P-40 turn rate/Flight model check

[ACG_KaiLae]

So, then the next step would be to have someone create in the mission editor a test track where this could be done. I assume then recording the test in the in game recorder for exact determination of times/distances would be used, and from there we could determine the data we need.

 

A test track like that strikes me as an overall good idea anyway that could have useful application beyond just testing the P-40 as well.

 

Mission editor is another thing that I have no knowledge about, so I think I will have to solicit a volunteer for this, unless someone here has that covered.

 

Unless I've misunderstood something?

[JtD]

Compressibility is not an issue if you fly low and slow - i.e. do a stall test at sea level.

 

However, you can set atmospheric conditions in the mission editor or you can use the autumn maps to fly in atmospheric standard conditions. At any rate, they are known.

All you need to do now is fly a certain distance, not even necessarily a test course, but yes, it might help. You can just check the map grid for a simple equivalent. Do that at various constant speeds with level auto-pilot (ideally in sea level atmospheric condtions to get around any speed conversions), do it at various speeds and check ratio IAS/TAS. Ideally you don't fly near the ground, to avoid ground effect, so this would mean you'd need to use the map editor to set up atmospheric conditions in a way 0m standard (will be shown on the cockpit gauge) are actually in 1000m (or so) above ground (shown on the HUD).

 

In the last 6 weeks I've spend about 20 hours at home, so I really don't have time for anything BoX related. But last time I checked:

TAS - determined from time over map grid distance.

CAS - the big number in the HUD - was not effected by pitch last time I tested

IAS - obviously what you see in the cockpit, used to show figures different from the HUD, but last time I took a quick look, it appeared to show the same figures the HUD did. I didn't have time to take a closer look.

[ACG_KaiLae]

I suppose the first step is to verify if the HUD display, and the cockpit gauge displays the same. 

[Crump]

In order for you to understand this better I suggest you read the paragraph that is written above what you have underlined in red in NACA's summary which details the "unusual corrections" that were needed to the wind tunnel results which is really a case in point for what I have been saying all along.

 

But this is getting off topic and if you have any more questions about aerodynamics and flight mechanics you can PM me.

 

The clean configuration data gives EXACT agreement with flight testing.

 

 

The issues of correction stem from the large size of the aircraft and high CLmax obtained WITH FLAPS.

 

 

High lift devices have always been problematic even today.

 

That is why Boeing had so many redesigns of their 767 wing.  If it was just a clean wing then CLmax prediction based off the measured 2D airfoil data is much less problematic requiring fewer redesigns.

 

 

 

Here is a interesting document, RAAF Attitude trials of Kittyhawk. Is it P-40N-20, not P-40E, but still pretty interesting. And before you ask - no, I do not have better copy of it.

 

 

If you have any documentation that list's Curtiss design CLmax, it would be pure aerodynamic gold for properly modeling the aircraft.

Edited December 10, 2016 by Crump

[BlitzPig_EL]

I suspect this may be of some help...

 

http://naca.central.cranfield.ac.uk/reports/1945/naca-report-829.pdf

 

NACA Report 829.

 

Wind tunnel tests, showing CL Max of US fighters.

 

Shoot...

 

No P40 in that bunch.

 

sorry

Edited December 11, 2016 by BlitzPig_EL

[ACG_KaiLae]

I've got a pile of RAF and RAAF data that I found here: 

 

http://web.archive.org/web/20160228081658/http://raafwarbirds.org.au/targetvraaf/p40_archive/p40_data.htm

 

What I don't have, and what I'd really love, is the factory data from Curtiss. Having said that, the information there isn't chump change. 

 

Update on the project, we should have a mission made soon that will allow us to do TAS testing and as soon as it's been confirmed that it has the correct settings I'll move forward on that. I'm also looking to expand the testing areas into multiple areas of the envelope if I can get some volunteers to help me. 

 

Update: Super Etendard has graciously volunteered to check roll rate. I have the following documents on this that I have been able to find:  

 

 

 

Also:

 

http://web.archive.org/web/20160228082058/http://raafwarbirds.org.au/targetvraaf/p40_archive/pdfs/Allied%20AC%20rollrate.pdf

 

As can be seen, I have one doc for a P-40F, which likely will have similar roll rate due to similar armament, and 2 for the P-40B, which should be higher. I would really like a P-40E doc, if one were to exist.

Edited December 13, 2016 by Kai_Lae

[BlitzPig_EL]

I would think the roll rates for the F should be pretty much the same for the E, as except for engine type they were way more similar to each other than they are to the Hawk 81s.

[Farky]

Roll rates for the P-40F and P-40E should be exactly the same (or very, very close). Tomahawk data are unfortunately useless for P-40E, since there was difference in aileron deflection between B and E model (among other things).

 

Measurement of Individual Aileron Hinge Moments and Aileron Control Characteristics of a P-40F Airplane ( Memorandum Report L5A29a ) - https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930092941.pdf

 

You have this already from Peril's pages, this is just much cleaner version.

 

 

[ACG_KaiLae]

Roll rates for the P-40F and P-40E should be exactly the same (or very, very close). Tomahawk data are unfortunately useless for P-40E, since there was difference in aileron deflection between B and E model (among other things).

 

Measurement of Individual Aileron Hinge Moments and Aileron Control Characteristics of a P-40F Airplane ( Memorandum Report L5A29a ) - https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930092941.pdf

 

You have this already from Peril's pages, this is just much cleaner version.

 

This is what I assumed. However, it's always best to have an exact match, if one were to be able to be found.

[BlitzPig_EL]

Came across this searching for CL max number...

 

http://arc.aiaa.org/doi/abs/10.2514/8.11348?journalCode=jans

 

It's a page from a Paper entitled "A Flight Investigation of the Effects of Surface Finish on Wing Profile Drag"  written by two Curtiss Wright people.  In it there is mention of CL between 0.15 and 0.35 depending on Mach number, for a P 40 F.

 

I'll stay on this hunt.

 

Edited December 14, 2016 by BlitzPig_EL

[Crump]

 

 

It's a page from a Paper entitled "A Flight Investigation of the Effects of Surface Finish on Wing Profile Drag"  written by two Curtiss Wright people.  In it there is mention of CL between 0.15 and 0.35 depending on Mach number, for a P 40 F.

 

The airfoil you are looking for is the NACA 2215 for the root and NACA 2209 for the tip.

 

We will keep looking.  I will hit up the NASM in the next few weeks once things settle down with my move and at work.

[ACG_KaiLae]

The test mission will not come up as a valid option when you run the program. I've PMed the designer for clarification.

 

Edit: Now working, but the distance to the first marker is too short. The speed of the plane when it reaches it is not stable and therefore it won't work. Have asked him to make it 10x longer so this won't be the case.

Edited December 16, 2016 by Kai_Lae

[ACG_KaiLae]

I have results for the speed testing. Using a mission made by KG200_Volker, who set the test range up so that at 1000m it would have sea level conditions, I was able to run and record the course for analysis. The mission contains 2 floating fires slightly offset to the aircraft's flight path 5km apart. The mission can be downloaded here:

 

https://www.dropbox.com/s/vv5pqxx8dujb96q/P%2040%20Test%202.7z?dl=0

 

The recorded track can be downloaded for analysis here:

 

https://www.dropbox.com/s/dljspmh8q436t3p/Tracks.rar?dl=0

 

Conditions for the analysis; I started the course and let the aircraft stabilize out at 198 MPH IAS with the autolevel on the whole time . This was the displayed speed on the HUD, which seemed to match exactly what was displayed on the speedometer in the dash. To answer a question therefore from before by JTD it therefore seems that the HUD display and the dash display are the same (I verified this several times in different conditions). I set the time to be 1/32 so for every 32 seconds of game (for highest accuracy of start/stop times), one second would pass. From arrival at the first fire, to arrival at the second fire, an elapsed time of 1804.63 seconds was recorded. Dividing that by 32 gets us 56.3945875 seconds of elapsed game time. This then equates to .01566519 hours of game time, which when divided by 5km resolves to:

 

TAS=319.17902 KPH (198.328648195 MPH).

 

I don't believe that the start and stop timing positions are incorrect, so the elapsed total time should be good. The only issue is that it is impossible to determine what the exact speed of the plane is with total certainty, only that it was between 198 MPH and 198.5 MPH.

 

Let me know if there's anything else I should do with regards to this to advance the FM check further. I know Crump is interested in also doing the F4 109, which I will do at a later date. 

[BlitzPig_EL]

Wait, are you saying the in game P40 does less than 200mph at sea level?

[ACG_KaiLae]

At roughly 51% throttle, yes. It's not a maximum speed check, it's a check to see the difference between IAS and TAS at sea level. Unless I've misunderstood something.

Edited December 18, 2016 by Kai_Lae

[BlitzPig_EL]

Ah, OK.

 

I didn't think she was that slow...

 

There should not be any difference between TAS and IAS at sea level, as far as I understand it.

 

Do we know if any of the maps are modeled with true "Standard Day" conditions?   This would be a big help.   Also, I believe the He 111 has a thermometer instrument in the cockpit, at least the one in 1946 did.  We used it back in the day to see of the temperature lapse rate was modeled in '46. It was BTW.  It would be helpful to know this as well in the new sim, just as a check on the fidelity of atmospheric modeling.  I'll have a look tonight when I get home.

[ACG_KaiLae]

Ok thanks. Just need someone with aeronautical knowledge to review the data and say what is the next step to proceed.

[unreasonable]

Ah, OK.

 

I didn't think she was that slow...

 

There should not be any difference between TAS and IAS at sea level, as far as I understand it.

 

Do we know if any of the maps are modeled with true "Standard Day" conditions?   This would be a big help.   Also, I believe the He 111 has a thermometer instrument in the cockpit, at least the one in 1946 did.  We used it back in the day to see of the temperature lapse rate was modeled in '46. It was BTW.  It would be helpful to know this as well in the new sim, just as a check on the fidelity of atmospheric modeling.  I'll have a look tonight when I get home.

 

The difference between IAS and TAS at sea level would be the PEC - ie an aircraft, instrument and speed dependent measurement error due to the position of the pitot tube.

 

Given that Kai-Lae's tests show TAS=IAS (if I have read them correctly) this suggests that either:

 

1) The game does not model PEC  (which would be my hypothesis), or:

 

2) It does (either generically or by aircraft), but at this speed range the PEC is very small ie within the test range of error

 

The only way to know for sure is to get a developer to tell you if or how PEC is modeled.

Edited December 20, 2016 by unreasonable

[ACG_KaiLae]

The test could of course be repeated at a different speed if needed. Would that be needed?

[JG13_opcode]

So, let me digress here for just a bit.

 

The aircraft has, in addition to the pitot tube, a static port for measuring ambient pressure. The port is just a small hole connected to a tube so that the altimeter and the ASI can get that info. The problem is that the pressure field around the aircraft is not the same at various angles of attack.

 

Since the angle of attack varies with speed (for example, imagine a super-low-speed pass at an airshow, and note the exaggerated nose-up attitude of the aircraft), one can expect the magnitude of the position error to also vary with speed.

 

I've only been skimming this thread every few days but that is why I believe JtD suggested to perform tests at a number of different speeds. If you note the IAS and TAS at each speed, then you can get insight into the PEC curve's shape.

[unreasonable]

I suppose it is possible that Kai_Lae's test just happened to be at a speed where the PEC is close to zero....easiest way to test would to do the test at a very high speed and a very low speed, to get the maximum differences for TAS-IAS. 

 

The problem is the precision with which the speed has to be maintained over the measured course, not sure I could do it, but doable in theory.

 

My money is on there not being any PEC modeled.  

[Dakpilot]

Pretty sure I remember one of the FM dev's saying, during a "debate" about  subject including stalls, (think it was evidence from a vid) that the IAS from gauge in game, could not be accurately relied upon during high AOA

 

however A. this was a long time ago and there have been many changes to game

 

and B. my memory is not 100% reliable 

 

Cheers Dakpilot

[ACG_KaiLae]

I'll run it at varying speeds then.

[Venturi]

Wonder if anyone with supposed aeronautical knowledge is working on this still. It is truly glaring when a 109 E completely outclasses the P40. It is by far the worst fighter in the game. I hope someone, somewhere will see the light and represent the aircraft historically.

[JG13_opcode]

supposed aeronautical knowledge

What exactly are you getting at, here?

 

For someone asking for help, this comes off rather ungrateful, arrogant, and condescending.

The problem is the precision with which the speed has to be maintained over the measured course, not sure I could do it, but doable in theory.

Yep, definitely harder to do with a $60 joystick and pedals than in the real aircraft. Military flight test standards typically specify speeds for things like this with a variation of +/- 2 knots or less being considered "good", and +/- 5 knots being considered "marginal". Test pilots are very well trained.

Edited December 22, 2016 by JG13_opcode

[Venturi]

I have to applaud Kai Lee for being so diligent with his testing. Let's hope its not a waste of his time...

[Stig]

It is truly glaring when a 109 E completely outclasses the P40. It is by far the worst fighter in the game. I hope someone, somewhere will see the light and represent the aircraft historically.

 

 

So just how did the 109e7 stack up against P40E-1 historically?

 

Btw, Kai Lae has on several occasions appealed for help testing the P40. Perhaps you should step up, Venturi.

[JtD]

I'll run it at varying speeds then.

Just do it at one more, preferably at a lower speed. If the second run also shows no significant difference between the three speeds, you're confirming my old findings, and testing time would then be better spend on other things. Thanks for taking the time and sharing your results!

[Venturi]

So just how did the 109e7 stack up against P40E-1 historically? https://forum.il2sturmovik.com/topic/26224-p40-engine-managment/?do=findComment&comment=413399

 

Btw, Kai Lae has on several occasions appealed for help testing the P40. Perhaps you should step up, Venturi. I think he's got it handled admirably, but thanks for the vote of confidence.

[Stig]

I thought you might have some documentation on 109e7's and P40E-1's meeting in combat and what the outcome was.

[ACG_KaiLae]

Any such data would be, IMO, worthless. This is because there would be no telling what the important factor in the equation is. What we're trying to do here is check aircraft performance, but in combat, that's only one factor. Pilot skill is much more important, as well as if the combat started advantaged vs disadvantaged, or the missions that the 2 combatants were on at the time. 

 

If you're asking what the consensus that seems to be around are, in speed they are roughly equal, the P-40 should be more maneuverable on the horizontal plane, the 109 much more maneuverable vertically and have a superior rate of climb, and the P-40 should dive better. 

 

I will be doing a low speed and high speed run and posting the results. If they turn out the same as the current run - in other words, no difference - I'll probably do a run in the F4 and see if it also agrees. If so I think we can stipulate that the F4 will also use the same system the P-40 uses.

Edited December 23, 2016 by Kai_Lae

[ACG_KaiLae]

I have to applaud Kai Lee for being so diligent with his testing. Let's hope its not a waste of his time...

 

Even if somehow the data we collect totally confirms their interpretation of the P-40, we will then have confidence that it is correct and historical. This will have value in of itself. In addition, we should have enough data that a very good pilots manual should be able to be assembled, which again, has great value. 

 

And it's Kai Lae. Not sure who this Lee dude is but the kamaaina quotient just went down considerably lol

Edited December 23, 2016 by Kai_Lae

[Venturi]

[Stig]

Any such data would be, IMO, worthless. This is because there would be no telling what the important factor in the equation is ....

 

 

 

That was sort of my point, in a roundabout way, admittedly. 

[Venturi]

Tell you what. Go ahead and buy these, read them, then get back to me about "evidence". By the way, they are mostly nothing but flight reports from front line fighter squadrons..

 

The problem with people like you, Stig from Denmark, is that you demand "evidence" and then discount it when it is presented. You are not interested in doing the work to understand, because your mind is already made up. 

 

I and many other people here have already presented much "evidence". Search function is your friend. Start there and start reading.

Edited December 24, 2016 by Venturi

[JG13_opcode]

Pretty hard to quantify "magnificent", don't you think?

[Venturi]

Not too hard to quantify "showed no tendency to spin out of the most violent changes in direction"

add in "extremely maneuverable"

 

The point is, gut check the models. Something is off.

Edited December 24, 2016 by Venturi

[Dakpilot]

But what does "showed no tendency to spin out of the most violent changes of direction" actually mean?

 

Is this Pilot saying the P-40 could not be stalled in in combat manoeuvres ? or rather that there is sufficient feedback to easily avoid such a situation seeing as spins are prohibited, at what speeds is he talking about?

 

How much experience does he have? Has he just transferred from flying Fairey Battles?

 

 

 

 James Edwards RCAF 260 sqdrn RAF WD 13 confirmed victories with P-40

 

"... not an easy aircraft to fly properly and as a result, we lost a good number of pilots while training." 

"In the first few months after conversion to Kittyhawks, all the squadrons lost heavily to the 109s." 

"I found that one had to have a very strong right arm to fly the Kittyhawk I during most maneuvers. In dive-bombing, the aircraft would pick up speed very quickly in the dive, but it had a great tendency to roll to the right. One could trim this out reasonably well with the left hand, but even then when one pulled up, it wanted to roll to the left quite violently So I learned to trim about halfway in the dive and hold the control stick central by bracing my right elbow against my right leg and the right wall of the cockpit. It was also distracting to have one's left hand on the trim all the time, when it should be on the throttle." 

"In a dogfight, with violent changes of speed, it was all one could do to fly the aircraft." 

"Kittyhawk II... was a definite improvement in lateral stability over the Kitty I." 

"Eventually, with the Mk IIIs, the Kittyhawk became a good, stable fighting aircraft, although it never did have enough power or climbing ability compared to the 109s or the Spitfire."

 

David Brown 112 sqdn 1942

 

 "The Kittyhawk, while offering a more roomy and comfortable cockpit than the Spitfire, with a bonus of improved visibility, was more sluggish on controls and inferior in performance when compared with the Spitfire V. Furthermore, even though we could cope with moderate aerobatics and mock dogfights, there was still a feeling of ‘touchiness’ about the P-40 so that you wanted plenty of altitude before you could relax…."

 

I am not saying your anecdote is less true than mine, but they can be traded all day 

 

anecdotes all have their use, but not in defining combat performance, unless every one available is taken into account, backed up with known and accepted performance figures

 

Cheers Dakpilot

Edited December 24, 2016 by Dakpilot

[JG13_opcode]

Not too hard to quantify "showed no tendency to spin out of the most violent changes in direction"

 

add in "extremely maneuverable"

I'd say the opposite. How can you derive a quantity from any of those things?

 

The point is, gut check the models. Something is off.

OK, but the trick is to determine what is off and by how much. Anecdotes don't tell you that.

[6./ZG26_Klaus_Mann]

I think in general the behaviour of the Aircraft is largely OK. Above 300kph it is perfectly Stable and Rock Solid at 400kph and more. The Stall Characteristics don't really come into play until you go slow. And then it is the case that as long as the Rear Tank is filled it behaves rather unpleasant in rapid Control Changes. Once it drinks from the Wing Tanks it is almost Unspinnable. 

 

This also shows in Landings. It has a far larger Tendency to Ground Loop with a Full Fuselage Tank, the less fuel you have, the lower that tendency becomes. 

 

As far as I think the different opinions stem from: Speed at which the Tests were conducted, and at which fuel Levels they did. If they flew it with unnecessarily large amounts of fuel, which can be hazardous when doing touch&go's or if they did it at lower loads, depending on who tested it for what and where and whatever. 

Pilots Differ wildly, all have different Biases and Comparisons. A guy that has flown a lot of Hurricane will think of it in a different way to someone mostly flying the far less Stable Biplanes. 

 

Coming from Gliders and TMGs (Rotax Falke) I think wildly different about a Piper Cub than the guy who learned on Cessna 152, DA-40, Ultralights and whatever else is out there. 

I think the Piper is absolutely lovely and easier to fly and taxi than the TMG due to less adverse Yaw and responisve Stick Controls, while the others think of it as loud, annoying to taxi, underpowered and unstable in Crosswinds, quite the opposite of my thoughts. 

 

This is why you will often find completely contradictory reports of the same Aircraft. 

Edited December 24, 2016 by 6./ZG26_Klaus_Mann