P-40 turn rate/Flight model check

[Blutaar]

It is discussed often, and often enough it gets a sour tone.

Hey,

i hope im not the one you referring to.

 

Dont worrie, i just wanna say thanks, i didnt know that a closed radiator is not allways the least drag, it makes sense, i can imagine the rads in the 109 are least draggy in closed position because of the split flap design or how it should be called.

Do you have an explanation why the oil cooler of the La5 has some effect on produced drag when you close it to 50%, i allways thought that to myself, its so tiny and the flap never really is in the airflow when fully opened, im just curios, it could be kind of a bug i dont know and i dont claim that, just to be clear?

 

Nice discoussion on the engine part, i hope the P40 will get some love, its a mean looking machine with that fat cooler under the engine, the sharktooth skin fits very well.

[19//Moach]

 

Do you have an explanation why the oil cooler of the La5 has some effect on produced drag when you close it to 50%, i allways thought that to myself, its so tiny and the flap never really is in the airflow when fully opened, im just curios, it could be kind of a bug i dont know and i dont claim that, just to be clear?

 

Nice discoussion on the engine part, i hope the P40 will get some love, its a mean looking machine with that fat cooler under the engine, the sharktooth skin fits very well.

 

 

could be the Meredith Effect -- I don't know if that's actually simulated and to what extent, but that would be a factor to offset the radiator drag (or even adding to net thrust, in some more advanced designs)

 

the P40 cowling seems theoretically capable of exploiting this potential, judging by its shape - by having the flaps positioned between neutral and closed, you'd have a convergent nozzle, and the heated air could be made to exit with a higher pressure than it entered... I don't know whether or not that cowling was designed with this in mind - though that would explain the purpose of the protracted oil cooler tubing towards the tail (which I have not yet managed to find an actual document about, by way of googling around)

 

that wouldn't really add much "raw power" anyways - this effect appears more at the higher ends of the speed envelope, so it's not the kind of thing that'd help save your bacon in a close quarters turning fight (the kind of mess you're not supposed to get yourself into with this plane) - though you could expect a few extra miles per hour on a dash, giving you more "zoom" to follow up on your "boom" 

 

 

the P40, and I think every plane too, has a large tendency to overcool in conditions where it should do the opposite, according to manuals and accounts - so a bit of attention to the radiators is due, as they're currently too good (we don't ask only for things that make planes better - "more realistic" often means stuff should be made a bit worse)

 

 

moreover - it could well be this "new rudder fix" could be the missing ingredient... the P40 being currently "allergic" to sideslips is my main suspect to be indirectly causing it's ultimate lower-than-expected performance, so it's possible that this may change things to a larger degree than anticipated (as has happened before with similar changes) and make for a whole different discussion

 

I expect they'll have to inevitably double check all planes after integrating it anyways, to address any previous "flight tuning" efforts that get deprecated by the new features - this is normal whenever a change is made that has a global impact in such a way - wouldn't be the first time they had to do that either...

 

so I guess we're gonna have to wait and see... 

Edited March 6, 2017 by 19//Moach

[Blutaar]

To be honest, the speed gain is very minimal and i just let it at 100% all the way.

If i look at my note i achieved 546 kph with oil radiator at 50% instead of 544 at 100%, but it could have a more noticible effect on the acceleration i dont know.

 

Thx for the response and the link, i will look at it.

[19//Moach]

you shouldn't fly above 140mph with it open past neutral - the later model P40s had a placard in the cockpit telling you not to do that, and they had the same cowl flap design as the E, so it's probably wise to take that for good advice...  I don't think they're built to withstand that much pressure put against them

 

of course, ingame you're probably not gonna break it by doing this -- yet, the P40 with its already much too effective cooling never really needs more than the neutral 30% anyways - despite it being or not recommended on the real plane

 

you won't get any boost from the radiator outlet (however we have depicted it in the sim, which is still unanswered in the devs Q&A thread) if you keep the flaps open wider than neutral - this because "neutral" means you'd have an exit about the same (-ish) size as the inlet, and thus, in theory, the flow should neither compress or expand upon leaving the radiator duct... hence "neutral" 

 

to get a little push from your rads effectively acting as a ram-jet, (aka: the Meredith Effect) you need a "convergent" nozzle - which means it has to be smaller towards the rear, which given how the now hotter air will have expanded some, gives you a higher pressure on the air going out than that going in, which gives you a small, but much desirable amount of jet thrust

 

on the P40, I'd expect it to at least offset some of the drag caused by that huge gaping maw it has for a lower cowling - though on more modern designs, (namely the P51) the cooling system actually provided positive thrust, making it faster with its cleverly designed radiator than it'd be if that wasn't there at all (as in, if cooling were done by "magic" instead)

 

 

this is why you want the radiator closed as tight as temperatures will allow, when going for speed - on a turn fight, neutral is fine, though if you're in that situation on the Kittyhawk, you certainly have some several much bigger problems to worry about... 

Edited March 7, 2017 by 19//Moach

[unreasonable]

you shouldn't fly above 140mph with it open past neutral - the later model P40s had a placard in the cockpit telling you not to do that, and they had the same cowl flap design as the E, so it's probably wise to take that for good advice...  I don't think they're built to withstand that much pressure put against them

 

of course, ingame you're probably not gonna break it by doing this -- yet, the P40 with its already much too effective cooling never really needs more than the neutral 30% anyways - despite it being or not recommended on the real plane

 

you won't get any boost from the radiator outlet (however we have depicted it in the sim, which is still unanswered in the devs Q&A thread) if you keep the flaps open wider than neutral - this because "neutral" means you'd have an exit about the same (-ish) size as the inlet, and thus, in theory, the flow should neither compress or expand upon leaving the radiator duct... hence "neutral" 

 

to get a little push from your rads effectively acting as a ram-jet, (aka: the Meredith Effect) you need a "convergent" nozzle - which means it has to be smaller towards the rear, which given how the now hotter air will have expanded some, gives you a higher pressure on the air going out than that going in, which gives you a small, but much desirable amount of jet thrust

 

on the P40, I'd expect it to at least offset some of the drag caused by that huge gaping maw it has for a lower cowling - though on more modern designs, (namely the P51) the cooling system actually provided positive thrust, making it faster with its cleverly designed radiator than it'd be if that wasn't there at all (as in, if cooling were done by "magic" instead)

 

 

this is why you want the radiator closed as tight as temperatures will allow, when going for speed - on a turn fight, neutral is fine, though if you're in that situation on the Kittyhawk, you certainly have some several much bigger problems to worry about... 

 

No it did not. There was a thread about this effect in the FM section long ago. I posted an article from one of the designers of the plane, stating that the thrust recovered about 80% maximum (IIRC) of the cooling drag at high speeds.

 

There is no magic: the extra work is provided by the heat of the engine, but to get enough thrust to provide a net positive you would need a lot more energy - ie burn fuel and make it a jet.

 

To the best of my knowledge, apart from the P-51 the benefit from this effect was negligible in all other  previous types. To make it work you not only need to get the compression as you say, but the airflow into and out of the system has to be free of turbulence. The Spitfire radiator was designed to achieve this - but did not. I have never seen any claim that this works on the P-40.

[ACG_KaiLae]

I have a request for the aeronautically employed among us. The airfoil on the plane - what was it, a 2212, someone remind me - somehow doesn't seem to be commonly listed in most reference sources? Correct me if I'm wrong. Can someone find it and dig it up so that we might be able to potentially learn something?

[ZachariasX]

I'm with unreasonable on this. You can't expect actual thrust from a radiator as they were applied in these planes. There is however a certain airflow at wich drag is minimal. Several planes were designed that way. The P-51 is not that spacial in that sense. It is mainly an aerodynamically much cleaner design with less parasitic drag than other planes. This way it had less drag despite a lager wetted area.

 

In the P-40 variants C/D, I've seen a placard indicating radiator position for high speed cruising (about 1/5 open) and combat/climb (about 2/5 open). You don't really open such rads (especially cooling gils of air cooled radials) more than about 60% while in flight. You risk bending the gils by external airflow. The open position is only for ground operations.

 

If you close them all the way, besides of getting a bit more drag, you have the time it takes to heat the whole water and oil in the system to the boiling point. I'm not sure that this is a desirable state in an aircraft.

 

I think it would really help getting more "audio"- feedback from the engine. Right now, except for the MAP gauge, there is little cue to judge how you are treating your engine.

I have a request for the aeronautically employed among us. The airfoil on the plane - what was it, a 2212, someone remind me - somehow doesn't seem to be commonly listed in most reference sources? Correct me if I'm wrong. Can someone find it and dig it up so that we might be able to potentially learn something?

I was hoping to find that in Crumps documents. I haven't seen any polars other than on the 2212 on the P-40.

[306_Eugenio]

Regarding Allison engine operating conditions. They are mentioned in it's maintenance instructions:

http://tradecoastcentralheritagepark.com.au/_dbase_upl/Allison_engine_handbook_1944.pdf

Page 136.

Military Rated Power c.a 1150 Hp - for 15 minutes

War Emergency Rating from 1360 to 1500 Hp depends on version for 5 minutes.

[Dakpilot]

I thought there was some more easily available detail on Hawk-75 wing which is the same, vaguely remember it is made up of two  'numbered' airfoil sections

 

pretty certain the info is in one of the many P-40 threads

 

Sorry but the whole Meredith effect with regards to P-40's is a wild red herring trail, the most relevant thing about P-40 oil cooler is that it is a gigantic thing sticking out in the airflow, looks cool for sharkmouth art though   wonder if there is a figure for P-40 overall drag somewhere that can be compared to its fighter contemporaries

 

Cheers Dakpilot

[unreasonable]

I'm with unreasonable on this. You can't expect actual thrust from a radiator as they were applied in these planes. There is however a certain airflow at wich drag is minimal. Several planes were designed that way. The P-51 is not that spacial in that sense. It is mainly an aerodynamically much cleaner design with less parasitic drag than other planes. This way it had less drag despite a lager wetted area.

 

 

Just to be clear - according to the designers, the P-51 radiator did produce thrust via the Meredith effect - quite a lot actually, but less than the drag of the radiator, so the net result was that the radiator unit was still a drag, but much less than for other types. It is a red herring for the P-40 [edit], but just to deal with it now here is the article.

 

Edited March 7, 2017 by unreasonable

[unreasonable]

I have a request for the aeronautically employed among us. The airfoil on the plane - what was it, a 2212, someone remind me - somehow doesn't seem to be commonly listed in most reference sources? Correct me if I'm wrong. Can someone find it and dig it up so that we might be able to potentially learn something?

 

According to this site it is:   Curtiss P-40 Warhawk NACA 2215 (inner) NACA 2209 (outer)

 

http://m-selig.ae.illinois.edu/ads/aircraft.html

 

The trouble is that from the NACA reports that have been posted we never quite get these, but we do get very similar ones from the same series. The performance figures would have been very similar to what we have seen. I am sure that this is not the source of any alleged discrepancy in the game's P-40 performance. 

 

I have asked Han in the Q's for developers thread why the critical AoA for the P-40 is so low, perhaps we will get something the next time he does a session of answers.....

[ZachariasX]

Just to be clear - according to the designers, the P-51 radiator did produce thrust via the Meredith effect - quite a lot actually, but less than the drag of the radiator, so the net result was that the radiator unit was still a drag, but much less than for other types. It is a red herring for the P-51, but just to deal with it now here is the article.

 

Atwood 1.jpgAtwood 2.jpgAtwood 3.jpgAtwood 4.jpg

Atwood 5.jpgAtwood 6.jpgAtwood 7.jpg

Net trust is what I meant. Thnx for the artice!

[Dakpilot]

To be honest the whole P-40 radiator/s and cowl outlet is a bit of an aerodynamic mess when compared to many other designs of the period, notwithstanding the large (comparative) frontal area

 

 

Cheers Dakpilot

 

 

[19//Moach]

I never said you'd get "extra thrust" from it on the P40, btw -- I said that maybe you could get "less total drag" - though probably not much less anyways, since that cowling isn't exactly the "uttermost pinnacle of super-slick streamlining"..

 

 

so yeah, I concur to that it is, indeed, a mess -  there's lots of stuff going on in that cowling... cannot help but wonder: "why the f...?"

 

 

but see how wide those things open - they probably wouldn't stand the pressure of a high speed dive in the fully deployed position - it'd be, uh... curious to see the results of that

 

they're also very "airbrakey" - so, best keep 'em as tight as possible, with that amount of drag you'll need anything that helps reduce it by even the slightest theoretical bit

Edited March 7, 2017 by 19//Moach

[JtD]

I've already posted a polar for the 2212.

 

And for what it's worth, the P-40 was by no means a draggy fighter for its time. NACA did extensive studies on it to reduce drag, and many of the details were successively worked into the plane.

 

If you compare a Merlin XX powered Hawker Hurricane II to a P-40F, you'll find that the P-40 is roughly 10% faster at the same power, while being considerably heavier.

If you compare a Merlin I,II,III powered Hawker Hurricane I to a Spitfire I, you'll find that the Spitfire is roughly 10% faster at the same power, while being somewhat lighter.

[ZachariasX]

 

 

they probably wouldn't stand the pressure of a high speed dive in the fully deployed position - it'd be, uh... curious to see the results of that

 

They don't. You open them much past 50% at normal or elevated flight speeds, things can break. You see bent metal and stuck flaps. Same applies for the cowling of the P-47 or any other large radial engine. In this game, at least there is an impossible way to damage your engine/cooler

[ACG_KaiLae]

I've already posted a polar for the 2212.

 

And for what it's worth, the P-40 was by no means a draggy fighter for its time. NACA did extensive studies on it to reduce drag, and many of the details were successively worked into the plane.

 

If you compare a Merlin XX powered Hawker Hurricane II to a P-40F, you'll find that the P-40 is roughly 10% faster at the same power, while being considerably heavier.

If you compare a Merlin I,II,III powered Hawker Hurricane I to a Spitfire I, you'll find that the Spitfire is roughly 10% faster at the same power, while being somewhat lighter.

Was going off of incorrect memory. Would like the actual airfoil used on the plane, the 2215 etc. I understand it should be close, but would prefer to peruse the actual article.

[unreasonable]

Was going off of incorrect memory. Would like the actual airfoil used on the plane, the 2215 etc. I understand it should be close, but would prefer to peruse the actual article.

 

I think the point is that as 2215 is the root, and 2209 the outer section, 2212 as posted by JtD will be very close to the average: the last 2 digits are the thickness of the airfoil as a % of the chord.

[Farky]

@ Zacharias X - your post #800 calls for much longer reaction with details, but here are just few things -

 

If the mixture is too lean, there is just a power loss. But increased mixture helps hetting additional manifold pressure (at the cost of impaired combustion efficiency). So if you WANT to have excessive MAP in the P-40, you can, but you have to go "full rich" and you will not get as much additional power past the 42' or so Hg, as you add A LOT MORE fuel to cool the mixture. It will start to smoke more, but you "have your high MAP". Thus, you can control detonation somewhat in your airplane. You can have excessive MAP to some degree, it is just not so efficient anymore. Then again, when you need to do that, you're deep in anyway.

 

First rule for mixture in all US WWII engines - NEVER use the FULL RICH position, I repeat, NEVER. Use FULL RICH only when automatic mixture unit in carburetor fails, because on FULL RICH, you bypass automatic device. In other words, you lose compensation for changes in both altitude and temperature. FULL RICH position was quite often sealed to prevent accidental use.

Always use AUTO RICH position (unless you need save fuel of course), is it same as FULL RICH, but with compensation provided by automatic metering unit in caburetor. AUTO RICH is designed for use in full range of engine power.

 

You will get lot of additional power past the 42inHg/3000rpm (1150 bhp), for example with 56inHg/3000rpm you get 1490 bhp, with 60inHg/3000rpm you get 1580 bhp.

 

 

There is also the strange impression I get that planes are fastest when ALL coolers are closed. If you go full power, you NEED to dissipate heat from 1200 Hp. Closing all coolers will make your engine overheat and break within a minute. Stalingrad winters or not. As long as you can dissipate heat, power production of an engine is not a problem. TORQUE is. Torque destroys crankshafts, bearings, gears... Heat as well as steel loses strenght at high teperatures. The hotter it gets, the sooner it will break. But people (telling from reading the forum) are getting most from their plane by flying them 1°C below cooking at highest power they can get.

 

Again, temperatures. In my opinion, temperatures should by fixed first, than we can talk about other things and how they can be improved.

 

 

Aircraft (such as the Spitfire etc.) have the position of minimal drag marked as lever setting. The Spitfire has a red triangle mark at the map box to indicate the lever position. I wonder when we get the Mk.V if that one also is faster with the rad closed instead of about open 1/3. The P-47 has these intercooler and oil rad positions indicated as "neutral".

 

Same with the P-40E, so called minimum drag position of radiator flaps was (and is in game also) marked as NEUTRAL.

 

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

 

Still same question - what do you recommend? What is your "concept" of engine operation in game based on existing game technology? This is not a passive aggressiveness, I'm genuinely curious about your opinion.

 

 

P.S. - I am thinking about starting new thread relating only to Allison engines, here are many things together and it is a little disorganized.

Edited March 7, 2017 by Farky

[ZachariasX]

Even if this is sidetracking here a bit, still we're pondering the P-40.

 

NEVER use the FULL RICH position, I repeat, NEVER.

First of all, yes, the recommendation of using "auto-rich" with engines that have auto mixture is definitely correct. Full rich bypasses that and gives an overly rich mixture. Why I said that is that an overly rich mixture (as performed with auto-rich, but as well as auto lean but less so when throttle is wide open) you can drown the engine further in gasoline cooling the mixture in conditions where you are blowing up the engine anyway. In full rich, you can do that even more so. You'll foul the sparks as well, but you may get another inch Hg. So, NEVER exceed the MAP that much, but if you do you might as well try to keep the engine from detonating. It's a silly situation and thou shalt not do that anyway.

 

At some point it's all about cooling the mixture and not so much anymore about maintaining an 8% mixture rate. The richer you go with mixture, the less specific energy (per ml fuel or per l air) you will get. This is illustrated when you activate water injection, say in the P-47, you will see no change in MAP, but you will get like 10-15% more power on the shaft as combustion is more efficient.

 

Still same question - what do you recommend? What is your "concept" of engine operation in game based on existing game technology? This is not a passive aggressiveness, I'm genuinely curious about your opinion.

I wish I'd knew. I can only come up with solutions that have caveats of some sort. What could you do? Off the top of my head, I see 3 different ways to go, but they all have upsides (+) as well as downsides (-).

 

1) Make full systems modelling like Accusim does.

+ Damage modelled according to your system load/temp on most parts, basically curing most of our issues here.

- It will come at a significant increase in price to make an aircraft viable commercially.

- Most parts will never see damage with a remote reasonable operation of the plane, as we get a new plane each time we take off. Most money is burnt for nothing.

 

2) Add more, different cues (accustic/vibration) to the engine.

- Makes stuff more complicated, more expensive for us customers, but not so much than 1).

 

3) Just be generous with MAP tolerance.

+ Simple

- Lots of 1470 Hp P-40 then on WoL.

 

In th end I don't know what is the real effort for each case, as we have an already very sophisticated system computing power and loads of the engines. As said before, I sypathisize with the devs for the current state of things as it requires the player to adhere to pulished power limits (or else).

 

My main concern is that currently we are ecouraged to fly at a power setting with high torque and lean mixture to get safely most power for any regime except take off. That we can do that and we somehow get the most of our planes when the engine are hot as hell and not just warm enough for the lubrication system to work properly, but certainly not hotter.

 

But I haven't come up with a way yet that (ideally) would force the player to fly the plane as it was flown back then.

 

What we definitely can do is continue to support the devs. So far, IMHO things are moving in the right direction. The cooling issues are a general one that I with continued success of the series can be mended reasonably. Maybe the devs will come up a way that also takes high torque into consideration. Then again this is something that will kill your engine in maybe some 5 flights, not in 5 minutes...

Edited March 7, 2017 by ZachariasX

[JG13_opcode]

I have a request for the aeronautically employed among us. The airfoil on the plane - what was it, a 2212, someone remind me - somehow doesn't seem to be commonly listed in most reference sources? Correct me if I'm wrong. Can someone find it and dig it up so that we might be able to potentially learn something?

 

It's actually 2215 at the wing root, and 2209 at the tip.  I'm afraid I have neither.

 

The 2212 that JtD posted will behave rather similarly.  The NACA airfoils can be defined by an equation:

 

https://en.wikipedia.org/wiki/NACA_airfoil#Four-digit_series

 

So the only difference between the 2215, 2212, and 2209 is the thickness.  That'll have an effect on lift but not a very large one.

Edited March 7, 2017 by JG13_opcode

[ACG_KaiLae]

Of interest:

 

"Crump, on 25 Dec 2016 - 15:01, said:

Pitot-Static.....

 

That is system that measures the difference between static pressure and dynamic pressure. The instruments which use this information (altimeter, VSI, and airspeed indicator) are your pitot static instruments. There is inherent error in altimetry and airspeed measurement that is quantified in a Position Error Correction unique to each installation.

 

He is asking because it is very important. Airspeed measurement was not accurate in the 1940's and a small error in measurement means a large error in the aerodynamic coefficients. If Position Error is not considered then large errors in relative performance will result due to the differences in the shapes of the Position Error Correction curves."

 

Han answers:

 

"For now measurement roughness is not modelled."

 

Think this means no instrument error?

[JG13_opcode]

That's how I interpreted his response, yep.

[ACG_KaiLae]

That means 95 mph in game stall is rock solid.

[unreasonable]

That means 95 mph in game stall is rock solid.

 

95 in game is the Tech Specs stall speed minimum, which I expect was at minimum operational weight. The maximum was 109 mph, presumably at maximum t/o weight.

 

If you are getting 95 mph in human tests at higher weights, you may be experiencing the effect CptBranko pointed out: because the stall is "mushy" it is difficult to tell exactly when it happens - you may be past the stall point or perhaps descending slightly. The Tech Specs tests were done using a robot so presumably their measurement is exact.

 

No instrument error in game as per several player tests and confirmed by Han.

[JG13_opcode]

That means 95 mph in game stall is rock solid.

Sure. Like I said previously, it's pretty accurate. IIRC it's only off by about 6% which is pretty good in my book.

 

If we (IMHO correctly) assume that most of the flight model is common between aircraft, then the stall speed is a red herring. If the aircraft parameters like Clmax, power, weight, drag polar, etc. are correct then the stall speed would be accurate.

Edited March 9, 2017 by JG13_opcode

[ACG_KaiLae]

95 in game is the Tech Specs stall speed minimum, which I expect was at minimum operational weight. The maximum was 109 mph, presumably at maximum t/o weight.

 

If you are getting 95 mph in human tests at higher weights, you may be experiencing the effect CptBranko pointed out: because the stall is "mushy" it is difficult to tell exactly when it happens - you may be past the stall point or perhaps descending slightly. The Tech Specs tests were done using a robot so presumably their measurement is exact.

 

No instrument error in game as per several player tests and confirmed by Han.

I don't believe that's the case. If it is, the stall speed is even more off than it should be. I suppose a good question would be to ask what defines the stall speed range on an aircraft? High end at max weight, low at minimum weight? Is this accounting for carried ordinance?

[unreasonable]

I don't believe that's the case. If it is, the stall speed is even more off than it should be. I suppose a good question would be to ask what defines the stall speed range on an aircraft? High end at max weight, low at minimum weight? Is this accounting for carried ordinance?

 

Well I have to say again this is completely unproven, since the numbers in manuals etc are AIS and we know that a) it is possible that there is significant instrument error near the stall speed, b) IL-2 does not model instrument error, and c) the speeds in manuals appear to be a physical impossibility for a plane of this weight and wing and are impossible to reconcile even with the speeds for the P-39 which uses a similar pitot configuration!

 

By all means ask exactly how the developers match up the weights and speeds: I simply assumed that the min speed was related to min weight, and so on. Calculating every plane CLmax using these match-ups gives two outcomes within about 0.02 for almost all planes, including the P-40, which is within rounding error, so I am happy with this procedure. 

 

The three planes that do not provide a close match are the 109E, Ju88 and Ju52. If I substitute the standard weight for either minimum or maximum in the spreadsheet I get much closer agreement, so it is possible that there is a testing inconsistency or data entry error for these three, alternately that external ordnance in the maximum weight scenario is having some  extreme effect. (Maximum t/o weight is just that - includes whatever the plane can carry).

 

The P-40 wing profile, BTW, is very similar to that of the Spitfire. NACA 2213 NACA 2209.4 -  average thickness about 1% of chord less than P-40. Different shape etc.

 

In game P-40 CLmax is 1.32-1.35   

RAE calculation for Spitfire I was 1.32

 

It will be interesting to see what the up-coming IL-Spitfire will do.

 

My money is still on some weirdness in the max AoA being responsible for many of the flying "feel" issues. Still awaiting Han's next answer session.

[19//Moach]

I have documents here listing stall speeds as low as 88mph (clean) - this is backed up by other sources such as RAF manuals and reports

 

below you'll find a number of manuals, bulletins and miscellaneous documentation about the type.  these are to confirm beyond any question that the simulation we have is significantly disparate from the real plane, and the most dominant flying characteristics we see are very inconsistent, and even contrary to those presented in the manuals and technical docs

 

 

 

these operating manuals also clearly evidence the error in the simulated startup procedure, as priming the engine is described without the need (or any mention whatsoever) to manually crank the propeller while performing this step -- the video posted earlier demonstrates a correct P40E startup taking place is a much shorter time than it requires in game

 

worth noting also, the published lower temperatures limits are generally impossible to observe in the sim, as the engine will always overcool on ground idle (and up to somewhat higher rpm), even in hot weather and radiator fully closed

 

 

another major aberration of the flight model, is the almost complete lack of right rudder pressure being required to overcome propeller effects - instead, our P40 is best flown with -60 to -100% (left) rudder trim, in sharp contrast to historical accounts such as "you can tell which ones are p40 pilots because of their muscular right legs" 

 

right rudder is effectively forbidden by the current FM, as it will force a violent departure at any speed at just about half deflection - this is not found in any documents (see references) and/or pilot reports - and very unequivocally confirms the incorrect modelling of the plane in the simulation

 

 

it is reasonable to suggest, that some undetected error may exist within the simulation parameters. this would account for the inexplicably discordant, incongruous behavior that we experience and very confidently dispute, against any rebuttals regarding how data used for the model does not disagree.  it must be considered that despite correct reference data, the implementation itself may contain a simple mistake (easily missed, even by the expert eye)  -- it is possible. maybe unlikely, but still a non-zero likelihood - so one must not rule out double-checking the program for that possibility

 

 

anyways - I do not believe there is any further doubt as to whether or not the P40 needs a thorough FM revision - here are a number of references to back up all claims made so far by myself and others:

 

 

http://www.avialogs.com/index.php/en/aircraft/usa/curtiss/p-40warhawk/curtiss-p-40-series-service-bulletins.html

http://www.avialogs.com/index.php/en/aircraft/usa/curtiss/p-40warhawk/pilot-training-manual-for-the-p-40.html

http://www.avialogs.com/index.php/en/aircraft/usa/curtiss/p-40warhawk/curtiss-p-40-flight-manual.html

http://www.avialogs.com/index.php/en/aircraft/usa/curtiss/p-40warhawk/to-01-25cf-1-handbook-of-operation-and-flight-instructions-for-the-models-p-40d-and-p-40e-pursuit-airplanes.html

http://www.avialogs.com/index.php/en/aircraft/usa/curtiss/p-40warhawk/Page-2.html

http://www.wwiiaircraftperformance.org/P-40/P-40.html

http://www.chuckhawks.com/p40.htm

http://www.aviation-history.com/curtiss/p40.html

https://davidpablocohn.com/flight/p-40-flight-report/

http://www.456fis.org/P-40_PILOT_MANUAL.htm

Edited March 12, 2017 by 19//Moach

[ICDP]

I have documents here listing stall speeds as low as 88mph (clean) - this is backed up by other sources such as RAF manuals and reports

 

below you'll find a number of manuals, bulletins and miscellaneous documentation about the type.  these are to confirm beyond any question that the simulation we have is significantly disparate from the real plane, and the most dominant flying characteristics we see are very inconsistent, and even contrary to those presented in the manuals and technical docs

 

 

 

these operating manuals also clearly evidence the error in the simulated startup procedure, as priming the engine is described without the need (or any mention whatsoever) to manually crank the propeller while performing this step -- the video posted earlier demonstrates a correct P40E startup taking place is a much shorter time than it requires in game

 

worth noting also, the published lower temperatures limits are generally impossible to observe in the sim, as the engine will always overcool on ground idle (and up to somewhat higher rpm), even in hot weather and radiator fully closed

 

 

another major aberration of the flight model, is the almost complete lack of right rudder pressure being required to overcome propeller effects - instead, our P40 is best flown with -60 to -100% (left) rudder trim, in sharp contrast to historical accounts such as "you can tell which ones are p40 pilots because of their muscular right legs" 

 

right rudder is effectively forbidden by the current FM, as it will force a violent departure at any speed at just about half deflection - this is not found in any documents (see references) and/or pilot reports - and very unequivocally confirms the incorrect modelling of the plane in the simulation

 

 

it is reasonable to suggest, that some undetected error may exist within the simulation parameters. this would account for the inexplicably discordant, incongruous behavior that we experience and very confidently dispute, against any rebuttals regarding how data used for the model does not disagree.  it must be considered that despite correct reference data, the implementation itself may contain a simple mistake (easily missed, even by the expert eye)  -- it is possible. maybe unlikely, but still a non-zero likelihood - so one must not rule out double-checking the program for that possibility

 

 

anyways - I do not believe there is any further doubt as to whether or not the P40 needs a thorough FM revision - here are a number of references to back up all claims made so far by myself and others:

 

 

http://www.avialogs.com/index.php/en/aircraft/usa/curtiss/p-40warhawk/curtiss-p-40-series-service-bulletins.html

http://www.avialogs.com/index.php/en/aircraft/usa/curtiss/p-40warhawk/pilot-training-manual-for-the-p-40.html

http://www.avialogs.com/index.php/en/aircraft/usa/curtiss/p-40warhawk/curtiss-p-40-flight-manual.html

http://www.avialogs.com/index.php/en/aircraft/usa/curtiss/p-40warhawk/to-01-25cf-1-handbook-of-operation-and-flight-instructions-for-the-models-p-40d-and-p-40e-pursuit-airplanes.html

http://www.avialogs.com/index.php/en/aircraft/usa/curtiss/p-40warhawk/Page-2.html

http://www.wwiiaircraftperformance.org/P-40/P-40.html

http://www.chuckhawks.com/p40.htm

http://www.aviation-history.com/curtiss/p40.html

https://davidpablocohn.com/flight/p-40-flight-report/

http://www.456fis.org/P-40_PILOT_MANUAL.htm

 

Do any of the tests or reports you listed verify or test for instrument error?  The point unreasonable is making is that the sim does not model instrument error due to high AoA and pitot position. If this is the case then its possible the P40 has correct stall speeds and the IAS is being reported wrong.

Edited March 12, 2017 by ICDP

[unreasonable]

@Moach   In terms of getting a useful response from the developers, it would probably be more productive to focus on specific issues highlighting a particular measurable behaviour does in game, and what relevant documentation says it should do.

 

Just generally telling Han that the P-40 FM is a mess, with hundreds of pages of unsorted references is unlikely to make much progress, since I doubt that the team has the time or inclination to do a ground up rebuild as you suggest, but no-one is stopping you trying.

 

In terms of specifics these seem to be good lines of enquiry:

 

- The rudder trim issue you mention might be a good candidate for a focussed question.  

 

- I have put in a Q? on the low critical AoA issue, if necessary will follow if we do not get a clear answer .

 

- The cooling issue seems to be general, according to another thread, probably best treated differently. 

 

- The stall speed/CLmax issue is still a puzzler, but pointing out that AIS figures from manuals do not match in game TAS figures is not proof that there is anything wrong with the FM as has been discussed here at great length. 

[19//Moach]

nobody is calling for a ground-up review -- the call is more for a general tune-up... 

 

I have only recently identified the rudder trim oddity, and it is indeed quite a good point of inquiry that might shed some light on the less-than-satisfactory rudder authority (we know it had rudder issues, but reports mention different symptoms for it)

 

 

as for the engine and cooling, those are indeed the most obvious "quirks" we have - but I do not think they're too much more than an additional factor on top of the real underlying cause of the performance shortcomings we're noticing - that itself remains a bit of a mystery

 

 

critical AoA does seem a bit low - but it's really hard to tell - from what I've experienced in the sim, the majority of stalls encountered were of the accelerated kind - and only on deliberate tests a flat stall is actually achieved

 

I gotta do some more tests with it in the sim, but I'm noticing an odd phenomena on low-speed high-power stalls (i.e. the losing end of a dogfight) which I can only describe as a "full rudder stall"

 

now, this shouldn't happen in those conditions, as the slipstream of the engine at full blast should retain at least a minimal degree of yaw authority (as it normally does on other types in the sim)

 

 

putting this together with the left-rudder trim issue then leads to the uncanny conclusion that.... the propwash is missing?! 

 

 

this is probably not the case - though the symptoms experienced are almost exactly what I'd expect if it were... yet then, how on earth can it steer on the ground with the tail unlocked? - this makes very little sense as of yet... 

 

 

I shall continue to explore the "bizarre end" of the problem, maybe by deliberately doing the very things that we consider "abnormal" we can get closer to an eureka moment

 

 

 

gotta break some eggs... or so they say...   

Edited March 12, 2017 by 19//Moach

[ACG_KaiLae]

Strange, can you post an exact quote?

 

 

Sorry for not responding earlier, but I had trouble finding this because I couldn't recall which document I saw it in:

 

http://www.avialogs.com/index.php/en/aircraft/usa/curtiss/p-40warhawk/pilot-training-manual-for-the-p-40.html

 

Page 10, right hand column. Seems to depend on altitude?

[Farky]

these operating manuals also clearly evidence the error in the simulated startup procedure, as priming the engine is described without the need (or any mention whatsoever) to manually crank the propeller while performing this step -- the video posted earlier demonstrates a correct P40E startup taking place is a much shorter time than it requires in game

 

You are right, priming animation is wrong. According manuals, propeller should be turn only if engine is cold (not warm-up) and before you start priming.

 

 

worth noting also, the published lower temperatures limits are generally impossible to observe in the sim, as the engine will always overcool on ground idle (and up to somewhat higher rpm), even in hot weather and radiator fully closed

 

Temperatures in P-40 are ridicilously low all the time. However, warm up the engine to minimum oil and coolant temperatures limits on the ground is possible in less than 5 minutes -

 

RADIATOR fully closed

RPM selector fully backward (0%) - even with full throttle, RPM will stay at maximum 1600 rpm.

THROTTLE fully forward (37inHg) - increase throttle from 0% to 100% VERY slowly, otherwise your RPM goes rapidly up (because rpm are rising faster then propeller governor "constant speeding" can handle). Remember, you want 1600 rpm or less.

 

IRL, this is not proper procedure for warm up of the engine in P-40E. You should be able easily warm up Allison engine with 1000 rpm, which is not possible in the game.

 

 

another major aberration of the flight model, is the almost complete lack of right rudder pressure being required to overcome propeller effects - instead, our P40 is best flown with -60 to -100% (left) rudder trim, in sharp contrast to historical accounts such as "you can tell which ones are p40 pilots because of their muscular right legs"

 

This seems ok in game to me (with the exception in a dive). At slow speeds, with power on, you need some right rudder (both in game and IRL). At high speed, you need left rudder, like in real P-40. Historical accounts about much stronger LEFT (not right, LEFT) leg of the P-40 pilots are related to behavior of P-40 in dive. Sadly, this well known characteristic of P-40 is in game completely absent.

 

"The airplane was a stable gun platform but required close attention on a dive-bombing run. To hit a target, the “ball” had to be centered (perfectly coordinated with no sideslip). At 400 mph, I had barely enough strength in my left leg to hold the “ball” in the center. There was a joke in those days—if a pilot’s left leg were twice the size of his right, you were looking at an old P-40 pilot with a lot of time standing on his left rudder during high-speed dive-bombing runs."

 

MICHAEL C. MCCARTHY, 57th Fighter Group pilot in WWII

Brigadier General, USAF, Retired

 

 Air-to-Ground Battle for Italy (ISBN 1-58566-128-7) , page 13.

 

 

right rudder is effectively forbidden by the current FM, as it will force a violent departure at any speed at just about half deflection - this is not found in any documents (see references) and/or pilot reports - and very unequivocally confirms the incorrect modelling of the plane in the simulation

 

Sideslip/rudder use at slow speed of P-40E is clearly wrong. Unfortunately, we don't know if this rudder issue is only due to incorrectly functioning rudder in game in general (which unfortunately affect P-40 the most), or something else. We IMHO need to wait for "general rudder fix", than we will see if this is/was problem of incorrect P-40E FM.

 

 

 

Sorry for not responding earlier, but I had trouble finding this because I couldn't recall which document I saw it in:

 

http://www.avialogs....r-the-p-40.html

 

Page 10, right hand column. Seems to depend on altitude?

 

I was waiting for this, because I checked this with documents and it seems you are right (and game is incorrect). But i need some time for double check this "issue".

[19//Moach]

Sideslip/rudder use at slow speed of P-40E is clearly wrong. Unfortunately, we don't know if this rudder issue is only due to incorrectly functioning rudder in game in general (which unfortunately affect P-40 the most), or something else. We IMHO need to wait for "general rudder fix", than we will see if this is/was problem of incorrect P-40E FM.

 

I have began studying the adverse habits of our P40, instead of focusing on what it "should do but doesn't" - I decided to explore "what it does but shouldn't" 

 

the results were fascinating - you should try this yourself

 

 

with full fine prop pitch, at 3000 rpm, the gyroscopic precession of the propeller appears to be exaggerated by a full order of magnitude - without an extreme amount of rudder to compensate, a hard bunt maneuver (hard nose down) will have the plane turn itself 180° in YAW almost before it can be brought to a vertical dive attitude

 

at 2600 the effect is still extreme, and requires the overwhelming rudder workload we've all become so familiar with to stay on the ball in response to even the softest pitch movements

 

 

 

 

at low speeds, the matter is hopeless - in order to bring the p40 out of a pre-stall condition (which is frequently done at full power with tracers going past both sides of the canopy) it is required to maintain the nose dead still - as any pitch motion will generate enough precession torque to physically drag the plane out of the flight envelope and into the infamous "p40 spin"  -- yaw maneuvers will cause similarly strong pitching moments, which can easily lead to a stall and/or a tree

 

 

on takeoff, the plane porpoises and slithers about, manhandled by the brutal forces of a propeller with gyro forces larger than those of a helicopter - we have all seen this - and the immediate conclusion is that maybe something is wrong with the tail - or maybe the wings, the fuselage... and there we have looked, and failed to find a good candidate for a cause of these unusual observations

 

I have reason to believe now, the main reason why it's been so hard to point out inaccuracies in turn radius and stall AoA is:  they aren't there

 

stalls tests are inevitably compromised, as the gyro effect will turn any flat stall into a spin, unless a generous amount of rudder is used to compensate (way more than the manuals suggest would be required) -- this hypothesis also clearly addresses the fact that upon cutting throttle (and nothing but) a spin will right itself, well in accordance to the published recovery methods

 

 

given the results of a recent series of experiments intended to explore this hypothesis - I thus conclude:

 

 

 

the P40 does not suffer from any relevant form of primary aerodynamic inaccuracy, to any extent beyond the trivial - the real underlying cause of the early departures and general pitch/yaw instability is found not on the airframe, but on the propeller. 

 

the gyroscopic precession forces are thus identified as the leading factor behind all of the observed aberrations in aircraft handling within the simulation - it can be estimated from the resulting moments that the output torques we're receiving are largely exaggerated, quite in excess of those experienced in such kind of airplanes, and closer to what is found on a medium-sized helicopter

 

 

the issue lessens considerably by running the engine at a lower RPM setting.  ~2400 rpm seems to provide a much smoother ride than the rated 2600 - this also seems indicative of a non-linear progression of the gyro forces (and/or them being affected by shaft torque, which is physically incorrect) -- alas, this compromise workaround also reduces power output, and is not compatible with the needs of combat maneuvering

 

 

 

more tests have yet to be done - but I am fairly confident that this is indeed the missing key to the p40 puzzle 

Edited March 12, 2017 by 19//Moach

[unreasonable]

 

 

with full fine prop pitch, at 3000 rpm, the gyroscopic precession of the propeller appears to be exaggerated by a full order of magnitude - without an extreme amount of rudder to compensate, a hard bunt maneuver (hard nose down) will have the plane turn itself 180° in YAW almost before it can be brought to a vertical dive attitude

 

 

more tests have yet to be done - but I am fairly confident that this is indeed the missing key to the p40 puzzle

 

"Appears to be"? That is a pretty big claim, if you want this to be believable you will have to show the calculations.

[Venturi]

I have a request for the aeronautically employed among us. The airfoil on the plane - what was it, a 2212, someone remind me - somehow doesn't seem to be commonly listed in most reference sources? Correct me if I'm wrong. Can someone find it and dig it up so that we might be able to potentially learn something?

 

2215 IIRC

That means 95 mph in game stall is rock solid.

 

Why?

 

PEC per RAF and USAAF docs is -3 to -4 mph at stall speed, which means that the ASI in the real life plane is reading fast at stall speed. This was put at 90mph by training documents.

 

In other words, TAS at stall was 86 - 87mph.

[Venturi]

Let's not forget JtD's efficiency table which shows the form drag or prop inefficiency of the P40E is ridiculously high.

 

There is no reason to think the prop was any less efficient, especially for the scale of inefficiency that JtD's table shows, than any other of its contemporary fighters. This means that it is the drag inefficiency which is ridiculous.

 

The P40E was an aerodynamically clean airfame, and the overall design was developed for high altitude interception using the turbo-supercharger mandated by the US Army and developed by Allison for the YP-37, later used for P-38. The fact that the YP-37 later morphed into the workhorse P-40 with single stage 1710 (which did not excel at high altitudes) did not change the overall aerodynamics of the airframe.

Edited March 12, 2017 by Venturi

[ACG_KaiLae]

2215 IIRC

 

Why?

 

PEC per RAF and USAAF docs is -3 to -4 mph at stall speed, which means that the ASI in the real life plane is reading fast at stall speed. This was put at 90mph by training documents.

 

In other words, TAS at stall was 86 - 87mph.

 

It means that the testing confirming the figures that 1CG have given is accurate, because no instrumentation error.

[Venturi]

Then stall should be 86-87mph indicated.

PEC is added to the ASI.

Training manual gives 90mph stall indicated, with PEC -3 to -4mph for instrumentation correction, gives 86-87mph TAS stall. PEC is instrumentation correction to TAS.

 

Since there is no instrument error modeled in the game, we use TAS, not indicated airspeed, and this should line up with the above. It is almost 10mph too fast.

Again, this is not the only issue, there are others. 

https://forum.il2sturmovik.com/topic/25323-p-40-turn-rateflight-model-check/?p=428013