SHOULD the P39 have been able to handle the Zero? Was it training or performance?

[parsifal]

Just a slight bit of pedantry but most Buffalo squadrons were officially RAF units, the only exception being 21 Sqn RAAF. There were 2 Article XV squadrons, 453 and 488 which later became RAAF and RNZAF units respectively but, at the time of Buffalo usage, were still strictly speaking RAF units manned with Australian and New Zealand personnel. Like I said...pedantry!

That is technically true,but it is indeed being very pedantic about the issue. Imperial defence of Malaya was being bankrolled by the dominions in the main from about fenruary 1941. After Japan signed her military ten year pact with Germany and Italy 27 September,1940, there were a series of meetings with the dominions that reappraised the air defence needs of the far east and PTO. It was determined that a minimum of 1404 a/c were required for imperial defence,but the british more or less immediately conceded that they lacked both the manpower and the financial depth to meet those commitments. Part of the response was to train and equip Australian airforce formations using british equipment, but Australian personnel in the main.

In July 1940, the RAAFs first operational bomber sqn,with modern equipment (Hudons),no 1 GRU was sent to singapore. a month later it was followed by No 8 sqn. these aircraft were part of the British "Cash and carry" purchases so they too were technically British aircraft (though I do note these hudsons were given Australian serialisations). technically. they had been paid for by the Australian govt, were fully manned by Australian personnel, so referring to them as "british aircraft" is more than a bit rich!!!

The conferences that followed the Axis September pacts led to the formation of firstly ABD and later ABDA. Part of the commitment to boost the Malayan defences was a commitment to send two Australian fighter squadrons to singapore. This presented a problem however. what fighters we did have were all obsolete (Gloster Gauntlets mainly) which we had been given to the RAAF in the middle east. the home based squadrons were all obsolete (Hawker demons I think). The three organisation within Australia building aircraft were contracted by the british to build types like the Beaufort , or were committed to building training a/c like the moth or the Wackett. The Wirraway was built as a GP a/c, with the RAAF believing the british delusions about how obsolete the JAAF was and deluding itself into believing the CA6 was good enough for front line service. It was in that climate of self delusion and downright baloney being fed to us by the British war organisation at the time that convinced the Australian govt that it could continue with Beaufort development (which by this stage was being deliberately stifled by the british with their embargo on the export of engine technologies. it would take until October 1941 for a substitute US engine production line to be founded),

With no domestic fighters in production, and existing resources otherwise committed, the Australian commitment to send two fighter sqadrons to Malaya was utterly dependant on the british supplying aircraft. At the time this deployment was being discussed (Fenruary 1941), menzies had wanted the units to be equipped with hurricanes, but was told that in the interests of standardisation the buffalo would need to do. It was stated at the time that the Brewster was more than adequate to deal with the IJAAF. In this period two units were so equipped.....453 and 21 sqns. both were officially RAAF units. both were manned, in the main by Australians. their deployment to Malaya required approval of the Australian Govt.. the aircraft supplied to them were British owned, but I have never, until now, heard any claim these formations were british formations. it is, indeed, a very big stretch to say that. if for some reason, the Australians had insisted those squadrons return home , they would have done so with those a/c on strength and available, as indeed survivor Buffaloes did (I know of at least two airframes that did, A51-10 and A51-11).

Some buffaloes eventually were serialised using Australian registration codes, though I believe they were ex-Dutch A51-1 to A-51-17 were all registered as Ä"series registered aircraft. this places them firmly under australian control.

 

[parsifal]

Thought this link on P-39s in Australia might be helpful

http://www.adf-serials.com.au/research/Airacobra.pdf

 

[Glider]

One aspect not mentioned is payload. The Typhoon and the P47 and P38 could carry a serious amount of bombs/rockets and were normally used as GA aircraft. The P39 wasn't even close in this area. If you commanded an air force you want flexibility and this the P39 didn't give you. It lacked payload and armour for GA work

I also like the others believe you are almost ignoring the difficulties that weight give you The P39's center of gravity problems were grave

 

[pbehn]

One aspect not mentioned is payload. The Typhoon and the P47 and P38 could carry a serious amount of bombs/rockets and were normally used as GA aircraft. The P39 wasn't even close in this area. If you commanded an air force you want flexibility and this the P39 didn't give you. It lacked payload and armour for GA work

I also like the others believe you are almost ignoring the difficulties that weight give you The P39's center of gravity problems were grave

As a fighter bomber the Typhoon had 350Kg of armour added around the radiator and under/ beside the pilot.

 

[Elmas]

"He remembers having a Japanese bomber in his gunsight and the cannon rounds from the P-39 falling short. "
"It was also the only American fighter that didn't have a fan club."
"P-400? A P-39 with a Zero on his tail..."

It seems that among American Pilots P-39 was not a beloved plane...

https://www.defensemedianetwork.com...39-airacobra-in-the-pacific-posed-challenges/

Bell P-39 Airacobra

WWII Planes: The P-39 Airacobra "Peashooter"

 

[Glider]

As a fighter bomber the Typhoon had 350Kg of armour added around the radiator and under/ beside the pilot.

I agree now lets see what happens to a P39 with that much armour and the 2,000lb of bombs

 

[pbehn]

I agree now lets see what happens to a P39 with that much armour and the 2,000lb of bombs

That 2000Ib bomb load is approximately the same as a Do-17 a few years before without the armour, but the Typhoon is a very competent and potent fighter when they have been dropped. That indication of how quickly things changed in WW2 which is what I find irksome in this discussion.

 

[CORSNING]

The P39 had an unspectacular record against Japanese fighters. Was it an issue of pilot training against an unfamilier enemy aircraft

Yes!, use altitude.

Or was the performance of the Zero the P39's undoing?

Long range, good speed and exceptional maneuverability, once again yes.

The P39 had a 30 or 40 mph speed advantage over the Zero,

Only at one altitude did any of the early P-39s have a speed advantage of
30 mph.: The P-39D'a maximum speed was 368 mph./13,800 ft. vs. 338 mph.
of the A6M2. The best the P-400 could do was 355 mph./13,000 ft. vs. 336 mph.
of the A6M2. That was the Airacobras best altitude speeds. At sea level the
Zero could manage 298 mph., the P-400: 301 mph. and the P-39D: 316 mph.
The P-39's reputation was being formulated in 1941-42. That would mean
the P-39D and P-400 models.

about the same as a Spitfire, so why couldn't the P39 use this speed and dive advantage to beat the Zero like the Hellcat did?

The Airacobras of the period did not have the altitude performance to get above the Zero
to do so, as has been pointed out by several others.


The overall performance of later P-39 actually increased dramatically IMO. The
overall performance of the later Zeros did not. But by the time the late 1942
P-39N appeared the reputation damage had been done. At this time the A6M3
Model 32 had been in service since April 1942.

 

[Shortround6]

And below 5km altitude (16500') the P-39Ns advantage in both speed and climb is huge. Now, please let me hear from all you "two speed" and crankshaft experts about how big an advantage low gear is. As you can see from the charts the two speed supercharger results in a "sawtooth" speed and climb curve while the single speed P-39N develops its maximum power at 3km (10000') and then gradually declines from there up to the combat ceiling. Most historians would have you believe that the Allison engine fell off the mounts and the plane tumbled to earth after crossing 12000'. This was a much better plane than history gives credit for.

Oh, boy.
There were basically 3 different engines used mass produced P-39s.

The E4, used in the P-39C, the P-400, the P-39D and the P-39F (different propeller)
These engines were rated at 1150hp for take-off, and would hold 1150hp from sea level to 12,000ft (42inMAP) no ram. after that power fell off, at 15,000ft you had 1020 hp, at 20,000ft you had about 830hp.
WEP was 1490hp (56in MAP) which is certainly a nice boost, HOWEVER, this was only good till 4,300ft at which point power declines to meet the 1150hp at 12,000ft, for instance power at 8000ft is about 1325hp. There is no tweaking of the boost control. The supercharger simply is maxed out and cannot supply any more air at that altitude and engine rpm. ANY over boosting above 56in requires the ram effect from forward speed, OR over revving the engine beyond 3000rpm, OR being below 4,300ft or a combination of the above.

The E6 engine was used in the P-39K and L, about 460 of these P-39s were built so they are not common. The engine got some stronger parts ( and a different reduction gear to the propeller)and was uprated to 1325hp for take-off (using 51in MAP) , but since it used the same supercharger gear and pretty much the same basic supercharger (minor details/improvements) it was still rated at 1150hp (42in MAP) at 12,000ft. No improvement in altitude performance. WEP was allowed to go to 1580hp at 60in of MAP but this was only good to 2500ft at which point power declined with altitude until.........surprise....... it was making 1490hp at 4300ft and then on to the 1150hp at 12,000ft. Over boosting above the 60in limit was limited to the three conditions already mentioned except the lower altitude limit.

3rd engine was the E18/19, only around 240 planes were built with E-18 (P-39Ms) and the primary difference was the reduction gear ratio to the propeller so both can be considered together. This is were the 9.60 gears show up.

The engine was rated at 1200hp for take-off (50.5in MAP) and with a bit fudging with the numbers, 1125hp at 15,500 (42in MAP). I say fudging because 1150hp probably fell on some odd number rather than a multiple of 500. Now you do have about 100hp more at 15,000 feet or so and at any higher altitudes, HOWEVER, you do NOT have more power at lower altitudes.
WEP was limited to 1410hp at 57in MAP. at very low levels (under 2500-3500ft) using MAP you have 80 hp less than the early engines and 170hp less than the scarce intermediate engines.
Allison was, as I have said, issuing stron warnings about over boosting this later engines.
Now, for all those people who think the automatic boost limiter was a gift from the aircraft gods and rendered 2 speed superchargers so much overweight junk lets take another look at the numbers.
The engines with the 9.60 gears made 125hp less for take-off using 0.5lbs less boost than the engines using 8.80 gears. WHY?
Because the higher gear ratio took more power to drive, 40-50hp? you had less power to the prop. You also had more heat going to the intake mixture and the air was less dense. Fewer pounds of air 10,000 cubic feet even at the same pressure. Please note the 3in drop in max pressure used for WEP power rating. A direct result of the high temperature in the supercharger/intake manifold due the faster spinning impeller. Over boosting beyond the approved 57in was coming closer to wrecking the engine that over boosting beyond 60 in on the older engines.

I would note that without RAM the Allison engines using 9.60 gears were rated at about 950hp at 20,000ft with about 37in of MAP (3 1/2 /bs boost) available at 3000rpm and no amount of "magic" from an automatic boost limiter is going to fix that.

The Allison with 9.60 gears was good for about 1020hp at 18,500ft compared to the Merlin V-1650-1 in the P-40 having 1120hp at 18,500ft.
In Low gear it had 1240hp at 11,500ft, both at 9lbs boost (roughly 48in MAP)
It had 1300hp for take-off.
Pretty much seems like a 100hp advantage for the 2 speed engine at may altitudes and I would be very careful about bringing up the WEP settings for the Allison as those HP ratings for the Merlin are Military ratings, not WEP and an overboosted Merlin can also have several hundred hp more on tap.

I would note that the Russian M-105 engines were also pretty crappy much above 12,000ft so the Russians don't have a lot to compare to.
The ASh-82 was also set up with low gear maxing out around 5400-6600ft and high gear maxing out around 13-15000ft(?) so altitude performance wasn't that great either. But then Russian gas wasn't that good so allowable boost was limited.

 

[RCAFson]

Zero versus P39:

http://www.wwiiaircraftperformance.org/japan/intelsum85-dec42.pdf

note the boost levels used on the P39.

 

[tomo pauk]

Oh, boy.
There were basically 3 different engines used mass produced P-39s.

The E4, used in the P-39C, the P-400, the P-39D and the P-39F (different propeller)
These engines were rated at 1150hp for take-off, and would hold 1150hp from sea level to 12,000ft (42inMAP) no ram. after that power fell off, at 15,000ft you had 1020 hp, at 20,000ft you had about 830hp.
WEP was 1490hp (56in MAP) which is certainly a nice boost, HOWEVER, this was only good till 4,300ft at which point power declines to meet the 1150hp at 12,000ft, for instance power at 8000ft is about 1325hp. There is no tweaking of the boost control. The supercharger simply is maxed out and cannot supply any more air at that altitude and engine rpm. ANY over boosting above 56in requires the ram effect from forward speed, OR over revving the engine beyond 3000rpm, OR being below 4,300ft or a combination of the above.

Seems like the -35 and -37 engines from late 1941 were not capable to make 1150 HP at 11800-12000 ft, but at just 11200 ft. Or 1090 HP at 12500 ft. (doc attached)
Coupled with 'shaded' ram air intake, the altitude performance is not going to cut it. BTW - late V-1710s on the P-39Q were making 1410-1420 HP on 57 in Hg and 3000 rpm, vs. 1480 on same boost and rpm on the P-40N and P-51A.

I would note that the Russian M-105 engines were also pretty crappy much above 12,000ft so the Russians don't have a lot to compare to.
The ASh-82 was also set up with low gear maxing out around 5400-6600ft and high gear maxing out around 13-15000ft(?) so altitude performance wasn't that great either. But then Russian gas wasn't that good so allowable boost was limited.

They have had AM-35A that made 1200 CV at 19700 ft in 1941, that will take V-1710 with 2-stage supercharger from late 1943 to beat.
Altitude performance of the ASh-82 was again 1200 CV at 20000 ft, again it will take a V-1710 with 2-stage S/C to best it. Boost figures of both of Soviet engines were hampered due to high compression ratio, 7:1.

 

[Shortround6]

Figures for early Allisons are all over the place due to different standards and minor equipement like backfire screens (more than one type) and intake manifolds (again, more than one type), while production engines may have been more standardized, prototype or early test samples sometimes differed from production examples.

Not at all helped in 1940-41 by the changes in fuel specifications. American 100 octane, American 100/125, British 100 octane and joint 100/130.
A number of Allisons were developed and tested using the 100/125 that was never (?) shipped overseas.


Point about the Russian engines is that the majority of Russian engines didn't have very good altitude performance. The AM-35 aside and since there were only a few thousand of them out of tens of thousands (hundred thousand?) of engines, most Russian pilots and air commanders had little or no experience with them.
SO by comparison the P-39s didn't look all that bad.

 

[Shortround6]

Zero versus P39:

http://www.wwiiaircraftperformance.org/japan/intelsum85-dec42.pdf

note the boost levels used on the P39.

Note that 70inches, which other sources claim could barely be reached at sea level, caused detonation and could not be used in the test. The US of 52-55in of MAP is firmly in WEP range. NO note is made of when the P-39 dropped down in the mid to low 40in pressure range due to altitude.

 

[P-39 Expert]

Seems like the -35 and -37 engines from late 1941 were not capable to make 1150 HP at 11800-12000 ft, but at just 11200 ft. Or 1090 HP at 12500 ft. (doc attached)
Coupled with 'shaded' ram air intake, the altitude performance is not going to cut it. BTW - late V-1710s on the P-39Q were making 1410-1420 HP on 57 in Hg and 3000 rpm, vs. 1480 on same boost and rpm on the P-40N and P-51A.



They have had AM-35A that made 1200 CV at 19700 ft in 1941, that will take V-1710 with 2-stage supercharger from late 1943 to beat.
Altitude performance of the ASh-82 was again 1200 CV at 20000 ft, again it will take a V-1710 with 2-stage S/C to best it. Boost figures of both of Soviet engines were hampered due to high compression ratio, 7:1.

Notice on the Temporary Specific Operating Instructions Chart in the upper left hand corner it says "Engine-V-1710-35 (with backfire screens) meaning the screens were still in the intake ports causing reduced MP and excess maintenance. These were removed from the engine permanently in mid 1942 about the same time that takeoff power was increased from 5 minutes to 15 minutes. Without the screens the -35 developed it's full 1150hp at 12000'.

 

[P-39 Expert]

Oh, boy.
There were basically 3 different engines used mass produced P-39s.

The E4, used in the P-39C, the P-400, the P-39D and the P-39F (different propeller)
These engines were rated at 1150hp for take-off, and would hold 1150hp from sea level to 12,000ft (42inMAP) no ram. after that power fell off, at 15,000ft you had 1020 hp, at 20,000ft you had about 830hp.
WEP was 1490hp (56in MAP) which is certainly a nice boost, HOWEVER, this was only good till 4,300ft at which point power declines to meet the 1150hp at 12,000ft, for instance power at 8000ft is about 1325hp. There is no tweaking of the boost control. The supercharger simply is maxed out and cannot supply any more air at that altitude and engine rpm. ANY over boosting above 56in requires the ram effect from forward speed, OR over revving the engine beyond 3000rpm, OR being below 4,300ft or a combination of the above.

The E6 engine was used in the P-39K and L, about 460 of these P-39s were built so they are not common. The engine got some stronger parts ( and a different reduction gear to the propeller)and was uprated to 1325hp for take-off (using 51in MAP) , but since it used the same supercharger gear and pretty much the same basic supercharger (minor details/improvements) it was still rated at 1150hp (42in MAP) at 12,000ft. No improvement in altitude performance. WEP was allowed to go to 1580hp at 60in of MAP but this was only good to 2500ft at which point power declined with altitude until.........surprise....... it was making 1490hp at 4300ft and then on to the 1150hp at 12,000ft. Over boosting above the 60in limit was limited to the three conditions already mentioned except the lower altitude limit.

3rd engine was the E18/19, only around 240 planes were built with E-18 (P-39Ms) and the primary difference was the reduction gear ratio to the propeller so both can be considered together. This is were the 9.60 gears show up.

The engine was rated at 1200hp for take-off (50.5in MAP) and with a bit fudging with the numbers, 1125hp at 15,500 (42in MAP). I say fudging because 1150hp probably fell on some odd number rather than a multiple of 500. Now you do have about 100hp more at 15,000 feet or so and at any higher altitudes, HOWEVER, you do NOT have more power at lower altitudes.
WEP was limited to 1410hp at 57in MAP. at very low levels (under 2500-3500ft) using MAP you have 80 hp less than the early engines and 170hp less than the scarce intermediate engines.
Allison was, as I have said, issuing stron warnings about over boosting this later engines.
Now, for all those people who think the automatic boost limiter was a gift from the aircraft gods and rendered 2 speed superchargers so much overweight junk lets take another look at the numbers.
The engines with the 9.60 gears made 125hp less for take-off using 0.5lbs less boost than the engines using 8.80 gears. WHY?
Because the higher gear ratio took more power to drive, 40-50hp? you had less power to the prop. You also had more heat going to the intake mixture and the air was less dense. Fewer pounds of air 10,000 cubic feet even at the same pressure. Please note the 3in drop in max pressure used for WEP power rating. A direct result of the high temperature in the supercharger/intake manifold due the faster spinning impeller. Over boosting beyond the approved 57in was coming closer to wrecking the engine that over boosting beyond 60 in on the older engines.

I would note that without RAM the Allison engines using 9.60 gears were rated at about 950hp at 20,000ft with about 37in of MAP (3 1/2 /bs boost) available at 3000rpm and no amount of "magic" from an automatic boost limiter is going to fix that.

The Allison with 9.60 gears was good for about 1020hp at 18,500ft compared to the Merlin V-1650-1 in the P-40 having 1120hp at 18,500ft.
In Low gear it had 1240hp at 11,500ft, both at 9lbs boost (roughly 48in MAP)
It had 1300hp for take-off.
Pretty much seems like a 100hp advantage for the 2 speed engine at may altitudes and I would be very careful about bringing up the WEP settings for the Allison as those HP ratings for the Merlin are Military ratings, not WEP and an overboosted Merlin can also have several hundred hp more on tap.

I would note that the Russian M-105 engines were also pretty crappy much above 12,000ft so the Russians don't have a lot to compare to.
The ASh-82 was also set up with low gear maxing out around 5400-6600ft and high gear maxing out around 13-15000ft(?) so altitude performance wasn't that great either. But then Russian gas wasn't that good so allowable boost was limited.

The Merlin made more power. I'm comparing the performance of the FW190A6 to the P-39N. With the Allison engine. P-39 was almost as fast but climbed much better, right? And it didn't have a two speed blower, like the FW, right?

 

[Shortround6]

You are comparing two different airframes, that differed in weight by 1800lbs with different types of engine, using different fuel and trying to draw a conclusion about the type of supercharger????

Lets try to compare apples to apples and not apples to brussel sprouts.

 

[parsifal]

Lets try to compare apples to apples and not apples to brussel sprouts.

Fruit to vegetables. Looks more like reality to fantasy to me.

 

[wuzak]

Right, the Spit held 100 American gallons and the P-39 held 120 American gallons.

After completion of the first 166 P-39Ns, the USAAF requested that four fuel cells be removed in order to reduce the internal fuel capacity from 120 to 87 US gallons, and so to reduce the maximum permissible gross weight from 9100 lbs to 8750 lbs. This kept weight down, but unfortunately it also restricted range.

Bell P-39N Airacobra

It seems that the bulk of the P-39Ns had only 87USG from the factory, though they could be brought back up to 120USG in the field.

Depending on the supvariant, it looks like the P-39Q could have between 87USG and 120USG.
Bell P-39Q Airacobra

 

[pbehn]

The Merlin made more power. I'm comparing the performance of the FW190A6 to the P-39N. With the Allison engine. P-39 was almost as fast but climbed much better, right? And it didn't have a two speed blower, like the FW, right?

As has been stated many times the problem of the FW190 was solved by the Spitfire MkIX at all altitudes before the P-39-N arrived. By the time the P-39N was available the F4-U and P47 were coming into service.

In operations from UK being slower than your opponent is not a minor issue, the minimum distance to France is 21 miles but it quickly increases to over 100, you cannot sneak in over water, at low level you are seen and in range of every man with a rifle or machine gun. You cannot disengage by climbing and if you are slower you cant run away.

 

[tomo pauk]

Notice on the Temporary Specific Operating Instructions Chart in the upper left hand corner it says "Engine-V-1710-35 (with backfire screens) meaning the screens were still in the intake ports causing reduced MP and excess maintenance. These were removed from the engine permanently in mid 1942 about the same time that takeoff power was increased from 5 minutes to 15 minutes. Without the screens the -35 developed it's full 1150hp at 12000'.

Military power duration went to 15 minutes, both take off ans WER were set at 5 min duration (though that duration was many times exceeded in heat of combat).
Thing with backfire screens removed in mid 1942 is that it does not help the RAF in 1941 or in 1st half of 1942. The P-39D even with engines making 1150 HP at 12000 ft will not cut it against the LW opposition, while P-39M/N is too late to matter for ETO.

The Merlin made more power. I'm comparing the performance of the FW190A6 to the P-39N. With the Allison engine. P-39 was almost as fast but climbed much better, right? And it didn't have a two speed blower, like the FW, right?

Fw 190 was capable to take off with much greater extenal load, almost 4000 lb total, due to having plenty of power for take off. Having the low speed S/C to choose from was worth 400-600 HP for take off. That also meant that it was capable to make 1900 HP at low level from mid-1943 on, time to climb to 26000 ft was reduced to just 8.5 min on 2700 rpm, speed went to 400+ mph above 13000 ft. link