Most Overrated aircraft of WWII.....?

[Milosh]

What Wiki said:
The USAAF later ordered 310 P-51As, which were essentially A-36s without the dive-brakes and nose mounted weapons, leaving an armament of four wing-mounted 0.50 in (12.7 mm) Browning machine guns.

What you said,

The last 310 A-36 were apparently ordered by USAAF without dive brakes per the Wiki.

That would mean only190 A-36s were produced which is definitely wrong.

 

[wuzak]

If you are wondering why Spitfires may not have the same range as some other aircraft types in spite of having a lot of fuel (as was speculated upon recently in this forum by Shortround though I can't remember if it was in this same thread)

The Spitfire certainly did not have "a lot of fuel".

Range was affected by drag, so would not fly as far as a P-51 on the same amount of fuel with the same engine.

 

[Schweik]

The Spitfire certainly did not have "a lot of fuel".

Range was affected by drag, so would not fly as far as a P-51 on the same amount of fuel with the same engine.

I see I'm gonna get picked apart for every shorthand comment unless I spell everything out to the nth degree. What I was specifically referring to was somebody making back of the envelope calculations comparing a Spitfire with I forget what other plane with twice the range, and working out how many gallons in the tank vs how many gallons per minute and concluding that the range numbers were all wrong because the Spits gas tanks held like 3/4 as much fuel or some such. I think they were talking about the Hellcat.

What the memo you found actually says is that the Merlin engines didn't run well when you were running them at 1600 RPM or below which they said in turn affected range.

S

 

[XBe02Drvr]

Hey guys, sounds like you're talking past each other here.
Now this is just speculation, based on my experience of the principles of aircraft performance and facts presented by various participants in this thread, but it sounds like the Spit, and to a lesser extent, the Merlin 'Stang are forced by the low RPM limitations of their engines to cruise at a speed higher than optimum for airframe aerodynamic range.(>than max L/D speed) The Merlin was less tolerant of "oversquare" (low RPM, high MAP) operation than the Allison. If you really want to cruise your Spit at max L/D for the airframe, you have to run your Merlin at 1600+ RPM with a really low manifold pressure, which will burn more fuel and negate the benefits of your slow cruise. Besides, this leaves you less able to respond quickly to a bounce. Not good.
Oversquare operation puts extreme stresses on an engine, as BMEPs are high and RPM is low and bearings and long "flexible" parts like crankshafts and camshafts are subject to heavy bending, torsional, and harmonic forces, and demand near perfect balance to keep vibration below destructive levels. There also needs to be adequate margin from pre-ignition and detonation as the high MAPs make the cylinders run hotter. The more efficient supercharger in the Merlin comes back to bite here, as charge temperatures are apt to be higher.
Cheers,
Wes

 

[wuzak]

That may be, but flying over contested air space at low speed cruise is not the cleverest thing to do.

Also, was it that the Merlin couldn't do it, or that it was rough doing it?

 

[XBe02Drvr]

Also, was it that the Merlin couldn't do it, or that it was rough doing it?

Don't know. I'm not a Merlin ex-spurt, but from I've read here and about, I think it had something to do with the vibration levels becoming a problem at or below 1600 RPM and high MAP, such that it threatened bearing failure. Whether this was a matter of bearing design and manufacture, engine balancing, bending strength of various parts, uneven mixture distribution, or any of a whole host of other potential problems, is a drgondog question.
Cheers,
Wes

 

[XBe02Drvr]

That would mean only190 A-36s were produced which is definitely wrong.

You missed the point here. 500 Apaches ordered, then 310 more, then 310 dive brakes and nose guns deleted, and; "Presto-Change-O", 310 P-51As miraculously appeared! Don't you just love that sleight of hand stuff?
Cheers,
Wes

 

[drgondog]

1942 was a very complex year to trace the evolution of NA-73 to NA-102. I'm not going to spend a lot of time on this because many events, political and technology driven shaped the emergence of the P-51B. I am a little hesitant in detailing the late 1941 through mid 1942 machinations and politics between NAA, the AAF CAS disciples who believed that airpower had a major role in battlefield air supremacy, the Bomber Mafia and the obstructionist Oliver Echols in charge of Procurement and Production. What is important is (IMO) the CAS wing were able to influence re-thinking about P-51 and bypass Material Command to unleash the P-51 testing from Wright Field to Eglin Field and gain momentum in keeping the NAA Mustang line going.

Several waves contributed to a perfect storm as 1.) the Dive Bomber was deemed a sitting duck re: airframes in existence and proposed because they simply were defenseless, b.) the attributes of the XP-51 became known, c.) the awareness of the Merlin 60 emergence in the Rolls Rolls product line to promise high altitude performance Without the AAF standard "turbo" preference. The critical period was (IMO) November 1941 through March 1942.

Neither the A-36 nor the P-51A was deemed the 'complete' solution by the CAS and they were the FIRST to direct earliest possible switch of P-51A to P-51B/Merlin in approximate August 1942. Echols was still trying to kill NAA fighter production and switch to B-25 as late as August 1942.

IMO, the primary deficiency of the Mustang I, IA, A-36 and P-51A in air to air combat from low level to 11-15K was the original aileron design combined with throw angles. The earlier Allison Mustang had +/-10 degree deflection. NACA and NAA improved the shape, sealed it to improve aero efficiency and increased the deflection angles for the P-51B-1. They were first tested on the NA-101 XP-51B.

The P-51-1/-2 had the -39, the P-51A had the -81 and the A-36 the -87. The latter developed maximum Hp at 5400 feet at 52", the -81 developed max HP at 11,800 feet at 57". All adequate to maintain a speed advantage from SL to mid altitude

The Brits achieved much better max HP by removing boost controls and as a result the Mustang I/IA were both faster and climbed about the same as the FW 190 and Bf 109 but they avoided engagement as much as possible as they would nearly always be at a tactical disadvantage based on altitude common to Rhubarbs. The A-36 were at a similar disadvantage - even with more powerful engine below 6000 feet. The A-36 was also slower than Mustang I at low to medium low altitude due to drag of bomb/fuel pylons and dive brake 'leakage' parasite drag.

All of these were similarly limited in roll performance. All were at a disadvantage in turn if the first deployment of flaps didn't achieve the desired effect of achieving deflection, simply because the increased drag hurt the primary advantage of the very clean airframe.

Against the Ki 43, the A-36 and P-51A (and P-51B/C) were simply overmatched in low speed maneuvering flight, as ALL US fighters found themselves, at low altitude.

That said, the P-51A achieved better than parity perhaps because the original deployment of the A-36 to CBI proved the case - Do NOT engage in low and slow gunfight with Japanese a/c. the 311th FG (primary destination for CBI P-51A) produced several aces including England and Mulhollem obtained all of their victories in them before converting to P-51C. The 23rd FG also received P-51A but at a later stage and were first to get P-51B-1 in very late 1943. Tex Hiil nailed two in the P-51A for example.

All that said, consider that both P-47D and P-38J Fighter pilots relegated to low level CAS had very few aces despite flying an order of magnitude more missions in the ETO/MTO.

 

[pbehn]

I thought it was something like that Dg.

 

[Schweik]

Very interesting post drgondog, much appreciated!

IMO, the primary deficiency of the Mustang I, IA, A-36 and P-51A in air to air combat from low level to 11-15K was the original aileron design combined with throw angles. The earlier Allison Mustang had +/-10 degree deflection. NACA and NAA improved the shape, sealed it to improve aero efficiency and increased the deflection angles for the P-51B-1. They were first tested on the NA-101 XP-51B.

This is probably the key issue right here.

The Brits achieved much better max HP by removing boost controls and as a result the Mustang I/IA were both faster and climbed about the same as the FW 190 and Bf 109 but they avoided engagement as much as possible

interesting that the Brits were doing this but not the USAAF groups? I'd look into it to find out if the latter did it too. The 1942 Allison memo about this exact thing being done with P-40 engines indicates that the practice started with the Australians but quickly spread to Americans in the North African Desert. Allison even acknowledged agreeing to an unofficial "WEP" setting of 60 Hg. The memo did also suggest that overboosting beyond that level would become more dangerous in terms of engine damage with the later model engines like the -81 due to the changed gear ratio.

All of these were similarly limited in roll performance. All were at a disadvantage in turn if the first deployment of flaps didn't achieve the desired effect of achieving deflection, simply because the increased drag hurt the primary advantage of the very clean airframe.

yeah you can't always use flaps in a turn for a variety of reasons, so turn was an issue too. i wonder if that was improved somewhat as well in later Mustang models?

Against the Ki 43, the A-36 and P-51A (and P-51B/C) were simply overmatched in low speed maneuvering flight, as ALL US fighters found themselves, at low altitude.

That said, the P-51A achieved better than parity perhaps because the original deployment of the A-36 to CBI proved the case - Do NOT engage in low and slow gunfight with Japanese a/c. the 311th FG (primary destination for CBI P-51A) produced several aces including England and Mulhollem obtained all of their victories in them before converting to P-51C. The 23rd FG also received P-51A but at a later stage and were first to get P-51B-1 in very late 1943. Tex Hiil nailed two in the P-51A for example.

That's interesting so there was in fact more than the one Allison P-51 Ace then? England and Mullhollem were P-51 aces?

P-40 squadrons with 23rd FG, 51st and 80th FG etc., did well against Ki-43 and other Japanese types like Ki-44. Aviation historian Robert Molesworth, not normally given to hyperbole, noted that "...the P-40 simply dominated the skies over Burma and China. They were able to establish air superiority over free China, northern Burma and the Assam valley of India in 1942, and they never relinquished it.". There were at least 70 P-40 Aces in the CBI and Pacific. According to a Thread I found on this forum, P-40s even did well against late model Japanese fighters like Ki 61 and Ki 84.

One of the tactics which developed for later model P-40s against Ki-43 or A6M was to extend in level flight, i.e. not by diving away, and then execute a sudden and very swift turn as soon as a certain distance was achieved and come back for a head-on attack. This technique, tested against a captured Zero as described in this War Dept memo (see page 7), is an example of something which may have been harder to do in an A-36 or P-51A given roll and turn rates.

Another technique described by P-40 Ace Robert DeHaven was the "Low yo-yo" to out turn an A6M or Ki-43, which if I understand correctly requires both good roll and turn capabilities.

All that said, consider that both P-47D and P-38J Fighter pilots relegated to low level CAS had very few aces despite flying an order of magnitude more missions in the ETO/MTO.

And yet you had quite a few Aces in P-40s at low altitude in the Med. At least 46 Commonwealth Aces and 14 USAAF, not to mention 45 in the CBI where they also did primarily FB sorties.

DAF squadrons flew a mix of missions but certain subtypes, like the P-40K, did mostly fighter-bomber sorties, and yet they scored many air to air victories.

Neither P-47 nor P-38 excel at low altitude, it's worth noting, in spite of the fact that they were often given such missions.

S

 

[Schweik]

To be clear, the reasons I bring all this up, are one to point out that the P-40 was indeed one of the more under estimated fighters in WW2 (and also the Ki-43 though I haven't gotten as deep into that deadly plane yet), but also to show what I think this fascinating deep dive into the early P-51 makes clear.

When evaluating fighters it's not sufficient to look at some basic numbers like top speed, firepower or range or what have you, you also need to look at the historical combat record. That in turn can help you find factors which can seem counter-intuitive, such as the subtle differences (like a relatively tiny adjustment to Aileron deflection angles, better ammunition or a new gun sight) which make an aircraft more suitable to achieve victory in a given Theater.

The recipe for victory is often reduced down to the obvious ones like speed and firepower. But sometimes, as with the Ki-43, or say, the Bf 109F, (comparatively) lightly armed planes with seemingly modest performance, proved to be some of the most effective war-machines of the war in terms of enemy aircraft destroyed.

In many cases, like with the B-239 or P-39, or the P-51, success seems to be a matter of developing suitable tactics and training for the enemy at hand, and finding both major (i.e. a new engine) and seemingly minor technical changes that are done as the result of early combat trials. Together technical modifications and training / tactics make the difference from poor or mediocre combat results to good or excellent ones. But of course this can take time, and how 'rough' the early combat debut of a fighter was has to do with how intense early combat experiences were before the bugs were worked out and the tactics optimized.

I.e. Allied planes which had their debut in 1940, 41 or the first half of 1942 may have faced a steeper and harsher learning curve (so to speak) than planes that rolled out in the second half of 1942 or later.

On the other hand perhaps this was an advantage that planes which were around from the beginning of the war and did get through that rough shakedown process, such as the Spitfire, Hurricane, Bf 109, A6M, Ki-43 or Yak 3 over some other later types which had to work out teething problems at a slower pace before they achieved excellence (like the P-51 or the Typhoon).

S

 

[drgondog]

To be clear, the reasons I bring all this up, are one to point out that the P-40 was indeed one of the more under estimated fighters in WW2 (and also the Ki-43 though I haven't gotten as deep into that deadly plane yet), but also to show what I think this fascinating deep dive into the early P-51 makes clear.

When evaluating fighters it's not sufficient to look at some basic numbers like top speed, firepower or range or what have you, you also need to look at the historical combat record. That in turn can help you find factors which can seem counter-intuitive, such as the subtle differences (like a relatively tiny adjustment to Aileron deflection angles, better ammunition or a new gun sight) which make an aircraft more suitable to achieve victory in a given Theater.

The recipe for victory is often reduced down to the obvious ones like speed and firepower. But sometimes, as with the Ki-43, or say, the Bf 109F, (comparatively) lightly armed planes with seemingly modest performance, proved to be some of the most effective war-machines of the war in terms of enemy aircraft destroyed.

In many cases, like with the B-239 or P-39, or the P-51, success seems to be a matter of developing suitable tactics and training for the enemy at hand, and finding both major (i.e. a new engine) and seemingly minor technical changes that are done as the result of early combat trials. Together technical modifications and training / tactics make the difference from poor or mediocre combat results to good or excellent ones. But of course this can take time, and how 'rough' the early combat debut of a fighter was has to do with how intense early combat experiences were before the bugs were worked out and the tactics optimized.

I.e. Allied planes which had their debut in 1940, 41 or the first half of 1942 may have faced a steeper and harsher learning curve (so to speak) than planes that rolled out in the second half of 1942 or later.

On the other hand perhaps this was an advantage that planes which were around from the beginning of the war and did get through that rough shakedown process, such as the Spitfire, Hurricane, Bf 109, A6M, Ki-43 or Yak 3 over some other later types which had to work out teething problems at a slower pace before they achieved excellence (like the P-51 or the Typhoon).

S

You tackle a complex evaluation, which as noted is not all about top speed or close in maneuver battles at low speed.

The P-51B and subsequent, were poster boys for Speed - at all altitudes - combined with near equivalent maneuverability at extremely long ranges. The P-51A was an interim solution leading to the emergence of the Rolls/Packard Merlin 1650-3 and 1650-7. Our fighter pilots entered operations with the P-51B-1 with highly trained pilots of the 354th FG, then 357th, then saddled up with combat experienced P-47D pilots of 4th, 352nd, 355th. You can't overlook combat pilot talent in any evaluation. The 23rd FG continued to kill with P-40N in conjunction with P-51B/C because they a.) knew their opponents Very well and had the experience and discipline to 'fight the fight' when the advantage was available - and extend when it wasn't.

The P-40E and F4F-3 did well against superb IJN pilots in SW Pacific for the above reasons. The Russians did very well with P-39D/Q/N when we were converting from the Iron Dog as fast as possible.

 

[drgondog]

Very interesting post drgondog, much appreciated!




yeah you can't always use flaps in a turn for a variety of reasons, so turn was an issue too. i wonder if that was improved somewhat as well in later Mustang models?

Yes - because both Turn and Climb are intrinsically linked to Power Required and Power Available - and the 1650-3 and -7 were very powerful engines throughout the flight envelope. That said, most good pilots were aware of the significant and deleterious effect of flap deployment on drag and associated reduction in both speed and associated Energy.

That's interesting so there was in fact more than the one Allison P-51 Ace then? England and Mullhollem were P-51 aces? YES

P-40 squadrons with 23rd FG, 51st and 80th FG etc., did well against Ki-43 and other Japanese types like Ki-44. Aviation historian Robert Molesworth, not normally given to hyperbole, noted that "...the P-40 simply dominated the skies over Burma and China. They were able to establish air superiority over free China, northern Burma and the Assam valley of India in 1942, and they never relinquished it.". There were at least 70 P-40 Aces in the CBI and Pacific. According to a Thread I found on this forum, P-40s even did well against late model Japanese fighters like Ki 61 and Ki 84.

One of the tactics which developed for later model P-40s against Ki-43 or A6M was to extend in level flight, i.e. not by diving away, and then execute a sudden and very swift turn as soon as a certain distance was achieved and come back for a head-on attack. This technique, tested against a captured Zero as described in this War Dept memo (see page 7), is an example of something which may have been harder to do in an A-36 or P-51A given roll and turn rates.

The Mustang I and P-51A could both 'Extend in level flight' faster than the P-40E through N, and the actual turn rates of the P40 vs P-51A were very close. The Only advantage that P-40 had over contemporary P-51 was Roll. The INITIAL turn rate of the P-40 was slightly faster due to initial roll and lower W/L than P-51A, but the cleaner airframe of the P-51A along with same HP gave the Power Available to Power Req'd edge back to parity for the Mustang due to cleaner airframe (MUCH cleaner).

Another technique described by P-40 Ace Robert DeHaven was the "Low yo-yo" to out turn an A6M or Ki-43, which if I understand correctly requires both good roll and turn capabilities.

And a superior pilot.

And yet you had quite a few Aces in P-40s at low altitude in the Med. At least 46 Commonwealth Aces and 14 USAAF, not to mention 45 in the CBI where they also did primarily FB sorties.

DAF squadrons flew a mix of missions but certain subtypes, like the P-40K, did mostly fighter-bomber sorties, and yet they scored many air to air victories.

Look to both Production comparisons, number of squadrons ushered into combat, length of time in combat operations. The P-51A and A-36 deployment was miniscule. The A-36 was replaced by P-40 and then P-47 because only 500 were ever built. The 27th and 81st FG hated to see the A-36 phased out in MTO but they accounted for over 40% of the production actually reaching combat ops.

Neither P-47 nor P-38 excel at low altitude, it's worth noting, in spite of the fact that they were often given such missions.

S

Like the A-36 and P-51A and F4F and P-40 and P-39 - the AAF and Commonwealth 'made do' with what they had. There is a reason that P-51B/D destroyed more than any Commonwealth or US fighter by a significant total.

 

[Schweik]

Like the A-36 and P-51A and F4F and P-40 and P-39 - the AAF and Commonwealth 'made do' with what they had. There is a reason that P-51B/D destroyed more than any Commonwealth or US fighter by a significant total.

Yes but partly the reason was that by 1943 / 44 the Axis Air forces were in decline. The Japanese Army and Navy pilots faced by Hellcat pilots in the Marianas in 1943 were very different than the ones faced in the Philippines in 1941. Similar for the P-51 pilots compared to the Spit pilots from the BoB.

Also that gyro gunsight helped a lot once they got it.

Do you know the difference in roll rate between P-51A and B? That would be interesting to see.

I think in general, the ability to disenage and extend away when a fight isn't going well seems to be one of the key factors that defines many, if not all good fighters in WW2. The P-51 certainly had that most of the time. The P-40 was able to do it too pretty easily in the CBI and Pacific, and they could in the Med too to some extent though not as easily. One of the flaws with the P-38 is that they couldn't use their weight and power to dive away from a fight, though in the Pacific and CBI they learned that they could disengage with a high-speed climb.

With the extended range and flying time duration, you also gain the ability to set yourself up to attack when, where and how you want to, pick your fight so to speak, especially in combination with high speed. Attack where the enemy is weak and avoid them where they are strong, almost like good cavalry in another era. Operational level flexibility you might say.

I've been reading a biography of Clive Caldwell which gets into a lot of detail into the problems they were having with the Spit V and one of the issues with endurance, was not so much range as in distance on the map, but the ability fly around, get up to altitude, and position themselves relative to the enemy before their fuel ran out. He wished they had Mustangs instead.

And I think he's right. With it's phenomenal range and two stage supercharger, the P-51 was be very good in this sense. Much better for defending Australia. Spit VIII worked out as well enough, though it came a little late for the "main show" at Darwin.

S

 

[wuzak]

P-51B would also have been late for Darwin.

 

[Schweik]

P-51B would also have been late for Darwin.

Perhaps but it was pretty close. Caldwell knew about Mustangs and wanted them for Darwin, that's quite clear from the biography.

The first significant Spitfire battle in Darwin was in March 1943. The first production P-51B flew in May 1943.

They were still having significant combat by May. One of the big engagements that damaged the rep of the Spit V was on 2 May, and significant raids were going on through July. I think they could have gotten P-51Bs there by then though it would have had to have been a priority. Not realistic politically but they could have gotten some there as early as June, probably.

P-38s or Spit VIIIs may have been more realistic but Darwin just wasn't that much of a priority, and I think that was Caldwells real beef. For the middle of 1943 the Spit V is a bit long in the teeth. The Aussies apparently asked for P-38s but were told they were all committed up in the Solomons etc.

S

 

[Milosh]

The first production P-51B flew in May 1943.

The first P-51Bs didn't arrive in Europe til late 1943.

 

[Peter Gunn]

Like the A-36 and P-51A and F4F and P-40 and P-39 - the AAF and Commonwealth 'made do' with what they had. There is a reason that P-51B/D destroyed more than any Commonwealth or US fighter by a significant total.

Music to my ears... or rather... eyes.

 

[Schweik]

The first P-51Bs didn't arrive in Europe til late 1943.

I was just reading on the Wiki, the raids went on into the fall of 43. Caldwell himself shot down a Ki-46 in August. The last two substantial raids (20+ aircraft and 9) took place in September and November so they definitely could have gotten P-51Bs to Australia by then. Point is moot though I don't think there was still a serious threat of invasion any more.

 

[Milosh]

Only if there was enough P-51B/Cs to go around. The ETO got most and a few to the MTO.

There never was a serious threat of invasion.