P-40 turn rate/Flight model check

[unreasonable]

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

 

I am going to keep saying this to the people who continue to insist that the P-40 stall is =<90 mph TAS - this implies a CLmax of over 2.00, much higher than the airfoil used in the wing. So far we have had three attempts at explanation of the paradox, and none of them will get a stall speed anywhere near this low.

 

Training manuals do not give a PEC at stall speed - this is pure extrapolation. The only measured PECs at stall speeds anyone has yet posted are for the Spitfire and 109 as per the RAE tests - where AIS is 20mph too low.

The P-40 system is a little different, but as far as I can see from available documents all pitot-static systems tend to under-pressure - ie undermeasure speed - at high AoA.

 

But do not let anyone stop you emailing Han and explaining to the team that the CLmax should be 50% higher than for every other fighter in the game.

[Venturi]

And I am going to keep saying this to people who don't understand. 

 

The training manual gives 90mph at stall, indicated.

 

Which with a PEC correction of -3mph, gives a TAS stall of 87mph. 

 

The documents to prove it are listed.

 

Everything else is cherry picking the data to fit your preconception.

Feel free to show documents proving your claims that the pitot system is incapable of providing accurate airspeed indication at STALL speed... you know, when it is most critical.

As Sherlock Holmes said, 

 

When you have eliminated the impossible, whatever remains, however improbable, must be the truth.

Edited March 13, 2017 by Venturi

[unreasonable]

And I am going to keep saying this to people who don't understand. 

 

The training manual gives 90mph at stall, indicated.

 

Which with a PEC correction of -3mph, gives a TAS stall of 87mph. 

 

The documents to prove it are listed.

 

Everything else is cherry picking the data to fit your preconception.

Feel free to show documents proving your claims that the pitot system is incapable of providing accurate airspeed indication at STALL speed... you know, when it is most critical.

As Sherlock Holmes said, 

 

When you have eliminated the impossible, whatever remains, however improbable, must be the truth.

 

I understand what you are saying perfectly, unfortunately some of it is just plain false.

 

Documents showing that pitot systems have measurement problems have already been posted - both the experimental results from the RAE reports showing a 20 kph error for 109 and Spitfire at the stall, and the NACA documents showing the variability of pressure readings in pitot-static systems at high AoAs, plus a detailed explanation of the physics that causes the errors. You have not provided a P-40 PEC at stall speed, only an extrapolation. While it is clearly possible that the P-40 system error was less extreme than that for the Spitfire and 109, the general physics of these systems suggest under-pressure - hence under-measurement of speed - is much more likely than the reverse at high AoA. Produce a document that actually measures this error for the P-40 and I will revise my view.

 

The TAS is not critical from a pilot's POV - all he needs to do is know the AIS.

 

The only preconception I have is that the P-40's CLmax cannot exceed that of similar contemporary designs by very much, since it was an entirely conventional design with standard airfoil. In game it does not. The TAS stall speeds you believe in imply a much higher CLmax than anything else, and much higher than that of the airfoil.

 

At no time have you given the slightest indication of an explanation of how this can be possible.

 

"When you have eliminated the impossible, whatever remains, however improbable, must be the truth" now this I can agree on. 

So which is more likely, that the P-40 operates under a different version of the lift equations, or that the quoted AIS figures do not accurately represent TAS at high AoA - as has been proven to be the case in a variety of circumstances?

 

 

As I said before, no-one is stopping you contacting the developers and telling them where they are wrong, either about their data entry or their equations: just do not expect everyone here to agree.

Edited March 13, 2017 by unreasonable

[Venturi]

I like this, 

 

You deride my post and then claim you have some magic documents which refute it, on aircraft which have no bearing to the one at hand. I see this as rude and unprofessional, not to mention unreasonable.

 

Post some proof of your claims here and we'll talk about it, nothing you have claimed is proof. Screenshots of period PEC corrections are, on the other hand proof. Including a modern USAF contractor reference source on instrumentation / PEC correction which I attached earlier.

 

Likewise, your claim doesn't pass the sniff test as no aircraft would have an airspeed indicator which could not read down to stall speed. Not a Cessna, not a Bf109, and definitely not a P40.

 

Otherwise, I've said what I wanted to. 

Edited March 13, 2017 by Venturi

[Venturi]

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

[unreasonable]

I like this, 

 

You deride my post and then claim you have some magic documents which refute it, on aircraft which have no bearing to the one at hand. I see this as rude and unprofessional, not to mention unreasonable.

 

Post some proof of your claims here and we'll talk about it, nothing you have claimed is proof. Screenshots of period PEC corrections are, on the other hand proof. Including a modern USAF contractor reference source on instrumentation / PEC correction which I attached earlier.

 

Likewise, your claim doesn't pass the sniff test as no aircraft would have an airspeed indicator which could not read down to stall speed. Not a Cessna, not a Bf109, and definitely not a P40.

 

Otherwise, I've said what I wanted to. 

 

Total misrepresentation. I never said that airspeed indicators do not go down to stall speed, that would be idiotic. The point is that pilots do not need to do a TAS-AIS calculation in their heads while stalling - they just have to know the AIS stall speed and check the instrument.

 

The other aircraft have a great deal of bearing: the apparent paradox between the AIS and the CLmax is also present for the Spitfire and the 109. (And the Hurricane BTW). The solution in this case is proven to be instrument error. The Spitfire has virtually the same airfoil configuration as the P-40, the CLmax cannot be very different. RAE thinks it is 1.32  Is the RAE wrong about the Spitfire? Or does the P-40, despite having virtually the same airfoil, have a CLmax 0.70 higher? Which is it?

 

 Yes we have all seen your PEC charts - none of which have original data points anywhere near stall speed. I have no problem with extrapolation as a way of forming a hypothesis, but if it leads to a physical impossibility this is a clear sign that your extrapolation is wrong. If you have not read the NACA documents on the physics of pitot-static systems that is your problem not mine. They have been posted here for all to read.

 

I am not disputing the data points from the manuals or PEC charts. But as I said, nothing you have presented solves the mystery of how the TAS you extrapolate from these can be reconciled with what we know about every other plane or the laws of physics. 

[JtD]

When you have eliminated the impossible, whatever remains, however improbable, must be the truth.[/size]

Absolutely true. And a cl of 2 at idle power absolutely qualifies as impossible. That's why we need to find whatever remains to explain the listed stall speeds. For this we have a few possibilities:

- lift (i.e. g-load and weight)

- dynamic pressure (air density and air speed)

- reference area

- aircraft configuration.

We've had good looks at them already, but haven't yet managed to find a good explanation. So what we need to do is to keep looking, we must not jump to impossible conclusions.

 

Edit: It might not even be a bad idea to summarize our current status and ask the developers if they have an explanation, or other sources that help to explain. Maybe TsAGI put the P-40 into a wind tunnel and the devs have the doc...

Edited March 13, 2017 by JtD

[unreasonable]

Edit: It might not even be a bad idea to summarize our current status and ask the developers if they have an explanation, or other sources that help to explain. Maybe TsAGI put the P-40 into a wind tunnel and the devs have the doc...

 

I agree and it may not be a bad idea if you were to do it, since a) you are, now that you-know-who has departed, generally trusted to be informed and objective, and b) you have already been in contact with the developers.

 

My suggested summary goes as follows, but this is purely a quick draft.

 

"Dear Han: For the P-40 there is an apparent conflict between the documented stall IAS and the in-game stall IAS, which since the game does not model instrument errors, equals TAS. This difference is far larger than your usual acceptable margin of error. The in-game stall speeds are between 5mph and 19 mph - depending on weight - higher than the 90 mph IAS quoted in the manual.

 

Using the in-game stall speeds gives calculated CLmax figures very similar to that of other single seat fighters, which seems reasonable (to most of us).

 

If we extrapolate from published PEC charts for the P-40, we derive a RL TAS at stall actually a little lower than the manual's AIS. But using this speed to calculate gives us a CLmax of about 2.00 - far higher than for any other single seat fighter in the game.

 

Possible reconciliations have included the following ideas:

 

1) The pitot static system under-measures at very high AoA, making extrapolation from PEC charts invalid and suggesting a RL stall TAS considerably higher than the manual's IAS - which matches what is currently implemented in-game. This idea is supported by the RAE tests for 109 and Spitfire.

 

2) Many aircraft have a "mushy" stall making it likely that the pilot's subjective stall is off from the true stall point, while in game your robot pilot is (presumably?) measuring the stall point exactly. 

 

3) The P-40 has a slightly higher effective lift area compared to it's reference area compared to other types, either because the fuselage is unusually narrow or because (controversially) the horizontal stabilizer is unusually large and acts as a lifting area at high AoA. This theory, however, can only account for a small part of the apparent discrepancy (edit JtD I think that is what you concluded?).

 

4) The P-40 is a wonderful and misunderstood creature.

 

Unfortunately there is no consensus on the conclusions, and this problem is still causing more heat that light.  Can the development team give us an idea of how they approach this problem?"

Edited March 13, 2017 by unreasonable

[BlitzPig_EL]

5)  The P 40 is American and therefore can't be any good.  

 

Sadly I think that thinking drives much of the way that US aircraft are treated in flight sims generally.

We will see how the P-39 is modeled in the Kuban expansion, this will be telling.

 

I mean no offense to anyone here, but sometimes I think this is the only explanation for the way US aircraft are modeled generally in sims since I started playing them.

 

[edited]

 

Devs Bias veiled accusation. Last warning

Edited March 13, 2017 by SYN_Haashashin

[LukeFF]

Here we go again... 

[Farky]

What are you talking about BlitzPig? I have flown many excellent, correctly modeled US airplanes in sims.

[ICDP]

I agree with JtD and unreasonable and while I am not even remotely versed in aeronautical engineering I don't think the P-40 was endowed with magic.

 

I do think the P-40 needs an FM or engine power revision.  But if we are to approach the devs and want a good chance of them listening, we cannot try to claim the P-40 had a CL max ox 2.00, or that it's because they are anti US of A.

What are you talking about BlitzPig? I have flown many excellent, correctly modeled US airplanes in sims.

 

I agree and BlitzPig should know better than making unsubstantiated claims of bias.

[Holtzauge]

I think unreasonable has summed up where things stand regarding stall speed and Clmax very well so no need to reiterate that other than to say that I agree with his analysis a 100%.

 

In addition, as far as I can see the most plausible explanation put forward so far for the performance gap between IRL anecdotal evidence and the IL-2 P-40 is simply that the pilots IRL used higher boost than recommended so no mystery there either. However, as much as I’d like to see the in-game P-40's performance come closer to how it probably performed in IRL combat situations, i.e. with the pilots being a bit liberal with the boost rules, I don’t think the developers either will or should allow higher boost than the official limits in-game because that would open up a world of pain and endless threads on which levels of boost should be allowed for which level of time not only for the P-40 but for all BoX aircraft with manual boost control.

 

Frankly, IMHO continuing to beat this horse that died pages ago seems futile and unless someone comes up with new data this carcass deserves some well earned rest…..

[JG13_opcode]

Screenshots of period PEC corrections are, on the other hand proof

 

Can you provide PEC curves for the stall speed and stall angle of attack?  I've never seen one, and the one you linked only goes to 120 mph.

 

I know you believe what has been posted is sufficient to convince Han but it's not.

Edited March 14, 2017 by JG13_opcode

[BlitzPig_EL]

Been looking over my copy of Curtiss Fighter Aircraft, a Photographic History 1917-1948, by Francis H. Dean and Dan Hagedorn, and came across this info on the P 40 wing.

 

Wing area: 236 square feet.

 

Horizontal tail area: 48 square feet

 

Airfoil at root NACA 2215

 

Airfoil at tip NACA 2209

 

Root chord 9 feet

 

Tip chord 3.88 feet

 

Wing incidence +1.0 degrees

 

Stabilizer Incidence +2 degrees

 

Wing dihedral 6 degrees

 

Wing aspect ratio 5.89

 

Wing twist 0 degrees

 

No mention of Cl Max of wing.

[JtD]

A couple of documents on a couple of issues, containing data also for the P-40. I found them fairly interesting, even if it is mostly about yawing and nothing definitive on the clmax.

 

Flight Investigation on a Fighter-type Airplane of Factors which Affect the Loads and Load Distributions on the Vertical Tail Surfaces During Rudder Kicks and Fishtails - P-40K investigated

Flight Investigation on a Fighter-type Airplane of Factors which Affect the Loads and Load Distributions on the Vertical Tail Surfaces During Rudder Kicks and Fishtails - Same but different.

Effects of Propeller Operation and Angle of Yaw on the Distribution of the Load on the Horizontal Tail Surface of a Typical Pursuit Airplane - Again P-40K investigated.

Compilation of Test Data on 111 Free-Spinning Airplane Models Tested in the Langley 15-Foot and 20-Foot Free-Spinning Tunnels - Wind tunnel model spin trials of about every US WW2 aircraft, including a couple of P-40 versions.

P-40 spin tests - In case you want to check how model wind tunnel tests and the real thing compare.

Effect of power on the stick-fixed neutral points of several single-engine monoplanes as determined in flight - Neutral points for several US aircraft up to a cl of 1.2, power on, power off, including a P-40.

Wind-tunnel Investigation of the Effect of Power and Flaps on the Static Longitudinal Stability Characteristics of a Single-engine Low-wing Airplane Model - A P-36 model, featuring the same wing as the P-40.

 

The last document contains limited information about the clmax, region 1.4@16° angle of attack. Mind you, tail experiments, model, and so on. Just indicative.

Edited March 14, 2017 by JtD

[ACG_KaiLae]

Can you provide PEC curves for the stall speed and stall angle of attack? I've never seen one, and the one you linked only goes to 120 mph.

 

I know you believe what has been posted is sufficient to convince Han but it's not.

Which is the whole point. Anyway, document update, is there is no update. Crump has gone dark, for whatever reason. I'm going to give this another week or two and if nothing by then, we will probably have to start from scratch. I did get an offer for someone to copy RAE docs, but without an index or pre-existing knowledge on what specifically to have him look for, I couldn't tell him what he should be getting.

[JtD]

So, I've send a PM to AnPetrovich, covering V1710, lift coefficient, turn time and directional stability. Unfortunately, as can be expected from this many topics, it's long as a novel which significantly reduces the chance for a thorough read and a meaningful response, in particular given the nature of mostly indicative snippets of evidence and little factual hard data.

[Venturi]

https://forum.il2sturmovik.com/topic/25323-p-40-turn-rateflight-model-check/?p=427673

[Thad]

5)  The P 40 is American and therefore can't be any good.  

 

Sadly I think that thinking drives much of the way that US aircraft are treated in flight sims generally.

We will see how the P-39 is modeled in the Kuban expansion, this will be telling.

 

I mean no offense to anyone here, but sometimes I think this is the only explanation for the way US aircraft are modeled generally in sims since I started playing them.

 

[edited]

 

Devs Bias veiled accusation. Last warning

Yes.. we will have to wait and see how well the P-39 and its flight model is presented. In Attack of the Airacobras: Soviet Aces, American P-39s, and the Air War Against Germany by Dmitriy Loza, two of the top four aces in Russia flew the Airocobra.

[unreasonable]

OK now I am puzzled. Dakpilot in another discussion referred to one of Han's posts replying to FM claims from October 2014, which contained the following:

 

 

13. Some planes can perform extremely low speed passes at high AoA, even down to 100km/h.

First: look at HUD airspeed, gauges on some planes shown wrong speed and they're to be corrected.

Second: it's not 100kmh actualy. Speed indicator is VERY depends on Angle of Attack. For example, on 90° AoA it will allways show 0km/h.

Clain is false, but it have shown another issue, corrected allready in updates.

 

Is it possible that BoS once-upon-a-time modeled the IAS error as noted by RAE and hypothetically advanced as an explanation for the P-40 game/manual discrepancy.... but took it out?  

[JtD]

Some sort of position error was modelled early on, it was more like an angular function of the speed, so cos(AoA)*speed. They took it out, probably because it caused a lot of misunderstanding.

[unreasonable]

Some sort of position error was modelled early on, it was more like an angular function of the speed, so cos(AoA)*speed. They took it out, probably because it caused a lot of misunderstanding.

 

I missed that. I was probably sulking about all the game design decisions, or just had no idea what they were talking about at the time.

 

Pity they took it out - it could have been tweaked a bit and we might have had exactly today's FM, generating an in-game cockpit IAS = the figure in the manual!

[BlitzPig_EL]

Or not.

 

Why speculate?

[unreasonable]

Or not.

 

Why speculate?

 

Speculation is entertaining. Anyway, it is not really speculation, just maths. 

 

Cos/angle (as per JtD's description of what was there) is how you calculate the projected area of a surface seen from an angle. A perfectly reasonable first order approximation for the error in a pitot tube at high angles of attack.

 

No doubt a better approximation could be built with sufficient work and knowledge of the layout of each type of pitot-static equipment. Had we had it, people would have already appreciated that getting the in-game IAS to correspond to the manual's IAS  is not just a matter of a correct FM - you have to have a correct 'IM" (Instrument model) as well.  

 

But taking out something because it is not perfect is not right. It is a model - of course it is not perfect. Taking out something because it is  "misunderstood" by ignorant people (and I would have included myself in this category before the hours of homework need to follow this thread), has another name. It is called "dumbing down".  

 

Mr Spock, engage Irony Drive: "Personally I find it terribly confusing that the IAS gives me an incorrect estimate for the distance traveled - especially at high altitude. It should be changed immediately to show only the horizontal ground speed. To avoid confusion." As you were Mr Spock.  

 

As it happens Cos/angle only gives a 3-6% variation in the stall AoA range, but even so the game Stall IAS for the P-40 would be 92-106 instead of 95-109. And that is at 14 degrees critical AoA, which I would still bet large sums is the main source of the handling problems. If it were 20 degrees ie about average for every other fighter, the game IAS at stall would be 89-103 mph, which might satisfy even the hardiest grumblers.  edit - or not

Edited March 24, 2017 by unreasonable

[JtD]

Bad news from AnPetrovich:

 

They have no time to review the P-40 at least until BoK is done. He says thanks for the research, though.

 

We don't have a good chance to get the V1710 limits raised, because they are in accordance with the current gaming mechanisms, and they'd have to make a global revision of the concept if they wanted to change the V1710.

 

It's probably a good idea to remind the developers every now and then that the P-40 needs some love, so that when they start assigning resources for the period after BoK, the P-40 gets a spot on the "to do" list.

Personally, I'd also like to see the global change for the engine limit concept...

Edited March 27, 2017 by JtD

[19//Moach]

well, from what I gather, that rudder fix just might do a good deal already to improve the handling of it, which as I have verified, after days of learning the ways of the "shittyhawk", produces a satisfactory turn radius, as long as the nose can be kept from waggling about like a bottle-quaffing drunkard (which is really really hard)

 

 

alas, the engine thing is still gonna be there, and there's also the exceedingly long and incorrect startup to remind us that this plane still needs a lot of love

 

 

the engine limit concept is also something that I've tested out, and discovered that it is not a "simple timer" which can be reset by briefly lowering power to "continuous mode" - at the very least, it seems to have a proportionally timed "cooldown" (which isn't indicated by any instruments in the cockpit, and does not reflect actual engine temperatures)...

 

the main issue I have with it, is how it runs perfectly fine, and has no problems with "almost breaking it", such that it's a "straw that breaks the camel's back" type situation - once it fails, it always fails catastrophically - regardless of having been pushed ever-so-slightly above limits, or ran prolongedly at "uber-max mega-balls-to-wall extreme no mercy or remorse" mode
 

it'd be nice if the failure was a bit more gradual... a slightly busted gasket isn't gonna end your flight right away - but currently, it makes no distinction between that and a fractured crankshaft

 

that goes for all planes

Edited March 27, 2017 by 19//Moach

[Dave]

This isn't flight test data, and you could argue it is not objective, but Bobby Gibbes was a straight talking realist who had the benefit of flying many types including the 109 F-4 and 109 G-2 who had the utmost respect for both the aircraft and their pilots. It is anecdotally interesting ...

 

 

 

The purpose had been basically to let them see - some of the new boys see - what a 109 looked like. But its performance was quite terrific. Kittyhawk could out turn it quite comfortably and if the Messerschmitt boys came in and tried to dog fight, they were gone. We could dive away from them. If we started with same speed and they dived away, we could catch them in the dive. But with climb, they could out climb us to blazes. 

[Dave]

 

Great video Dakpilot. Thanks.

[BlitzPig_EL]

If the P40s that should be in the Pacific are going to be modeled they will have to rethink the engine limits, or have a fair few Allied pilots at their door with torches and pitchforks...

 

Dave, the quote from Squadron Leader Gibbes is completely in line with every account I've ever read about the relative performance of the Hawk 81 and 87 vs. the 109s they faced.  There are a large number of such pilot summations of the P 40's abilities, even if they don't have the numbers, these observations of the Hawk's performance are just hard to ignore, and they shouldn't be ignored.

 

Hopefully the changes to the airflow modeling will bring some relief to us long suffering P 40 drivers.

Edited March 27, 2017 by BlitzPig_EL

[ACG_KaiLae]

Waiting to see how the new FM changes affect the plane. After that depending on the results I'll determine the path forward.

[unreasonable]

So Han has had an answer dump - critical AoA in tech specs is of the whole plane - so presumably to compare AoA of wings between planes one must add in the incidence of the wing for each type which I do not have. I would be surprised if it accounted for much of the difference.  

 

He did not really answer the question as to why P-40 critical AoA is so low at all. 

[JtD]

I think he assumed that the 17.6 you quoted as an example are for the P-40. So he probably was happy to reply that the figure falls in line with all the other aircraft in game...

 

I also think that the angle of incidence is available for most planes modelled in game, but generally they are between 0 and 2 degrees. The P-40 falls into the middle of that range, so it does not explain a 3 degree difference.

Edited March 28, 2017 by JtD

[Farky]

Can we just stop for a little moment and appreciate that developers of this game did for the first time in combat simulators aircraft engine without automatic MAP regulator?

 

Just think about it for a moment.

 

...

 

And now, back to our regular scheduled programming ...

 

If the P40s that should be in the Pacific are going to be modeled they will have to rethink the engine limits, or have a fair few Allied pilots at their door with torches and pitchforks...

 

 

If some P-40s are going to be modeled in the future, I bet this will be "late" models like P-40K or N. Problem with engine limits will resolve itself, since overboost wasn't possible in late models of P-40 due to automatic MAP regulators. Only other P-40 without automatic MAP regulator used in combat was P-40B/C (btw, correct P-40 model for the Battle of Moscow, not the P-40E). The chances that will fly over CBI, Philippines or Africa in 1941-42 and therefore get P-40B/C is minimal. Anyway, after BoK this simulator will be "navy show" for next few years, so no other P-40s is in sight.

 

 

We don't have a good chance to get the V1710 limits raised, because they are in accordance with the current gaming mechanisms, and they'd have to make a global revision of the concept if they wanted to change the V1710.

...

 

Personally, I'd also like to see the global change for the engine limit concept...

 

 

In my opinion, sooner or later they will have to change that concept. We'll see what happens with Battle of Midway, we will get at least 5 US airplanes without automatic MAP regulators, so hard MAP limits can't be forced in these planes. I really don't want to see Wildcats or Dauntlesses flying on "overboost" most of the time in combat and I don't want see engine failures after just few seconds of very little "overboost" either. Is it very tough nut to crack.

[-=PHX=-SuperEtendard]

Han in the Q&A talked about the engine limitations:
 

P40 - there are very controversal sources on it's engine time limitations. We have used 1941's soviet sources which limits engine very hard. Later sources are not so strict in it, but it's not our time period. We using sources which are closest to supposed airplane Theater of War (Battle of Moscow in this case).

 

From what I read the P-40Es arrived at Murmansk in May 1942, are there pilot manuals available from mid-1942 showing the approved engine management at that time? I fear Soviet P-40 manuals for late 1941 would apply for the Tomahawk's engine?  I guess that would be the best compromise, giving the P-40E mid 1942 limits, covering it's use as the top P-40 version in that time (Before K, M, etc)

Edited March 28, 2017 by -=PHX=-SuperEtendard

[ACG_KaiLae]

My question vis-a-vis stall speeds got answered, with something of a non answer:

 

"It depends on airplane weight"

 

So, logically, this means that the lowest number is minimum weight, and the highest is at max. Listed speed range for P-40 is 95-109 mph. While I'm still not sure exactly what maximum weight can be defined as - is that full fuel, or full fuel with maximum possible external ordinance as well - minimum weight is self explanatory. Should be almost no fuel at all or no fuel. So, this is showing that the stall speed of the P-40 is at minimum weight above what is listed in the manual when stalled at max, and max weight..well above that for sure. Meaning clmax for in game is probably off given previous discussion because incorrect assumptions were used. 

[unreasonable]

My question vis-a-vis stall speeds got answered, with something of a non answer:

 

"It depends on airplane weight"

 

So, logically, this means that the lowest number is minimum weight, and the highest is at max. Listed speed range for P-40 is 95-109 mph. While I'm still not sure exactly what maximum weight can be defined as - is that full fuel, or full fuel with maximum possible external ordinance as well - minimum weight is self explanatory. Should be almost no fuel at all or no fuel. So, this is showing that the stall speed of the P-40 is at minimum weight above what is listed in the manual when stalled at max, and max weight..well above that for sure. Meaning clmax for in game is probably off given previous discussion because incorrect assumptions were used. 

 

Those are the weight assumptions I have used throughout. Minimum weight is explained explicitly in the Tech Specs - 10% fuel and no ammo. Maximum t/o weight is full fuel + ordinance and will be defined by the manual.

 

And no, it does not mean that the CLmax is probably off, since the speed numbers given in the Tech Specs do not include the instrument error that was probably (almost certainly IMHO) present in the IAS quoted in the manual  - and so are not directly comparable. The manual's figures correctly represent what the RL pilot sees on his instruments - but his instruments are misleading. The game's figure show what the pilot would have seen in RL - in their opinion - if the instruments had no error induced by high AoA.

 

So the game's figures at SL = TAS, but the manual's figures do not, and cannot be used to calculate CLmax.

[unreasonable]

I think he assumed that the 17.6 you quoted as an example are for the P-40. So he probably was happy to reply that the figure falls in line with all the other aircraft in game...

 

I also think that the angle of incidence is available for most planes modelled in game, but generally they are between 0 and 2 degrees. The P-40 falls into the middle of that range, so it does not explain a 3 degree difference.

 

I took this more as a "shut up and go away, we are not going to answer that" type of response, but it is possible he misunderstood - adding a twin engine plane to the comparison hardly inspires confidence.

 

Anyway I am happy to wait now for the Spitfire and the roll/yaw work. 

[ACG_KaiLae]

Those are the weight assumptions I have used throughout. Minimum weight is explained explicitly in the Tech Specs - 10% fuel and no ammo. Maximum t/o weight is full fuel + ordinance and will be defined by the manual.

 

And no, it does not mean that the CLmax is probably off, since the speed numbers given in the Tech Specs do not include the instrument error that was probably (almost certainly IMHO) present in the IAS quoted in the manual  - and so are not directly comparable. The manual's figures correctly represent what the RL pilot sees on his instruments - but his instruments are misleading. The game's figure show what the pilot would have seen in RL - in their opinion - if the instruments had no error induced by high AoA.

 

So the game's figures at SL = TAS, but the manual's figures do not, and cannot be used to calculate CLmax.

 

I'm assuming the game figures are derived directly from the software, since it was apparently generated by a robot pilot. Max weight, since they haven't said what that is, is unknown, as well as minimum weight, exactly. Again I speak only to what is in game. 

 

Though, I'm wondering how many common WW2 fighters of this time period had a stall at 109 MPH for comparison purposes.

[JtD]

Can we just stop for a little moment and appreciate that developers of this game did for the first time in combat simulators aircraft engine without automatic MAP regulator?

I had this in original Il-2 already.

 

In my opinion, sooner or later they will have to change that concept. We'll see what happens with Battle of Midway, we will get at least 5 US airplanes without automatic MAP regulators, so hard MAP limits can't be forced in these planes. I really don't want to see Wildcats or Dauntlesses flying on "overboost" most of the time in combat and I don't want see engine failures after just few seconds of very little "overboost" either. Is it very tough nut to crack.

Yes, you're right. I haven't thought this far. It would be almost necessary for them to re-think it for Midway.

 

From what I read the P-40Es arrived at Murmansk in May 1942, are there pilot manuals available from mid-1942 showing the approved engine management at that time? I fear Soviet P-40 manuals for late 1941 would apply for the Tomahawk's engine?

To my knowledge, the limits were officially raised by the end of the year 1942 to include war emergency ratings and higher take off settings. Tests for these clearances were conducted earlier in 1942, and required the 5 minute WER to be run for 5 hours inside a 7.5 hour test (from 'Vees for victory').

 

adding a twin engine plane to the comparison hardly inspires confidence

I took it he quoted it to show there's a plane with a very low stall angle of attack, so the P-40 is no exception.

 

Max weight, since they haven't said what that is, is unknown, as well as minimum weight, exactly.

This is what the devs state about it:

 

Indicated stall speed in flight configuration: 153..176 km/h

Minimum weight (no ammo, 10% fuel): 3264.2 kg

Standart weight: 3819.1 kg

Maximum takeoff weight: 4414 kg

The heaviest loadout given is 3819.1kg + 522kg for the bomb = 4341kg.

We know exactly what weight they refer to.

 

153km/h@3264kg gives a lift coefficient of 1.32, 176km/h@4414kg gives 1.35. A plausible difference due to more rearward CoG and less elevator deflection with the heavier load.

 

Edit: Thought about it and changed the bit about the P-40 lift coefficients.

Edited March 29, 2017 by JtD