Jump to content
ACG_KaiLae

P-40 turn rate/Flight model check

Recommended Posts

The research question to the stall angle of attack P-40 in the game

https://sites.google.com/site/ishadross/NII_VVVS/reports/report1

 

The research WER Study for the P-40

 

https://forum.il2sturmovik.ru/topic/5644-r-40-i-r-39-dva-samoleta-odin-dvigatel/?view=findpost&p=514614

 

from the Russian community.

You have to work hard with the translation. But the work is worth it.

Edited by =MG=Dooplet11
  • Upvote 3

Share this post


Link to post
Share on other sites

Did you get any feedback from the developers on the Russian board?

 

Personally, 1.43 would be a figure I'd be happy with right now, it matches my expectations.

Share this post


Link to post
Share on other sites

At the FW-190 changes were made. P-40, unfortunately, left unattended for one year. If You look, there are six studies on various important issues of the game.

https://sites.google.com/site/ishadross/NII_VVVS/reports

https://sites.google.com/site/ishadross/NII_VVVS/reports/report5

 

But again, You have to work with the translation yourself.  :salute:

Edited by =MG=Dooplet11
  • Upvote 2

Share this post


Link to post
Share on other sites

At the FW-190 changes were made. P-40, unfortunately, left unattended for one year. If You look, there are six studies on various important issues of the game.

https://sites.google.com/site/ishadross/NII_VVVS/reports

https://sites.google.com/site/ishadross/NII_VVVS/reports/report5

 

But again, You have to work with the translation yourself.  :salute:

 

Google translate only for me, unfortunately, but that is enough to see that a) the conclusions here agree with ours in the main substance, especially that P-40 critical AoA is far too low and b) they are way ahead in terms of finding the data!

 

Thanks for posting.

  • Upvote 1

Share this post


Link to post
Share on other sites

Thanks for linking and interesting way of calculating. As far as I can tell from the interpretation provided by google, the estimates seem to be based on some method for rule of thumb calculations used to derive an estimated Clmax.

 

So this is yet another calculated theoretical number. This one arrives at 1.51 for the P-40 when "fuselage corrections" have been applied it seems.

 

Then an additional correction is applied for (as far as I can tell) the paint job and surface imperfections and apparently the assumption here is that the La-5 had a poorer finish than the P-40 because the La-5 gets a reduction of 10% and the P-40 5%. So why 10 and 5%? Why not 14.35 and 7.45% or some other number? For example assuming the same paint job on the P-40 (10% reduction) we get a Clmax of 1.36......

 

Google translate from the linked pages:

 

Accounting fuselage effect : multiply C Y at (S KR + S FYUZ * 0,5) / S (base:. Mechanized wings Sutugin 1948, p 297..):

La 5: 1.58 * 0.92 = 1.45

P-40: 1.6 * 0.94 = 1.51

Accounting for the effects of color wing cracks and other deviations from the ideal surface:

La-5: 1.45 - 10% (base - purging TSAGI) = 1.3

P-40: 1.51 - 5% (basis - no cracks in the junction of the wing with slats) = 1.43

Share this post


Link to post
Share on other sites

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)

 

This is little bit complicated and confusing, I'll try my best summarize it clearly and briefly as possible -

 

When in early 1941 production of Allison V-1710-39 starts, USAAF in cooperation with Allison company set limits of engine mainly with respect to Time Between Overhauls (TBO). Therefore, these limits were pretty conservative -

 

Take-off - 45.5inHg @ 3000 rpm * Maintain constant throttle settings until pressure is reduced to 42inHg

Maximum climb + high speed for 5 min. - 42inHg @ 3000 rpm

Normal climb + high speed - 37.2inHg @ 2600 rpm

...

Limits for V-1710-39 used by RAF since 1941 were little bit different, even more conservative -

Take-Off (3 Mins. Limit) - 44.5inHg @ 2800 rpm

Climbing - (30 Mins. Limit) - 37inHg @ 2600 rpm

Cruising - 37inHg @ 2600 rpm

Emergency (5 Mins. Limit) - 42inHg @ 3000 rpm

...

Before December 1941, USAAF changed limits for V-1710-39. This wasn't most probably change initiated by Allison, but by user (namely USAAF Materiel Command at Wright Field). Limits from December 1941 -

Take.Off - 46.2inHg @ 2800 rpm (5 Min. Duration only)

Military Rated Power - 43.9inHg @ 3000 rpm (5 Min. Duration only)

Normal Rated Power - 38.7inHg @ 3000 rpm (Highest Permissible Continuous Power)

 

RAAF in Pacific did use same limits, since they got their P-40Es from USAAF.

 

RAF do not follow these limits, they were still using old ratings.

...

In June 1942, USAAF slightly changed limits for V-1710-39 again -

Take Off - 46.2inHg @ 2800 rpm (5 minute duration only)

Military rated power - 44.6inHg @ 3000 rpm (5 minute duration only)

Normal rated power - 38.5inHg @ 2600 rpm ( Highest permissible continuous power and climb)

 

RAAF in Pacific used these limits as well, RAF was still operating with old ratings.

...

Meanwhile, P-40Es began to operate in the USSR. Soviet manual dated November 13, 1942 shows following limits -

Take Off - 45.5inHg @ 3000 rpm

Military rated power (Forsazh, 5 min. limit)- 42inHg @ 3000 rpm

Normal rated power (Nominal) - 37.2inHg @ 2600 rpm

 

So, this Soviet manual was using old early 1941 USAAF engine limits. To be fair, these limits were still officialy recommended by Allison company for V-1710-39.

...

During 1942, various reports from combat units have mentioned use of overboost on V-1710-39 (among other engines). USAAF and Allison company investigated this possibility and the result was introduction of War Emergency Rating. This engine rating was mainly established and regulated by USAAF, it was maximum possible authorized engine power with very little margin of safety. Nobody cared much about Time Between Overhauls (TBO) anymore. But, Allison engineers recommended use of War Emergency Rating only with automatic Manifold Pressure regulator, USAAF agreed with them. For 2 main reasons -

1. Since WER is very close to safety limit of engine (structural/mechanical in case of V-1710s, not close to detonation point), even small exceeding of the limit could lead to fatal engine failure. Automatic MAP regulator will ensure that this exceeding does not happen.

2. Position of throttle lever in cockpit for WER (lever fully forward) can be sealed, so everytime pilot used WER, he must break the seal (wire across throttle quadrant, essentially breakable stop). This was clear sign for ground crew that WER was used, so they have to pay special attention to the engine.

 

Anyway, new War Emergency Rating limit for V-1710-39 was 56inHg @ 3000 rpm.

...

In April 1943, limits recommended by Allison company were as follows -

Take Off - 45.5inHg @ 3000 rpm ( for 5 minutes only)

Military rated power - 42inHg @ 3000 rpm (for 5 minutes only)

Normal rated power - 37.2inHg @ 2600 rpm

War emergency rating - 56inHg @ 3000 rpm (for 5 minutes only) Note: allowed only with automatic MAP regulator

...

USAAF manual for P-40E, also dated April 1943 shows folowing limits -

Take Off - 45.5inHg @ 3000 rpm (for 5 minutes only)

Military rated power - 44.6inHg @ 3000 rpm (for 5 minutes only)

Normal rated power - 38.5inHg @ 2600 rpm

 

No War Emergency Rating is mentioned, since P-40Es do not have automatic MAP regulator.

...

RAF manual from June 1943 for Mustang I with V-1710-39 shows -

Max. Take Off to 1000 ft. - 45.5inHg @ 3000 rpm

Max. continuous - 38.5inHg @ 2600 rpm

Max. combat 5 mins. limit - 45.5inHg @ 3000 rpm

Emergency boost 5 mins. limit - 56inHg @ 3000 rpm * if automatic boost control is fitted

...

Engine limits for V-1710-39 in Soviet P-40 manual dated 1943 are same as in Soviet 1942 manual -

Take Off - 45.5inHg @ 3000 rpm (5 minutes limit)

Military rated power (Forsazh, 5 min. limit)- 42inHg @ 3000 rpm

Normal rated power (Nominal) - 37.2inHg @ 2600 rpm

...

 

After autumn 1943, there were again some changes in limits for V-1710-39. But we don't care about them (well, at least I don't care), since at that time all P-40Es were already out of combat units.

 

So, to summarize it somehow -

V-1710-39 was able to safely operate at 56inHg @ 3000 rpm. Although use of this power was officially allowed only with automatic MAP regulator, from a technical standpoint, it really doesn't matter. Since the introduction of WER did not require any design changes of engine or different fuel, therefore 56inHg @ 3000 rpm was safe to use from very beginning of production of this engine in 1941. Ergo, "we are using time period engine limits" is wrong assumption.

 

Again, there were no P-40E in Battle of Moscow anyway, only Tomahawks (P-40C).

 

Very important note - I know very well about overboosting of V-1710-39 beyond 56inHg @ 3000 rpm. This post is only about official, well documented safe engine limits. Brutal overboost is another story for another day.

 

Edit - word possible changed to authorized, so it can not result in some misunderstanding.

Edited by Farky
  • Upvote 7

Share this post


Link to post
Share on other sites

Wait ... so the P40E wasnt even in Moscow? I thought they had both types available (C as well as E)

Edited by 4./JG52_Riksen

Share this post


Link to post
Share on other sites

Thanks for linking and interesting way of calculating. As far as I can tell from the interpretation provided by google, the estimates seem to be based on some method for rule of thumb calculations used to derive an estimated Clmax.

 

So this is yet another calculated theoretical number. This one arrives at 1.51 for the P-40 when "fuselage corrections" have been applied it seems.

 

Then an additional correction is applied for (as far as I can tell) the paint job and surface imperfections and apparently the assumption here is that the La-5 had a poorer finish than the P-40 because the La-5 gets a reduction of 10% and the P-40 5%. So why 10 and 5%? Why not 14.35 and 7.45% or some other number? For example assuming the same paint job on the P-40 (10% reduction) we get a Clmax of 1.36......

 

Google translate from the linked pages:

 

Accounting fuselage effect : multiply C Y at (S KR + S FYUZ * 0,5) / S (base:. Mechanized wings Sutugin 1948, p 297..):

La 5: 1.58 * 0.92 = 1.45

P-40: 1.6 * 0.94 = 1.51

Accounting for the effects of color wing cracks and other deviations from the ideal surface:

La-5: 1.45 - 10% (base - purging TSAGI) = 1.3

P-40: 1.51 - 5% (basis - no cracks in the junction of the wing with slats) = 1.43

Thanks for a careful study of this work! Amendment to the La-5 with 10% made on the basis of the recommendations of the study " Mechanized wings ", the author Sugutin, and the "Manual for designers" (RDK), 1943 . The result coincided with the values obtained by blowing the aircraft La-5 in a wind tunnel of SAGI. The wing P-40 has no slats, in contrast to the wing of the La-5. No cracks. On this basis, the amendment adopted, less 5%. Yes, this is an estimated calculation. But the method of calculation verified by the calculation of the Yak-3 in addition, the result coincides with the value of full-scale wind tunnel. Sorry for my bad English
  • Upvote 1

Share this post


Link to post
Share on other sites

P40C is the correct plane. It also happened to be better performing (less weight, engine basically was capable of same power).

 

P40E was just rolling in via Lend Lease and was basically rare on Soviet front. In Dec 41 the US and RAF desperately needed fighter airframes for the pacific. Whole squadrons were equipped with for instance P-26 Peashooters still, etc. P-40E was most advanced fighter in US arsenal at this time and fully comparable (Brits considered it better except at altitude) to Hurricane of same vintage.

 

BtW nowhere is it mentioned in Vees that the V1710-39 or even the earlier -33 variant as used in P40C had structural failure at very high power output levels. The closest I could find was a 7hr test for -33 at 56" MP (official military rating was at ~45" IIRC) which at the end still did not show failure, rather only stress crack in the crank journals of the engine block. I have posted earlier about this finding in the engine thread (derailed by Crump).

 

TBO was at least double for the V1710 when compared to DB601 or 605 series or Merlin and this has direct bearing on the official allowed power ratings. USAAF was extremely conservative in the pre war and early war years (for the US this was 1942 to 1943), and this mindset was one of the things which changed as war experience was gathered by the US.

Thanks for a careful study of this work! Amendment to the La-5 with 10% made on the basis of the recommendations of the study " Mechanized wings ", the author Sugutin, and the "Manual for designers" (RDK), 1943 . The result coincided with the values obtained by blowing the aircraft La-5 in a wind tunnel of SAGI. The wing P-40 has no slats, in contrast to the wing of the La-5. No cracks. On this basis, the amendment adopted, less 5%. Yes, this is an estimated calculation. But the method of calculation verified by the calculation of the Yak-3 in addition, the result coincides with the value of full-scale wind tunnel. Sorry for my bad English

Your English is fine

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?

This is true and an important point. Having done much work for this, to have it ruined by limits interpretation especially when a realistic way of illustrating the limits is so easily done, it is a shame.

 

I have written how such limits might be imposed before for all planes and have PMed Han in the past and even got a response. Again for details see engine thread. It didn't happen.

Edited by Venturi
  • Upvote 2

Share this post


Link to post
Share on other sites

I still am awaiting an official response to JtDs efficiency table which also shows large aerodynamic factors at play, beyond the obviously too high stall speeds.

 

It reminds one of Einsteins "cosmological coefficient" adjustment, added in to make equations fit preconceptions

Share this post


Link to post
Share on other sites

I wonder if perhaps some of the P-40s tested were fitted with bomb racks under the wings. That could cause some spoilage of lift, but I doubt that its magnitude would be enough to cause the type of discrepancy that we're seeing.

 

edit: The RAE AK 572 P-40 appears to be clean. It says such in the report.

Edited by Silavite

Share this post


Link to post
Share on other sites

I wonder if perhaps some of the P-40s tested were fitted with bomb racks under the wings. That could cause some spoilage of lift, but I doubt that its magnitude would be enough to cause the type of discrepancy that we're seeing.

 

edit: The RAE AK 572 P-40 appears to be clean. It says such in the report.

https://forum.il2sturmovik.ru/topic/5616-podemnaya-sila-samoletov/page-3?do=findComment&comment=514307

https://forum.il2sturmovik.ru/topic/5616-podemnaya-sila-samoletov/page-3?do=findComment&comment=514765

Share this post


Link to post
Share on other sites

Excellent posts...Farky's 889 shows something that I was going to bring up later, that the 1941 -39 and the 43 -39 are the same engine. Only difference is the printed materials issued with it.

  • Upvote 1

Share this post


Link to post
Share on other sites

 

Victor, and model airplane P-40 will be reviewed. More precisely, the modes of the engine and control response at PH ?

 

About the P-40 - can't say for certain, because it all depends on the time and edit PH will affect all, not just the P-40

(PH)- the rudder

Edited by =MG=Dooplet11

Share this post


Link to post
Share on other sites

Would you mind giving us the gist of it?

 

The developer was asked: will the engine modes change, as well as the flight model of the P-40 airplane taking into account the rudder steering changes.
Answer: nothing definite due to time deficit, Changes in the rudder direction will affect all aircraft.

Share this post


Link to post
Share on other sites

 

 

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 (RAAF) operated the P40E in the PTO - specifically Guadalcanal and New Guinea. The after action report that I provided in another thread which documented a P40E evading a Zero on the deck at ~70" of manifold pressure for about 15 minutes (pulling these numbers from memory) was written up by a P40E pilot.

Share this post


Link to post
Share on other sites

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

 

 

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)

 

I question the validity of that entire argument (Han's) because the date at which people's expectations (and therefore documentation) were revised doesn't have to coincide with the engine's capabilities.

 

What I'm trying to say is that the specific V1710 engine used in the P40E didn't suddenly improve - what changed was the operators' understanding of its capabilities which to that point had been greatly underestimated.

Share this post


Link to post
Share on other sites

To be honest, my knowledge of the P40 is limited,

 

but this discussion which was alternated between me learning new things, finding amusement, and wondering where the popcorn is...

 

has made me wonder if it would ever be possible to add another layer to the game, and how to go about it without there being a paying to fix these instead of a time penalty.

Which is; in Daves example of the P40 pilot evading the Zero, lets assume that those figures are correct, if this was allowed in game, there should be a possibility of engine damage in your next flight even if you hadn't done anything strenuous to the engine that sortie (like the Jumo 004's had in real life, going by Franz Siglers account in the book "A higher Call").

How that would be implemented in game I'm not sure in regards to would there be a warning message flash up when you hit refly that say's "due to overboosting etc your engine may fail, would you like to wait 5-10 minute while a new engine is installed" (but still giving you the option).


I have often thought that there should be the added layer in SP, which is that you start with a under performing plane and as you prove your worth your ride improves (you get the hand me downs until you can prove that you deserve a new ride),

and in MP that there should be a respawn time penalty for battle damage etc (not optional, and can't buy your way out of it)

Edited by novicebutdeadly

Share this post


Link to post
Share on other sites

The problem is, because a single aircraft is anecdotally documented as surviving for 15 mins at 70" boost should all aircraft of that type be modelled in that way..

 

I have chatted and drank with many pilots discussing aircraft we have both had experience of, some individual stories get..er..expanded on  :) younger pilots who will never fly these types often get an exaggerated perspective of some of these aircraft and 'legends' are born

 

It is a difficult issue, but I for one will be disappointed if the P-40 is modeled as a "best example" and performs better than the vast majority of historical reports, even though I like and respect the aircraft for it's War duties, if it was as good as some people seem to want it to be, it would never have been replaced as a front line fighter and the Allison engine would not have been replaced by the Merlin in the first P-40's used by USAAF in the Med

 

General Golodnikov mentions that although it was used, he, only on a single occasion during his career , overboosted his P-39 by pushing the throttle and braking the safety wire, if the type of P-39 with MAP limiter was available in BoS it would spend it's life with the throttle through the wire

 

It is a very hard subject to get overboost/engine life/damage represented correctly and a realistic way to get people to treat the engines in a reasonably historical manner, as mentioned above with Stiegler and his operation of later model Me-109

 

Am sure that Dev's will come up with a system that keeps all sides happy, even if it does take longer than many will be comfortable with

 

* P-40E-1 was used at Moscow defence from May 42 with 126 IAP and in Leningrad region from March 42 with 154 and 159 IAP's

 

The 126 IAP was transferred to Stalingrad front in late August and withdrawn to the rear 18 Sept having suffered extreme attrition in heavy fighting, re-equipping with La-5

 

Cheers Dakpilot

  • Upvote 2

Share this post


Link to post
Share on other sites

If the aircraft manual restricts a certain power ouput by the engine for the time, even if we know the engine later was allowed to perform at a higher level, I think the FM should stick with the manual for that particular time frame. Afterall this is what happened to the Bf-109 G2 ... We know its engine is capable of more but it is restricted as it was for the timeframe. I consider this a more fair approach, don't you think? Note Im not saying that there isnt anything wrong with the plane as I dont even have it. This is just my general opinion on the engine limits ... correct me if Im wrong

Share this post


Link to post
Share on other sites

The problem is, because a single aircraft is anecdotally documented as surviving for 15 mins at 70" boost should all aircraft of that type be modelled in that way..

 

Man I am certain you know that isn't what I was saying or even why I mentioned that example.

The point of that example was that it was one that could be found in this forum that proved the P40E was used to war's end in the Pacific by at least the RAAF and they weren't all "late model" P40s in the PTO as Farky seemed to believe.

 

For the record - if you check every P40 thread here you will see that I have always suggested a realistic indicative "limit" of 60" for 20 minutes - despite evidence presented of widespread setting of WEP to 66"Hg in WDAF units in the North African desert in 1942. 

Edited by Dave

Share this post


Link to post
Share on other sites

If the aircraft manual restricts a certain power ouput by the engine for the time, even if we know the engine later was allowed to perform at a higher level, I think the FM should stick with the manual for that particular time frame. Afterall this is what happened to the Bf-109 G2 ... We know its engine is capable of more but it is restricted as it was for the timeframe. I consider this a more fair approach, don't you think? Note Im not saying that there isnt anything wrong with the plane as I dont even have it. This is just my general opinion on the engine limits ... correct me if Im wrong

Maybe read the other threads on P40 engine limits rather than risk that topic being reborn here.

Share this post


Link to post
Share on other sites

Maybe read the other threads on P40 engine limits rather than risk that topic being reborn here.

 

Could please direct me (link) to that one?

 

Thxs

Share this post


Link to post
Share on other sites

If the aircraft manual restricts a certain power ouput by the engine for the time, even if we know the engine later was allowed to perform at a higher level, I think the FM should stick with the manual for that particular time frame. Afterall this is what happened to the Bf-109 G2 ... We know its engine is capable of more but it is restricted as it was for the timeframe. I consider this a more fair approach, don't you think? Note Im not saying that there isnt anything wrong with the plane as I dont even have it. This is just my general opinion on the engine limits ... correct me if Im wrong

The G2 engine changed. The DB605 was derated in response to multiple engine issues, which were later solved. In the -39 case, the instructions changed but the engine didn't.

Share this post


Link to post
Share on other sites

The G2 engine changed. The DB605 was derated in response to multiple engine issues, which were later solved. In the -39 case, the instructions changed but the engine didn't.

 

But the instructions changed after the time period we are simulating for the Battle of Moscow, correct? There is a time frame manual for that particular time that clearly sets a inferior limit to it, even if nothing has changed. IMHO, we should stick by the manual accordingly even if the engine did not change there was obviously some concern at the time that justified not using it at higher rating and this is historical.

Share this post


Link to post
Share on other sites

Man I am certain you know that isn't what I was saying or even why I mentioned that example.

The point of that example was that it was one that could be found in this forum that proved the P40E was used to war's end in the Pacific by at least the RAAF and they weren't all "late model" P40s in the PTO as Farky seemed to believe.

 

For the record - if you check every P40 thread here you will see that I have always suggested a realistic indicative "limit" of 60" for 20 minutes - despite evidence presented of widespread setting of WEP to 66"Hg in WDAF units in the North African desert in 1942. 

 

No worries I was not citing you specifically at all, (which is why i didn't quote you)but in many of the P-40 threads similar comments have been generally used about 70" boost.

 

The P-40E-1 in Soviet use is also a unique situation compared to Western use, they did not have spare engines at that time, shown by having to resort to adapting Klimov engines resulting in worse performance, the mechanics/ground crew had rudimentary training on a "foreign" design with little local language documentation (at that time), compared to many years of type experience and training and closer access to factory (Alisson and Curtiss) personnel in the West

 

Pure speculation on my part, but I imagine by the time the P-39 was in full use with VVS the engine was better understood with more experience and a more critical phase of the war behind them

 

Russian fuel and oil have been shown to have been used with documented issues, I still have not seen a specific comment from Russian pilots about regularly using high boost, except for maintaining higher RPM and flying at much higher speeds at all times to avoid the poor acceleration issue.

 

There is also the fact that the aircraft we have in game does not have an MAP gauge that shows these higher MP boost levels that people are quoting, as was historically fitted to many (most?) P-40E-1, 50" max versus the 70" max fitted to later models

 

However if we had a Western Desert or Pacific P-40 I would be much more inclined for a better performing Alisson and feel the western docs to be more relevant.

 

Hopefully the FM update may cure some of the general flying issues and a slight change to engine limits will give a (historical) slightly better performance envelope, same as we have now, but can be accessed for a little longer in a way that keeps everyone happy

 

Cheers Dakpilot

Edited by Dakpilot

Share this post


Link to post
Share on other sites

Thanks for a careful study of this work! Amendment to the La-5 with 10% made on the basis of the recommendations of the study " Mechanized wings ", the author Sugutin, and the "Manual for designers" (RDK), 1943 . The result coincided with the values obtained by blowing the aircraft La-5 in a wind tunnel of SAGI. The wing P-40 has no slats, in contrast to the wing of the La-5. No cracks. On this basis, the amendment adopted, less 5%. Yes, this is an estimated calculation. But the method of calculation verified by the calculation of the Yak-3 in addition, the result coincides with the value of full-scale wind tunnel. Sorry for my bad English

 

And thank you for posting this and the other links to the Russian forum. I enjoyed reading all of it and I think this kind of exchange of data between the forums is beneficial to everyone involved!

 

Note that I'm not critical of the method described above as such which I think seems quite sound in principle. It is only we have to stack a number of assumptions on top of each other to arrive at a number which makes prediction of an accurate number difficult.

 

We have also in this forum been discussing estimates of the Clmax based on 2d profile data and models from NACA testing. There are also some good NACA reports on the effects of surface imperfections, gun ports, leakage etc to go on. But even it there are wind tunnel tests, these are usually done with models and as such require corrections for Reynolds numbers and the surface imperfections or in the case of full-scale wind tunnel tests, corrections for wind tunnel wall and blockage effects.

 

This is why we have been trying to find data from flight trials using reliable measuring equipment like a trailing pitot which was used to determine Spitfire and Me-109 Clmax by British RAE. Unfortunately so far we have not seen such data for the P-40 which is why some of us think there is really no basis to change what we have for the P-40 today which is approximately 1.35.

 

Concerning the slat correction for a gap I would say that that would be appropriate to count as a negative factor for drag but actually for Clmax, the slats are good since it allows you to build a wing with no twist like on the Me-109 as opposed to the wash-out on the P-40 that detracts from the Clmax. In fact I think that is part of the explanation why the Me-109 has such a high Clmax (about 1.4)

 

Finally, I think your English is good and perfectly understandable, much better than my google translate based understanding of Russian! :)

  • Upvote 3

Share this post


Link to post
Share on other sites

We (RAAF) operated the P40E in the PTO - specifically Guadalcanal and New Guinea. The after action report that I provided in another thread which documented a P40E evading a Zero on the deck at ~70" of manifold pressure for about 15 minutes (pulling these numbers from memory) was written up by a P40E pilot.

...

The point of that example was that it was one that could be found in this forum that proved the P40E was used to war's end in the Pacific by at least the RAAF and they weren't all "late model" P40s in the PTO as Farky seemed to believe.

 

 

 

This is misunderstanding. I was talking about additional models of P-40 in game, we already got P-40E.

 

I know that RAAF operated P-40Es, 163 of them. They were backbone of RAAF fighter operations in 1942, they were withdrawn from combat units during 1943. Story of 75. squadron over Port Moresby is epic and is it my favorite. RAAF P-40Es never operated from Guadalcanal, only in New Guinea and Australia. Proper models of P-40 for Guadalcanal are P-40F (USAAF) and P-40M (USAAF and RNZAF), maybe even P-40K (RNZAF).

 

I don't know which thread you mean, but I know about that combat report you are talking about. This report was posted on this forum by me at least twice, I found Sgt. Butler's combat report in NAA too, few years ago.

Share this post


Link to post
Share on other sites

Some experiences with Allison engines in soviet use ( P-39)

 

 In most cases the engine failed, either upon takeoff or during combat. For example, in the 19th Guards IAP, there was one catastrophic failure and four accidents in the first two weeks; in the 153d IAP, one catastrophic failure and one accident. At first everyone blamed the Allison, in general a decent, light, and powerful engine that did not, however, want to work on Soviet-refined oils. It was real "picky", however, only at the beginning, and not without reason. After filtration, which removed dross and other debris, the Allison stopped "self destructing". Another defect required a great amount of investigation, the so-called "throwing of rods". This allegedly occurred when because of frequent running at the engine's operating limits (without which, of course, aerial combat was unthinkable) the aforementioned parts broke loose, came through the crankcase and destroyed everything in their path, in particular the control rods. A number of flight and laboratory tests were undertaken which enabled the test engineers to recommend the most favorable operating regimes of the engine to combat pilots, and succeeded in reducing the level of this type of failure.

 

http://lend-lease.airforce.ru/english/articles/romanenko/p-39/index.htm

 

It was good, but weak in terms of engine hours, and not very good if you flew with too much throttle. I will tell you about it. This was not a fault of the airplane, but ours. Because our gasoline was not suitable.
We flew on our fuel—B-78. The Cobra had a limiter [governor]. The normal supercharger pressure on the Cobra was 67 pounds per square inch. They set the governor on the Cobra so that it would not exceed 45 pounds. Kinematics supported this; it was ours, already developed. It would not give any more with our fuel. Therefore, if one were using our fuel, the connecting rods in the engine would snap. 
That’s not all. They glued a piece of paper on the throttle slot. Paper, ordinary paper. You could set the throttle to get only 40 pounds. Maximum 40. But in combat it was possible to get 45 pounds, but only by tearing the paper. Then you had to report this to the mechanics later. They could see this themselves; they then would remove the filters from the engine to check for [metal] filings.
What was dangerous about the Cobra? Its coolant fluid was Prestone [antifreeze], and it burned better than gasoline. In the event connecting rods would snap, a fire would break out. And in most cases—right away.

 

http://lend-lease.airforce.ru/english/articles/ovsyannikov/index.htm

 

although both these are about the later - 63 engine, and the second example is from 43/44, I only post this as a sample that Russian experience was not always the same as that with the Allies in the Med or Pacific

 

Cheers Dakpilot

Share this post


Link to post
Share on other sites

Pure speculation on my part, but I imagine by the time the P-39 was in full use with VVS the engine was better understood with more experience and a more critical phase of the war behind them

 

Well, in the case of the P-40E, the Soviets had some months of previous experience with earlier P-40B/C, and the first P-40Es came in the same convoy as the first P-39s if i'm correct, so I would say both planes would have the same "evolution" in regards to how the mechanics were used to them.

 

In regards to fuel used, the current P-40E is modelled with US 100 octane fuel, because with the US lower grade 90 octane fuel, the max allowed manifold pressure was 37" with 2650 as max RPM. So with Soviet local fuel it would have similar limitations I think.

 

I also wonder why the M-105 P-40 performed poorly... I guess they were non PF versions? because the PF's 1200 HP as nominal power would fit the P-40 very well (from the continuous 900 HP and 1150 HP as few minute long combat power), maybe they used a different propeller which wasn't good for the plane?

 

 

I know that RAAF operated P-40Es, 163 of them. They were backbone of RAAF fighter operations in 1942, they were withdrawn from combat units during 1943. Story of 75. squadron over Port Moresby is epic and is it my favorite. RAAF P-40Es never operated from Guadalcanal, only in New Guinea and Australia. Proper models of P-40 for Guadalcanal are P-40F (USAAF) and P-40M (USAAF and RNZAF), maybe even P-40K (RNZAF).

 

I guess the P-40M would be from the later parts of the Guadalcanal campaign (1943)? because that one had he V-1710-81, same engine as the P-40N. For 1942 period they were only Merlin engined P-40s? As 1942 Allison variants I would guess there would be late production Es and Ks?

Share this post


Link to post
Share on other sites

Manual for the pilot contains two types of data: 1. Description of the reaction of the plane on the control action and the environment. It must be done , says the manual. Or to take it into account. 2. Limitations. This is a milestone for the occurrence probability of the event. The probability should be evaluated in other documents: the records of the trials at the limit regimes, reports on operation, technical descriptions, calculations .

Share this post


Link to post
Share on other sites

 

 

I guess the P-40M would be from the later parts of the Guadalcanal campaign (1943)? because that one had he V-1710-81, same engine as the P-40N. For 1942 period they were only Merlin engined P-40s? As 1942 Allison variants I would guess there would be late production Es and Ks?

 

First USAAF unit with P-40s arrived on Guadalcanal in November 1942, this squadron was equipped with "long tail" P-40Fs. At the end of April 1943, RNZAF began operating from Guadalcanal with P-40Ms and few "long tail" P-40Ks. USAAF Guadalcanal units were in summer 1943 replenished with P-40Ms. And that's about it.

Share this post


Link to post
Share on other sites

what we have for the P-40 today which is approximately 1.35.

 

 

Based on?

Share this post


Link to post
Share on other sites

Roughly,


 


155km/h = √((2*3820kg*9.81m/s2) / (1.225kg/m3*21.92m2*CLmax)) 


  155km/h=√(76125.6kg*m/s/ 26.852kg/m*CLmax)


  1854m2/s2=(2791m2/s2)/CLmax


  


In game CLmax = 1.505


 


Yet the clean stall speed found above by OP's testing (96mph) is still too high when compared to the P40E historical performance by at least 6mph, according to official USAAF manuals as well as Curtiss documents and testing by RAF, etc. Additionally the RAF gives exact weight for the plane tested, so we know for a fact this is a real speed. If we add in PEC correction for stall speed of -2 to -3 mph as given by period RAF and USAAF PEC documents, this discrepancy increases.


 


I have already posted all these documents in this thread, earlier.


 


And keep in mind this is the in-game "real world" aircraft, so you would add an additional 10% as a ballpark figure to arrive at the actual "design CLmax". This would then be a CLmax of 1.66. But this is just an aside.


 


To illustrate my point of how far off the plane is, we can use the derived in-game "real world" CLmax of 1.505 to solve for what weight of the aircraft would need to be to achieve a historical correct stall speed (90mph ASI) as listed in the USAAF training manual and elsewhere.


 


145km/h=√((2*[WEIGHT]*9.81m/s2) / (1.225kg/m3*21.92m2*1.505))


  145km/h=√(([WEIGHT]*19.62m/s2) / (40.412kg/m))


  1618m2/s2=([WEIGHT]*19.62m/s2) / (40.412kg/m)


  (1618m2/s2*40.412kg/m)/19.62m/s2 = [WEIGHT]


 


WEIGHT needed to achieve 90mph stall at CLmax of 1.505 = 3333 kg


 


As you can see, these weights are so different as to be ludicrous (weight in game is 3820kg for "standard load").


 


Something is rotten in the state of Denmark.


 


145km/h = √((2*3820kg*9.81m/s2) / (1.225kg/m3*21.92m2*CLmax)) 


  145km/h=√((76125.6kg*m/s/ 26.852kg/m*CLmax))


  1618m2/s2=(2791m2/s2)/CLmax


 


"real world" CLmax needed for historically documented 90mph stall at 3820kg = 1.72


 


And finally, if we were to use the often-bandied about and incorrect CLmax figure of 1.35, then for a weight of 3820kg, we achieve the following stall speed:


 


[sPEED]=√((2*3820kg*9.81m/s2) / (1.225kg/m3*21.92m2*1.35))


  [sPEED]=√((3820kg*19.62m/s2) / (36.250kg/m))


  [sPEED]2=(74948kg*m/s2) / (36.250kg/m)


  [sPEED]2=2067.531m2/s2


 


SPEED at clean stall for 3820kg at CLmax of 1.35 = 102mph


 


Some people believe this is the true CLmax and weight of the P40E (and therefore the actual stall speed). I would argue based on the evidence above and earlier in this thread, that they have ulterior motives.


Edited by Venturi

Share this post


Link to post
Share on other sites

"Some people believe this is the true CLmax and weight of the P40E (and therefore the actual stall speed). I would argue based on the evidence above and earlier in this thread, that they have ulterior motives."


 


And that is why you are making yourself look ridiculous.


 


1.32-1.35 is the calculated CLmax using the Tech Specs stall speeds and weights. If you think that the developers are incapable of determining the stall speeds of the aircraft in their own game why not just come out directly and say so.


Using their figures from their "robot pilot" is the only way we can compare planes with one another inside the game with any consistency.


 


Now you are saying the weight they use is wrong too - all the documents posted so far in this thread that I have seen say that they have the weight right.


 


The only other major variable is the speed (leaving aside JtD's reference area theory as making too little difference). We know for a fact - empirically proven and theoretically explained - that IAS measurements at high AoA are very unreliable. Not once have you addressed this issue. Instead we are now getting personal attacks on the motivations of people who disagree with your conclusions. Pathetic.


 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...