P-40 turn rate/Flight model check

[ACG_KaiLae]

I've recently seen some information that when tested by the Russians at 1000m, the P-40E had a 19s turn time. I haven't seen more details than this (I suspect I'd need to speak Russian) for what speed the aircraft was doing at the time or what engine power was being used. However this seems to be better than what we are currently seeing in game. Can someone find the relevant data?

Edited November 28, 2016 by Kai_Lae

[303_Kwiatek]

P-40 E tested by VVS

 

 

[ACG_KaiLae]

Thanks - I can't read Russian though, could someone tell me what it says?

[6./ZG26_Klaus_Mann]

Thanks - I can't read Russian though, could someone tell me what it says?

Go by context. 

Left is Hurricane Mk.IIa

Middle is P-40C

Right is P-40E. 

 

1280

1055 

1150

Are obviously Horsepower

 

3170

3390

3840

Weight

 

23.9

21.92

21.92

Wing Area

 

Below those are Ground Speeds and Topspeed with altitude. The Star Marks Combat Rating.

 

Time to Climb to 5km.

 

360° turn at 1km

[ACG_KaiLae]

I don't see on this document, but does on previous pages it say were all aircraft tested at the same speed? What was that speed?

[Bert_Foster]

Thanks - I can't read Russian though, could someone tell me what it says?

[Venturi]

In N Africa, most of the 109F drivers would start out above the P40E drivers and would dive down through then climb back up. There wasn't much the P40 drivers could do against this if the attacking 109 pilots were smart, which they generally were as only the wing leader would really attack at any one time while the rest stayed up at alt.

 

It helped that the P40E pilots were using wrong doctrine in the "wagon wheel" formation, and also didn't routinely patrol as high, but there are instances in the several direct mission reports I've read that indicate in situations which the P40 could bounce the 109, the P40 more than held its own as it had greater horizontal maneuverability and could outdive the 109s due to their loss of control response at high dive speeds. Typically for this reason, the 109s would attempt to equalize energy and then out limb the P40s. But it was hairy for them until that happened because the P40 could out maneuver them, could outdive them(no split s) and with the P40 having more e from the dive, immediate climbing was not a good option for the 109s as the P40 could catch them.

[unreasonable]

I don't see on this document, but does on previous pages it say were all aircraft tested at the same speed? What was that speed?

 

I think it is more likely that they were all tested at a power rating; perhaps combat power - ie the recommended rpm and manifold pressure for combat for each aircraft. From a pilot's pov, that is what you want to know.

[ACG_KaiLae]

Well I am obviously interested in how this compares to in game. Pilot accounts generally all say the same thing - the P-40 could horizontally outturn a 109, but the 109 could dominate it vertically. Right now, the P-40 only turns fairly well at faster speeds in game. The listed turn time is 24+ seconds at sea level and 36s at 9842 feet (3000m). Logically, this would mean that at 1000 m, it would have more than 24s turn time. This is a big discrepancy in data, depending on speed used. IL-2 data sheet seems to use 167.7 mph for turn speed, regardless of aircraft. I'm not sure if this is the cause of the difference, because I don't know what speed the Russians performed their turn test at (I assume sustained, but that is again a guess).

 

Right now, when slow, it seems like bf-110s outturn you, and I'm not sure if this is accurate.

[303_Kwiatek]

Accordind to VVS test and what we could read about turning ability of P-40 it looks that in BOS is way inaccurate. P-40 E should sustained turn at 1 km below 20 second.

Edited September 21, 2016 by 303_Kwiatek

[JtD]

This has been brought up like 85 times on this board already. Sustained turn times of less than 20s for a 4t aircraft with not even 1150hp are not plausible. Didn't happen. The document is worthless because it either contains wrong numbers, or incomplete information.

[303_Kwiatek]

P-40 pilots ( also Russians) clameid that it outturns Bf 109 at low alts. It is confirmed by VVS test.

Edited September 21, 2016 by 303_Kwiatek

[ACG_KaiLae]

Is there other sources available?

[JtD]

P-40 pilots ( also Russians) clameid that it outturns Bf 109 at low alts. It is confirmed by VVS test.

And since pilots cannot overcome limits imposed by physics, we'll have to acknowledge that pilot accounts also don't give the complete picture.

A P-40 at low altitude, low on fuel and ammo, throttle well open could well achieve turn times below 20s, however, this has nothing to do with that tables 1150hp power and near 4t weight. Just like you can in game chop 5 off the 24.3 seconds given by the devs, if you fly it light and at full power.

 

Is there other sources available?

None that I am aware of. Edited September 21, 2016 by JtD

[ACG_KaiLae]

This has been brought up like 85 times on this board already. Sustained turn times of less than 20s for a 4t aircraft with not even 1150hp are not plausible. Didn't happen. The document is worthless because it either contains wrong numbers, or incomplete information.

Not saying you're incorrect, but pretty sure an I-15 has less hp than that and a lower turn time. What makes you say that in this case? I'd assume hp vs weight?

[303_Kwiatek]

Maby Russians used emergency power in turn test for P-40, also strange for me is only 14 deg critical angle of attack for BOS P-40 - it looks very low value but i dont have RL data for P-40 wing polar.  Still P-40 E got lower wing loading then 109 F4 or Lagg-3 even at standart take off weight.

Edited September 21, 2016 by 303_Kwiatek

[JtD]

Not saying you're incorrect, but pretty sure an I-15 has less hp than that and a lower turn time. What makes you say that in this case? I'd assume hp vs weight?

The I-15 is not even 1400kg heavy, if the P-40 came at that low weight with nothing else changed, it could achieve turn times of maybe 5-6s sustained.

 

Maby Russians used emergency power in turn test for P-40, also strange for me is only 14 deg critical angle of attack for BOS P-40 - it looks very low value but i dont have RL data for P-40 wing polar. Still P-40 E got lower wing loading then 109 F4 or Lagg-3 even at standart take off weight.

So, lowering wing loading helps with a lower stall speed. That's like 30% of low speed turning performance. It sucks at power weight, and it's clearly worse than the 109 at span loading, which is another 60% of turning performance.

Certainly, the P-40 in game is modelled somewhat poorly, see the other topic on the subject which I opened up yesterday. It doesn't mean it should get to 19s if it was modelled somewhat more optimistically.

Stalling angle - the P-40 landing gear was reworked because the aircraft displayed a tendency for ground looping in the early versions, owing to the wing being above stalling angle of attack while on the ground. It wasn't with the longer tail wheel of later models. Feel free to read up to which condition this applied WRT flaps, I don't remember. Other than that, it used the same airfoil the Spitfire uses so maybe you can find references there.

Edited September 21, 2016 by JtD

[II./JG77_Manu*]

So all those Russian, Italian, German and US pilots who said, that the P40 can outturn the 109 are wrong? 

German officers telling their 109(F4) pilots to never get into a prolonged turnfight with a P40 were talking nonsense? 

 

I get where you are coming from with your science JtD, but there are numerous sources from several countries out there, both numerical (19s), and anecdotal that the P40 (C, E, F) was a very good horizontal turner. I don't think they are (all) lying to be honest. I rather think you might have missed something. Those 1150hp probably not the power pilots back then used to fight with. Rather 1500. In WW2 they didn't have engine breakdowns after one minute (or 15). They slammed the throttle forward as long as neccessary. No artificial engine limits, when your life is at stake

[=362nd_FS=Hiromachi]

 

 

So all those Russian, Italian, German and US pilots who said, that the P40 can outturn the 109 are wrong?

Not necessarily, one must understand that sustained turn =/= instantaneous turn. In first one very important factor is Power to Weight ratio, in latter one stall speed. P-40 had relatively lighter controls and with its quite decent stall speeds its entirely possible that 109s would be outturned during combat. But in prolonged turn ? 109 with its great Power to Weight ratio should be able to keep up and gain advantage. Though point you mentioned about running at higher settings, there is (or was) that discussion about P-40 E running at higher MAP, and thus having quite a bit more power than standard 1150 HP.

[JtD]

Absolutely true, Manu. I'm not saying that the P-40 could not turn, I'm just saying that anecdotal evidence gives an incomplete picture. And that either the 19s are wrong, or also incomplete.

 

I can get our 'conservative' P-40 in game to do turning at about 19s, wouldn't call it sustained because I blow the engine in like two turns if I do. Of course I also need to mention that this is the 4 gun version with 10% fuel without ammunition, and with 100% throttle at sea level in standard conditions. And that's the sort of complete information that is lacking from the sources. Conditions can easily make a 5 seconds difference. That's all I am saying.

 

For pilot accounts, the context is even more important, and for tactical advice, even more still.

 

For instance, why would any sane Bf109 pilot go into a turning fight with an enemy airplane, that is outclassed in many other aspects of performance? Not only is sustained turning a suicidal tactic, it is also where the relative performance of the two is closest. If I was a Bf109 veteran and had to give advice to some noobs fresh from the academy, I'd say to never enter a prolonged turnfight with any opponent, period. No matter if the Bf109 had the advantage, or not. What would you do?

[II./JG77_Manu*]

Not necessarily, one must understand that sustained turn =/= instantaneous turn. In first one very important factor is Power to Weight ratio, in latter one stall speed. P-40 had relatively lighter controls and with its quite decent stall speeds its entirely possible that 109s would be outturned during combat. But in prolonged turn ? 109 with its great Power to Weight ratio should be able to keep up and gain advantage. Though point you mentioned about running at higher settings, there is (or was) that discussion about P-40 E running at higher MAP, and thus having quite a bit more power than standard 1150 HP.

 

Germans have been warned especially to not go into prolonged(!) turnfights against P40, because "they will eventually get the upper hand in a turning duel".

 1470 hp was the WEP power of P40E, probably used in emergency situations (like turnfight on equal energy state). With full fuel the P40 had a power/weight 0,383hp/kg. Exactly the same like Lagg-3 with PF engine. Considering that the P40E probably rarely used a full tank in front line missions, power/weight would be even better (comparable to Yak1 with PF). Add bigger wings. There you have your turning machine. Shame that it isn't apparent in the game.

 

 

For instance, why would any sane Bf109 pilot go into a turning fight with an enemy airplane, that is outclassed in many other aspects of performance? Not only is sustained turning a suicidal tactic, it is also where the relative performance of the two is closest. If I was a Bf109 veteran and had to give advice to some noobs fresh from the academy, I'd say to never enter a prolonged turnfight with any opponent, period. No matter if the Bf109 had the advantage, or not. What would you do?

 

Sure, that alone is far from a proof of performance. But other accounts - i remember an Italian guy - saying that the P40E is at least equal to an F4 in a prolonged turning fight should not been overlooked. If you'd take that ridiculous engine limits away in the game, it would definitely promote the P40 at least into a usuable fighter plane. Right now i'd rather take an IL2 for a dogfight. 

[JtD]

If the P-40 in game as aerodynamically efficient as the LaGG-3, it would be at 20.5s, if it was as aerodynamically efficient as the Yak-1, at 22s. See other topic. I don't know why the devs went with the figure we have, as already said, I consider game performance conservative.

Il-2's probably still worse.

[Solty]

I've also read and heard from the pilots that the P-40 was able to outturn the 109. One of the pilots (Wayn Reynard)even said that it was their tactic was to make the German turn with them and they did 2 circles which was enough to shoot him down.

https://youtu.be/Lu5vX86TdIU?t=7m48s

https://youtu.be/Lu5vX86TdIU?t=8m33s

 

What we do not know weather he was talking about the P-40E or the P-40F, nor what 109 it was. Maybe it was G6?

 

And it is interesting that some sources give it under 20sec turn time, and I have not seen a single one that states otherwise.

Edited September 21, 2016 by =LD=Solty

[ACG_KaiLae]

The point of the thread was that I strongly suspect that the p-40 FM underperforms, but suspicions don't get things changed, facts do. The biggest things that stand out to me as seeming off are the fragile engine limits, even with lots of combat reports stating otherwise, and the horizontal manuverability. However, how do we prove that this is the case?

[Venturi]

What JtD and others have said is that engine power matters a lot, airframe drag matters a lot, and wing performance matters a lot.

 

Take all three, put them on the low end of plausible, and you get a result.

[Venturi]

By the way, the engine used in the P40E was the Allison V-1710-39, which was mechanically rated as capable of safe operation at 56" manifold pressure for 5min. This generated approx 1470hp at 3000rpm. That is fact.

 

Failure timers should start after that guaranteed 5min.

 

This does not even touch on the multiple documented accounts of pilots using their V-1710-33 (P40B) and -39 Allisons at much higher power outputs, and living to tell about it.

[Matt]

Yes, but we can currently use 56" and 3000 RPM for 5 minutes according to the description. The problem is knowing when you actually have 56" because the needle stops at 50". That raises the question, if the needle should actually stop there or if it would've been possible for it to move past the 50" position.

[Kurfurst]

I've recently seen some information that when tested by the Russians at 1000m, the P-40E had a 19s turn time. I haven't seen more details than this (I suspect I'd need to speak Russian) for what speed the aircraft was doing at the time or what engine power was being used. However this seems to be better than what we are currently seeing in game. Can someone find the relevant data?

 

Same thing with the G-2 though, it takes turns in 22 secs, whereas the Soviet captured example could complete a sustained turn in 20 secons, at 1000m.

 

It could be though that it's an  effect of different in-game atmospheric conditions that increases turn times, to me it seems that all aircraft have higher turn times than in the documentation.

[6./ZG26_Klaus_Mann]

Same thing with the G-2 though, it takes turns in 22 secs, whereas the Soviet captured example could complete a sustained turn in 20 secons, at 1000m.

 

It could be though that it's an  effect of different in-game atmospheric conditions that increases turn times, to me it seems that all aircraft have higher turn times than in the documentation.

Ingame they have a nebulous thing called "Performance Turn". It's not a sustained turn. 

The G-2 takes about 20 Seconds sustained. 

[Venturi]

Yes, but we can currently use 56" and 3000 RPM for 5 minutes according to the description. The problem is knowing when you actually have 56" because the needle stops at 50". That raises the question, if the needle should actually stop there or if it would've been possible for it to move past the 50" position.

The gauge doesn't dictate what the engine could do, mechanically. Quite the opposite. But if you meant, should we be able to read the gauge past 50", my opinion right now is that the standard early P40E gauge went up to 50" and stopped, based on a picture I've seen of the inside of one of these gauges. Whether it was the actual same MAP gauge as in a P40E, I do not know. Most vacuum/boost gauges I've been around will travel indefinitely until the needle is actually stopped on the gauge face.

 

In fact it is not unusual to see vacuum gauge needles make more than one complete revolution when under high vacuum in my experience. Obviously that means the gauge is not calibrated to accurately measure the overly large amounts of vacuum it is seeing, but it does give you a rough idea of where the measurement is. Pilot accounts speak of the needle going past the 50" mark and actually breaking the gauge because of the high boost, whether this was because the needle came off when put against its stop by the large boost, is hard to say. It is plausible.

 

Later P40E MAP gauges went up higher. Which version should we have? Hard to say.

 

My opinion, Matt, is that the pilots didn't pay a whole lot of attention to it during fighting, as it would have been very hard to maintain a consistent MAP anyways. Most likely the throttle went forward and the pilots fought for some minutes, either getting out of trouble, winning, or getting shot down. Then the throttle went back to cruise settings. When unregulated as in the P40E, MAP will tend to vary with the load on the engine, along with the currently modeled variables of airspeed (ram effect), RPM, and altitude. It would have been next to impossible, realistically, to maintain the MAP at a given level under those conditions in combat.

 

If modeled realistically, the engine would be gauranteed 5min on that power setting and then the chances for bad things would start to happen, the chance increasing with the amount of time, and in a random sort of way. I think this way of modelling the situation would give the most realistic outcomes, even with a gauge that only goes up to 50". Less min/maxing that way.

Edited September 23, 2016 by Venturi

[MiloMorai]

[Libel]

Well, I do know that The Fighter Collection here in the UK has an airworthy P-40B and P-40F... could we ask them about performance perhaps? Long shot, but hey.

[Venturi]

 

Thanks MM, but that doesn't quite look like a vacuum/boost gauge. Rather, a pressure gauge such as you would have on a container of pressurized gas.

 

This is more of a vacuum/boost gauge such as is commonly used on engines [attached]. Note that there is a mechanical stop on the needle travel, or the needle would go past and continue around on the "opposite" side with excess boost or vacuum.

 

There are many types, the interior of the one I'm showing here uses the expansion or contraction of the airtight copper arm, which occurs with boost or vacuum, to mechanically move the needle. In this arrangement, the interior of that copper arm is actually in continuity with the column of pressure or vacuum which is being generated. Obviously with this arrangement, the needle could continue moving just as long as the copper arm withstands the vacuum or boost pressure, or until the needle was stopped by a travel limit pin on the gauge.

Edited September 24, 2016 by Venturi

[ACG_KaiLae]

While I suspect the sim is incorrectly doing the information required to determine the correct turn rate of the plane, it's also obvious that the engine is bugged. The dev diary information is not remotely close to what is in game; that's at least a text issue. I have bug reported the engine:

 

http://forum.il2sturmovik.com/topic/12262-armament-and-equipment/?p=393397

 

If you all could add useful supporting information, I'd appreciate that. 

[Farky]

Engine was discussed in detail here - http://forum.il2sturmovik.com/topic/21234-p-40-engine-settings-i-found-them-bit-weird/

[MiloMorai]

Venturi, yes the photo is not an actually vacuum/boost gauge but the principle of how it works for boost or vacuum is the same.

 

As for stopping, I had an expensive water speedometer that that had the C tube bent because the boat it was mounted on went faster than upper speed on the dial. How much faster I don't know but the dial went to 90mph. The pin will stop the needle from moving but as it is only a press/friction fit on the center pin it won't stop the C tube from moving.

 

A vacuum/boost gauge is a lack of pressure/over pressure gauge.

 

I went to college for industrial instrumentation and repaired and overhauled a/c instruments for a living for a few years.

[Venturi]

Definitely works on the same principle, and as you say, given lack of a stop on the face, needle will go past 50".

[LLv34_Flanker]

S!

 

 Hard to determine the performance figures as we do not know the circumstances. Was the plane new or used in combat? For example RAF officers told Finnish delegation that came to buy Hurricanes that they lost 20mph of speed very quickly due the wear and tear under combat stress. Hawk 75A marketing brochure(which I have as PDF) has fantasy values for the plane compared to a combat ready plane etc. What equipment was installed? Radios, guns, ammo, armor, pilot equipment? How much fuel etc.

 

  The game tries to represent FM as the planes were "factory fresh", but again they rely on data from archives using data from captured/repaired planes etc. For example the P40's delivered to VVS were not spanking new thus that could have affected the performance negatively. How about the fuel used? Was it the higher octane "western fuel" or the 70-80oct domestic fuel? Were the VVS P40's using these higher engine boosts or the factory values? As long as the devs do not share their sources, we can not know and the arguing goes on forever, sadly.

[19//Moach]

please let us not derail into a discussion about the ENGINE, when this thread is originally about the flight characteristics of the airframe in a turn

 

I will add that I have heard accounts on many a documentary featuring P-40 veterans who report the plane WAS capable of out-turning the 109 in a horizontal fight

 

ingame this behavior is largely inaccurate, either by fault of the 109s stall onset not being as abrupt and imbalanced (slats opened asymmetrically, leading to frequent violent spins) - or by the exceedingly tight stall envelope of the P40 (which should hold out better than the 109, with less wing loading, but doesn't)

 

this might also be a factor of a combination of both, and/or include various other reasons why the BOS flight model does not match veteran accounts and documents against the 109 in a flat turning fight

 

this comparison against the enemy fighter is not in itself a good set of data - reports are largely anecdotal and there are too many uncontrolled variables in a typical ingame encounter to verify with any certainty

 

however - it seems to me that this document claiming better than modelled turning rate DOES bear out in accordance to the veteran's accounts, and to the many players' claims that the P40 does not hold out on a turn as well as it should (as well as by my memory of it in previous IL2 titles)

 

 

it is thus strongly recommended that the turn performance of this model is revised - including factors like induced drag and pre-stall dynamics -- there is enough evidence and reports to justify at least a good verification

[Crump]

Here is a quick analysis I did a few weeks ago.  I do not have good airfoil or wing design data on the P-40 so I had to extrapolate from several stall testing to ballpark the Clmax.  The Bf-109F4 has good data and I used Mtt's published CLmax for their wing design.

 

This is the Bf-109F4 at 1.42ata @ 2700U/min and take off weight of 6503 Lbs as per Kennblatt.

 

The P-40 is using 52"Hg Standard Emergency Power at 8626 Lbs take off weight.

 

The Sustainable Load Factor limit:

 

 

Rate of Turn:

 

 

Acceleration:

 

 

What it basically tells us is that the P-40 needs to get the Bf-109 low and slow.  The P-40 can turn at airspeeds the Bf-109 cannot even fly.  That being said, if the Bf-109 stays in his envelope, he matches the P-40 and even has a slight advantage in Rate of Turn at his best turn speed.