P-39 vs P-40

[Schweik]

Apparently they had some success with P-39s as strafers / ground attackers in Italy

350th Fighter Group - Wikipedia

 

[Dimlee]

If you look at the wings of the I-16 and Mig-3, I think you'll find them remarkably similar in shape and that the Mig-1 is actually an evolution of the I-16.

This is interesting theory. Mkoyan's team was de-jure part of Polikarpov's organisation, indeed. But in my opinion, young designers tried to "revolutionise" existing fighter's designs, not to continue to develop them further.

 

[CORSNING]

If you look at the wings of the I-16 and Mig-3, I think you'll find them remarkably similar in shape and that the Mig-1 is actually an evolution of the I-16.

Kevin,
I always thought many of the Russian planes had similar designed wings
until I took a much closer look at them in the last several years. The Mig-3's
wing was much different than the very straight wing of the I-16. However if
you continue on the Polikarpov lineage, the Mig-3's wing compares more
closely to the I-185's slightly bent wing.

 

[Dimlee]

However if
you continue on the Polikarpov lineage, the Mig-3's wing compares more
closely to the I-185's slightly bent wing

MiG-1 was based on Project 61 (a.k.a. project/fighter "K") initially developed by Polikarpov's team and later given to newly formed department of Mikoyan/Gurevich - along with over 80 of staff. So the route of this lineage is known.

 

[CORSNING]

OK then, back on topic. I have not had the time to do the fine tuned
comparison of these two from start to finish like I did with the P-51 vs.
F4U. But I did manage to put together a comparison of the height of their
WW2 performance versions. For just a little fun, I added the similar engine
P-51A. The first set of figures are for P-39N No. 42-4400. Figures in
[parenthesis] are for P-40N-1 No. 42-9987 (P-40K with same drag conditions
as P-40N). Third figures are for P-51A No. 43-6007.

P-39N-1 @ 7,301 lb. .[ P-40N-1 @ 7,413 lb. ]. P-51A @ 8,000 lb.

Altitude / Speed / Climb
Meters / MPH / FPM
S.L........344 / 3980 .[ 332 / 3520 ]. 376 / 3500
1,000..362 / 4145 .[ 345 / 3600 ]. 387 / 3625
2,000..381 / 4220 .[ 360 / 3680 ]. 400 / 3750
3,000..398 / 3940 .[ 375 / 3465 ]. 412 / 3405
4,000..394 / 3460 .[ 375 / 2965 ]. 413 / 2925
5,000..388 / 3060 .[ 373 / 2480 ]. 410 / 2455
6,000..382 / 2985 .[ 367 / 2025 ]. 405 / 2025
7,000..376 / 2230 .[ 362 / 1635 ]. 399 / 1605
8,000..367 / 1745 .[ 356 / 1265 ]. 389 / 1160
9,000..356 / 1310 .[ 348 / -.940 ]. 367 / -.765

Full Throttle Height: 398.5 mph./2,957 m. .[ 378 mph./3,215 m. ]. .415 mph./3,170 m.
Critical Altitude: 4360 fpm./2,225 m. .[ 3720 fpm./2,438 m. ]. .3785 fpm./2,255 m.

Turn Time 360 degrees: 19 seconds. .[ 16.6 seconds. ]. .21 seconds.

Maximum roll rate: 75 deg./sec./235 mph. .[ 95 deg./sec./270 mph. ]. .86 deg./sec./400 mph.

Combat Ceiling (1,000 fpm. climb): 31,820 ft. .[ 28,920 ft. ]. .27,650 ft.
Service Ceiling (100 fpm. climb): 38,500 ft. .[ 38,200 ft. ]. .35,100 ft.

Range (clean): 360 ml. .[ 650 m. ]. .1,000 ml.

Maximum War Emergency Power: 1,420 hp. .[ 1,480 hp. ]. .1,480 hp.

Wing loading (at take-off): 34.15 .[ 31. 41 ]. .34.33 lb. / sq. in.

Power loading (take-off weight at maximum engine power): 5.122 .[ 5.009 ]. .5.405 lb./hp.

 

[CORSNING]

MiG-1 was based on Project 61 (a.k.a. project/fighter "K") initially developed by Polikarpov's team and later given to newly formed department of Mikoyan/Gurevich - along with over 80 of staff. So the route of this lineage is known.

Dimlee,
You are absolutely right sir. Thank you for the added information.

From 'Soviet Combat Aircraft' page 65 (with a little help):

" M. Gurevich and V. Romodi, who had great experience and vast academic qualifications,
became deputies of (Artyom) Mikoyan. The OKO staff comprised engineers and designers
from the Polikarpov Design Bureau, and though this was not ethical with respect to Nikolay
Policarpov, he made light of the situation upon his return from Germany. During his absence
his project (I-200) had been slightly altered. The length of the fuselage was increased to
improve longitudinal stability, wing centre section fuel tanks were installed in addition to
the fuselage fuel tanks, and the airframe became a mixed structure instead of all-metal.
Nevertheless, it was still undoubtedly Polikarpov's aerodynamic configuration."

" Polikarpov was more concerned about the division of his design bureau into two parts.
With one half he at once began work on another project, the I-185 fighter. Although the
design and mock-up construction of the I-185 proceeded faster than the I-200 project.
The OKO team had a great advantage owing to the powerful industrial base of Plant 1."

 

[CORSNING]

The P-39 had the quickest climb rate of the three in my post #405 right up to its
maximum ceiling. The P-51 was the speed king right up to its maximum ceiling.
The P-40 was without a doubt the most maneuverable.

 

[Schweik]

Where did you get your turn times from?

 

[Schweik]

OK then, back on topic. I have not had the time to do the fine tuned
comparison of these two from start to finish like I did with the P-51 vs.
F4U. But I did manage to put together a comparison of the height of their
WW2 performance versions. For just a little fun, I added the similar engine
P-51A. The first set of figures are for P-39N No. 42-4400. Figures in
[parenthesis] are for P-40N-1 No. 42-9987 (P-40K with same drag conditions
as P-40N). Third figures are for P-51A No. 43-6007.

P-39N @ 7,301 lb. .[ P-40N-1 @ 7,413 lb. ]. P-51A @ 8,000 lb.

Altitude / Speed / Climb
Meters / MPH / FPM
S.L........344 / 3980 .[ 332 / 3520 ]. 376 / 3500
1,000..362 / 4145 .[ 345 / 3600 ]. 387 / 3625
2,000..381 / 4220 .[ 360 / 3680 ]. 400 / 3750
3,000..398 / 3940 .[ 375 / 3465 ]. 412 / 3405
4,000..394 / 3460 .[ 375 / 2965 ]. 413 / 2925
5,000..388 / 3060 .[ 373 / 2480 ]. 410 / 2455
6,000..382 / 2985 .[ 367 / 2025 ]. 405 / 2025
7,000..376 / 2230 .[ 362 / 1635 ]. 399 / 1605
8,000..367 / 1745 .[ 356 / 1265 ]. 389 / 1160
9,000..356 / 1310 .[ 348 / -.940 ]. 367 / -.765

Full Throttle Height: 398.5 mph./2,957 m. .[ 378 mph./3,215 m. ]. .415 mph./3,170 m.
Critical Altitude: 4360 fpm./2,225 m. .[ 3720 fpm./2,438 m. ]. .3785 fpm./2,255 m.

Turn Time 360 degrees: 19 seconds. .[ 16.6 seconds. ]. .21 seconds.

Maximum roll rate: 75 deg./sec./235 mph. .[ 95 deg./sec./270 mph. ]. .86 deg./sec./400 mph.

Combat Ceiling (1,000 fpm. climb): 31,820 ft. .[ 28,920 ft. ]. .27,650 ft.
Service Ceiling (100 fpm. climb): 38,500 ft. .[ 38,200 ft. ]. .35,100 ft.

Range (clean): 360 ml. .[ 650 m. ]. .1,000 ml.

Maximum War Emergency Power: 1,420 hp. .[ 1,480 hp. ]. .1,480 hp.

Wing loading (at take-off): 34.15 .[ 31. 41 ]. .34.33 lb. / sq. in.

Power loading (take-off weight at maximum engine power): 5.122 .[ 5.009 ]. .5.405 lb./hp.

The P-51A had some kind of problem with the ailerons which was fixed on the P-51B/C and later. I think later versions had a very good roll rate.

This is interesting though I think it would make more sense to compare P-40K or L to the others as they were contemporaries. P-40N wasn't used that much in combat (by the RAF as a bomber in Italy, by the RAAF a bit in the Pacific and by the USAAF in Burma and India.

By contrast the P-40K was widely used from Russia to Tunisia to the Solomon Islands and China, and the L, along with the F, were the main variants used by the USAAF against the Germans.

But it is harder to find those numbers.

If you are going to use P-40N note that at 57" / WEP the climb are a little lower initially but hold up better to a little bit higher altitude

http://www.wwiiaircraftperformance.org/P-40/A29-412-climb-WEP.jpg

it starts from 3100 fpm and peaks at 3380 at 6800 ft.

 

[CORSNING]

it starts from 3100 fpm and peaks at 3380 at 6800 ft.[/QUOTE]

These figures are for an R.A.A.F. P-40N-1 loaded to 7,900 lb. I used load figures
of all three aircraft in their "interceptor" mode.

The turn time for the P-39N are from Russian figures.

The turn time for the P-40N-1 came from calculations from Henning Ruch. I do
not like using calculated figures if I can help it. However, I have found that Mr. Ruch
has been very accurate in his calculations to date. The P-40C weighing 7,475 lb.
(USSR figures) was capable of 18.0 seconds. The P-40N-1 was a much higher
powered improved version weighing 7,413 lb.

The turn time for the P-51A is much harder to come by. Russian figure for the
Mustang I is 23 seconds. In Erik Pilawskii's Fighter Aircraft Performance of WW2
he states the P-51B turn time at 4,000 m./ 21 seconds. The turn time I gave
for the P-51A at 1,000 meters is an educated estimation.

 

[Shortround6]

This is interesting though I think it would make more sense to compare P-40K or L to the others as they were contemporaries. P-40N wasn't used that much in combat (by the RAF as a bomber in Italy, by the RAAF a bit in the Pacific and by the USAAF in Burma and India.

By contrast the P-40K was widely used from Russia to Tunisia to the Solomon Islands and China, and the L, along with the F, were the main variants used by the USAAF against the Germans.

There were about 1300 P-40Ks built, There were over 5000 "N"s built, granted many Ns never left the US and the last few hundred went straight to storage/scrap.

The Ns were lightest short nosed P-40s built (the aluminium radiators, oil coolers, magnesium wheels and things done) and so should perform the best. The N-1 should be the ultimate Allison P-40 as it also had only 4 guns, 201-235 rpg (?), the forward fuel tank taken out. The electric starter was not installed, a smaller battery and a few other bits left out (like all blind flying instruments).

What is somewhat puzzling is that slightly later versions of the P-40 (like N-5s) were over 20mph slower than the prototyped N-1 (converted K) at similar powers.

Some units did get their older P-40s replaced by P-40N only to have P-51s and P-47s replace them in a few months. Probably in an effort to cut down on the amount of types the logistics chain had to support.

Interestingly the The US Armies inventory of P-40s peaked in April of 1944 at 2499 planes, I believe that includes the ones used as trainers in the US (?)

 

[michael rauls]

There were about 1300 P-40Ks built, There were over 5000 "N"s built, granted many Ns never left the US and the last few hundred went straight to storage/scrap.

The Ns were lightest short nosed P-40s built (the aluminium radiators, oil coolers, magnesium wheels and things done) and so should perform the best. The N-1 should be the ultimate Allison P-40 as it also had only 4 guns, 201-235 rpg (?), the forward fuel tank taken out. The electric starter was not installed, a smaller battery and a few other bits left out (like all blind flying instruments).

What is somewhat puzzling is that slightly later versions of the P-40 (like N-5s) were over 20mph slower than the prototyped N-1 (converted K) at similar powers.

Some units did get their older P-40s replaced by P-40N only to have P-51s and P-47s replace them in a few months. Probably in an effort to cut down on the amount of types the logistics chain had to support.

Interestingly the The US Armies inventory of P-40s peaked in April of 1944 at 2499 planes, I believe that includes the ones used as trainers in the US (?)

I've read ( I believe on Wikipedia so take with a grain of salt) that the reason some of the later production blocks of p40Ns were slower was that they were fitted with additional armor for the ground attack role.

 

[Shortround6]

Armor, if internal, doesn't have much effect on speed. If fitted outside where it might disrupt airflow then things may be different.

Effect on climb is much different,

A Spitfire IX lost about 22mph at low altitudes by adding a 500lb and an unfaired rack.

Blaming a few hundred pounds of armor (which should have much less drag than a 500lb bomb) for a 20mph or so speed loss seems a bit out out line.

One estimate for the P-51 said that an extra 1000lb INTERNAL was good for 3mph speed loss. That may have been optimisc.

Many accounts of aircraft blame weight increases for loss of speed while taking no account of the increase in drag of some bits and pieces, going back to the Spitfire, the early external BP glass windscreen was figured to be worth 6mph. Weight was not all that much, a few dozen pounds?

Adding and subtracting guns in the wings (protruding gun barrels) can change the airflow pattern (and lift) slightly in the area of the gun bay/s. the ejection slots cause drag.

differences in weights are much easier to come by that changes in drag.

Later P-40s got the full 6 gun armament, they got bigger under wing racks, the electric starters and bigger batteries went back in (in fact many of the light P-40N-1s had the starters changed, bigger batteries put in, the front tank replaced in the field, some even got two .50 cal guns added)

 

[Schweik]

The later model P-40Ns were much heavier but also were flown at lower power ratings. Rated HP was down from ~1300 something to ~1200 hp. I think that is the main reason for the speed difference.

 

[Shortround6]

ALL P-40Ns got the 9.60 gear engines, the -81,-99 and -115 engines all had the same power ratings.

The 9.60 supercharger gear engines made less power down low and more power at "higher" altitudes, Higher starting at under 10,000ft.

Which engine is going to give more speed in a P-40 depends on what altitude you are flying.

The Engine in K was rated at 1325hp for take-off which has little or no bearing on speed in the air, The engine in the N was rated at 1200hp for take off,

However the engine in the K was only good for 1150hp at 12,000ft (no ram) while the "lower powered: engine in the N was good for 1150hp at 15,500ft (also no ram)
as a rough guide you are going to loose about 2.5% of power per 1000ft of altitude as you go up from 10,000ft and a little bit more per 1000ft if you start from 15,000ft (most engines drop to zero HP at about 55,000ft, they can't make enough power to exceed internal friction without a rather extraordinary supercharger set up)

The engines in the N could make over 1400hp at around 10,000ft using WEP while the engine in the K with it;s slower turning supercharger impeller was close to running out of breath. Perhaps 5-6% more power than the 1150hp at 12,000ft. Perhaps a bit more due to RAM?

 

[Schweik]

Well it may just be how they reported the tests, but all the books I have say the early "interceptor" version of the P-40N-1 through N-15 I think, had a V-1710-81 rated for 1,360 hp (WEP) while later ones N-20 through N-35 had the V-1710-99 which were rated only at 1,200 hp. Then the last batch, P-40 N-35 (only ~ 250 made) had the V-1710-115 which again was rated at ~1,300 hp.

That could just be a matter of recommended throttle settings I don't know.

There is a table in "The Curtiss Hawks" on P 231 which gives the following max HP values:

V-1710-39 (P-40E) was rated at 1470 hp @ 56" Hg for WEP
V-1710-73 was rated 1550 hp at 60" Hg for WEP
V-1710-81 through 115 all say they are rated at 1360 hp @ 57" Hg for WEP but they show a lower "normal rated" power of 955 vs. 1,000 for the -39 or -73

So it's possible the lower speed shown for the later model P-40Ns (usually around 348 mph vs. 378) may just be because they rated the speed at military power instead of WEP. This kind of thing is done a lot in aviation books.

As Shortround noted weight seems to have less effect on speed than drag does, though it does eventually also have an effect and the later model P-40Ns were much more heavily loaded than the N-1. I could go either way on the reason.

 

[Shortround6]

V-1710-39 (P-40E) was rated at 1470 hp @ 56" Hg for WEP
V-1710-73 was rated 1550 hp at 60" Hg for WEP
V-1710-81 through 115 all say they are rated at 1360 hp @ 57" Hg for WEP but they show a lower "normal rated" power of 955 vs. 1,000 for the -39 or -73

HP ratings without altitudes are almost useless.

I am not blaming you Schweik, or trying to say that you are in anyway trying to shade the argument. All to many books, magazine articles and websites overlook this "little detail"
either through ignorance or if they are trying to push an agenda of their own. ANd then these figures are copied over to other articles and become part of those tropes you object to.

Try plotting some of these power ratings on graph.

The -39 was good for 1490hp at 56in at 4300ft, It was good for 1150hp at 11,700ft.
The -73 was good for 1580hp at 60in at 2500ft, it was good for 1150hp at 12,000ft.
Both use the 8.80 supercharger gear.
Forget the pressure for now, just plot the power vs altitude and then run the lines down to sea level and up as far as you care to go, they should hit zero on the mid 50,000ft range. You can get arguments as to exact figure.

Now do the same for the -81 and up engines, 1410hp at 9,500ft and 1150hp at 15,500ft.
This later engine was rated at 1360hp at sea level but that is because the throttle is part closed at sea level (so were the 8.80 engines, just not as much) and the resulting losses and extra heat created by the faster spinning impeller pushed the engine/fuel combination closer to the detonation limit. As the plane climbed the throttle could be opened more and more.

Then add in 1-3,000 ft worth of altitude depending on RAM (forward speed)

 

[Schweik]

Not debating it but where do you get 1410 hp @ 9,500 ft for the -81? And where do you get the altitudes for WEP ratings for the -39 and -73? My books just say 'Sea Level' for WEP. I'm always looking for new and more accurate sources.

Aside from the critical altitude ratings for HP which I agree with you should be standardized and consistent, they also more generally just need to standardize whether they are showing cruise, military, takeoff or WEP power for a given aircraft. They should probably show all of the above.

Wasn't 60" approved for later model P-40E / V-1710-39 as well as for the -73?

I gather P-40K was mainly good for high speed quite low but that did have it's uses.

The -81 series engines were reportedly good up to about ~17,000 ft which is much higher than the other P-40s, the P-40E and K basically had performance ceilings of about 12,000' which is actually worse than the Tomahawk (V-1710-33) which was rated useful up to 15,000'.

The F and L / Merlin XX ones were good up to 20,000 and apparently still combat worthy at around 25,000' which is a big difference and a major improvement

Is it true what some people are saying that Merlin XX had weak power down low?

S

 

[CORSNING]

This is interesting though I think it would make more sense to compare P-40K or L to the others as they were contemporaries. P-40N wasn't used that much in combat (by the RAF as a bomber in Italy, by the RAAF a bit in the Pacific and by the USAAF in Burma and India.

The first P-40 N-1s were delivered in March 1943. The first P-39Ns were delivered in November
1942. The first P-51As were delivered in March 1943. I would say using the P-40N-1 would be
a contemporary comparison. The first long fuselage P-40Ks (-10) were delivered in October
1944.

 

[Schweik]

Delivered in 43 maybe, but I'm not sure when that means they were in action... and I'm not certain about P-39 variants but I can tell you for 100% certain that P-40F, L and K and A-36 (P-51) were all flying in combat together, (with some kinds of P-39s though I don't know what variant) quite a bit in Italy and the Med in 1943 and early 1944.

I know that P-51A and P-40K were also in combat together in Burma but P-40N may have been as well. That would be later in 43 or into 44.