P-40 turn rate/Flight model check

[-WILD-AlbinoHA5E]

The Two Threads have become confusing. Well, the Videos are about the 30° Turn Claims, and Close to Stall Behaviour. And the Points made there fit the Ingame P-40.

Straight Line Stalls at full fuel for me are at 95mph at full fuel, gentle Drop of a Wing, immediate recovery just by centering controls. She can be gotten down to 92mph and still be controlled by Rudder.

 

The Speeds don't change with Neutral Altitude.

Edited November 27, 2016 by CuteKitten94

[Crump]

 

 

Straight Line Stalls at full fuel for me are at 95mph at full fuel, gentle Drop of a Wing, immediate recovery just by centering controls.

 

That is ~14% pessimistic and very close to the results I am getting. 

[ICDP]

I have done a number of tests with P40 in game.

 

Stall in clean condition: 92-95mph IAS (cockpit gauge)

Stall with gear and flaps down: 80-85mph

 

The hardest part is keeping it flying reasonably level before the departure.  After a bit of practice it is possible to maintain altitude before the stall.

 

I think the stall speeds of the P40 are close to real specs.  The issue I have is with the engine cooling.

[Crump]

 

 

I think the stall speeds of the P40 are close to real specs. 

 

What data are you looking at?  I am referencing the POH and several P-40E flight test's. 

[ICDP]

What data are you looking at?  I am referencing the POH and several P-40E flight test's. 

 

- The P40N (lighter than P-40E) training manual states.

 

Stalling speed for P-40 is 84 mph with wheels and flaps down and about 90 with wheels and flaps up.  (These speed vary slightly among individual airplanes.)

 

- America's Hundred Thousand gives the same numbers

 

- I have seen an RAF Kittyhawk I (P-40E) report stating 83 mph clean and 79 mph in landing configuration but this report does not clarify if this was power on or not.  For reference, P-40D E pilots manual states power on stall of 85 mph IAS with flaps and gear up and 75 mph with flaps and gear down.  So I suspect the RAF report is showing power on stall results.

 

Unless there is more accurate that contradicts this?  I assume from my research that the power off stall speed of the P-40E was ~90 mph clean and ~80 mph flaps and gear down.

 

My original tests were done at 75% fuel and full ammo on the Moscow Autumn map.  With 25% fuel and no ammo (assume returning from mission) I can get stall speeds of ~87 clean and 75-78 mph gear and flaps down.

Edited November 27, 2016 by ICDP

[ACG_KaiLae]

I'm going to go with numbers for the N mean nothing for the E. The next question is based on the testing so far, what's the next step?

[Farky]

- The P40N (lighter than P-40E) training manual states.

 

Stalling speed for P-40 is 84 mph with wheels and flaps down and about 90 with wheels and flaps up.  (These speed vary slightly among individual airplanes.)

 

This cited training manual is not specifically about P-40N, but P-40s in general. Pilot's flight operating instructions for P-40N (AN 01-25CN-1) states approximate stalling speeds for normal operational load (8260 lb.) -

 

Landing gear up - flaps up .........................88 mph

Landing gear down - flaps up .....................90 mph

Landing gear up - flaps down .....................78 mph

Landing gear down - flaps down .................79 mph

 

 

- I have seen an RAF Kittyhawk I (P-40E) report stating 83 mph clean and 79 mph in landing configuration but this report does not clarify if this was power on or not.  For reference, P-40D E pilots manual states power on stall of 85 mph IAS with flaps and gear up and 75 mph with flaps and gear down.  So I suspect the RAF report is showing power on stall results.

 

Undoubtedly power on stall speeds in this test. Unfortunately this is test of airplane with experimental propeller (slightly worse than the standard propeller).

 

 

Unless there is more accurate that contradicts this?  I assume from my research that the power off stall speed of the P-40E was ~90 mph clean and ~80 mph flaps and gear down.

 

 

I agree, 100%. A&AEE (RAF) Kittyhawk I report states Stalling speeds (at load 8480 lb.) -

 

Flaps and undercarriage UP - 90 m.p.h. A.S.I.

Flaps and undercarriage DOWN - 80 m.p.h. A.S.I.

 

RAF Pilot's notes for Kittyhawk I states -

 

Undercarriage up and flaps up - 92 I.A.S.

Undercarriage down, flaps up  - 94 I.A.S.

Undercarriage up, flaps down  - 80 I.A.S.

Undercarriage down, flaps down - 82 I.A.S.

 

NOTE - The above stalling speeds are subject to plus or minus 2 m.p.h. , depending on load.

 

See pictures of cited documents here - http://forum.il2sturmovik.com/topic/25323-p-40-turn-rate/?p=413707

[ICDP]

I'm going to go with numbers for the N mean nothing for the E. The next question is based on the testing so far, what's the next step?

 

They do mean something, they show the stall speeds for a later (and lighter) model of the P-40 with same wings and slightly longer fuselage than E model.  Regardless the P-40E manual gives power on stall of 85 mph IAS with flaps and gear up and 75 mph with flaps and gear down.  So the power off stall speeds will be marginally higher.  There is enough official reports and evidence showing the P-40E stalls speeds were:

 

~90 mph clean

~80 mph in landing configuration

 

I get close enough to those numbers in game.  So any issues with turn rate on P-40E are not likely to be stall speed.  The devs need proper info to be able to fix the turn-rate (if it's wrong) and spending time investigating stall speeds will not help.

 

So in answer to your question, "what is the next step?".  I would suggest looking at something other than stall speeds.

[ACG_KaiLae]

Numbers I got are from testing are roughly 155-153 KPH, which is 96-95 MPH. That's still a 6% difference over what you're listing. 

 

I'll change the OP title if I can, as I'm interested in basically checking the P-40 FM overall. Turning times - because multiple pilot reports say that you could outturn 109's horizontally and that was a preferred tactic if you could get the german to cooperate (which would be dumb for him, but still). High speed maneuverability, which was also noted to be good, seems underwhelming as well. The last sore thumb is engine power, which is just flat wrong in game and needs to be corrected, but one check at a time.

 

The RAF thought that the P-40 was a better plane than the hurricane and tried to replace as many of them as they could. Right now, I don't see how that conclusion could be made on a plane that is outturned by any of the one engine aircraft in game, can't climb, and isn't faster than the german planes. The only thing you can do is dive, and if you don't kill the enemy on that pass you will likely not survive. While some of those characteristics I've listed are noted historically as deficiencies, and the aircraft was never a world beater, it doesn't make sense to build as many as they did if it was so badly outclassed by everything.

 

Basically my BS meter is indicating. 

[II./JG77_Manu*]

Turning times - because multiple pilot reports say that you could outturn 109's horizontally and that was a preferred tactic if you could get the german to cooperate (which would be dumb for him, but still). High speed maneuverability, which was also noted to be good, seems underwhelming as well.

 

Can confirm this from "the other side", German reports say the same.  

 

Something just doesn't feel right with this aircraft. It feels like a barn door is nailed on the roof. Despite the big wings so unstable and draggy feeling..i know it has a big cowling, but still. Feels overdone. I hope there are some experts to get to the bottom of things - in technical terms - , like it happend for the 190.

Edited November 28, 2016 by II./JG77_Manu*

[-WILD-AlbinoHA5E]

Can confirm this from "the other side", German reports say the same.  

 

Something just doesn't feel right with this aircraft. It feels like a barn door is nailed on the roof. Despite the big wings so unstable and draggy feeling..i know it has a big cowling, but still. Feels overdone. I hope there are some experts to get to the bottom of things - in technical terms - , like it happend for the 190.

Big Wing = more Leverage =/= Stability;

Long Wing Span = Increase in Adverse Yaw = "Instability";

 

"Stability" requires a long tail and large Surfaces and a Far Forward Center of Gravity. A Fully fuelled P-40 has only one of these ingredients.

It requires "Happy Feet" but after some time with it it really isn't so troublesome anymore.

 

However, it does feel as if it produces too little lift at high AoAs, while creating the appopiate Drag at these AoAs, so most of the time when flying at low speeds it creates too much drag.

I think increasing the Lift over AoA curve towards Lift will improve it by a lot.#

 

 

Adverse Yaw doesn't effect Motorpilots that much since the engine normally already has a stabilizing effect and the Flow around the rudder does keep the Aircraft Stable as well, however in a Glider the long wings exaggerate that effect and you have to put in a lot of Rudder in order to roll without Spinning.

In Fact only using Ailerons to turn will reliably end you in a stall/spin in many classic and aerobatic types, like the K-13 or Habicht 13m or even a modern LS4. You have to use Rudder to live.

 

And the same is true for Aerobatics in the P-40. It has the largest Fighter Wings ingame (not counting Bf110) and thus a lot of adverse yaw while the tail is too short to reliably stabilize it if only ailerons are used. The Fw190 also suffers from this due to it's tail Layout.

And there are no really "Stable" Fighters, because "stability" often combines with stiff Controls at high Speeds.

 

 

 

PS: try the Sopwith Strutter or Pup and just waggle your Ailerons at a frequency of 0.5 complete movements per second. You will find yourself in a Spin rather quickly, only due to Adverse Yaw.

The Gotha is another cool/extreme example that can be controlled on the Ground only using Adverse Yaw, and will spin as soon as you use any amount of Ailerons without Rudder input.

 

That little Piece of String is the most important instrument in a Glider, since it tells you wether you are flying clean or slipping.

Edited November 28, 2016 by CuteKitten94

[ICDP]

Guys according to America's Hundred Thousand, the P-40E had the worst acceleration of any USAAC early war fighter.  Add to this it had the worst climb rate of all early war USAAC fighters, a top speed some 40-50 mph slower than Bf-109F4 and Fw-190A3.  In 1942 the P-40E was woefully outclassed, so you begin to understand why it was seen as unsuitable for ETO.

 

While I agree it should out-turn Bf-109 at slow speeds and it doesn't, so yes something is wrong.  It does already out-urn the Fw-190 and Bf-110 at slow speeds.  So it's not a major improvement required.  In real life The P-40E was not a match or better than a contemporary 109F, or 190A apart from dive and slow speed horizontal turn.  If we get a minor improvement in slow speed horizontal turn rate it will give it a more realistic comparison to its contemporaries.

 

Kai_Lae, what fuel and ammo load are you using for your stall tests?  For example 100% fuel and ammo is unrealistic.

[II./JG77_Manu*]

 

 

However, it does feel as if it produces too little lift at high AoAs, while creating the appopiate Drag at these AoAs, so most of the time when flying at low speeds it creates too much drag.

 

That's more or less what i meant. With unstable i meant that it starts waggling it's wings at very low stick movement, and that's not what i read about this aircraft. 

[-WILD-AlbinoHA5E]

That's more or less what i meant. With unstable i meant that it starts waggling it's wings at very low stick movement, and that's not what i read about this aircraft. 

It would have no effect on stability. You have to coordinate your Stick Movements with appropiate Rudder. The Prop Vortex also changes  with differing AoAs.

 

The only reason I can think of is the lacking Lift at high AoAs leading to the wings Shadowing the Rudder, thus creating instability around the vertical axis.

I think in the end adjusting the Lift/AoA Curve for more Lift will aleviate many of the Problems.

[ACG_KaiLae]

Guys according to America's Hundred Thousand, the P-40E had the worst acceleration of any USAAC early war fighter.  Add to this it had the worst climb rate of all early war USAAC fighters, a top speed some 40-50 mph slower than Bf-109F4 and Fw-190A3.  In 1942 the P-40E was woefully outclassed, so you begin to understand why it was seen as unsuitable for ETO.

 

While I agree it should out-turn Bf-109 at slow speeds and it doesn't, so yes something is wrong.  It does already out-urn the Fw-190 and Bf-110 at slow speeds.  So it's not a major improvement required.  In real life The P-40E was not a match or better than a contemporary 109F, or 190A apart from dive and slow speed horizontal turn.  If we get a minor improvement in slow speed horizontal turn rate it will give it a more realistic comparison to its contemporaries.

 

Kai_Lae, what fuel and ammo load are you using for your stall tests?  For example 100% fuel and ammo is unrealistic.

 

Both at 100% as directed for testing. Also, I'm not sure about outturning a 110, as in my experience, the 110 outturns the P-40. If the assumption is that the information that 1CG has listed in dev diary 123 is correct with regards to flight performance, this is also borne out by what it says about turning times of both planes:

 

P-40:

Maximum performance turn at sea level: 24.3 s, at 270 km/h IAS.

Maximum performance turn at 3000 m: 36.1 s, at 270 km/h IAS.

 

Bf-110:

Maximum performance turn at sea level: 27.4 s, at 270 km/h IAS.

Maximum performance turn at 3000 m: 35.4 s, at 270 km/h IAS.

 

Unless this information is incorrect (and so far, there's no reason to think so), the turn performance of the 110 is slightly worse at sea level, but BETTER than the P-40 at 3000m. The P-40 turns roughly about as well as the twin engined 110. This is another reason that I strongly suspect an error, in that it makes no sense that an airplane that anecdotally was a good turner is outturned in game by a twin engine plane not noted at all for being very maneuverable.    

 

However, anecdotes are worthless. Data matters. Unless there's some way to define the error that's causing the situation with a high degree of confidence, there's no way to fix the issue. So, again, what's the best way to move forward? 

Edited November 28, 2016 by Kai_Lae

[ICDP]

The Bf-110 was regarded to have good maneuverability for its size.  But it shouldn't out-turn a P-40E and I do acknowledge there (seems) to be an issue with the BoM P-40E, I just don't believe it's due to stall speed.

 

As CuteKitten suggests, it may be lift/drag related.

 

According to America's Hundred Thousand we have the following level flight acceleration data for the P-40E.  Starting at 250 mph, Sea Level and applying military power.

 

P-40E

Mil HP: 1150

Weight Lb: 8700

Thrust Lb: 1380

Drag Lb: 1049

Accel FT/SEC/SEC 1.23

 

For comparison a similar engined P-39D returned 2.13

Edited November 28, 2016 by ICDP

[unreasonable]

 

I get close enough to those numbers in game.  So any issues with turn rate on P-40E are not likely to be stall speed.  The devs need proper info to be able to fix the turn-rate (if it's wrong) and spending time investigating stall speeds will not help.

 

 

 

The stall speed and the CLmax are connected - get one wrong and the other will be too. If the CLmax is wrong, so will be the maximum AoA.  So if you get the stall speed wrong, you necessarily get the turn wrong too. (Correct me if I am wrong on this last point, it seems intuitive, but who knows....)

 

Not only that, but because the relationship requires the stall speed to be squared in calculating CLmax, the error in the CL max will be magnified.

 

Having said that we do not know what the FM uses as an input and what is a calculated output.

 

In-game stall speeds are 153-176 kph  (95 - 109mph) IAS  (F+G up) over the range of weights they use, (see DD 123) compared to the two estimates of 90 and 92 given in Farky's post.

 

I take the minimum stall speed in DD 123  153 kph as being at the minimum weight: 3264 kg, > CLmax of 1.32

At maximum stall speed - 176 kph I assume "maximum takeoff weight"  4414 kg. > CLmax 1.35

Somewhere in the middle, "standard weight"  3819kg, speed (153+176)/2 = 165kph > CLmax  1.34

 

Some rounding error in here probably but pretty consistent.

 

All cases wing area 21.9m^2 and standard conditions with no correction for IAS-TAS. This might throw the CLmax result off about 0.02 for each kph or adjustment, but it will be almost the same error in each case, so for comparison purposes this is not too important.

 

By comparison Farky's report gives 90 mph at 8480 lbs > CLmax of 1.73!  Are you sure the weight is correct? (Also I am unfamiliar with A.S.I - I assume this is equivalent to CAS?)

 

 

So there really does seem to be a significant difference in the game stall speeds and the reports posted, and it could cause - or be caused by - a difference in the CLmax, CriticalAoA and turn performance.

 

Disclaimer: I have no opinion on what the right answer is! 

Edited November 29, 2016 by unreasonable

[ICDP]

The numbers the devs published in DD 123 cannot be taken at face value without in game tests.  Testing over various weights I get from 87 mph to 95 mph clean stall speeds.  This is over a range of weights from 25% fuel and no ammo, to 100% fuel and full ammo.  Bear in mind the 100% fuel tests are not realistic because it takes time and fuel for a plane to climb to test altitudes.

 

I agree the P-40E in real wartime conditions should generally out-turn a Bf-109 at slow speeds and there seems to be an opinion that in game it doesn't.  I have never tested online to be sure.  The problem is nobody flies in combat at zero throttle, so rather than power off stall speeds the issue must lie somewhere else IMHO.

 

I will do some sustained turn time tests in both aircraft to get an idea.

Edited November 29, 2016 by ICDP

[unreasonable]

The numbers the devs published in DD 123 cannot be taken at face value without in game tests. 

 

 

The numbers from the DD are taken from in game tests - but using their robot pilot to reduce human error, IIRC, so they are definitive.

 

Han said (DD 123) "Characteristics presented below were measured in the game, which took almost two weeks of hard work. In the end we've got informative and standardized data for all planes in the game we'd like to present you below:"

 

Perhaps their robot is giving them exactly level flight upto the stall, while your tests that show slightly lower figures are not? You would only have to be descending a fraction to account for the difference. Come to think of it, the same could be true of RL tests.

Edited November 29, 2016 by unreasonable

[JG13_opcode]

Where did you read about this robot pilot?

[unreasonable]

Where did you read about this robot pilot?

 

I am sure Han discusses it somewhere in relation to in-game tests, I will see if I can find the reference. (Do not think I was just dreaming, but who knows....) Wait, out.

 

Found it: post 259 of the DD123 discussion thread, back in the "good old days" when Han laid into everyone

 

I was not my test - we using robots to control aircraft to have realy clear tests in game. Even little shaking or 0.5% of throttle may cause deviations.

Edited November 29, 2016 by unreasonable

[Farky]

By comparison Farky's report gives 90 mph at 8480 lbs > CLmax of 1.73!  Are you sure the weight is correct? (Also I am unfamiliar with A.S.I - I assume this is equivalent to CAS?)

 

 

Yes, I am sure the weight is correct. A.S.I. equals IAS, it is just other form of writing IAS used in some WWII reports.

 

Weight of P-40E -

8480 lbs was actually standard weight of P-40D (8475 lbs  8485 lbs to be exact), since aircraft used for stall tests in RAF report was D model with 4 MGs.

Standard full weight (100% internal fuel + full ammo - 1686 rounds) of P-40E was 8500 lbs.

This data are from RAF reports and are in complete agreement with other primary sources such as Soviet pilot's manual for P-40E .

 

Note: do not use RAAF report on A29-129 for weight data. There is a 122 lbs. error in tare weight for some reason.

 

Now, what we have in game and with what weight is P-40E tested here?

Standard "full" weight of P-40E in game is 3819 kg - 8419 lbs. This is not wrong, since is it 100% of fuel, but only 1410 rounds of .50 cal ammo.

P-40E in game supposed to be tested with extra ammo (1686 rounds total), because this loadout get you to 3857 kg - 8503 lbs.

Btw, these numbers match exactly with the Soviet manual for P-40E.

 

EDIT : 8475 lbs changed to 8485 lbs.

Edited November 29, 2016 by Farky

[ICDP]

Yes, I am sure the weight is correct. A.S.I. equals IAS, it is just other form of writing IAS used in some WWII reports.

 

Weight of P-40E -

8480 lbs was actually standard weight of P-40D (8475 lbs to be exact), since aircraft used for stall tests in RAF report was D model with 4 MGs.

Standard full weight (100% internal fuel + full ammo - 1686 rounds) of P-40E was 8500 lbs.

This data are from RAF reports and are in complete agreement with other primary sources such as Soviet pilot's manual for P-40E .

 

Note: do not use RAAF report on A29-129 for weight data. There is a 122 lbs. error in tare weight for some reason.

 

Now, what we have in game and with what weight is P-40E tested here?

Standard "full" weight of P-40E in game is 3819 kg - 8419 lbs. This is not wrong, since is it 100% of fuel, but only 1410 rounds of .50 cal ammo.

P-40E in game supposed to be tested with extra ammo (1686 rounds total), because this loadout get you to 3857 kg - 8503 lbs.

Btw, these numbers match exactly with the Soviet manual for P-40E.

 

 

 

If the RAF tests were with D model with 4 wing guns then should we test with 2x wing guns removed?

Edited November 29, 2016 by ICDP

[Dakpilot]

If tests were IRL were conducted with full fuel, what would be reasonable fuel burn to simulate Start/Taxi and flight to area to begin test?

 

Cheers Dakpilot

[ICDP]

I would estimate around 20% giving time to climb and any distance to test area.  After all they would not just take off and climb to a few thousand fee over the airfield to begin tests.

 

Or take off from the ramp in a fully loaded P-40E (with 4x wing guns to match RAF test aircraft P-40D) and climb to 10,000 - 15,000 feet.  I doubt stall tests would be done any lower than this for obvious reasons.

Edited November 29, 2016 by ICDP

[Farky]

If the RAF tests were with D model with 4 wing guns then should we test with 2x wing guns removed?

 

We can if we want, 4 MG version with extra ammo (2460 rounds total) in game actually is P-40D, not P-40E. Tiny little problem, with this loadout (100% fuel, 2 MGs removed, extra ammo) our weight will be 3870 kg ( 8532 lbs.), 52 lbs. more than weight in report (8480 lbs.). But we can get rid of this excess fat with "fuel diet" - if we use only 94% of fuel, we are very close to weight in RAF report. But I don't know if there will be any measurable difference between 6 gun and 4 gun version (with the same weight), most probably not.

 

 

If tests were IRL were conducted with full fuel, what would be reasonable fuel burn to simulate Start/Taxi and flight to area to begin test?

 

Cheers Dakpilot

 

Good question. Report do not say anything about that and I don't know.

 

All of the fuel weighs some 403 kg (888 lbs), if the game follows Soviet pilot's manual (and I believe it does). So even after consumption of let's say 20% of fuel, stall speed should not change dramatically.

[ACG_KaiLae]

Thanks for the help guys. My background is electronics and robotics and I just don't have the knowledge to get things done here. 

[Crump]

Do not account for fuel. The weight is corrected to take off weight so use 100% internal fuel.

 

Stall speeds are always power off unless specifically noted otherwise.

[ACG_KaiLae]

Do the stall tests need to be redone again using 4 MGs and extra ammo? Just trying to figure out what the next step is.

[Crump]

We can if we want, 4 MG version with extra ammo (2460 rounds total) in game actually is P-40D, not P-40E.

 

The data I have is for a 6 gun P-40E. 

 

 

I agree the P-40E in real wartime conditions should generally out-turn a Bf-109 at slow speeds

 

The P-40E has a commanding low speed turn rate advantage over the Bf-109F4(below 130KEAS) in terms of relative performance.  

 

 

For example 100% fuel and ammo is unrealistic.

 

That is what the data is corrected for and what you should use in testing. 

 

 

This cited training manual is not specifically about P-40N, but P-40s in general. Pilot's flight operating instructions for P-40N (AN 01-25CN-1) states approximate stalling speeds for normal operational load (8260 lb.) -   Landing gear up - flaps up .........................88 mph Landing gear down - flaps up .....................90 mph Landing gear up - flaps down .....................78 mph Landing gear down - flaps down .................79 mph

 

These can give us an idea for the P-40E but require proper airspeed conversion as well as weight conversion. 

 

 

For reference, P-40D E pilots manual states power on stall of 85 mph IAS with flaps and gear up and 75 mph with flaps and gear down.  So I suspect the RAF report is showing power on stall results.

 

I see that.

 

That represents a heavier aircraft and slower airspeed than the data I am using which is not labeled power on.

 

(-2.5 mph PEC)

 

The speeds I used appear to be power off and fit well with the other data I have seen on the type.

Edited December 2, 2016 by Crump

[Farky]

 

Do the stall tests need to be redone again using 4 MGs and extra ammo? Just trying to figure out what the next step is.

 

I don't think so. Honestly, if stall speed is really off, you should notice that immediately regardless of weight (with 100% fuel) or the number of guns. But always remember, even in real aiplanes there was some deviation from "book numbers".

 

 

The data I have is for a 6 gun P-40E.

 

I wonder what data you use, what is your source?

 

Data should be the same because take off weight of P-40D and P-40E (100% fuel, full ammo) was same (plus minus some 20 lbs.).

 

 

For example 100% fuel and ammo is unrealistic.

 

That is what the data is corrected for and what you should use in testing.

 

RAF report does not explicitly say "data were corrected for this weight", but you are most probably right. Anyway, in case of testing 4 MG version with extra ammo, correction need to be made via use of 94 % of fuel. Well, to be honest, difference is negligible - results do not change if we use 94% or 100% of fuel.

 

 

 

This cited training manual is not specifically about P-40N, but P-40s in general. Pilot's flight operating instructions for P-40N (AN 01-25CN-1) states approximate stalling speeds for normal operational load (8260 lb.) -   Landing gear up - flaps up .........................88 mph Landing gear down - flaps up .....................90 mph Landing gear up - flaps down .....................78 mph Landing gear down - flaps down .................79 mph

 

These can give us an idea for the P-40E but require proper airspeed conversion as well as weight conversion.

 

Of course. It was reaction on something else, we don't need data for P-40N at all since we got data for P-40E/D.

 

 

For reference, P-40D E pilots manual states power on stall of 85 mph IAS with flaps and gear up and 75 mph with flaps and gear down.  So I suspect the RAF report is showing power on stall results.

 

I see that.

 

That represents a heavier aircraft and slower airspeed than the data I am using which is not labeled power on.

 

(-2.5 mph PEC)

 

The speeds I used appear to be power off and fit well with the other data I have seen on the type.

 

Hmm, now I am really curious about data you used.

 

Btw, all data for stall speeds I posted are not corrected for position error. Which is ok, because we don't read CAS in the game neither.

 

[Crump]

 

 

Btw, all data for stall speeds I posted are not corrected for position error. Which is ok, because we don't read CAS in the game neither.

 

Using IAS can introduce huge errors when comparing relative performance.  Properly converted and used it is good for a quick look and putting things in a perspective that is useful to the pilot.  

 

It is not good for comparing designs based on their IAS.

It is simply impossible to correctly compare aircraft performance based upon their perspective Indicated Airspeeds.

 

 

Of course. It was reaction on something else, we don't need data for P-40N at all since we got data for P-40E/D.

 

It can be used as the wing design is the same but it must be properly converted.  At its face value, it is useless. 

[Crump]

RAF report does not explicitly say "data were corrected for this weight", but you are most probably right.

 

FWIW....

 

Listing the weight on the flight test is standard convention that makes it useful to the engineer.  That is the weight all the performance is mathematically corrected too.   The stall speeds in the POH will be at clean configuration take off weight for a representative aircraft as found in the Weight and Balance data listed in the operating instructions.

 

If it deviates from the convention, it will be specifically noted in the report.  It is like a standard atmosphere.  All performance is under standard conditions unless otherwise specifically noted otherwise.  Same thing with lift polars, the standard is polars are done at the representative Re number unless otherwise noted.  That is why we had the issue with the Chalais-Meudon polar as it was under other circumstances than a representative Re. 

[Farky]

Using IAS can introduce huge errors when comparing relative performance.  Properly converted and used it is good for a quick look and putting things in a perspective that is useful to the pilot.  

 

It is not good for comparing designs based on their IAS.

It is simply impossible to correctly compare aircraft performance based upon their perspective Indicated Airspeeds.

 

Data in reports and manuals for P-40E are in IAS, so you must use IAS for stall speed tests. First you have to find out if the stall speed in game matches the stall speed in the manuals and reports. If you find out that everything is "by the books", you can compare stall speed of P-40E with stall speed of other airplanes and you need CAS for this of course. But I do not know why it is necessary to compare P-40E with other airplanes - if data from game matches with data in documents, than everything is as it should be and issue is something else (too low stall speed of Bf 109 for example).

[Crump]

 

 

Data in reports and manuals for P-40E are in IAS, so you must use IAS for stall speed tests.

 

The PILOT must use IAS....

 

Remember, that is simply a reference for him to gauge the relative ratio of dynamic pressure to static pressure.

 

Airplanes are the only vehicles in existence with speed and altitude indicators that do not tell you anything specifically about how fast or high you are actually going.  

 

If you do not properly account for that in determining relative performance then you will have an erroneous aircraft performance picture. 

 

 

 

But I do not know why it is necessary to compare P-40E with other airplanes - if data from game matches with data in documents, than everything is as it should be and issue is something else (too low stall speed of Bf 109 for example).

 

Because the relative performance is the most important performance in the game.  For example, if you just use IAS to determine stall speed performance between an FW-190A3 and a Spitfire Mk V you will introduce ~20% error in their relative performance.  That is a huge error and greatly effects the type of fight the FM's are capable of doing.

 

The holy grail in the P-40E stall and turning performance would be to find the manufacturers measured CLmax.  Then we could eliminate all airspeed/weight measurement errors. 

[JG13_opcode]

For example, if you just use IAS to determine stall speed performance between an FW-190A3 and a Spitfire Mk V you will introduce ~20% error in their relative performance.

Due to CEC? (or lack thereof?)

 

That'd only be the case in a simulator if the game models each pitot-static installation individually, otherwise the compressibility error (if even present in game) would be the same for each aircraft and you'd still get the proper relative lineup. I strongly doubt that this sim is that sophisticated.

Edited December 2, 2016 by JG13_opcode

[Crump]

Due to CEC? (or lack thereof?)

 

That'd only be the case in a simulator if the game models each pitot-static installation individually, otherwise the compressibility error (if even present in game) would be the same for each aircraft and you'd still get the proper relative lineup. I strongly doubt that this sim is that sophisticated.

 

 

Lack of a Position Error Correction...

[JG13_opcode]

Okay, same deal then.

 

It'd sure seem logical to me, from an efficiency standpoint, for a 60$ consumer grade sim to model all the pitot systems as the same.

 

Perhaps developers can confirm.

Edited December 2, 2016 by JG13_opcode

[Crump]

Okay, same deal then.

 

It'd sure seem logical to me, from an efficiency standpoint, for a 60$ consumer grade sim to model all the pitot systems as the same.

 

Perhaps developers can confirm.

 

 

That is why IL2:1946 thru the original used EAS....

I do not think it would not be that hard to do the FM in EAS and write a script for each aircraft airspeed indicator to show the IAS.  

Compressibility is a universal correction and that same EAS would be the mathematical basis for determining the correction.  

if it does not do that JG_13 Opcode...is not going to be a very good air combat simulator at all.  I would be surprised if the devs did not account for PEC and CEC in the FM.  The biggest problems is the fact many WWII designers do not account for CEC and the PEC is subject to wide errors of mass manufacture.

 

Having the designers CLmax would eliminate all of that error.

[JG13_opcode]

That is why IL2:1946 thru the original used EAS....

TIL

 

I do not think it would not be that hard to do the FM in EAS and write a script for each aircraft airspeed indicator to show the IAS.   Compressibility is a universal correction and that same EAS would be the mathematical basis for determining the correction.

Yes, exactly. That is why I'd wager that you can, in fact, compare indicated speeds in-game because to model each ASI differently would be a large investment in person-hours with negligible return.