about the same and small differences can't cause large errors.

Kettenhunde
01-06-2007, 06:12 PM
The pitot tube of the Yak-3 seem to be located near wing tip so there should be no large problems with airspeed readings.


http://forums.ubi.com/images/smilies/35.gif

http://forums.ubi.com/images/smilies/16x16_smiley-sad.gif

The location of the pitot tube tells you much about the difference in the in the local air velocity and the free stream velocity.

Hint, think static port Gripen.....


360-380km/h indicated is roughly 380-400km/h true at 1000m.

Very very very roughly.....without knowing the difference in the in the local air velocity and the free stream velocity. Once again we come to this very very basic issue.


Well, unlike some others, I corrected weight twice, first from 2692kg to 2600kg and then to 2400kg to check out the effect.

In your defensiveness you have completely missed the point. If those who conducted the flight test simply recorded the time without correcting it to the test weight then SWAG's will be very misleading as to what the aircraft actually did in the air.


I can't follow your argument here

Yes I know. It is obvious you are having some trouble. IMHO due to the fact you are not formally trained on aerodynamics and have no practical experience in aircraft.

You understand some things but your lack of understanding in putting the picture together severely hampers your conclusions.


These all can be about the same and small differences can't cause large errors.

I will let the FAA know that. I am sure the average of 17% CFIT deaths would be glad to know too. Companies do not need to spend anymore money developing TAWS either.

I have to conclude you have never in your life converted altitude measurements.

You are a smart guy much smarter than I am!

Good luck with your conclusions.

All the best,

Crumpp<div class="ev_tpc_signature">

Support the White 1 Foundation!

The White 1 Foundation was started to facilitate the museum quality conservation, display, study, restoration, and operation of the Focke Wulf FW 190 F8, known by its WWII call sign, White 1. In doing so, we are preserving parts of World history in a living memorial to all people who lost their lives in the war. We are preserving an integral part of great aerial battles which once filled the skies.

Of some, parts of this aircraft are the only traces which remain.

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Wurkeri
01-06-2007, 06:35 PM
Originally posted by Kettenhunde:
The location of the pitot tube tells you absolutely nothing about the difference in the in the local air velocity and the free stream velocity.

Hint, think static port Gripen.....


Perhaps you should form an argument instead hinting something.



If those who conducted the flight test simply recorded the time without correcting it to the test weight then SWAG's will be very misleading as to what the aircraft actually did in the air.


Well, the results are given as 16-17s at 360-380km/h indicated so only possible correction is IAS/TAS correction. I just calculated what was required for that turning performance, seems that you have some kind of problem with that.


I will let the FAA know that.

I think they allready know that sometimes conditions are quite near standard conditions.

Kettenhunde
01-06-2007, 07:13 PM
Perhaps you should form an argument instead hinting something.


I will be glad to spoon-feed you since you were so helpful to those following the thread earlier.

Position error correction occurs most commonly due to the location of the static port. It is simply very difficult to put a hole in the plane in a location that the local velocity exactly equals the free stream velocity throughout the envelope.

While it is not instrument error it is commonly lumped in with instrument error into one correction chart.

These corrections can vary considerably. Enough to make a "SWAG" based on IAS without a correction chart just a "G". Conclusions reached under such circumstances are far from definative and certainly no basis to refute measured results.

http://www.onpoi.net/ah/pics/users/503_1168135824_calib2.jpg

All the best,

Crumpp<div class="ev_tpc_signature">

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Of some, parts of this aircraft are the only traces which remain.

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Wurkeri
01-06-2007, 10:37 PM
Originally posted by Kettenhunde:
Position error correction occurs most commonly due to the location of the static port. It is simply very difficult to put a hole in the plane in a location that the local velocity exactly equals the free stream velocity throughout the envelope.


Generally the static hole (or infact holes) are integral with the pitot tube. A good and simple presentation can be found from the link below:

http://www.grc.nasa.gov/WWW/K-12/airplane/pitot.html

The beauty of this arrangement is that several static holes balance the error due to airstream. In addition the position error (due to angle of attack) can only decrease pressure difference between the static and total pressure.

In the case of the Yak-3 the pitot tube is located to wing tip so the device should be clear from errors caused by propeller etc. In addition the claimed 360-380km/h indicated speed is certainly well above the sealevel so the true speed is also certainly above that speed; 20km/h is rough but fairly good estimate. Only the Fw 190 proto in your chart shows about 20km/h error at 360-380km/h indicated while the others show around 10km/h or less error. As an example the best turn speed calculated by you (for VK-107 powered Yak-3) was about 300km/h true (at Cl 1,5) so the difference is about 60-80km/h at minimun. Note that your chart is for level flight while the best turn is at AoA corresponding Clmax.

WWMaxGunz
01-06-2007, 11:59 PM
Originally posted by Kettenhunde:
knowing the difference in the in the local air velocity and the free stream velocity.

Perhaps a basic explanation would benefit many like myself. From what I can't dredge up on
the web I can only guess that free stream is air a ways out from the moving object (wing,
fuselage, golfball, whatever) while local is what, air on or close to the object?

I am sure I miss 1+ somethings.....

Kettenhunde
01-07-2007, 05:49 AM
Hi Maxguns,

Typical pitot tube system with the static port highlighted:

http://www.onpoi.net/ah/pics/users/503_1168174496_position_errordiagram.jpg

In airflow around a symetrical object the point where the airflow "splits" is referred too as the stagnation point. Here the pressure is equal to the total freestream pressure. That is why pitot tubes are round and pointed with the hole always being in the middle.

http://www.onpoi.net/ah/pics/users/503_1168171492_stagnationpoint.jpg

Great link that has a good explainiation for compressibility corrections too:

http://www.efunda.com/designstandards/sensors/pitot_tub...tot_tubes_theory.cfm (http://www.efunda.com/designstandards/sensors/pitot_tubes/pitot_tubes_theory.cfm)

Can you screw up a pitot tube location? Certainly but it is actually much harder to do and not the most common reason for position error. Locating it on the leading edge is fine. Many pitot tubes are located on the wing.

The static port is the source of the vast majority of position error. You can locate a static port anywhere on the aircraft. Some airspeed indicators have the static port as part of the pitot tube. The more expensive ones locate it as far away as possible.

It is very difficult to find a location however that the local air velocity always equals the freestream velocity. Not only do you have such things as skin friction interfering with your measurement but many times the plane itself gets in the way.

In a high angle of attack (a) pressure difference caused by other parts of the aircraft will cause the local air velocity to be different from the free stream velocity.

For example, the fuselage side is a common location for the static port in low wing aircraft:

http://www.onpoi.net/ah/pics/users/503_1168173355_winginterference.jpg

So the source of position error in general is the static port.

From Dole/Lewis "Flight Theory and Aerodynamics":

http://www.onpoi.net/ah/pics/users/503_1168174483_position_errortext.jpg

All the best,

Crumpp<div class="ev_tpc_signature">

Support the White 1 Foundation!

The White 1 Foundation was started to facilitate the museum quality conservation, display, study, restoration, and operation of the Focke Wulf FW 190 F8, known by its WWII call sign, White 1. In doing so, we are preserving parts of World history in a living memorial to all people who lost their lives in the war. We are preserving an integral part of great aerial battles which once filled the skies.

Of some, parts of this aircraft are the only traces which remain.

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Kettenhunde
01-07-2007, 07:15 AM
Just to be clear on our definitions:

Freestream velocity is the velocity of our airmass free from interference.

In the continuity equation it is the fluid mass velocity before it goes into the pipe!

http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif

To get airspeed, all we are doing is taking the total air pressure <pitot tube> minus the pressure perpendicular of the outside air perfectly still or static air pressure. The static port is a way to measure the actual drop in pressure according to Bernoulli's equation.

Because we know that pressure perpendicular to a moving fluid will decrease we can solve for the dynamic pressure or q.

q=1/2pV^2

In fact, in a nutshell, an airspeed indicator does nothing more than mechanically solve Bernoulli's equation re-arranged for us.

Make sense?

Wurkeri
01-07-2007, 07:34 AM
Well, the NACA link above shows the basic calculations needed for total and static pressure. The location of the static port was generally in the body of the pitot tube in the case of the WWII fighters; the main reason for this was strong prop wash effects which made fuselage located static ports unreliable. Below is couple googled picture links showing the pitot tubes of the Bf 109 and the Spitfire, the Russian fighters had very similar arrangement:

http://www.netlabor.hu/roncskutatas/modules/myalbum/photo.php?lid=1731

http://cgi.ebay.co.uk/Spitfire-Pitot-tube_W0QQitemZ1200...yZ2983QQcmdZViewItem (http://cgi.ebay.co.uk/Spitfire-Pitot-tube_W0QQitemZ120069481795QQihZ002QQcategoryZ2983Q QcmdZViewItem)

The static ports can be seen in the body the pitot tube and the pictures also show the multiple port arrangement which balances the error caused by airstream.

zugfuhrer
01-07-2007, 07:44 AM
I think that we arnt enough humble to the engineers that constructed machines 50 years ago.
They didnt got computers to do the job for them but they where better educated in the basics of math, mechanich and physics.
Things like airframes and wings where tested more by trial and error than by complex calculations, but they certainly know what they did.

Kettenhunde
01-07-2007, 08:00 AM
I think that we arnt enough humble to the engineers that constructed machines 50 years ago.


I very much agree. In fact many of the very practicalities they worked with on a familiar basis have become unfamiliar in the modern engineer's curriculum.

There just are not very many 2000hp piston engine propellers designs on the engineering drawing boards of today. The very high powered piston aircraft just are not in big demand.

Surprisingly subsonic aerodynamics has not changed much since the 1940's. Most of the advancements have been in the transonic and supersonic realms.

All the best,

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The White 1 Foundation was started to facilitate the museum quality conservation, display, study, restoration, and operation of the Focke Wulf FW 190 F8, known by its WWII call sign, White 1. In doing so, we are preserving parts of World history in a living memorial to all people who lost their lives in the war. We are preserving an integral part of great aerial battles which once filled the skies.

Of some, parts of this aircraft are the only traces which remain.

http://www.white1foundation.org/

Kettenhunde
01-07-2007, 08:02 AM
The static ports can be seen in the body the pitot tube and the pictures also show the multiple port arrangement which balances the error caused by airstream.


That is why they don't include a position error chart in the POH in WWII fighters...

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Support the White 1 Foundation!

The White 1 Foundation was started to facilitate the museum quality conservation, display, study, restoration, and operation of the Focke Wulf FW 190 F8, known by its WWII call sign, White 1. In doing so, we are preserving parts of World history in a living memorial to all people who lost their lives in the war. We are preserving an integral part of great aerial battles which once filled the skies.

Of some, parts of this aircraft are the only traces which remain.

http://www.white1foundation.org/

Wurkeri
01-07-2007, 08:07 AM
Originally posted by Kettenhunde:
That is why they don't include a position error chart in the POH in WWII fighters...


Hm... There is several WWII fighter manuals around showing at least rough position error charts. So if a pilot was interested about it, the information was available in some cases.

But that has pretty much nothing to do with this discussion.

Kettenhunde
01-07-2007, 10:35 AM
There is several WWII fighter manuals around showing at least rough position error chart


Sure, guess sarcasm is lost on you, Gripen.

Those position error can be quite substantial as the chart I posted earlier shows:

http://www.onpoi.net/ah/pics/users/503_1168135824_calib2.jpg

Here are the pictures that are not showing up on the link in my other posting:

http://www.onpoi.net/ah/pics/users/503_1168191167_staticerror.jpg

http://www.onpoi.net/ah/pics/users/503_1168191219_airspeedindicator.jpg

As I stated earlier, any "Scientific Wild Azz Guess" <SWAG> is just "Guess" without the correction chart.<div class="ev_tpc_signature">

Support the White 1 Foundation!

The White 1 Foundation was started to facilitate the museum quality conservation, display, study, restoration, and operation of the Focke Wulf FW 190 F8, known by its WWII call sign, White 1. In doing so, we are preserving parts of World history in a living memorial to all people who lost their lives in the war. We are preserving an integral part of great aerial battles which once filled the skies.

Of some, parts of this aircraft are the only traces which remain.

http://www.white1foundation.org/

Wurkeri
01-07-2007, 02:01 PM
Well, no one denies here the existence of the position error. But it simply can't explain the minimum 60-80km/h difference if some one tries to explain the claimed turn speed values with much higher Cl. Generally position error is much less than 20km/h at the speeds we have been talked about (infact below 10km/h in most cases).

Viper2005_
01-07-2007, 02:26 PM
Chances are that the position error charts relate to straight and level flight. At the higher alpha associated with turning flight, all bets are off!

Wurkeri
01-07-2007, 02:55 PM
Yep, usually position error chart is for level flight. The simple way to estimate the effect of the AoA is read error at lower speed where the AoA is the same as in the turn. But overall I can live with around 10km/h errors, these do not cause large difference in the turn calculation.

In the RAE the stall tests were done using the swivelling pitot head which eliminates the AoA error and the static port was located to the end of 60ft cable to eliminate static pressure error.

Kettenhunde
01-08-2007, 04:43 AM
I forgot about the Turning Fairy.

Your right, as soon as the wings are banked it does become a standard day and all position error disappears.

Interesting on that RAE set up. Do you have more information on that?

All the RAE trailing combs I have seen or have diagrams for are trailing edge combs. Accurate for low angles of attack but once that wing gets in the way all bets are off.

Until the Turning Fairy sprinkles some magic powder that is....

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Support the White 1 Foundation!

The White 1 Foundation was started to facilitate the museum quality conservation, display, study, restoration, and operation of the Focke Wulf FW 190 F8, known by its WWII call sign, White 1. In doing so, we are preserving parts of World history in a living memorial to all people who lost their lives in the war. We are preserving an integral part of great aerial battles which once filled the skies.

Of some, parts of this aircraft are the only traces which remain.

http://www.white1foundation.org/

Wurkeri
01-08-2007, 08:07 AM
In the stall speed measurements even a small error can cause large difference. As an example lets assume 10km/h difference for a stall speed for a plane with 20m2 wing weighing 3000kg. 150km/h stall speed at 1km results Clmax 1,52 and 160km/h results Clmax 1,34. In the case of the sustained turning 10km/h difference causes around 0,5s difference for a plane like Yak-3. Basicly small speed errors do not matter much in the turn calculations.

Information on RAE stall tests can be found from various RAE reports like tests on Brewster Buffalo and Bf 109E.

Trailing edge combs used in the high speed testing have nothing to do with the equipment used for stall testing.