Selected Stall Speeds

[Stoney]

Ok Gents,

Ran some tests to get some stall speeds in-game.  I'm posting these so folks can give me a comparison to what they have from both in-game tests and out-of-game source material.

These speeds are for the aircraft, at the weight listed, in the clean, power-off condition.  Speeds were recorded using the auto-pilot auto level function.  Throttle was retarded slowly to give about a 1 mph IAS deceleration per second, so it was a more precise reading.  As soon as a visible burble or wing-dip was identified, the speed was recorded.  Fuel burn set to zero.

FW-190A5 2XMG151 Fuel State 25% 50% 75% 100% Weight 7962 8167 8375 8584 Vs IAS 100 101 102 102 FW-190A8 2XMG151 Fuel State 25% 50% 75% 100% Weight 8600 8854 9108 9360 Vs IAS 104 105 106 107 FW-190D9 Fuel State 25% 50% 75% 100% Weight 8793 8998 9206 9415 Vs IAS 105 106 107 108 Ta-152H1 Fuel State 25% 50% 75% 100% Weight 10318 10711 11105 11499 Vs IAS 106 107 110 111 If you see any errors outside of a +/- 2% margin of error, let me know.

[thorsim]

can i ask why you are testing the light loads on the As ?

a8 in game does not give a specific variant so that one will be tough to confirm ...

and as data varies what is the source or sources you wish us to use to validate the numbers?

[Stoney]

can i ask why you are testing the light loads on the As ?

a8 in game does not give a specific variant so that one will be tough to confirm ...

and as data varies what is the source or sources you wish us to use to validate the numbers?

I figured if we tested the light armament configurations, we'd have the lightest weight/lowest stall numbers.  As an approximation, the stall speeds for the various weights among all the A models and the D model will be very similar, given the wing area, airfoil, and planform are identical.  So, for example, an A5 at 9100 lbs (if they can get that heavy) should stall at the same speed as the A8 at 9100 lbs.  However, I can set those various configurations up to be thorough, if desired.

If it looks like a legitimate source, its good enough for consideration.  Right now I'm merely looking to see if my numbers are consistent with real world numbers at the same weights, +/- a small margin of error.  This will validate the technique I used to determine the stall speeds.

[thorsim]

i'm not so sure as i am pretty sure both the wing and the fuselage changed in TRW between the types ...

i know the wing was redesigned how much the shape of the airfoil changed i am not positive but somehow they managed according to my source to strengthen and lighten the wing between the a-6 and a-7 and when the heavier engine was added i am pretty sure the rear fuselage was lengthened to re-establish the COG ...

so depending on the detail of the FM the results may not be the same because the actual airframes were to the best of my knowlege different between the A-5 and the A-8

if someone strongly disagrees i will look into my sources and understanding of them but on memory i am pretty sure of what i posted above.

BTW is there a "HUDRECORD" command or some kind of flight data recording command available in the game?  that would make all this testing and graphing much easier. 

+S+

t

[Kweassa]

How did you define "stall" when you tested it out?

IIRC a stall is defined as the point where a plane cannot stay level and maintain altitude at the given speed.

[Stoney]

How did you define "stall" when you tested it out?

IIRC a stall is defined as the point where a plane cannot stay level and maintain altitude at the given speed.

As soon as a visible burble or wing-dip was identified, the speed was recorded.

And, just to expound a bit.  Flying into the stall with the aircraft properly trimmed is difficult.  So, using the auto-level feature keeps the plane perfectly trimmed for the stall.  Luckily, the aircraft tested still had a conspicuous (or what I thought was conspicuous) "burble" or wing dip at the speed I listed.  I went back and hand flew a few to see if it was consistent, and it appeared to be.  While the entire wing may not be "stalled", IMO, tip stall that interferes with maneuvering the aircraft is a "stall".

[FLS]

Minor point. The wingtip should stall later than the root due to washout. You'll see the movement at the tip but the stall is probably occurring at the inner part of the wings.

[Stoney]

Minor point. The wingtip should stall later than the root due to washout. You'll see the movement at the tip but the stall is probably occurring at the inner part of the wings.

Well, maybe if they hadn't designed so much airfoil thickness taper into the wing design.  Almost all of the planes in-game suffer from tip stall before root stall.  That's why they want to roll over on their backs when they stall.  Washout, IMO, is overrated, and in the case of most WWII aircraft that had it, useless.

[thorsim]

And, just to expound a bit.  Flying into the stall with the aircraft properly trimmed is difficult.  So, using the auto-level feature keeps the plane perfectly trimmed for the stall.  Luckily, the aircraft tested still had a conspicuous (or what I thought was conspicuous) "burble" or wing dip at the speed I listed.  I went back and hand flew a few to see if it was consistent, and it appeared to be.  While the entire wing may not be "stalled", IMO, tip stall that interferes with maneuvering the aircraft is a "stall".

FYI i believe that game stall behavior is directly contradicted in the flight tests, which was my original point in another thread.  i.e. why does the 190 behave that way in the game, and how does that effect comparative playability.   

[Stoney]

FYI i believe that game stall behavior is directly contradicted in the flight tests, which was my original point in another thread.  i.e. why does the 190 behave that way in the game, and how does that effect comparative playability.   

How so?  Basically what I'm describing is the wing tip stalling before the root.  This makes the aircraft extremely unstable around the roll axis and usually leads to the plane wanting to flip over on its back.  Are you saying that the actual flight test data states it has benign stall behavior?  Again, we have to discuss exactly what "benign" meant.  How far into the stall did they fly it? 

My flight instructor and I never performed a fully developed power-on stall in my AA-1B because those planes have some very nasty spin habits.  I've never experienced a really bad, poorly coordinated stall in that aircraft because I don't want to.  Most of the stalls I performed were very gentle, right on the edge of the buffet-type stalls.  Given some of the caution expressed in those reports about not pranging the captured aircraft, in order to preserve it for training, I doubt they got as aggressive with it as I did in-game.

[thorsim]

How so?  Basically what I'm describing is the wing tip stalling before the root.  This makes the aircraft extremely unstable around the roll axis and usually leads to the plane wanting to flip over on its back.  Are you saying that the actual flight test data states it has benign stall behavior?  Again, we have to discuss exactly what "benign" meant.  How far into the stall did they fly it?  

My flight instructor and I never performed a fully developed power-on stall in my AA-1B because those planes have some very nasty spin habits.  I've never experienced a really bad, poorly coordinated stall in that aircraft because I don't want to.  Most of the stalls I performed were very gentle, right on the edge of the buffet-type stalls.  Given some of the caution expressed in those reports about not pranging the captured aircraft, in order to preserve it for training, I doubt they got as aggressive with it as I did in-game.

yes if you go through the tests you can find online the power on stall is described as drama free with no tendency to roll off one way or another and a simple recovery ...

for example here is a USAAF d9 flight test posted on these boards recently, see part g ...

http://www.wwiiaircraftperformance.org/fw190/wright-field-fw190d-9.pdf

they all (that i remember) are worded a bit different but they all concur pretty much across the types
(not positive about the 152) with the possible exception of that USN test i took issue with elsewhere.

+S+

t

[Charge]

"i know the wing was redesigned how much the shape of the airfoil changed i am not positive but somehow they managed according to my source to strengthen and lighten the wing between the a-6 and a-7 and when the heavier engine was added i am pretty sure the rear fuselage was lengthened to re-establish the COG ..."

The airfoil did not change. The structure was lightened but I have no information that it would have got stronger, only lighter -maybe it was just a bit overdone in earlier variants? The rear fuselage length was not changed. It was lightly modified structurally e.g. the aux tank access hatch was put in and side access hatch was larger in A8.

When considering the wash-out keep in mind that while the inboard thickness was 15% of the chord the tip thickness was only 9% of the tip chord affecting the maximum allowable AoA quite much. While wash-out of 2 deg brings the AoA tolerance of the tip closer to that of the root they are not the same unless the closeness of fuselage and the greater dynamic pressure of the wing tip even things up.

"As an approximation, the stall speeds for the various weights among all the A models and the D model will be very similar, given the wing area, airfoil, and planform are identical."

I though that for basic lift equation you do not need to know airfoil properties or planform aspect ratios, just wing area, especially if you already have an approximation of the CL of the wing?

-C+

[jdbecks]

How so?  Basically what I'm describing is the wing tip stalling before the root.  This makes the aircraft extremely unstable around the roll axis and usually leads to the plane wanting to flip over on its back.  Are you saying that the actual flight test data states it has benign stall behavior?  Again, we have to discuss exactly what "benign" meant.  How far into the stall did they fly it? 

My flight instructor and I never performed a fully developed power-on stall in my AA-1B because those planes have some very nasty spin habits.  I've never experienced a really bad, poorly coordinated stall in that aircraft because I don't want to.  Most of the stalls I performed were very gentle, right on the edge of the buffet-type stalls.  Given some of the caution expressed in those reports about not pranging the captured aircraft, in order to preserve it for training, I doubt they got as aggressive with it as I did in-game.

Might sound like a silly question, when you fly a real plane, does the plane buffet on the edge of the stall? or is that a visual aid for a simulator?

[hitech]

Might sound like a silly question, when you fly a real plane, does the plane buffet on the edge of the stall? or is that a visual aid for a simulator?

Some do some don't.

Accelerated stalls in P51's gave me no warning what so ever.

Cessna's give a nice little buffet.

Marcheties (spelling) sound like elephants stomping on the wings.

RV gives a nice little tickle. Inverted stalls are very nasty and produce nice 270 degree snaps with out trying. (first inverted push at top of loop, nice way of finding out inverted stall speed very high:) )

HiTech

[Charge]

If the stall is uneven you will feel buffeting as one part of the wing has lost lift and the flow becomes heavily turbulent. A wing that stalls evenly may not warn you at all in higher speeds but it stalls right away, where as in slower speed there is time to notice the slight buffeting when the flow above the wing starts to become turbulent as the airflow replaces the small local lower pressure areas above the wing, also causing rumbling noise and bumpy feel of motion. How radical the stall is depends on the wing thickness and profile. Thicker profiles tolerate more AoA and stall quite slowly above max AoA where as thinner profiles stall at low AoAs and very quickly once max AoA is exceeded, and at what speed that happens depends on profile properties e.g. where the maximum chord thickness is located.

-C+