Japanese Zero vs Spitfire vs FW 190

Mike Williams · Dec 16, 2019

nuuumannn said:
It was, yes, although the DH props were of American origin - their 'Hydromatic' and counterweight props had appeared on bombers before fitting to fighters, but these were licence built Ham Std units. Rotol was the exception in Britain, but had limited application initially. The Rotol two position prop was first fitted to Spitfires with 54 Sqn in November/December 1939. This was initially limited to 54 Sqn however and the two position DH props were introduced in the Spring of 1940 - these were bracketed counter weight props. The DH and Rotol C/S props were fitted round about the same time as each other, from June/July 1940.

Schweik · Dec 16, 2019

So by around 1941 seems like most fighters had CS propellers, was there anything after that?

Schweik · Dec 16, 2019

Just blundered across something which answered another nagging question I'd had for a long time. We all know about the infamous Vokes filter, with some debate as to how bad it was, then replaced by the "Aboukir" filter which was superior. I always wondered why Kittyhawks didn't seem to have this kind of problem. I was just reading an interview with Bobby Gibbes and he mentioned something interesting about filters. He said "Buck Abou Kir" developed an air filter for the Kittyhawks which was later adopted by Curtiss Wright! Gibbes himself used to test fly the aircraft with the new filters. Gibbes said that prior to the new filter being adopted, engine life was down to 60-70 hours due to dust, (which isn't much better than what the Russians were reportedly getting with P-40s). With the filter he said it went up to about 120 hours. Gibbes also noted that a German pilot told him the German engines were failing after 20-30 hours.

"Yes. Well turning to the more technical side of it in terms of servicing aircraft, how good were those facilities?

(20.00) Well back .... We used to have two flights plus a base camp, and if any major damage was done the aircraft would be serviced by the base camp. But basically, out in the field, out in the desert, we'd ... each flight would do its own maintenance. They couldn't do anything really major but they kept things flying. Motors used to chop out after sixty or seventy hours. They were finished. We had an engineer called Buck Abou Kir - Shirley Abou Kir's father - and he designed an air filter, and I did the test flying for his air filter. Later that air filter was adopted by Curtiss Wright and fitted into all the Kittyhawks. I think it was from Buck's filter - probably got a few mods - but that .... Our engine hours went up to about 120 then. I was talking to a German pilot who was commanding officer of JG 27 in North Africa. He said the Messerschmitt engines didn't .... They got no more than twenty or thirty hours before they would cut out. "

Tried googling this Abou Kir, I found this person Shirley Abicair, daughter of a Wing Commander in the RAAF but it doesn't give his name. I know there was a town called Abou Qir or Abukir in Egypt where they had a major RAF air base, and I always thought that was the origin of the name of the filter. Not sure what the actual link is here...

S

tomo pauk · Dec 16, 2019

Schweik said:
I'm well aware but the V-1650-1 was an American version (so probably slightly different) of the Merlin XX right? So that is different from a Spit V which used a Merlin 45 or 46 or 45M right? I thought the Spit V had a higher critical altitude.

Apart from using US-spec prop spline, different carb and IIRC different type of supercharger drive (Wright-designed instead of Farman licence), rest was pretty much the same.
For altitude power (in this case, say, 13000 ft and above), Merlin XX and 45 have had about same power, probably in single digits percantage. Merlin 46 have had a bigger impeller (10.85" vs. 10.25 in), and it was making a bit more power above ~20000 ft, and a bit less under ~18000 ft than Merlin 45. The Mk.46 sacrificed a lot of power under 10000 ft, and was not produced in great numbers.
Merlin 45M (M means here that impeller was cut down to 9.50" diameter) went the opposite way - it sacrificed hi-alt power to gain low-alt power.
As one can see 1-speed S/Ced engines means compromises to be made; the variable-speed, as well as 2- and 3-speed S/Ced egines are more flexible in altitude-power regard.
Spit V have had a high critical altitude, low-drag wing and pointy nose, however the small details kept it from being top fighter from mid-1941 on.

Right but all versions of the P-40 had lower and higher drag / weight configurations like that. P-40L was four guns out of the factory.

I don't agree that there was such a choice - as-produced, the P-40E was exclusively a 6-HMG overweight fighter, while P-40B was a fighter of reasonable weight. P-40L and N started as improved types from the get go, the N reverted to full fuel & gun laod pretty quick.

Interesting. Yes on the P-39 though for some reason they seemed to struggle to get rated performance in the field (at least in American use) for reasons I never fully understood. Maybe that was another way the Russians got more out of them. P-51A was super fast but suffered from bad ailerons, fixed in later versions. The A version didn't seem to be a very good air to air combat aircraft.

P-51A was produced in very small numbers (310 total?), so an accurate assesment is hard to make IMO.
Early P-39s the AAF used were not that good, especially once past 13000 ft. The P-39 that went beyond 380 mph was too late to matter - USAAF needed range, and P-39 was not up to the task. However they came in just in time for Soviets, that will need more than a year to produce indigenous fighter that can beat the P-39N/Q.

Schweik · Dec 16, 2019

He also had an interesting comment about the Italians and the MC 202:

"Were the Germans in your estimation better pilots than the Italians, or was it simply that they had better aircraft?

No, I think possibly, if anything, the Italian might have been a better pilot than the German. He is certainly a very very good aerobatic pilot. The Germans probably were stauncher, they'd push on a bit more than the Italian. The Germans had better aeroplanes than the Italians, although the Macchi 202 was probably a better plane than the Messerschmitt. It was really a fine aeroplane, and if they had been flown by Germans, we probably would have even been worse off. As it was, we handled them all right. But they would turn with us - the Messerschmitt wouldn't - and it put a rather different complex on our combat methods. "

Schweik · Dec 16, 2019

tomo pauk said:
Apart from using US-spec prop spline, different carb and IIRC different type of supercharger drive (Wright-designed instead of Farman licence), rest was pretty much the same.
For altitude power (in this case, say, 13000 ft and above), Merlin XX and 45 have had about same power, probably in single digits percantage. Merlin 46 have had a bigger impeller (10.85" vs. 10.25 in), and it was making a bit more power above ~20000 ft, and a bit less under ~18000 ft than Merlin 45. The Mk.46 sacrificed a lot of power under 10000 ft, and was not produced in great numbers.
Merlin 45M (M means here that impeller was cut down to 9.50" diameter) went the opposite way - it sacrificed hi-alt power to gain low-alt power.
As one can see 1-speed S/Ced engines means compromises to be made; the variable-speed, as well as 2- and 3-speed S/Ced egines are more flexible in altitude-power regard.
Spit V have had a high critical altitude, low-drag wing and pointy nose, however the small details kept it from being top fighter from mid-1941 on.

Interesting. I'd been given to understand that the Spitfire V had a considerably higher combat ceiling / critical altitude. At any rate, I would expect the Spit V to have very good acceleration as it had a power to mass ratio of around .20 to .23 depending, which is excellent for any aircraft in the war. Better, generally speaking than the Bf 109 or MC 202 types operating at the same time, better than the P-40 and the other British fighters, and certainly better than any Japanese fighter operating in 1941-43. So it may have had a better combat speed than the top speed figure implies.

I don't agree that there was such a choice - as-produced, the P-40E was exclusively a 6-HMG overweight fighter, while P-40B was a fighter of reasonable weight. P-40L and N started as improved types from the get go, the N reverted to full fuel & gun laod pretty quick.

It's actually a bit more complex than that. Light vs. heavy, or you might say fighter vs. fighter bomber variations of the P-40 were being done in the field as far back as Java, the Philippines and Darwin in early 1942, when they first started taking guns, ammunition and fuel out and other things to lighten the aircraft so they could climb better during interceptions. P-40s were overloaded with full fuel, six guns with full ammunition, sway bars and an external tank. This gives a climb rate of about 2,000 feet per minute or less. With four guns, half fuel, 200 rounds per gun, and a few other things taken out (apparently some oil cooler armor which is repeatedly mentioned though this still gets debated) and higher boost it could be up to 3,000 fpm or more.

The P-40D / Kittyhawk I was originally a four gun model, the US didn't use any but some 560 went to the RAF. Some had 6 guns but some had 4. The F models were stripped by US mechanics down to four guns, with several other things stripped out. This was then copied by Curtiss with the L, which came standard with four guns, 200 rounds per gun and the forward wing fuel tank removed. Both types would be given six guns if they were using them more for fighter bomber missions. This also sometimes depended on the unit. For example 325th FG which flew mostly escort missions for a long time was using four guns, whereas 324th was always using six guns. When 325th started doing more FB missions they added the extra guns and ammunition in.

The very early P-40N-5-CU through N-10-CU were 'interceptor' versions with 4 guns and several other things stripped out - including some like removing the starter which were unpopular changes. These were the 378 mph version. Then there were later versions (N-15-CU through N-35-CU) with a lower rated engine and much heavier configuration which were intended as fighter bombers (this was basically the only mission for the P-40N in British use as the Kittyhawk IV for example). Fully loaded these had a top speed of ~ 340 mph. In the CBI and Pacific however there was still a need for faster and higher flying (CBI over the Himalayas) or climbing (New Guinea / Solomons) versions so the field stripping started again, and Curtiss responded with other fast four gun versions with the higher rated engine (N-40-CU). These were fast like the N-5 and N-10.

The M was intended for export as a fighter bomber (most went to the British). The K was kind of it's own niche with the high-rated (1,500+ hp) low altitude Allison V-1710-73 and it was pretty fast even with six guns.

However all of those changes could be and were done in the field. If they were facing a lot of air to air combat with fighters or needed to scramble to intercept raids it was routine to take 2 guns out and then other things.

P-51A was produced in very small numbers (310 total?), so an accurate assesment is hard to make IMO.

Well by my understanding there were 150 NA-91 / P-51 (no letter) / Mustang IA, around 700 NA-99 / P-51A / Mustang II, and 500 A-36 "Apache" dive bombers from what I understand, so that is around 1,350 produced. The Mustang IA and II was in somewhat wide use by the British who liked them as recon / day intruder planes, but were also flown by some US units mostly in the CBI where it was hoped to be a kind of savior. They had a poor combat record in air to air combat, only one Ace for example out of all of those aircraft. We had a long discussion about it on here and it turned out the problem was small ailerons, which were improved in the P-51B onward.

Early P-39s the AAF used were not that good, especially once past 13000 ft. The P-39 that went beyond 380 mph was too late to matter - USAAF needed range, and P-39 was not up to the task. However they came in just in time for Soviets, that will need more than a year to produce indigenous fighter that can beat the P-39N/Q.

Some of those later model P-39s were around in the Med and though initially (after a couple of bad maulings) consigned to coastal patrol, later were used rather widely as fighter-bombers in Italy under fairly hairy circumstances. Which I think they did reasonably well but they never seemed to find a niche as fighters except in Russia.

tomo pauk · Dec 16, 2019

Schweik said:
It's actually a bit more complex than that. Light vs. heavy, or you might say fighter vs. fighter bomber variations of the P-40 were being done in the field as far back as Java, the Philippines and Darwin in early 1942, when they first started taking guns, ammunition and fuel out and other things to lighten the aircraft so they could climb better during interceptions. P-40s were overloaded with full fuel, six guns with full ammunition, sway bars and an external tank. This gives a climb rate of about 2,000 feet per minute or less. With four guns, half fuel, 200 rounds per gun, and a few other things taken out (apparently some oil cooler armor which is repeatedly mentioned though this still gets debated) and higher boost it could be up to 3,000 fpm or more.

The P-40D / Kittyhawk I was originally a four gun model, the US didn't use any but some 560 went to the RAF. Some had 6 guns but some had 4. The F models were stripped by US mechanics down to four guns, with several other things stripped out. This was then copied by Curtiss with the L, which came standard with four guns, 200 rounds per gun and the forward wing fuel tank removed. Both types would be given six guns if they were using them more for fighter bomber missions. This also sometimes depended on the unit. For example 325th FG which flew mostly escort missions for a long time was using four guns, whereas 324th was always using six guns. When 325th started doing more FB missions they added the extra guns and ammunition in.

The very early P-40N-5-CU through N-10-CU were 'interceptor' versions with 4 guns and several other things stripped out - including some like removing the starter which were unpopular changes. These were the 378 mph version. Then there were later versions (N-15-CU through N-35-CU) with a lower rated engine and much heavier configuration which were intended as fighter bombers (this was basically the only mission for the P-40N in British use as the Kittyhawk IV for example). Fully loaded these had a top speed of ~ 340 mph. In the CBI and Pacific however there was still a need for faster and higher flying (CBI over the Himalayas) or climbing (New Guinea / Solomons) versions so the field stripping started again, and Curtiss responded with other fast four gun versions with the higher rated engine (N-40-CU). These were fast like the N-5 and N-10.

Field modification != version. One is done in field (doh), another is what actually manufacturer produed.
There was no 6 gun P-40D. All P-40Ns were powered by, for all intents and purposes, same engine - same rpm, same boost allowed, same critical altitude, same take off power, same WER.

The M was intended for export as a fighter bomber (most went to the British). The K was kind of it's own niche with the high-rated (1,500+ hp) low altitude Allison V-1710-73 and it was pretty fast even with six guns.

It was pretty fast at low altitudes. That's okay, if not what USAAF really wanted by 1942.

However all of those changes could be and were done in the field. If they were facing a lot of air to air combat with fighters or needed to scramble to intercept raids it was routine to take 2 guns out and then other things.

Kinda points out that 'short-nose' P-40s needed much more power than it had, especially at altitude (15000 ft and up) - between 8300-8670 lbs, it weighted about same as the Fw 190.
Removing fuel tanks is self-defeating, even if removing the guns is not.

Well by my understanding there were 150 NA-91 / P-51 (no letter) / Mustang IA, around 700 NA-99 / P-51A / Mustang II, and 500 A-36 "Apache" dive bombers from what I understand, so that is around 1,350 produced. The Mustang IA and II was in somewhat wide use by the British who liked them as recon / day intruder planes, but were also flown by some US units mostly in the CBI where it was hoped to be a kind of savior. They had a poor combat record in air to air combat, only one Ace for example out of all of those aircraft. We had a long discussion about it on here and it turned out the problem was small ailerons, which were improved in the P-51B onward.

You do know that P-51, A-36 and P-51 were very different aircraft?
310 of Mustang II/P-51A produced, 1st delivered in March 1943, 1st use Sept 1943.

Schweik · Dec 16, 2019

tomo pauk said:
Field modification != version. One is done in field (doh), another is what actually manufacturer produed.
There was no 6 gun P-40D.

In this case, while it's true that the field modification is not the same as the version, the two very much overlapped. P-40L is just the factory version of a field modified P-40F from the second half of the production run. It could be and was reconfigured like an "original" P-40F in a few hours. So I really don't see the difference. One of the features of the P-40 by the time the mid-run series came out was that it was very much a known quantity and what could be done with it could vary quite a bit. Original specs also limit bomb load to one 250 lb or 500 lb bomb on center line and some 40 lb bombs on the wings, but in the field they put 1,000 lb bombs on the centerline and sometimes also 2 x 500 lb bombs on the wings, and various other combinations. Also rockets. All field variations, but also standardized.

My understanding is that there was a four gun P-40D- not for the US but for the British, though it's unclear how many were delivered as such. It was also possible to put two guns back in if it came with four since there was provision for another pair at some point in the production run.

All P-40Ns were powered by, for all intents and purposes, same engine - same rpm, same boost allowed, same critical altitude, same take off power, same WER.

My understanding is that they used different versions of the V-1710 ranging from 1,300 hp for takeoff (V-1710-81 / F20R) on the N1 through N 10, to 1200 hp for takeoff (V-1710-99 / F26R) for N -15 through N 35, back to 1,350 hp for takeoff (V-1710-115 (F31R) on the N-40. There were other differences, some were optimized (gear ratio) for a higher critical altitude, others for harder running (higher boost). There was of course overlap but that was the general tradeoff. WEP power ranges from 1480 hp for the -99 to closer to 1,550 hp for the 115. The boost control on the -99 prevented overboosting.

Internally of course I'm sure they were very similar but in terms of actual use, there were differences.

It was pretty fast at low altitudes. That's okay, if not what USAAF really wanted by 1942.

Very true, but the USAAF wasn't the only customer. The British liked them (though they didn't get many), the Australians got relatively a lot of them and loved them. Same for the Russians - the P-40K was the variants they had the best results with and the most aces and HSU flying them. Not sure about the New Zealanders. US units also did get a lot out of the -K variant as it seemed to be the most successful for the 23rd FG and the 49th FG, both units that often fought at low altitude.

As we have discussed before, there clearly was a niche for low -medium altitude fighters, hence the cropped wing / cropped impeller Spitfires.

Kinda points out that 'short-nose' P-40s needed much more power than it had, especially at altitude (15000 ft and up) - between 8300-8670 lbs, it weighted about same as the Fw 190.
Removing fuel tanks is self-defeating, even if removing the guns is not.

Removing fuel (and fuel tanks) was apparently considered a normal tactic for many aircraft when they had to scramble. It was also done with Hurricanes and Buffalos in the SW Pacific.

You do know that P-51, A-36 and P-51 were very different aircraft?
310 of Mustang II/P-51A produced, 1st delivered in March 1943, 1st use Sept 1943.

A-36 (500 produced) was different because it had airbrakes, but the P-51A, Mustang IA and II were not very different except for armament IMO. And there were enough of those produced and into combat for a realistic evaluation.

tomo pauk · Dec 16, 2019

Schweik said:
...
My understanding is that there was a four gun P-40D- not for the US but for the British, though it's unclear how many were delivered as such. It was also possible to put two guns back in if it came with four since there was provision for another pair at some point in the production run.

The P-40D was a 4-gun type.

My understanding is that they used different versions of the V-1710 ranging from 1,300 hp for takeoff (V-1710-81 / F20R) on the N1 through N 10, to 1200 hp for takeoff (V-1710-99 / F26R) for N -15 through N 35, back to 1,350 hp for takeoff (V-1710-115 (F31R) on the N-40. There were other differences, some were optimized (gear ratio) for a higher critical altitude, others for harder running (higher boost). There was of course overlap but that was the general tradeoff. WEP power ranges from 1480 hp for the -99 to closer to 1,550 hp for the 115. The boost control on the -99 prevented overboosting.
Internally of course I'm sure they were very similar but in terms of actual use, there were differences.

Boost control allowed 'carefree' overboosting; no over-boosting = no WER.
The V-1710-81, -99 and -115 were all with S/C gear ratio 9.60:1, take off power 1200 HP, mil power 1125 HP at 14500-15000 ft. WER was 1480 HP at 7500 ft (going lower can allow for more boost = more power, if engine can take it).

Removing fuel (and fuel tanks) was apparently considered a normal tactic for many aircraft when they had to scramble. It was also done with Hurricanes and Buffalos in the SW Pacific.

With Buffaloes - probably it was the case. With Hurricanes - nothing to remove, it was already shorter ranged than the P-39, that Gen Kenney loathed (he was barely satisfied with range of P-40).

A-36 (500 produced) was different because it had airbrakes, but the P-51A, Mustang IA and II were not very different except for armament IMO. And there were enough of those produced and into combat for a realistic evaluation.

P-51A and Mustang IIwere the same aircraft - one with US name, other with British name. Engine with critical alt at ~15000 ft (1125 HP there). Has drop tanks.
Mustang IA (P-51) was cannon-armed version of Mustang I (~XP-51). Engine with critical alt at 12000 ft (1150 HP there). No drop tanks.
A-36 - powered by low-alt V-1710.

All of them performed differently at any given altitude, P-51A being the best of the lot in fighter role, not just due to 410+ mph speed.
I'd certainly suggest the two books: 'American hundred thousand' and 'Vee's for victory'.

fubar57 · Dec 16, 2019

MikeMeech · Dec 16, 2019

Schweik said:
Just blundered across something which answered another nagging question I'd had for a long time. We all know about the infamous Vokes filter, with some debate as to how bad it was, then replaced by the "Aboukir" filter which was superior. I always wondered why Kittyhawks didn't seem to have this kind of problem. I was just reading an interview with Bobby Gibbes and he mentioned something interesting about filters. He said "Buck Abou Kir" developed an air filter for the Kittyhawks which was later adopted by Curtiss Wright! Gibbes himself used to test fly the aircraft with the new filters. Gibbes said that prior to the new filter being adopted, engine life was down to 60-70 hours due to dust, (which isn't much better than what the Russians were reportedly getting with P-40s). With the filter he said it went up to about 120 hours. Gibbes also noted that a German pilot told him the German engines were failing after 20-30 hours.

"Yes. Well turning to the more technical side of it in terms of servicing aircraft, how good were those facilities?

(20.00) Well back .... We used to have two flights plus a base camp, and if any major damage was done the aircraft would be serviced by the base camp. But basically, out in the field, out in the desert, we'd ... each flight would do its own maintenance. They couldn't do anything really major but they kept things flying. Motors used to chop out after sixty or seventy hours. They were finished. We had an engineer called Buck Abou Kir - Shirley Abou Kir's father - and he designed an air filter, and I did the test flying for his air filter. Later that air filter was adopted by Curtiss Wright and fitted into all the Kittyhawks. I think it was from Buck's filter - probably got a few mods - but that .... Our engine hours went up to about 120 then. I was talking to a German pilot who was commanding officer of JG 27 in North Africa. He said the Messerschmitt engines didn't .... They got no more than twenty or thirty hours before they would cut out. "

Tried googling this Abou Kir, I found this person Shirley Abicair, daughter of a Wing Commander in the RAAF but it doesn't give his name. I know there was a town called Abou Qir or Abukir in Egypt where they had a major RAF air base, and I always thought that was the origin of the name of the filter. Not sure what the actual link is here...

S

Hi

I doubt if the "Buck Abou Kir" story is true, mainly as No. 103 MU at ABOUKIR dealt with this sort of problem as in the Spitfire. Many sources mention the MU being concerned with changing the 'Vokes' intake, eg. reference the Spitfire, Morgan and Shacklady in 'Spitfire, The History' pages 154-155, there is the following:

"The large Vokes tropical intake was not liked by the services and it was not long before unofficial modifications began to appear, the most successful designed and installed by that most resourceful team at No 103 MU at Aboukir. They trimmed the filter back to a much smaller unit, one that was more efficient and drag reducing. It was named the Aboukir filter and the Vokes Aero-Vee, fitted to the Mk IX Spitfire, was based on this local modification."

The Mk VIII had the smaller type filter. I doubt if a filter fitted to the P 40 was too much of a problem for them.

Dust problems also arose in Normandy causing severe engine wear to the Napier Sabres of the Typhoon force operating from the forward airstrips, a 'filter' was fitted to the engine to solve this problem, this was done by Napier, although it had to go through a modification process to completely solve the problem. Again I see no severe difficulties with 103 MU fitting a filter to the P 40 intake as well. Although it is probably hard to tell from general photographs of the aircraft if there is a filter fitted to the P 40 as only a close up image of the Typhoon intake will show its filter, and a Mk VIII Spitfire's is basically invisible, unlike the Vokes on the Spitfire V. The Bf 109G's filter is a quite distinct addition as well and can be visible on images, so I suspect most aircraft operating in desert type conditions would have a filter fitted although maybe not immediately visible.

The names mentioned in the quote are too similar to 103 MU's location to be a coincidence.

Mike

Schweik · Dec 16, 2019

tomo pauk said:
The P-40D was a 4-gun type.

Ok we are agreed then. So it was one of four manufactured P-40 variants with four guns: D, L and early N.

Boost control allowed 'carefree' overboosting; no over-boosting = no WER.
The V-1710-81, -99 and -115 were all with S/C gear ratio 9.60:1, take off power 1200 HP, mil power 1125 HP at 14500-15000 ft. WER was 1480 HP at 7500 ft (going lower can allow for more boost = more power, if engine can take it).

Right, and usually tension between pilots who sometimes wanted more boost (especially if intense air to air combat or repeated scrambles) vs. aircraft and engine company and the military hierarchy who wanted to keep engines running for more than 60 hours. I think the -81 allowed a higher WEP setting than the -99 did, and the 115 went back to the high setting, basically. Of course if a pilot wanted to override the boost limitation, especially in say Australian service or in American units in remote places like China or Burma, they could just have the mechanic do what they wanted. Or even put in a different engine for that matter.

I thought there was some slight variation in the gear ratios between the three types but I'll take your word for it.

With Buffaloes - probably it was the case. With Hurricanes - nothing to remove, it was already shorter ranged than the P-39, that Gen Kenney loathed (he was barely satisfied with range of P-40).

Well, they routinely took out a pair of cannon in the Hurricane IIcs, and up to 4 -6 x .303s in the earlier mks, in attempts to save weight. That was done both in the Pacific and in the Western Desert.

P-51A and Mustang IIwere the same aircraft - one with US name, other with British name. Engine with critical alt at ~15000 ft (1125 HP there). Has drop tanks.
Mustang IA (P-51) was cannon-armed version of Mustang I (~XP-51). Engine with critical alt at 12000 ft (1150 HP there). No drop tanks.
A-36 - powered by low-alt V-1710.

All of them performed differently at any given altitude, P-51A being the best of the lot in fighter role, not just due to 410+ mph speed.
I'd certainly suggest the two books: 'American hundred thousand' and 'Vee's for victory'.

I have both Americas Hundred Thousand (which I think isn't as good as everyone said it was) and Vees for Victory.

My point being that none of the above Allison engined variants of the P-51 did that well in air to air combat, or in my opinion lived up to their potential. The problem wasn't the Allison but was rather with the ailerons, apparently. I think if they had made NA-91 through 99 types with the bigger / better ailerons they could have had an excellent low altitude fighter out of it.

tomo pauk · Dec 16, 2019

Schweik said:
Right, and usually tension between pilots who sometimes wanted more boost (especially if intense air to air combat or repeated scrambles) vs. aircraft and engine company and the military hierarchy who wanted to keep engines running for more than 60 hours. I think the -81 allowed a higher WEP setting than the -99 did, and the 115 went back to the high setting, basically. Of course if a pilot wanted to override the boost limitation, especially in say Australian service or in American units in places like China or Burma, they could have the mechanic do what they wanted. Or even put in a different engine.

There is slim and no chance that different engines were installed on pilot's preference, and Slim has alsready left the town.
You can see at the table that -81 and -99 have had same boost ratings. Mechanic's doing with engine what pilots preferred instead of what they were trained and ordered to do? Sounds great until engine is wrecked in mid-air.

I thought there was some slight variation in the gear ratios between the three types but I'll take your word for it.

Don't take my word for it, check at Vee's for victory.

Well, they routinely took out a pair of cannon in the Hurricane IIcs, and up to 4 -6 x .303s in the earlier mks, in attempts to save weight. That was done both in the Pacific and in the Western Desert.

?? You:
Removing fuel (and fuel tanks) was apparently considered a normal tactic for many aircraft when they had to scramble. It was also done with Hurricanes and Buffalos in the SW Pacific.

Fuel != guns.

I have both Americas Hundred Thousand (which I think isn't as good as everyone said it was) and Vees for Victory.

Even though they contain a mistake or two, those are great books.

My point being that none of the above Allison engined variants of the P-51 did that well in air to air combat, or in my opinion lived up to their potential. The problem wasn't the Allison but was rather with the ailerons, apparently. I think if they had made NA-91 through 99 types with the bigger / better ailerons they could have had an excellent low altitude fighter out of it.

The V-1710 was part of the problem, had they installed V-1650-1 it would've been a prime Allied fighter in 1942-43. Another part of the problem was that P-51A was too late and too few to matter.

nuuumannn · Dec 16, 2019

Mike Williams said:
Not quite I think:

Actually, I dunno why, but I'm slightly annoyed by the fact that your only contribution to this conversation so far is to correct something I posted... :C

But thank you for the extra information, I only wish I had access to that sort of thing.

Shortround6 · Dec 16, 2019

I would note that not filling fuel tanks was a pretty normal tactic in the early part of the war, and was part of the planning. The Buffalo for instance having weight charts showing either 110 gallons or 160 gallons. They just didn't fill the two wing tanks full. They didn't take anything out since the Buffalo (aside from the F2A-3) only had two fuel tanks and they were actually sealed compartments using the front and rear spars as the front and back wall of the tank/s. A bit hard to take out without the wing falling apart.

The P-36/Mohawk used the tank behind the pilot as a ferry tank, it was never intended for combat. With the longer heavier V-12 engines the tank behind the pilot became part of the balance weight to maintain the CG. They might not fill it but they sure weren't going to take it out.
The weight charts for the F4F and F4U also show less than full tanks and less than full ammo although I don't think they were every used in combat that way (or at least not much)

As for the late P-40s, the engines were functionally identical, the different dash numbers indicated changes to the engine controls. The last engine having essentially the single lever control some people rave about the Germans having.

nuuumannn · Dec 16, 2019

PAT303 said:
The Spitfire's development line went from the MkI then II then V and IX, if it had gone from the MkIII, a totally different aircraft we would have had the MkVIII and then the XIV instead. The MkIII air frame was a generation ahead of the MkII, two speed engine, shorter cleaner wings, retractable tail wheel, covered main gear and internal bullet proof windscreen. The MkIII gave the RAF an honest 385mph fighter with 650 mile range in 1941, 415 mph in 1942 accompanied by the Griffon powered XII and XIV from 1942 onwards.

Yeah, I know this. Doesn't change my criticism at all about your comments. The Mk.III was developed by joe Smith and had a Merlin with a two speed supercharger and other refinements that went into other variants, it's clipped wings in the 'V and retractable tailwheel into the Mk.VIII for example, but the Merlin 45, although having a single stage supercharger offered greater poower and higher manifold pressures and this was put in the 'V. Remember, the performance the 'III offered was that of a prototype, which didn't have guns, ammo or armour, so its performance was not representative of what it would have been in service. It was overtaken by events and the Air Ministry's desire to adopt the Mk V as an interim. One of the prototypes of the Mk.III became the first Spitfire to be fitted with a 60 Series Merlin, which promised greater performance again than existing Spitfires. By the time it was to have been put into production, the edge it might have had in 1940/41 would have been lost to the Fw 190. The 'V and 'IX were based on the same airframe; putting them into production as an expeditious measure made far more sense in terms of the swiftly developing war. Also, the HF.VII and Mk.VIII with refinements and 60 Series Merlin offered much more over time and it was a Mk.VIII that became the prototype of the 'XIV.

PAT303 · Dec 16, 2019

nuuumannn said:
Doesn't change my criticism at all about your comments.

The MkIII air frame was better than the MkII in every way, as good as the IX was, the MkVIII was better, it was aerodynamically cleaner with a greater internal fuel load, the two things the Spit needed most. I'll stand by my comments that the Spit wasn't developed into the plane it could have been.

tomo pauk · Dec 17, 2019

nuuumannn said:
Yeah, I know this. Doesn't change my criticism at all about your comments. The Mk.III was developed by joe Smith and had a Merlin with a two speed supercharger and other refinements that went into other variants, it's clipped wings in the 'V and retractable tailwheel into the Mk.VIII for example, but the Merlin 45, although having a single stage supercharger offered greater poower and higher manifold pressures and this was put in the 'V. Remember, the performance the 'III offered was that of a prototype, which didn't have guns, ammo or armour, so its performance was not representative of what it would have been in service.

I'd mostly disagree.
Spitfire III sported an internal BP glass (IIRC worth 6-7 mph vs. external), fully retractable & covered U/C (again less drag = more speed), plus of course the Merlin XX - a best fighters' engine of 1940 in the world. Being a prototype, the fit&finish was as good as possible. That was not proceeded with had a lot to do with everyone needing/wanting Merlin XX, mostly the Hurricane so it can close the performance gap vs. Bf 109E, so there was a lack of XXs.
Merlin 45 (= roughly Merlin XII with improved ram air inlet from Merlin XX) was not offering greater power under 10000 ft and above 13000 ft vs. Merlin XX, and was a bit later engine (6 months?).
Granted, a part of 400 mph claimed speed for the Spit III was due not being outfitted with guns.

It was overtaken by events and the Air Ministry's desire to adopt the Mk V as an interim. One of the prototypes of the Mk.III became the first Spitfire to be fitted with a 60 Series Merlin, which promised greater performance again than existing Spitfires. By the time it was to have been put into production, the edge it might have had in 1940/41 would have been lost to the Fw 190. The 'V and 'IX were based on the same airframe; putting them into production as an expeditious measure made far more sense in terms of the swiftly developing war. Also, the HF.VII and Mk.VIII with refinements and 60 Series Merlin offered much more over time and it was a Mk.VIII that became the prototype of the 'XIV.

Having a 390 mph combat-worthy Spitfire III is an improvement over the 365-375 mph SPitfire V against the 390-410 mph Fw 190 and Bf 109F-4. A bit greater fuel tank can also help with greater cruise speeds, and clipped wings left less of an advantage for the Fw 190 wrt. rate of roll.
In 1942, install the Merlin 60 series for extra 20 mph.

XBe02Drvr · Dec 17, 2019

RCAFson said:
by 1939 most UK fighters (and the Skua/Roc) were using a UK designed VP (2) pitch prop which was somewhat superior to a fixed pitch prop,

The two speed prop is a good intermediate step between fixed pitch and constant speed, with the benefit that after making the necessary mods to install it, you're most of the way there. Prop pitch changes are made by the application of pressurized engine oil through two galleries bored into the spine shaft, one driving course and one driving fine. This requires a high pressure oil pump to drive it and a shuttle valve that sends pressure to one gallery or the other or to both equally. This shuttle valve is attached to the prop pitch lever. You now have a prop that can be a "climb" or a "cruise" prop, but in either position, behaves like a conventional fixed pitch prop, meaning the pilot must control RPMs with the throttle.
You now have a prop that has everything it needs to be converted to a constant speed installation by replacing the shuttle valve with a prop governernor. This device sends oil pressure to the appropriate gallery, changing pitch to correct whenever revs deviate from the desired speed.

Schweik said:
I have some questions on pitch settings for climb and dive and so forth (manual override?) and which aircraft had the best / most efficient prop pitch control (constant speed was the gold standard I gather, but what other options were there if any?)

IIn most cases there is no way for a manual override to work, as the governor itself is a pretty robust, simple device, not much given to failure. The most likely failure would be a rupture of a seal in the propeller or spline shaft/crank case interface, releasing the pressurized oil, defeating a manual control system, and driving the prop to its coarse or fine pitch limits where it will act as a fixed pitch prop.

slaterat said:
By June 1940 all Hurricanes and Spitfires had three bladed, two pitch props.
By August 15, 1940 1051 Spitfires and Hurricanes in the field were equipped with constant speed propellers with automatic boost control. Production lines were also being converted to constant speed props.

This sort of implies that Automatic Boost Control is somehow related to propeller control. It's not. In fact, a reliable constant speed prop reduces the need for boost control, as boost excursions are generally tied to RPM excursions, at least with direct drive superchargers. Fluid coupled drives are another matter. The only other cause for an overboost (direct drive only) is overenthusiastic throttle jockeying while ignoring the Manifold Pressure gage. That's like ignoring Vne, Gmax, or Bingo fuel. Take care of your ride and she'll take care of you.

slaterat said:
The RAF was at the forefront of propeller technology in 1940.

MANIFESTUS ABSURDUM! Yeah, they could have been, if certain ass-tute individuals hadn't decided that the benefits of that investment weren't worth the expense. That's right up there with cavalry officers making procurement decisions for the Air Corps.
Cheers,
Wes

XBe02Drvr · Dec 17, 2019

Schweik said:
Yes on the P-39 though for some reason they seemed to struggle to get rated performance in the field (at least in American use) for reasons I never fully understood.

I believe they struggled to get rated performance, because they were originally rated under somewhat "optimistic" conditions and configuration, rather than realistic field conditions. Larry Bell tended to be that way.
The Russians liked to reduce weight and drag by deleting wing guns, some of the electronics and some fuel, and they discovered they could get away with overboosting their Allisons, turning it into a "hotrod".
Cheers,
Wes

Japanese Zero vs Spitfire vs FW 190

Senior Airman

Banned

Banned

Creator of Interesting Threads

Banned

Banned

Creator of Interesting Threads

Banned

Creator of Interesting Threads

Attachments

General

Senior Airman

Banned

Creator of Interesting Threads

Major

Major General

Major

Tech Sergeant

Creator of Interesting Threads

2nd Lieutenant

2nd Lieutenant

Users who are viewing this thread

Similar threads