The P40 thread

[216th_Lucas_From_Hell]

It needs noting that Gavrick (flight engineer extraordinaire at 1CGS) has found two problems with the Kittyhawk flight model that are making a bigger problem of the engine limits than they really are. From memory, one is related to the overall FM problems with rudders and all that which caused instability, while the other was a mistake which made it lose energy at an extremely high rate during turns and other manoeuvres. With the aircraft able to retain energy better, even with the current limits it should become more competitive (something like a LaGG-3).

 

TBO Allison 700 hrs

TBO Merlin 400 hrs

TBO DB601 150hrs

Enough said

From which year and under which operational conditions is the Allison TBO?

[ACG_KaiLae]

Apparently the new update will adjust something to do with "inductive resistance" which I'm sure is a translation thing. I think this may mean drag coefficient. Anyway even with that, and the change in stability, if you were to change the engine settings it wouldn't still likely fix the plane issues. But we'll see. 

 

Then again, maybe they're measuring the amount of millihenrys the radio has :/.

Edited August 11, 2017 by Kai_Lae

[19//Moach]

 "inductive resistance" 

 

isn't that translatorish for "induced drag"?  - would make perfect sense... the P40 does seem to suffer plenty from it.  a fix there would make a world of difference

Edited August 11, 2017 by 19//Moach

[ShamrockOneFive]

I missed that part about the drag coefficient or whatever they are referring to. I'm pretty excited to see how much that might change the character of the P-40!

[BlitzPig_EL]

Keeping my fingers crossed.

 

 

Still need more realistic engine operating limits though.

[216th_Lucas_From_Hell]

Could you folks find the link to the quotes again? I can put together a quick and dirty but accurate translation for future reference.

[Venturi]

From which year and under which operational conditions is the Allison TBO?

 

750hrs in combat theaters, 1000hrs under training conditions.

 

Pg 390 & 391, Whitney's "Vees for Victory".

[216th_Lucas_From_Hell]

Nice, thanks!

[unreasonable]

Could you folks find the link to the quotes again? I can put together a quick and dirty but accurate translation for future reference.

 

AnPetrovich said that P-40 had "ощутимо завышенное индуктивное сопротивление" (i.e. inductive resistance was too big) - https://forum.il2stu...-52#entry542513 +  https://forum.il2stu...-52#entry543035

 

Edited by bivalov, 09 August 2017 - 18:08.

[216th_Lucas_From_Hell]

AnPetrovich's (not Gavrick as I'd thought, my bad) first post:

 

I've finished my part of the FM re-tune (though Jason asked me to go over the P-40 again), and now things are headed to the final step - re-tuning peripherics. I hope to get thst done soon.

 

Second post:

 

Throughout winter, additional calculations have shown that generally the performance of our P-40 (level and climb speed) is affected by excessive lift-induced drag, which translates to a loss of energy during manoeuvres. Logically, after these corrections it should turn better. And after the fixes to rudder controls the P-40 has become, first of all, much more stable, and second, it doesn't snap or enter spins when the pedals are pressed like in the current client version.

[6./ZG26_Klaus_Mann]

Well, it should be somewhere inbetween. Regular Spin Entry for the P-40 was by stalling and pushing the Pedal. http://www.wwiiaircraftperformance.org/P-40/P-40E_40-633_PHQ-M-19-1398-A.pdf

Edited August 12, 2017 by 6./ZG26_Klaus_Mann

[19//Moach]

Well, it should be somewhere inbetween. Regular Spin Entry for the P-40 was by stalling and pushing the Pedal. http://www.wwiiaircraftperformance.org/P-40/P-40E_40-633_PHQ-M-19-1398-A.pdf

 

 

yes, that is the correct procedure for any airplane.  

 

but I believe what was meant, which is truly incorrect of the current P40 model, is that pushing the pedal WITHOUT stalling will cause it to enter a (rather violent) spin. 

 

 

this phenomena has been dubbed "The Death Slide" - and it is wonderful to have proper confirmation that it will be addressed with the new FMs.  a breath of new life for this much afflicted warbird.

 

 

a Death Slide™  is wholly distinct from an asymmetric stall leading to a spin, as can be verified ingame by deliberately stalling while holding the plane in a controlled sideslip.

this has to be done very carefully, as to avoid exceeding the Angle of Death, thus causing a Death Slide instead of a normal spin

 

if done correctly, you can then notice the very different manner in which the inside wing abruptly drops, and with quick correction, the incipient spin can be countered before it develops into a full departure.

 

the Death Slide itself feels very different. it has no discernible moment when a wing drops. instead, it is more recognizably marked by a gradual, but very strong sideways pulling "force", which as often as not, is impossible to counteract even with the sharpest reaction and full opposite rudder (sometimes that makes it worse). 

 

you can try a Death Slide by entering it with the nose held level, pointed at the horizon the whole time, while gradually increasing your slip angle past 12° or so. at that point, you should start feeling a strong yaw force in the same direction of the slip.  the only way to help prevent it developing further is by rapidly cutting the engine. however, this is not always effective, and most times you'll have to ride it out as it inevitably induces a very nasty spin, from perfectly level flight. 

 

beware though, that the spin which results from the Death Slide is not an incipient one, as the aircraft enters it at such an extreme attitude it is most likely impossible to prevent a full departure.  it's extremely violent at any speeds, even more so than a regular spin would be (even with the known violence of P40 spins which made them prohibited by the manuals) -- do not try this at low altitude. unless you want a new crater on your lawn

 

 

 

 

so it should not actually be "in between" - there are no documents or manuals anywhere that even hint at a possibility that the P40 would spin simply by applying full rudder in level flight.

 

I reckon something like THAT would be printed in big block letters, were it actually the case.

Edited August 12, 2017 by 19//Moach

[Venturi]

Any aircraft will spin by entering a stall and applying rudder.

[216th_Lucas_From_Hell]

Fellas, it's lost in translation - what AnPetrovich means is thst at this time, in regular flight, any kind of rudder input stalls the aircraft and sends it into a spin.

[ACG_KaiLae]

Which is what Moach is talking about.

[Multimetal]

Thought you guys might be interested in this-Kermit Weeks recently uploaded a detailed walk-around video of his TP-40, it's awesome to see this bird up close!  Lots of neat little details about operating the hydraulic systems, etc.  Part 1 is up, 2 and 3 should be coming soon-

Edited August 14, 2017 by Multimetal

[Jade_Monkey]

I'm pretty excited to see how much that might change the character of the P-40!

It can't be much worse than the current plane, it's hard to believe that a plane with these flight characteristics actually got any kills against German and Japanese planes.

 

Im just finishing the Osprey book on the P40 and the author's conclusion is that the succesive models did very little to improve the speed and agility of the P40-E, remaining practically the same all the way till 1944 when it was replaced by P38 in the pacific and the P47 in europe.

[216th_Lucas_From_Hell]

"An official opinion regarding the Kittyhawk in the Soviet VVS can be found in the "Summary of combat activities of the 4th Air Army for April 1943": "In its flight and tactical characteristics, the Kittyhawk fighter lags behind the Airacobra and Bf-109F and G. It is capable of successful combat with the Bf-109 in horizontal maneuver but is inferior in vertical maneuver. It can successfully accomplish the mission to intercept bombers and reconnaissance aircraft. Pilots have developed the opinion that the Kittyhawk can be a good aircraft for the following missions: provide cover for our own ground forces, escort bombers, and conduct reconnaissance."

 

From Romanenko's book on lend lease aircraft. He also mentions that in Kuban, 45 IAP found that after using WEP for 10 minutes the engines were done for and the aircraft failed to go past 350-400km/h afterwards. I have the aerial numbers of four 45 IAP P-40Es, does anyone know how to find their origin (ie new, ex-USAAF or ex-RAF) based on that?

[purK]

Here's part 2

 

[unreasonable]

"An official opinion regarding the Kittyhawk in the Soviet VVS can be found in the "Summary of combat activities of the 4th Air Army for April 1943": "In its flight and tactical characteristics, the Kittyhawk fighter lags behind the Airacobra and Bf-109F and G. It is capable of successful combat with the Bf-109 in horizontal maneuver but is inferior in vertical maneuver. It can successfully accomplish the mission to intercept bombers and reconnaissance aircraft. Pilots have developed the opinion that the Kittyhawk can be a good aircraft for the following missions: provide cover for our own ground forces, escort bombers, and conduct reconnaissance."

 

From Romanenko's book on lend lease aircraft. He also mentions that in Kuban, 45 IAP found that after using WEP for 10 minutes the engines were done for and the aircraft failed to go past 350-400km/h afterwards. I have the aerial numbers of four 45 IAP P-40Es, does anyone know how to find their origin (ie new, ex-USAAF or ex-RAF) based on that?

 

Only that serials starting with AH, AK and AN are RAF.  There are quite a few serials noted in this long article (edit by the same author )  about lend lease p-40s, perhaps something there.

 

 http://lend-lease.airforce.ru/english/articles/romanenko/p-40/index.htm

Edited August 16, 2017 by unreasonable

[216th_Lucas_From_Hell]

Couldn't find anything there. They're 136943, 136948,136949 and 136950 from what I know, no letters so by your information they're likely USAAF or brand new. That website is pretty good for lend lease aircraft information

[216th_Lucas_From_Hell]

Nothing conclusive under those four construction numbers, but this list says a number of P-40Es were sent to the Soviet Union from USAAF units between 1942 and 1944.

 

http://cgibin.rcn.com/jeremy.k/cgi-bin/gzUsafSearch.pl?target=&content=P-40E

Edited August 16, 2017 by 216th_Lucas_From_Hell

[unreasonable]

US serials start with the last two numbers of the year - ie 41-12345 (edit yr-5 digits) for a plane registered in 1941.  The numbers you have could be the manufacturer's numbers? 

 

Every USAF serial number since 1922 here  http://www.joebaugher.com/usaf_serials/usafserials.html

Edited August 16, 2017 by unreasonable

[216th_Lucas_From_Hell]

Yep, my bad. They're c/n, not s/n.

[Farky]

I have the aerial numbers of four 45 IAP P-40Es, does anyone know how to find their origin (ie new, ex-USAAF or ex-RAF) based on that?

 

 

 

Couldn't find anything there. They're 136943, 136948,136949 and 136950 from what I know, no letters so by your information they're likely USAAF or brand new.

 

 

Yep, my bad. They're c/n, not s/n.

 

 

These aren't construction numbers, but serial numbers as they were written on the aircraft. USAAF haven't used first number from serial on airplanes, so these are 41-36943, 41-36948, 41-36949 and 41-36950.

They were brand new P-40E-1s, delivered directly from USA to USSR via Lend-Lease in June 1942. Airplanes were allocated from RAF order (RAF numbers EV689, EV694,EV695 and EV696).

[Venturi]

He also mentions that in Kuban, 45 IAP found that after using WEP for 10 minutes the engines were done for and the aircraft failed to go past 350-400km/h afterwards. 

 

What WEP?

 

Does he mean throttle fully forward?

 

There is no definition of WEP for V1710-39 at this time in the war. 

I suspect this "WEP" is the full manifold pressure as able to be supplied by the supercharger.

 

Not 56" Hg, as was later defined when the P40 was stipulated to have a manifold pressure regulator (this stipulation occurred after P40E was withdrawn from front line use).

[216th_Lucas_From_Hell]

Excellent investigative work, Farky! Thanks!

 

This is an interesting turn then. You see, according to most Soviet records these four aircraft arrived as part of a large shipment through Iran, in November 1942 or later. These were first sent to 25 ZAP in Azerbaijan, then 9 went onto 45 IAP as combat aircraft - one loss occurred, and they didn't like it for anything but air defence. 16 GIAP received four P-40s in March 1943, one from 25 ZAP, one from 25 ZAP (either used or new), one from 45 IAP (used) and two from 84 IAP. They flew about four missions, and after being judged as unsuited for frontline fighter combat they were passed on to air defence units in the area.

 

If those aircraft were delivered in June 1942, it's likely they actually arrived through the northern route then (unless USAAF earmarked them in June '42 but didn't register the shipping/delivery date). If this hypothesis is true, other units in the north (either reserve or frontline units) could have flown them for those five months prior to their arrival at 25 ZAP, which, once again if and only if true, could have exacerbated the problems southern units had with them.

 

I also wonder about the camouflage - as those were from an RAF order, can we assume they were painted in RAF colours from the factory? Or did USAAF throw olive drab onto them?

 

Venturi, I haven't got a clue. Did 1942 or 1943 manuals specify some kind of combat power or take-off setting that lasted around ten minutes? This is probably a matter of translation since in Russian you only have one term for all regimes above continuous power

Edited August 16, 2017 by 216th_Lucas_From_Hell

[Venturi]

This leaves it open to interpretation then. 

 

My thought would be, if the pilots were flying an aircraft with poorer climbing ability than they were used to, that they would use all available power.

 

Especially if those pilots were used to types with manifold pressure regulators.

It is a relevant discussion, not only to the P40, as there will be many American aircraft whose engines also operate this way.

[216th_Lucas_From_Hell]

Probably. The pilots involved were mostly transitioning from the 1942 Yak-1 which didn't have any particular ratings, firewalling even if for a few seconds was second nature and it caused a few crashes and mechanical failures along the way. A couple of incidents also happened due to overspeeding propellers in dives.

 

I found an article which mentions that a unit flying the P-39Q-15 had problems with pilots using too much power - the aircraft flew just fine, but the engines only made it to 60-70% of the specified TBO before needing a replacement or crashing due to mechanical failure.

 

It is my understanding that the P-39L-1 did have a regulator though, no? Also, is the Merlin 46 in any way comparable? I gather the overall impression of the engine modelling there is positive.

Edited August 16, 2017 by 216th_Lucas_From_Hell

[Farky]

This is an interesting turn then. You see, according to most Soviet records these four aircraft arrived as part of a large shipment through Iran, in November 1942 or later.

...

I also wonder about the camouflage - as those were from an RAF order, can we assume they were painted in RAF colours from the factory? Or did USAAF throw olive drab onto them?

 

 

 

It should be "allocated for delivery to USSR in June 1942" rather that "delivered to USSR in June 1942" I think. I am pretty sure that Soviet sources are right about delivery to 25.ZAB via Southern Lend-Lease route on 19th November 1942. RAAF did get P-40E-1s with lower serial numbers in September 1942.

As regards camouflage - most likely RAF colour scheme.

 

 

It is my understanding that the P-39L-1 did have a regulator though, no?

 

 

No, P-39L-1 did not have automatic MAP regulator.

[Venturi]

Also, is the Merlin 46 in any way comparable?

 

In general, the Merlin 45/46 is similar to the Allison V1710 regarding bore, stroke (and therefore, swept displacement), engine weight, operating RPM - and generally speaking, absolute manifold pressure limits.

 

+8 boost = 23PSI = 47 inches Hg

+12 boost = 27PSI = 55 inches Hg

+16 boost = 31PSI = 63 inches Hg

 

When operated at similar manifold pressures, the Allison generated slightly more power. It was also capable of running at leaner mixtures than the Merlin, which allowed a theoretical longer range for a given amount of fuel.

 

It is different in that it had 1/3 more parts in it than the Allison and had a shorter TBO time. It was not reputed to be as durable as the Allison.

 

Regarding the modeling of the Merlin 45/46 in the game, when using "boost cut out" AKA "boost", the Merlin 45/46 IS NOT like the Allison V-1710-39 without manifold pressure regulator. Operating the "boost cut out" switch simply raises the maximum allowed boost on the engine.

 

However, on earlier Merlin engines, the "boost cut out" switch actually DID allow potential delivery of the full supercharger effect to the engine - this was potentially +17 boost (32PSI, 65 inches Hg) - which is very similar to the maximum supercharger output of the Allison at low altitudes, per Hazen's letter.

Edited August 16, 2017 by Venturi

[216th_Lucas_From_Hell]

Thanks for the very detailed info, Farky. Time to redo those skins I did for these four aircraft

 

Cheers, Venturi. I'm curious to see how the Cobra will be modelled and how its final performance will be.

Edited August 16, 2017 by 216th_Lucas_From_Hell

[Venturi]

I'm interested in fixing the P-40E.

[Tag777]

Thanks for the very detailed info, Farky. Time to redo those skins I did for these four aircraft

 

Cheers, Venturi. I'm curious to see how the Cobra will be modelled and how its final performance will be.

I hope they will model it correctly, but hope they also will solve the issues with the Allison engine, otherwise we will have another disappointing plane   

[6./ZG26_Klaus_Mann]

Proverbs 25:25, otherwise I am in Trouble. 

[Venturi]

Here is my post on the weight of the aircraft. It is too heavy in the sim.

https://forum.il2sturmovik.com/topic/25323-p-40-turn-rateflight-model-check/?p=428125

 

Keep in mind the P40 was not a particularly heavy aircraft when compared to other American designs like the Mustang, Corsair, Hellcat. The Hellcat which was known for being quite maneuverable, weighed 200lbs more empty than the P40's maximum loaded weight.

 

The P40 is only heavy when compared to the very small European fighters like the Yak, Bf109, and Spitfire.

Edited August 17, 2017 by Venturi

[Venturi]

When you combine excess weight, poor turning aerodynamic efficiency (see JtD's excellent analysis here: https://forum.il2sturmovik.com/topic/25336-another-look-turn-times/?p=391785 ), extreme lateral instability, and insufficient engine power...

 

then you get a collector's plane which is totally unworthy of being purchased, let alone flown.

 

It is a very important plane and was used all over the world by the allies. It should be treated fairly.

[Jade_Monkey]

When you combine excess weight, poor turning aerodynamic efficiency (see JtD's excellent analysis here: https://forum.il2sturmovik.com/topic/25336-another-look-turn-times/?p=391785 ), extreme lateral instability, and insufficient engine power...

 

then you get a collector's plane which is totally unworthy of being purchased, let alone flown.

 

It is a very important plane and was used all over the world by the allies. It should be treated fairly.

I agree, as much as I love this game and i want people to support it, I would have a hard time recommending it to someone in its current state.

[216th_Lucas_From_Hell]

Romanenko's Airacobra book has a table on operating the V-1710-63 with 100 octane fuel. Not the same aircraft or exact engine model as the P-40, but the fuel consumption column might be good for planning a flight.

 

The top row reads regime, Horsepower produced, rotations per minute, altitude (ft, m), fuel consumption (litres per hour). The regimes are take-off (up to 5 minutes), WER (up to 5 minutes), combat (up to 15 minutes), nominal (up to 30 minutes), cruise (0.75 of nominal), cruise (0.6 of nominal). The footnote reads "in the technical manual of the P-39K and L there are no instructions on WER".

 

Edited August 18, 2017 by 216th_Lucas_From_Hell

[-=PHX=-SuperEtendard]

That's good information, specially for the P-39L. Do you know from which timeframe are these specs? Everything is in line with the P-39L manual (except the 60" which doesn't figure as clarified in the Russian chart), which you can find as a 1944 revision of the 1942 original. However I have seen 1943 manuals for the P-39N (which has the V-1710-85) allowing 50.5" for 5 minutes.

Having 60" (1580 HP very nice) would turn the P-39L into a pretty powerful plane, having similar speed to the La-5 with boost at the deck and climbrate of that of the Bf 109G, according to some performance test I have seen with the P-39N with it's -85 engine at 57" (developing a similar amount of power, around 1400 HP).

Edited August 18, 2017 by -=PHX=-SuperEtendard