P-40 turn rate/Flight model check

[JtD]

A rearward centre of gravity increases maximum lift because you don't need as much downforce from the elevator in order to raise the nose. So while you find my statement not especially convincing, you're already into the effects.

 

You can also look into report 618 already referenced by unreasonable to find all sorts of investigation into that matter - including figure 17 where it is shown that the maximum lift coefficient tail on is about 0.05 lower than that with tail off if elevator is set for stall angle of attack. Different aircraft, different effects.

Edited January 2, 2017 by JtD

[Crump]

 

 

A rearward centre of gravity increases maximum lift because you don't need as much downforce from the elevator in order to raise the nose. So while you find my statement not especially convincing, you're already into the effects.

JtD I do not care if you have misconception.  Your journey in life is your own.  Your evidence is a decade older than the report I posted and deals with a biplane.btw.

 

 

I just relate what I was taught college and my experience.  The values for CLmax given by Grumman for the NACA 230015/NACA23009 for example show a Clmax of 1.55 at the forward CG, 1.58 at normal CG, and 1.61 at the rearward CG location. 

[Venturi]

A rearward centre of gravity increases maximum lift because you don't need as much downforce from the elevator in order to raise the nose. So while you find my statement not especially convincing, you're already into the effects.

I find your statement unconvincing because it seems to me that it is not always the case that the elevator provides net negative lift, whereas you do not even allude or admit to this possibility. It depends on the design, and we do not know for the P40, except for the model I've already shown you of it, albeit different airfoils, which with the tail gives it a CLmax increase!

 

I will actually use an example everyone is familiar with to illustrate my point: The Bf109. It does not require much back stick at all, in fact sometimes none, when at neutral stab trim to begin attempting to achieve CLmax! So right there, it seems that the design is such that the plane needs much POSITIVE tail lift (negative stab trim!) to fly level, not negative tail lift!

 

Why then would all designs need to have negative lift from the tail?

Edited January 2, 2017 by Venturi

[JtD]

I find your statement unconvincing because it seems to me that it is not always the case that the elevator provides net negative lift, whereas you do not even allude or admit to this possibility. It depends on the design, and we do not know for the P40, except for the model I've already shown you of it, albeit different airfoils, which with the tail gives it a CLmax increase! for something else, but it was quite thorough for its reasoning.

in a wind tunnel the tail assembly is typically fixed, while in flight the elevator will be angled upwards and induce a downwards force or at least less lift than in the wind tunnel

True, I didn't "allude" or "admit", I stated it plainly.

[unreasonable]

Your evidence is a decade older than the report I posted and deals with a biplane.btw.

 

 

Just a correction here - it is about a high wing monoplane - Fairchild 22 - as you can see on the front page.  http://naca.central.cranfield.ac.uk/reports/1938/naca-report-618.pdf

 

As JtD points out, this example shows a horizontal stab whose removal increases Clmax - so the point is just that it is unwise to draw too general conclusions from the opposite result in the models in 824.

 

Personally I am not sure that all designs need negative lift from the tail - it must surely just be a function of the relative position of the centre of lift and the centre of gravity. This will vary not just by design by by how much fuel if on board, plus it can be trimmed out to a degree anyway for most planes in normal flight, so I expect that this line of argument is not generally helpful unless one has very specific data.

 

I would expect the elevator to be up during a stall test or landing, however: having back pressure on the stick must be a better position from which to make adjustments I would think. You are after all gradually increasing the AoA until you reach the stall: hard to do that without up elevator unless it had been trimmed in strong down position in level flight, which seems unlikely.

 

In game using Han's official figures the Clmax for the three weight options are almost the same, (+/- 0.01) so it does not look as though having a change of CoG from fuel use makes any difference. (I think fuel/CoG is modeled in game, not sure).

 

The example you give of GoG effect is only +/- 0.03 from the centre position, so if this is representative it is not closing the gap much between the 1.73 (Boscombe data, assuming zero PEC), 1.60 ish (probable airfoil/wing ball park) and 1.35 (game). 

[Crump]

JtD,

 

Your study is almost a decade earlier than the one I posted however it concludes:

 

 

Determinations of the power off maximum lift of a Fairchild 22 airplane were made in the N. A. O. A. fullscale wind tunnel and in flight . The results from the two types of test were in satisfactory agreement.

 

 

It was found that the rate of angular change was very important during the test.  If careful attention is paid by the design team to the details, then everything will agree.

 

 

It was found that, when the airplane was rotated positively in pitch through the angle of stall at rates on the order of 0.1° per second, the maximum lift coefficient was considerably higher than that obtained in the standard tests, in which the forces are measured with the angles of attack fixed.

 

Report 618:  https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930091693.pdf

 

 

What that is saying is if you fix the angle of attack you will not get good results but must pay attention to the rate of angular change.

 

That is in perfect agreement with the conclusions of the later study:

 

 

So we can say for a fact that properly done, flight testing and wind tunnel full scale testing gives good agreement.  Properly done, Full scale Wind Tunnel agrees with a scale Model wind tunnel investigation.  Properly done, a scale model agrees with measured 2D airfoil data.  That is how it works.

 

 

So I am not sure why you think attainment of design CLmax is some unreachable goal.  It is not attainable by a design team, it is an imperative.

Edited January 2, 2017 by Crump

[Crump]

Just a correction here - it is about a high wing monoplane - Fairchild 22 - 

 

Yes I see that.  It is however an earlier study that gives good agreement with later studies.  Simply put, not being able to achieve good agreement from airfoil to wing to airplane would simply invalidate aeronautical engineering.  A design must achieve its design Clmax.  Not being able to achieve means serious implications in terms of stability and control, landing/take off performance, structural loads, useful loads, and a host of other issues that would simply make the aircraft unusable.  It would not be the machine the designer set out to create nor could it do the job it was designed to do.

 

From JtD's NACA Report 618:

 

 

 

 

 

In game using Han's official figures the Clmax for the three weight options are almost the same,

 

 

The effect of weight is to change velocity not AoA or CLmax of the stall point.  See, this is a good example of not understanding how the relationships work and drawing the wrong conclusions.

 

 

 

Personally I am not sure that all designs need negative lift from the tail - it must surely just be a function of the relative position of the centre of lift and the centre of gravity. This will vary not just by design by by how much fuel if on board, plus it can be trimmed out to a degree anyway for most planes in normal flight, so I expect that this line of argument is not generally helpful unless one has very specific data.

 

Yes, there are different ways to design a tail and it is dependent on the AC to CG relationship of the aircraft.  The normal design which encompasses most World War II fighters including the P-40 is to exhibit a downforce.  That will reduce wing CLmax at the forward Cg limit and increase it at the Rearward CG Limit.  That is simply a fact.

 

The largest issue in those whole is the misinterpretation of NACA reports leading to erroneous conclusions.  Why?  People do not know the details and cause/effects relationships.

 

We saw that in the Chalais Meudon Polars.

[Holtzauge]

Just as JtD pointed out earlier the effect of the tail on a stable plane is to lower the airplane Clmax not increase it. This is why you will get a higher Clmax as you lower the stability margin because you are lowering the downforce of the stabilizer/elevator combination but the tail will not increase the airplane Clmax, only lower it to various degrees from the plain wing Clmax depending on the stability margin.

 

While I have not read the details of the testing in NACA 824, I am familiar with the effects of a tail in wind tunnel testing and most likely the reason for the higher Clmax with tail on the model is that the test was run with the elevator fixed and this is what happens when you simply mount the model on a sting and run it in the tunnel: You will get a reading higher that the IRL airplane Clmax because your model is out of trim and your tail is lifting and not providing the downforce needed for a plane balanced in pitch. Running wind tunnel tests with models balanced in trim is tricky business and this is also why you have the tailless model:  If you run the test like that you simplify the problem of calibration.

 

Concerning power effects that could very well contribute in some way but looking at the Spitfire, this had a Clmax of approximately 1.36 power off and 1.8 at full throttle. At idle that number would be very close to stall so no way you will see an idle power Clmax in the vicinity of 2 for the P-40.

 

I still think the most plausible explanation is that the P-40 airspeed indicator IAS reading at stall is too low and that that is what we will find out in the end because a plain wing no flap Clmax of 2 for the P-40 using the reference area 21.92 sqm is simply not going to happen because it is a physical impossibility using a NACA 2209/2215 combination. Most likely the PEC simply cannot be extrapolated in the way we have been assuming so far. Could very well be some unlinear effects close to stall due to some separation of flow that affects the static ports or some other effect which we don’t see in the higher speed PEC curves we have.

 

Anyway, this discussion is now just going in circles with the same test and PEC arguments being dogmatically reposted with alternating theories on why they have to be right so I’m planning to take a break from this discussion until some new data surfaces but my money is still on an erroneous IAS estimate being the culprit but let’s wait and see.

[ZachariasX]

So you think an IAS error of up to 8% or so at stall speed (where I would say accuracy matters most) would be (implicitly) tolerated by the designers of back then?

[Holtzauge]

Well, if I have to choose between something which is physically impossible like a Clmax of 2 and an instrument error reading of 8% which while unpalatable is physically possible then yes!

 

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." - Arthur Conan Doyle

[Venturi]

Or in other words, the plane stalled at 100mph even though the training manual specifically states 90...

 

Edit, That is sarcasm btw

Edited January 3, 2017 by Venturi

[ZachariasX]

If that is the choice Holtz, we're definitely on the same page there. But it is a choice between two evils.

 

Like you say, it is bare nonsense that there would be more lift than the theoretical maximum of a given profile. But the alternative is also not satisfactory. If a dial is off the mark, you at least have a sticker next to it pointing out real values... People notice deviations like those.

 

I guess we're still missing something here. I hope that once we have more detailed documents from the archives, we can understand better what they did to obtain their published values.

Edited January 2, 2017 by ZachariasX

[Holtzauge]

Yes, sure we are missing something and I'm not saying it HAS to be the IAS, it just seems the most plausible explanation. In the best of worlds the archive search will turn up some stall tests which were done using some reliable speed measuring equipment like a trailing pitot system but until then............

[Dakpilot]

Surely Pilots are only interested in IAS, if they are told it stalls at 90mph in training, and it does when looking at the gauge, the PEC is irrelevant at these speeds to the operator?

 

or am I missing the point 

 

Cheers Dakpilot

[Crump]

If that is the choice Holtz, we're definitely on the same page there. But it is a choice between two evils.

 

Like you say, it is bare nonsense that there would be more lift than the theoretical maximum of a given profile. But the alternative is also not satisfactory. If a dial is off the mark, you at least have a sticker next to it pointing out real values... People notice deviations like those.

 

I guess we're still missing something here. I hope that once we have more detailed documents from the archives, we can understand better what they did to obtain their published values.

 

There is some huge misconception being perpetrated.  I will go thru the NACA report on flight and wind tunnel investigations in an attempt to walk the reader thru how to read the report.  It is not a test of the designers Clmax but rather a comparison of methodology and the validity of wind tunnel testing to flight testing.

 

It is being presented to the community as proof designers cannot achieve their design Clmax however and that is patently false.

Surely Pilots are only interested in IAS, if they are told it stalls at 90mph in training, and it does when looking at the gauge, the PEC is irrelevant at these speeds to the operator?

 

or am I missing the point 

 

Cheers Dakpilot

 

 

Yes you are kind of missing the point.  You are correct in that IAS is pretty much all a pilot needs but this is a aerial combat simulation.  That means we are simulating the relative performance and tactical advantages of each design.  That means EAS/TAS (for mach effects) are important.  IAS has inherent error and if that error is not accounted for properly then we will end up with huge errors in relative performance of the airplanes.  

 

Just using IAS values can introduce errors as large as 20% and completely reverse the actual relative performance as we see in the case of the P-40 vs Bf-109F4.

[Crump]

 

 

Just as JtD pointed out earlier the effect of the tail on a stable plane is to lower the airplane Clmax not increase it. This is why you will get a higher Clmax as you lower the stability margin because you are lowering the downforce of the stabilizer/elevator combination but the tail will not increase the airplane Clmax, only lower it to various degrees from the plain wing Clmax depending on the stability margin.

 

You will have a range of Clmax depending on CG location that goes from a high mark at the rearward CG to a low mark at the Forward CG.

 

 

 

Yes, sure we are missing something and I'm not saying it HAS to be the IAS, it just seems the most plausible explanation.

 

 

Yes, as I have pointed out to you many times, accurate airspeed measurement was problematic at best in the 1940's.  That is why normal force coefficients were used in flight testing Clmax because airspeed measurement was just too inaccurate.

[Dakpilot]

I should have quoted/replied

 

two more posts popped up 

 

I was really replying to the idea of needing a sticker pointing out real values on the gauge

 

carry on

 

Cheers Dakpilot 

[Venturi]

Correction - the relationship is linear and has a coefficient of zero at about 120 knots.

 

From

http://www.spaceagecontrol.com/USNTPS-FTM-C2.pdf

Edited January 2, 2017 by Venturi

[Venturi]

Here is the other term.

[Venturi]

In other words, the Boscombe trials pec curves data look OK in general, although I think their curve is off.

 

EDIT - added graph...

EDIT 2 - added USAAF pec curves (now that I know the equation) using both 2nd degree polynomial (taking into account overall curves of pec) and exponential trendline (as the Boscombe testers did it). It appears that the Boscombe testers likely did not know they should use a polynomial rather than exponential trendline.

Edited January 3, 2017 by Venturi

[ACG_KaiLae]

@Farky, do you have one of those indexes as well for the Allison engine company where we could also pull documents for the V-1710-39 and -73 engines? We might as well get everything we would need once. Also, perhaps one for Bell Aircraft for the P-39?

[unreasonable]

 

The effect of weight is to change velocity not AoA or CLmax of the stall point.  See, this is a good example of not understanding how the relationships work and drawing the wrong conclusions.

 

 

Actually this part of your post is a good example of you drawing the wrong conclusions, presumably because you have not been reading the thread.  

 

What I showed was that Han's numbers had a range of weights and a range of stall speeds, and if you calculate Clmax for the stall speeds that probably correspond to the weights, you get the same answer in each case (within rounding error)  - just as you should.  See my post 320, repeated in 359. 

 

So I neither misunderstood the relationships nor drew the wrong conclusions. Do not blame me if you have not been following the thread.

 

Edit but see 369 below - the 0.03 difference I put down to rounding errors might be the CG shift.

Edited January 3, 2017 by unreasonable

[Venturi]

The CLmax should change if the fuel level is changing.

But apparently, does not.

Because presumably, the fuel is not located at the exact cg.

[Venturi]

Attached files, again, showing what I mean.

[unreasonable]

 

 

It is being presented to the community as proof designers cannot achieve their design Clmax however and that is patently false.

 

 

No it is not. It is being presented as proof that operational aircraft with the usual manufacturing imperfections plus gun ports etc cannot meet the design Clmax of a smooth model.

 

No doubt a design team could take a plane built with special care and attention, seal off cracks, remove gun ports etc, and get results much closer to the design maximum that in the case of the NACA tests.

 

That is not the point, The issue is the degree of the difference.

 

The "satisfactory agreement" you quote from the 618 report alludes to "maximum lift coefficient measured in flight and those measured in the full-scale wind tunnel". ie it is between flight tests and wind tunnel tests of the same physical aircraft as the report makes crystal clear: not of a model or airfoils.

 

The quote from 829 is slightly less clear but still compares "full scale tunnel with flight measurement of an airplane " . Again, comparing flight test with tunnel test for the same plane - not comparing the plane with a model, or the wings.

 

So it has absolutely no bearing on the issue of the airfoil>wing>plane differences.  Indeed it even refutes your claim that Clmax determination from flight testing is worthless.

 

So much for drawing the wrong conclusions.

Edited January 3, 2017 by unreasonable

[Crump]

 

 

No it is not. It is being presented as proof that operational aircraft with the usual manufacturing imperfections plus gun ports etc cannot meet the design Clmax of a smooth model.

 

Nope.  The design CLmax include all of that unreasonable for an operational aircraft. 

[unreasonable]

The CLmax should change if the fuel level is changing.

But apparently, does not.

Because presumably, the fuel is not located at the exact cg.

 

Well actually it might do based on my calculations : maximum weight 1.35, minimum 1.32, so if the fuel is used from fuselage tank first and usage shifts CG forwards then this is consistent with the rear CG = higher Clmax.

I had thought it was just rounding or whatever, not having thought about this issue, but perhaps not.

 

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

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

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

 

I do not know if the CG changes in game with fuel use in fact - just got that impression from reading a couple of posts by people who fly the P-40 in game a lot, but it is possible they were just so "immersed" that they imagined it.... 

 

Anyway the effect is still rather small, not enough to explain the mystery.

[unreasonable]

Nope.  The design CLmax include all of that unreasonable for an operational aircraft. 

 

It may well do so, but that design Clmax is then not the airfoil or wing Clmax. If you can find a document showing the design Clmax for a P-40,  that takes into account all these factors, please post it.

 

So far we have not seen any of that - just speculation based on different but similar wings or models. And the NACA reports explicitly point out that the achieved plane CLmax is difficult to reconcile with that of the airfoils.

 

The problem here seems to be that you are conflating the airfoil or wing Clmax with the design Clmax of an operational aircraft. 

[Venturi]

Anyway the effect is still rather small, not enough to explain the mystery.

 

It might not actually be SUPPOSED to be that small, is my point.

 

The P51 had such dramatic changes in CG from fuel load, for instance, that it became highly unstable when the rear fuse tank was filled. So much so, that pilots had to be very careful with it until the tank was empty.

 

So the effect can be very large, and the P40 has a relatively large fuel capacity.

It is still unclear if this can account for the CLmax issue. But to all the information at hand including the PEC, flaps up stall should be at 86-90mph TAS. Regardless of the other stuff. That means we are stalling at anywhere up to 10mph TAS too fast.

Again, it is unclear what this is from, but ultimately the effect it has is to radically change the behavior of the plane throughout its envelope, and most likely is the reason why the plane does not fit the historical accounts.

And by definition, ASI airspeed is corrected to TAS by the PEC...

at sea level

[unreasonable]

I understand, but that just means you have to have the facts for the fuel usage and GoG change. 

 

For instance, someone posted a description that the P-40 requires half of the fuselage tank to be used up just to warm up the engine. Similarly, assuming RL stall tests are carried out at a safe height, the climb would probably use much of the rest of that tank. Emptying that tank shifts the CoG forwards, so it is highly unlikely that the trial/manual figures were derived from tests with an extreme rearwards CoG, unless a plane was refueled while running after warm up and then some brave pilot carried out stall tests immediately after take off.

 

The other issue is whether it is the Clmax as such or the critical AoA that is changing the behaviour of the plane. If you have a Clmax/AoA curve, and decide that your Clmax should be higher, do you extend the existing line up to the new Clmax and therefore increase Critical AoA pro-rata, or do you maintain the old AoA and steepen the curve?

 

To put it another way, do you maintain the lift increment per degree of AoA, or do you increase it?

 

It might be easier to persuade the developers that they have the wrong critical AoA than Clmax - I suppose it depends on how the variables are linked in their model.  

[unreasonable]

There is a P-40 checklist that includes fuel management here, if you wanted to do detailed calculations:

 

http://www.aerofiles.com/checklist-p40.html

[unreasonable]

Also just for general interest for anyone who has not seen it before is an old set of usenet exchanges between Erik Shilling, ex AVG and various others. Informative about how to fight in the P-40 (do not dogfight) and also funny: you can just imagine the old airman fuming at the impertinence of his questioners but just about keeping a lid on it to get his message across.  

 

Tangential but not completely off-topic. 

 

http://yarchive.net/mil/p40.html

[Venturi]

For instance, someone posted a description that the P-40 requires half of the fuselage tank to be used up just to warm up the engine. Similarly, assuming RL stall tests are carried out at a safe height, the climb would probably use much of the rest of that tank. I would like to see that evidence, because I doubt it. The engines warm up very quickly on the ground.. also, a very simple exercise to find out if the game simulates cg changes would simply to see if trim needs to be adjusted as fuel or ammunition is consumed. I believe trim does change through the flight - at least for other aircraft - but would like to find out from someone else too. In my experience in the P40, the trim hardly needs changing at all, which doesn't make a lot of sense to me as that was not the reputation for the P40.

 

The other issue is whether it is the Clmax as such or the critical AoA that is changing the behaviour of the plane. If you have a Clmax/AoA curve, and decide that your Clmax should be higher, do you extend the existing line up to the new Clmax and therefore increase Critical AoA pro-rata, or do you maintain the old AoA and steepen the curve?

To put it another way, do you maintain the lift increment per degree of AoA, or do you increase it? I suspect that angle of attack may be off as well, it is 14deg currently and 16deg on the the 2212 which is the nearest we have to the 2215. Until we have design specs for at least the 2215 airfoil and better, for the entire aircraft, it is somewhat pointless to speculate. Obviously the CLmax is way off unless all of the documents we have are lying about stall speed.

 

It might be easier to persuade the developers that they have the wrong critical AoA than Clmax - I suppose it depends on how the variables are linked in their model. The evidence points to both being wrong, right now.

And the conversation with Eric Shilling, who fought highly maneuverable Japanese planes, definitely brings out the point that it is the relative differences between aircraft that truly matter. In a fight against a Me109F, the P40 has a different set of advantages than over a Ki43.

Edited January 3, 2017 by Venturi

[ACG_KaiLae]

Do not dogfight against Japanese aircraft, this is not the same operational advice that you get against German planes. In fact that thread repeatedly says you can outturn an E-3 and it's slightly faster. I don't think that the E-7 in game is substantially different than the E-3 other than a slightly more powerful engine aircraft wise?

[Venturi]

It is heavier and has the same engine.

[Venturi]

There is a P-40 checklist that includes fuel management here, if you wanted to do detailed calculations:

 

http://www.aerofiles.com/checklist-p40.html

 

I found some interesting things out just now.

 

Attached is the relevant page from the USAAF P40E pilot handbook.

 

Empty weight is 5962 lbs for the P40E, or 2704kg!

 

Right now, IL2 dev numbers list empty weight at 6775lbs, or 3073kg!

 

The normal internal max fuel load for the P40E was 120gal of fuel,

that included 32gal in the front wing tank, 51gal in the rear wing tanks, and 37gal in the fuselage tank.

 

However, for very long flights, the fuselage tank could be overloaded with an additional 25.5gal for a total of 145.5gal of fuel.

 

The weight for the standard max load for the P40E, aka "the design load" - which  included 6 guns, 1410rds of ammunition, and 120gal (454 liters) of fuel. The standard design load with those options was 8011.5lbs.

 

There were additional "options" which could be added to this, up to "the maximum alternate load" - this included things like a 52gal drop tank, extra 25.5gal fuselage tank fuel, 6x 20lb bombs, and extra 460rds of ammo. The maximum alternate load was 8845lbs!

 

The weight for the additional 25.5gal of fuse tank fuel was 153 lbs.

 

So, for 100% fuel in the game (listed as 148gal?), with 6 guns, and 1410rds of ammo, the P40E should weigh 8,164lbs! 

 

Right now, it weighs 8,420lbs for "standard load" which I assume means 100% fuel, but who knows, it might be for 120gal of fuel instead!

 

The weight for the optional additional 460rds of .50cal ammunition was 138 lbs, but the IL-2 description says that it is only 38kg or 84lbs!

 

 

In other words!!! There's a big problem!

[unreasonable]

Do not dogfight against Japanese aircraft, this is not the same operational advice that you get against German planes. In fact that thread repeatedly says you can outturn an E-3 and it's slightly faster. I don't think that the E-7 in game is substantially different than the E-3 other than a slightly more powerful engine aircraft wise?

 

Yes he does say that P-40 can out-turn an 109 E-3 in one post, but unlike Shilling's comments about fighting the Japanese this is not based on personal experience.

 

The later long post about P-40 vs 11109s is based on a US report on a 1943 engagement, probably with G-2s (?), the US claims of which have been thrown into doubt elsewhere: like all claims they are probably wildly inflated.

[unreasonable]

I found some interesting things out just now.

 

Attached is the relevant page from the USAAF P40E pilot handbook.

 

Empty weight is 5962 lbs for the P40E, or 2704kg!

 

Right now, IL2 dev numbers list empty weight at 6775lbs, or 3073kg!

 

 

 

Or just a different definition of "empty weight"? That looks to me like "empty weight means excluding everything else below.

 

Take the empty+radio 5892, add in guns armour and misc equipment for wing guns, gets you 6779.

 

Add pilot+chute, oil 300, gets you 6779lbs - as per game, just about. edit Soviet pilots are thinner

 

Take the 5982 and add in all the parts in the RH column relevant to P40 E - get 8012: same as design gross weight at bottom of table. ie empty in Il-2 means no fuel or ammo.

Edited January 3, 2017 by unreasonable

[Venturi]

Yes, read again -

 

design weight + extra fuel... IE "IL2 standard load"... is listed in the operating manual as 8164lbs, and from the devs as 8420lbs!

That is assuming that "il2 standard load" isn't actually 120gal of fuel - not 100% fuel! - in which case, the actual weight listed in the handbook is 8012lbs, not 8420lbs!!

In other words, the P40 in game is being given an extra 260 - 410lbs of weight!

[ACG_KaiLae]

I've got other docs that list fully loaded weight as 8480 or 8500 pounds so something is up. Could explain the very high calculated clmax though?