P-40 turn rate/Flight model check

[Crump]

Ok I tried to grab some data, but screwed up the power off part. Will try again tonight. One question though is with power off, in order to get the slow speed decrease specified, you basically need to be in a dive. Is this right?

 

 

I assume you are asking about the 1G power off stall speed?  In that case, the answer would be a firm, NO!  You do not want to be in a dive.

 

Keep the wings level and maintain heading.  You will do this with the rudder by increasing your rudder pressure as the airplane slows down.

 

Use the airspeed indicator to gauge how fast you are changing the angle of attack.  Loose about 2 mph per second and maintain altitude.  Take the aircraft to the full stall.  It will become harder to control the slower it goes until you experience uncommanded movement at the stall point. 

[ACG_KaiLae]

Ok, 2 mph per second is not 2 kph, will give it a go.

[ACG_KaiLae]

Hopefully, this is close enough to be of some use. TL/DR: The stall speeds of the P-40 and Bf-109F are nearly identical, within a few KPH of each other.

 

[Venturi]

Yes, now add in the severe lateral instability of the P40, horrible acceleration and climb rate, and you see it is by far a worse aircraft to fly at the current moment at low speeds.

[JG13_opcode]

Yes, now add in the severe lateral instability of the P40, horrible acceleration and climb rate, and you see it is by far a worse aircraft to fly at the current moment at low speeds.

I've never flown it: Is it *actually* unstable in the lateral axis, or is it merely "sim pilot unstable"?

[Venturi]

I'm not a warbird pilot. But maybe I can get you a direct answer if you're curious and it would matter to the P40 model.

[JG13_opcode]

I'm not a warbird pilot. But maybe I can get you a direct answer if you're curious and it would matter to the P40 model.

I'm asking because if it's actually unstable, that should be a slam-dunk case that would be easy to get fixed. The real P-40 was not laterally unstable. The USAAF would never have put a fighter into service with unsatisfactory control characteristics. "Unstable" actually has a precise mathematical definition, and unstable aircraft are pilot-killers without computer-assist like in very very modern fighters such as (IIRC) the PAK-FA.

 

The problem is that too many people say "unstable" when they really mean something else.

Edited November 24, 2016 by JG13_opcode

[Dakpilot]

I have not heard of any lateral instability in P-40, however there were issues that forced a fuselage extension in later models, even the designer was unhappy with that solution, and accepted it as unsatisfactory, but 'forced' upon by "budget reasons" from higher up

 

Cheers Dakpilot

[Venturi]

I agree the plane should not be unstable in the lateral. But, it currently will enter a flat spin which is nearly unrecoverable if rudder is used at low speeds.

 

The plane actually was longitudinally unstable, but not laterally unstable. Sources with hundreds of hours in the airframe under combat conditions have noted that the plane would "tumble" if stalled in the vertical, but was otherwise difficult if not impossible to spin. I have previously quoted these sources on these forums.

 

I don't care about mathematical dogma, that's for the software developers to figure out. What I care about is how the plane behaves, and it doesn't behave as it should. Finis.

Edited November 24, 2016 by Venturi

[Venturi]

even the designer was unhappy with that solution, and accepted it as unsatisfactory, but 'forced' upon by "budget reasons" from higher up

 

Cheers Dakpilot

Yes, there was a tail extension. In the later models, when the P40 ceased to be the main airframe the American Air Force relied upon in front line duty.

 

But I think I see. My argument here is that this is a critically important airframe, historically, for the American air forces around the world. Including the pacific. It was well respected by the Japanese in particular. It is important to get this early series of P40 right, before the series continues beyond this airframe.

[JG13_opcode]

I don't care about mathematical dogma, that's for the software developers to figure out. What I care about is how the plane behaves, and it doesn't behave as it should. Finis.

It's not dogma, nor mumbo-jumbo. They didn't design these planes without a significant amount of mathematics.

 

But okay, message received, I'll stay out of it. Enjoy your P-40

[Dakpilot]

Yes, there was a tail extension. In the later models, when the P40 ceased to be the main airframe the American Air Force relied upon in front line duty.

 

But I think I see. My argument here is that this is a critically important airframe, historically, for the American air forces around the world. Including the pacific. It was well respected by the Japanese in particular. It is important to get this early series of P40 right, before the series continues beyond this airframe.

 

I think pretty much all the success in Western desert by USAAF in P-40's (checkertails etc.) which would be said to be frontline duty, was with the long tail version

 

I would suggest that the fact that spins were prohibited in the P-40 E model would give thought for a reason?

 

Spin behaviour mention in this vid of flight test/checkride of E model

 

 

agreed that P-40 is important and needs to be right 

 

Cheers Dakpilot

[-WILD-AlbinoHA5E]

I think pretty much all the success in Western desert by USAAF in P-40's (checkertails etc.) which would be said to be frontline duty, was with the long tail version

 

I would suggest that the fact that spins were prohibited in the P-40 E model would give thought for a reason?

 

Spin behaviour mention in this vid of flight test/checkride of E model

 

 

 

 

 

agreed that P-40 is important and needs to be right 

 

Cheers Dakpilot

Did he just call the Mustang a "Bag of Cement"? What Heresy is this?

 

Honestly though, Very cool find. Thanks, great Watch.

 

"Any Speed Change requires and immediate Trim Change"

Edited November 24, 2016 by CuteKitten94

[Venturi]

Excellent video. Keep in mind you can induce a spin in the P40 right now, by simply giving high deflection of the rudder at low speeds.

 

The P40 had plenty of success in the Pacific.

 

Points from video:

 

- Maingear currently too tall on 3d model which is obvious - appears as if currently they are modeled as being fully extended even when the plane is stationary on ground.

- Coolant flaps are open even in flight, appears about 35%, coolant near overheat on short taxi and takeoff even with full coolant flaps. Multiple mentions of coolant flap needing to be open in slow speed conditions.

 

Quotes:

-"Much more maneuverable than a Mustang, really a good maneuvering bird, a lot like a Pitts with a Allison in it" 9:25 in video

-"Wonderful ailerons, better than a Mustang"

-"Has the best maneuverability of the American fighters, I'm saying this after having written a book saying it was the worst" (wondering if he ever flew a Hellcat)

-"This is a very docile airplane in stalls, there is very little you've got to worry about" 10:30

-"Like any ww2 bird, if you stall in a bank without the ball being centered you can go into a spin, and it can be violent" (good luck getting the other planes to do that)

-"You have to stand on the left rudder to keep the ball centered in a 400mph dive"

-"Every speed and power change requires an immediate trim change, it can be a handful in a dive or loop"

-148gal internal fuel capacity, burns about 48gal/hr with extended cruise settings"

-"Full flap will make this airplane come right out of the sky, I mean NOW"

-"This is a mainwheel landing airplane only, not a three point lander"

-"Easy to land"

-"Not unusual to see the coolant warning light come on when taxiing as the coolant gets hot" (non functional right now!)

Edited November 24, 2016 by Venturi

[Dakpilot]

I would (guess) suggest that the cooling issue is more related to that individual aircraft, than the type in general, it would otherwise be difficult to reconcile its success and reputation for ruggedness in PTO/CBI and Desert temperatures 

 

Cheers Dakpilot

[Venturi]

I just took it out and could induce an immediate flat spin while level cruising at 200mph by simply giving 60% left rudder..

[ACG_KaiLae]

The stall testing needs to be redone. I'm not a test pilot by trade and dove too much. It looks like something might be off though. If anyone can do parallel testing I would encourage them to do so (I'll give it another try this weekend).

[Farky]

I have not heard of any lateral instability in P-40, however there were issues that forced a fuselage extension in later models, even the designer was unhappy with that solution, and accepted it as unsatisfactory, but 'forced' upon by "budget reasons" from higher up

 

 

Let's talk about those issues that forced a fuselage extension -

 

1. Directional control difficulties in dive. In every P-40, even with longer fuselage, you have to stand on the left rudder to keep the ball centered in dive. This is very well known feature of P-40s, there was even a joke about it in WWII. It is mentioned in every test report of P-40. No such thing appear in BoM.

 

2. Rudder force reversals in sideslip. I think that the game tries to simulate this (maybe), but in very unfortunate way. This is of course difficult to simulate, since they don't have any forces to work with, but behavior in game is a disaster.

 

Here is a NACA report which deals with those issues - https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930092648.pdf

 

There was another issue with rudder on P-40Es - rudder lock. Quote from document - "It has been found that it is possible to cause locking of the rudder in the full left position if the aircraft is skidded with almost full left rudder fairly low speed and power then suddenly applied. This causes air loading on the rudder to be reversed and the more the power is applied the more the left rudder tends to remain locked in the left position. Under these conditions rudder cannot be centralized until power reduced and aircraft drops rapidly and either stalls inverted or requires approximately 4000 feet recovery in dive. Instructions to pilots should be issued that remedy is to throttle back centralize rudder and hold stick neutral."

 

How serious this defect was? Investigation revealed that this was very rare and no big deal. RAF report - "Although full left rudder was held for a considerable time there was no tendency for the airplane to spin, but it would go into a sideslip and finally the nose would drop. "

 

 

I think pretty much all the success in Western desert by USAAF in P-40's (checkertails etc.) which would be said to be frontline duty, was with the long tail version

 

I would suggest that the fact that spins were prohibited in the P-40 E model would give thought for a reason?

 

 

USAAF in Africa used both version (short and long tail) with same succes, you can hardly find any US pilot report or story complaining about short version. Not to mention successful Commonwealth pilots in Africa flying P-40Es. Spins were prohibited in every P-40 model, including "long tail" airplanes.

 

 

I would (guess) suggest that the cooling issue is more related to that individual aircraft, than the type in general, it would otherwise be difficult to reconcile its success and reputation for ruggedness in PTO/CBI and Desert temperatures

 

P-40s were known for cooling issue, especially on the ground (both version, Merlin or Allison powered). Well, isssue ... every airplane need to be in air for really sufficient cooling, so it's not a issue.

 

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

 

 

Combat report of S/Ldr. Chapman (No. 3. sqn RAAF) -

 

"Kittyhawk handled magnificently and proved extremely manouvreable, showing no tendency to spin out of even the most violent changes of direction"

 

Same feelings with P-40E in game anyone?

[Venturi]

That all matches with my research, Farky.

 

The airframe does not behave at all this way in game.

 

Edited November 25, 2016 by Venturi

[-WILD-AlbinoHA5E]

That all matches with my research, Farky.

 

The airframe does not behave at all this way in game.

 

 

Just a general Remark, NEVER use Ailerons to correct bank while at Stalling Speed, only use rudder. Aileron is used to enter Spins.

Edited November 26, 2016 by CuteKitten94

[Venturi]

Is 200mph stalling speed? It is not.

Edited November 26, 2016 by Venturi

[Crump]

I have been playing around with the Bf-109F4.  At 3000 meters, full fuel, clean fighter configuration I am getting about 155kph stall speed.

 

That appears to be somewhat optimistic (~6%) based on the manufacturer's published CLmax for the design.

 

We need a Position Error Correction on the Bf-109F4 too.  That would be definitive. 

 

Kai-Lae stall testing was not perfect but was averaging about 155kph stall speed as well.

 

That means the P-40 in BoS cannot outturn a Bf-109F4 under any circumstances.

 

Can we get some good stall test's filmed in order to submit a bug report?

 

 

Is 200mph stalling speed? It is not.

 

it is if you exceed the usable angle of attack (CLmax) 

[ACG_KaiLae]

That means the P-40 in BoS cannot outturn a Bf-109F4 under any circumstances.

 

Can we get some good stall test's filmed in order to submit a bug report?

 

 

I will be giving this another go tomorrow, but I'll add that being unable to outturn a 109 matches what I've seen in game. 

[Venturi]

it is if you exceed the usable angle of attack (CLmax) 

 

Honestly, did you hack the voting machines in Michigan?

 

Edited November 26, 2016 by Venturi

[Crump]

 

 

I will be giving this another go tomorrow, but I'll add that being unable to outturn a 109 matches what I've seen in game. 

 

That would be great.

 

I will try and get a film of the Bf-109F4.

[Crump]

 

 

Honestly, did you hack the voting machines in Michigan?

 

 

Your first film shows aileron input and then we cannot see the controls.  

 

Your second one is better and I cannot read your speeds.

 

Rudder can induce a stall so without more information it is impossible to tell.  In fact a common cause of arrival stall/spins in IMC is pilots attempting to rudder the airplane around to a heading without banking.

[Farky]

[Crump]

Farky,

 

There are many kinds of stalls and stall behavior.  The POH is referring to a 1G coordinated stall.  A rudder induced stall is anything but a 1G coordinated stall.  It is two very different conditions of flight and nothing you have posted covers that condition.

 

Again though...without more information it is impossible to tell if the behavior is right or wrong.  The P-40E does have a huge rudder area..

 

 

http://www.dtic.mil/dtic/tr/fulltext/u2/a800732.pdf

 

Curtiss aircraft certainly investigated the fact rudder authority was causing inadvertent spins in P-40E aircraft.  World War I aircraft had similar problems when designers tended to oversize the rudder.

 

The best empennage design for stability and control was a reduction in rudder area and an increase in vertical stab area.  This represents an increase in directional stability and a reduction in the effectiveness of the rudder to eliminate the fact pilots could induce a rudder stall.

 

You can do the same thing with rudder balance and increasing the arm (fuselage extension).  That is easier to manufacture than making new rudder and vertical stab jigs in complete tail redesign.

 

It is actually kind of neat that BoS attempts to include that level of detail.  It is one of the things that make a P-40E a P-40E.

 

Let's investigate the stall speeds of the Bf-109F4 and the P-40E that Kai-Lae noted in his initial testing.  The best test possible would be the aircraft side by side stall testing and films of the individual airplanes under the same condition of flight.

 

If they are the same, then there is an error and we can point the devs in the right direction to fix it.

 

That will return the P-40 to its relative performance place in the line up and it will be able to outturn the Bf-109 at slow speeds.

 

edited to combine two post's into one.

Edited November 26, 2016 by Crump

[Dakpilot]

The fact that Dev's have acknowledged that there is an issue of roll coupling and over effective rudder,

 

and that this will be addressed for all aircraft in future update,

 

gives rise to thought that with a large rudder and some known R/L issues perhaps these attributes may be a bit more exaggerated in the P-40 E1 in the current format of the overall  FM

 

Cheers Dakpilot

[Crump]

 

 

gives rise to thought that with a large rudder and some known R/L issues perhaps these attributes may be a bit more exaggerated in the P-40 E1 in the current format of the overall  FM

 

 

I do not doubt it.  Blanket statements without measured facts though will get us nowhere.....

[Farky]

Crump,

you are testing 1G stall, in my post are some data about it. That's it, I am not trying say something.

[Dakpilot]

It is a measured fact that Dev's have discovered an issue with roll coupling and will be addressed and patched for all aircraft

 

You yourself say that P40 E has large rudder and I will accept that as a fact

 

It is not a huge leap to think that this issue will affect the P-40 more than other aircraft, I don't see this as a 'blanket statement'

 

more likely it would be better to wait for the update before trying to get work done on an individual case (unlikely) that may well be fixed by the global change

 

Tests of stall speeds are of course good and any unusual info is good for Dev's

 

Cheers Dakpilot

[Venturi]

Your second one is better and I cannot read your speeds.

 

Rudder can induce a stall so without more information it is impossible to tell.  In fact a common cause of arrival stall/spins in IMC is pilots attempting to rudder the airplane around to a heading without banking.

 

Really?

An additional note, given that the current sim engine uses the 3d model to determine aeronautical results, perhaps the fact that the tail is not correctly modeled vis-a-vis the original P40, but rather is actually TOO LARGE, is contributing to the problem? I have previously written a post on this subject...

See attached.

[ACG_KaiLae]

Here's the latest run. Since A1 test pilot I'm not, I just did a lot more of them hoping that some of them would be useful.

 

[Crump]

Here's the latest run. Since A1 test pilot I'm not, I just did a lot more of them hoping that some of them would be useful.

 

Good job Kai-Lae and I hope the P-40 fans appreciate your efforts at doing something instead of just complaining about things.

 

We are still in a descent at the stall.  However, the average of those is about ~151kph.

 

That is pretty high for a P-40E.  Using P-40E A29-129 RAAF at 8626lbs and the type POH with a PEC curve, I get a stall speed of ~134 kph IAS and a CLmax of 1.44.

 

For a clean configuration normal fighter Bf-109F4 at 6503lbs, I get a stall speed of 165 kph and a CLmax of 1.4

 

Right now in the game, it appears the Bf-109F4 is stall ~6% optimistic while the P-40E stall is almost 13% pessimistic.  That would represent a 20% error in the relative performance.

 

Now that is just a quick swag based off my testing and Kai-Lae.  I think it warrants further investigation.  

 

Does anybody have a good Position Error Correction curve on the Bf-109F4?

Edited November 26, 2016 by Crump

[Crump]

Really?

An additional note, given that the current sim engine uses the 3d model to determine aeronautical results, perhaps the fact that the tail is not correctly modeled vis-a-vis the original P40, but rather is actually TOO LARGE, is contributing to the problem? I have previously written a post on this subject...

See attached.

 

 

The rudder does look slightly larger.  If that is case, then it is going to aggravate the rudder issue in an airplane with an already oversized rudder.  That being said, I have given you the data on how the rudder should be performing.  

[ACG_KaiLae]

Good job Kai-Lae and I hope the P-40 fans appreciate your efforts at doing something instead of just complaining about things.

 

We are still in a descent at the stall.  However, the average of those is about ~151kph.

 

That is pretty high for a P-40E.  Using P-40E A29-129 RAAF at 8626lbs and the type POH with a PEC curve, I get a stall speed of ~134 kph IAS and a CLmax of 1.44.

 

For a clean configuration normal fighter Bf-109F4 at 6503lbs, I get a stall speed of 165 kph and a CLmax of 1.4

 

Right now in the game, it appears the Bf-109F4 is stall ~6% optimistic while the P-40E stall is almost 13% pessimistic.  That would represent a 20% error in the relative performance.

 

Now that is just a quick swag based off my testing and Kai-Lae.  I think it warrants further investigation.  

 

Does anybody have a good Position Error Correction curve on the Bf-109F4?

 

It should be noted that I couldn't really hold it level at stall speed. Stick full deflection back and was still sinking right at the end. Perhaps someone else can do better. I encourage anyone else to not only stall test it but to also recheck the data that it indicates.

 

If you combine possibly the wrong lift amount being generated from the wing, as well as the in game use of the wrong engine settings, this creates a flying boat anchor. I'd be interested in also confirming things like top speed and other elements of the envelope. It's important that this plane - as well as all others in the sim - work the way they are supposed to, especially with pacific war expansions coming where it will likely play a role as well. 

[Crump]

 

 

It should be noted that I couldn't really hold it level at stall speed.

 

I did notice a large change in vertical speed on the VSI as you got near the stall break.  Does anyone else experience this when stalling the P-40 in BoS? 

[-WILD-AlbinoHA5E]

I made my Bitchboy Brother Record these Vids: Watch how little Control Input is necessary right up to the point of stall. It's off from the Document maybe 5mph, but since we don't know at which fuel load he made these control tests, and how tha Aircraft was fitted for these Handling Trials, I would say it's within tolerance.

 

Also, the claim about 200mph rudder iduced spins, BS, as shown in the second part of second video.

 

 

 

 

This is why I think of the Fuselage Tank as mostly a Range Extender. It would definetly have adverse effects on Handling, and it is definetly the first Tank that gets emptied.

 

Edited November 27, 2016 by CuteKitten94

[Crump]

 

 

I made my Bitchboy Brother Record these Vids: Watch how little Control Input is necessary right up to the point of stall. It's off from the Document maybe 5mph, but since we don't know at which fuel load he made these control tests, and how tha Aircraft was fitted for these Handling Trials, I would say it's within tolerance.

 

You are in a 4000fpm descent and a turn.  It is pretty much a worthless test.

 

The data in the real world test is corrected to the weight listed.  For example the RAAF test  P-40E A29-129 is at 8626lbs.  Otherwise it would not be useful to the engineers.

 

I did notice that descent came on suddenly.

 

​Can anyone else hold altitude and heading.  If the aircraft goes into a uncommanded sudden descent...guys that is a stall.