A Critical Analysis of the RAF Air Superiority Campaign in India, Burma and Malaya in 1941-45

[RCAFson]

I found this in: Ethell's Mustang, a documentary history of the P-51 but then found it on Mike Williams' site:

TACTICAL COMPARISON WITH SPITFIRE IX

14. A very close comparison can be made because the engines are of very similar design and capacity. The tactical differences are caused chiefly by the fact that the Mustang III is a much cleaner aircraft, is slightly heavier, and has a higher wing loading than the Spitfire IX (43.8lbs. per sq.ft of the Mustang III. against 31 lbs. Per sq.ft)

Endurance
15. The Mustang III with maximum fuel load has between 1.5 and 1.75 the range of a Spitfire IX with maximum fuel load. The fuel and oil capacities are 154 gallons and 11.2 gallons respectively, as opposed to 85 gallons 7.5 gallons of the Spitfire IX, both without long-range tanks. With long range tanks, the Mustang can carry a total of 279 gallons of petrol (2 62.5 gall. long range tanks) as opposed to the Spitfire IX's maximum of 177 gallons (1 90 gall. "Slipper tank").

16. The fuel consumption at similar boost and rev settings is approximately the same for the two aircraft, but the Mustang is approximately 20 mph faster in level flight. Therefore if the ranges are compared directly according to the fuel capacities of the two aircraft when the long-range tanks are fitted, the Mustang will still have something in hand.

Speeds
17. The official speed curves are not yet available. This Unit's speeds runs have therefore not been confirmed. They show, however, that in general for the same engine settings the Mustang III is always 20-30mph faster in level flight at all heights. This is also true for the maximum engine setting of 3,000 r.p.m. 67" (+18 lbs.) or whatever is available, depending on the height. The best performance heights are similar, being between 10,000 and 15,000 ft., and between 25,000 and 32,000 ft.

Climbs
18. The Mustang III has a considerably lower rate of climb at full power at all heights. (In a formation take off, Spitfire IX maintains formation with 5 lbs. less boost). At other engine settings and 175 m.p.h. the two aircraft have a similar climb. The Mustang has, however, a better zoom climb in that it can dive 5,000 feet or more and regain its original altitude at a greater speed. It needs less increase of power to regain its previous altitude and speed.

Dives
19. The Mustang III pulls away very rapidly in a slight dive. At the same revs the Spitfire IX requires from 4 to 6 lb. more boost to remain in formation.

Turning Circle
20. The Mustang is always out-turned by the Spitfire IX. Use of flaps on the Mustang does not appear to improve the turning circle. There is adequate warning of the high-speed stall in the form of elevator buffeting, followed by tail buffeting.

Rate of Roll
21. Although the ailerons feel light, the Mustang III cannot roll as quickly as the Spitfire IX at normal speeds. The ailerons stiffen up only slightly at high speeds and the rates of roll become the same at about 400 m.p.h.

Search
22. The all-round view from the pilot's cockpit is the same as the Mustang 1, therefore generally inferior to the Spitfire IX, but better forwards and downwards on either side of the fuselage. A sliding hood has been designed and is being fitted to service Mustangs. This makes its rear view at least equal to, if not better than the Spitfire IX.

Sighting View and Firepower
23. The aircraft is fitted with an American 70 m.p.h. sight. A bracket for the G.M.2 sight has been designed and is fitted to most aircraft. If it is not fitted, a universal adaptor as shown at Appendix 'B' (not included here) can be made and fitted by the squadron. Due to the fact that it is most unlikely that the aircraft will be used against ground targets, the highest possible setting for the guns and sights has been chosen to produce the maximum amount of sighting view over the nose. This gives a vertical view of 180 m.p.h. cruising speed, increasing to an unrestricted view at approximately 45° to the vertical, with guns ¾° cocked from aircraft datum. This is considerably better than the Spitfire IX. The guns are cocked up about 2° above the aircrafts cruising line of flight. The fire-power consists of four .5 Browning's in the wings. This is very little compared with the Spitfire.

Armour
24. Armour plating on the Mustang III is provided for the pilot by means of two plates located behind the pilots seat. One 5/16" thick extends from just below the bottom of the seat to a point just level with the pilots shoulders. The other 7/16" thick is attached to the top of this plate and affords protection to the pilot's head. Otherwise protection is provided by the ¼" armour plate fire-wall, the engine, and the 1½" armour plate glass windshield. ¼" armour plate is also located immediately forward of the coolant tank on the forward end of the engine. There is no armour plate on the fuel tanks, but the tanks themselves are self-sealing.

BRIEF TACTICAL COMPARISON WITH SPITFIRE XIV
Maximum Endurance
25. By comparison the Spitfire XIV has no endurance.

Maximum speed
26. There is practically nothing to choose in maximum speed.

Maximum climb
27. The Spitfire XIV is very much better.

Dive
28. As for the Spitfire IX. The Mustang pulls away; but less markedly.

Turning Circle
29. The Spitfire XIV is better.

Rate of Roll
30. Advantage tends to be with the Spitfire XIV.

Conclusion
31. With the exception of endurance, no conclusions should be drawn, as these two aircraft should never be enemies. The choice is a matter of taste.



Mustang Tactical Trials

If we look at a Spitfire VII/VIII (especially the HF) we note that the internal fuel comparison is 124IG versus 150IG for the Mustang, and these Spitfires narrow the gap slightly in terms of speed. It would have been interesting to compare the Spitfire XIV with the 90IG slipper tank to the Mustang and to a Mustang with the rear fuselage tank 1/3 full.


Ethell makes it clear that the speed improvement over the Spitfire was due to the Mustang's overall low drag design, especially the wings. He states emphatically that the radiator and cooling design of the Mustang was not a factor and that the Mustang did not benefit from the "Meredith effect".

 

[RCAFson]

The Slipper Tank Advantage​

Mustang with 2 x 62.5IG DTs:

COMBAT PERFORMANCE WITH LONG-RANGE TANKS
Speed

52. There is a serious loss of speed of 40-50 mph at all engine settings and heights. It is, however, still faster than the FW.190 (BMW.801D) above 25,000 ft. Although slower than the Me.109G.

Climb
53. The rate of climb is greatly reduced. It is outclimbed by the FW.190 (BMW.801), Me.109G and FW.190 (DB.603).

Zoom Climb
54. The Mustang III is still good in the zoom climb (attack), but is still outstripped (defense), if being followed all the way by the FW.190 (BMW.801D), and definitely outstripped by the Me.109G.

Dive
55. So long as the tanks are fairly full, the Mustang still beats the FW.190 (BMW.801D) and the Me.109G in a power dive.

Turning Circle
56. The tanks do not make quite so much difference as one might expect. The Mustang III can at least turn as tightly as the FW.190 (BMW.801D) without stalling out and therefore definitely more tightly than the Me.109G.

Rate of Roll
57. General handling and rate of roll are very little affected.

Conclusions
58. The performance of the Mustang III is greatly reduced when carrying drop-tanks. Halfhearted attacks could still be evaded by a steep turn, but determined attacks would be difficult to avoid without loosing height. It is still a good attacking aircraft especially if it has the advantage of height

Spitfire XIV and 90IG ST:

COMBAT PERFORMANCE WITH 90 GALLON LONG-RANGE TANKS

50. As the Spitfire XIV has a very short range it has been assumed that when a long-range tank is to be carried, it is most likely to be the 90 gallon tank rather than the 30 gallon or 45 gallon. Pending further instructions, no drops or trials have been carried out with the 30 gallon or 45 gallon tanks. The aircraft's performance with either can be estimated from the results given below of trials with the 90 gallon long-range tank.

Drops
51. The aircraft was fitted with assistor springs as for the Spitfire IX. Two drops were made with empty tanks at 50 ft and 25,000 ft, A.S.I. 250 mph, with no trouble. Cine photographs were taken and show the tank dropping quite clear of the aircraft. Further trials would be necessary to check these results thoroughly.

Speeds
52. About 20 m.p.h. is knocked off the maximum speed and correspondingly off the speed at intermediate throttle settings. The aircraft is still faster than the FW.190 (BMW.801D) and the Me.109G above 20,000 ft.

Climb
53. Climb is most affected. With a half-full tank its maximum climb becomes identical with the Spitfire IX without the tank. Even with a full tank it can therefore climb as fast as the FW.190 or Me.109G. Its zoom climb is hardly affected.

Dive
54. So long as the tank is more than 1/3 full, the dive acceleration is similar.

Turning Circle
55. The Spitfire XIV now has a definitely wider turning circle than before, but is still within those of the FW.190 (BMW.801D) and Me.109G.

Rate of Roll
56. Similar.

Conclusions
57. Even with the 90 gallon tank, the Spitfire XIV can equal or outclass the FW.190 (BMW.801D) and the Me.109G in every respect. Its main advantages remain the tight turn and maximum climb.

So the 90IG ST causes a loss of ~20mph on the Spitfire whereas twin 62.5IG DTs cause a loss of ~45mph on the Mustang.

 

[RCAFson]

How Mustang Range was Calculated:

This is from Ethell and was drawn from USAAF sources. The stated cruise conditions are not very strenuous. Theoretically a stock Spitfire VIII with a 90IG slipper would have about a 325 mile radius using the above assumptions.

 

[wuzak]

Here you go !

The Packard Merlin: How Detroit Mass-Produced Britain's Hand-Built Powerhouse - Tested.com

Few engines throughout history have achieved a near mythical status among its admirers. Fewer still can share credit for the rescue of an entire nation. Perhaps only the Rolls-Royce Merlin engine can claim both distinctions. During the Battle of Britain, it was the Merlin that powered the Royal Air Force Hurricanes and Spitfires that were England's only effective defense against German air attacks. With the battle won, and the engine's reputation thus established, the Merlin would become the stuff of legend and the powerplant of choice for numerous other aircraft.

Even before the 1940 air battles over England, it was apparent that demand for the Merlin was far outpacing Rolls-Royce's ability to produce them. The Ford Motor Company was asked to build 9,000 Merlins for both England and the US. Ford initially accepted the deal, but later reneged. Henry Ford explained that he would only produce military items for US defense. Interestingly, Ford of Britain in Manchester, England ultimately produced 36,000 Merlin engines, beginning at the same time period. Of course, Ford's American factories would indeed become vital to the war effort. They manufactured unfathomable quantities of airplanes, jeeps and other war materiel--but not Merlins.

Two Countries Divided By A Common Language

There are many obvious challenges posed by producing a British-designed engine in America. Just the task of converting all of the measurements from metric imperial to US Standard units was daunting enough. This job was made even more difficult by the unprecedented complexity of the Merlin. The 1,649 cubic inch V-12 engine is comprised of more than 14,000 individual parts (knoll that!). It was, and still is, often called "a watchmaker's nightmare.

Engineers at Packard soon discovered that Rolls-Royce did not design the Merlin for mass-production. The manufacturing tolerances were much looser than Packard's standards. This was because Rolls-Royce had never implemented mass-production techniques to their assembly lines. Rather, they employed highly-trained "fitters" to assemble the engines. The fitters filed or otherwise massaged individual parts to achieve a precise fit. They even tightened critical bolts by trained feel, rather than with calibrated torque wrenches. In effect, each Rolls-Royce-manufactured Merlin was a hand-built engine that reflected the company's traditions of premium quality and craftsmanship.

You don't think there is a bit of patriotic chest thumping there?

Comparing parts counts between the Allison and the Merlin has to take into account the fact that Rolls-Royce used a multitude of small fasteners in places where Allison used a smaller number of large fasteners.

Packard Merlins were all 2 speed engines (apart from the experimental -11), compared to most V-1710s which were single speed. That meant extra gears, clutches, shafts, fasteners.

The statement "Just the task of converting all of the measurements from metric imperial to US Standard units was daunting enough" shows that the article is not entirely accurate. They originally stated metric, but changed it to imperial, which means they are saying it was a difficult job for Packard to convert the drawings from inches to inches.

 

[Dan Fahey]

The reality is that in the early days of WW2 quite a few Allied pilots were pretty hastily trained in terms of actual fighter combat. They usually had pretty good basic flight training but quite often little or no marksmanship, formation flying, or air combat maneuvering training. Many went into combat unaware of the specific flight envelope of the aircraft they were fighting in, some went into action within days of their first flight in a real fighter.

In early days nobody had any real fighter combat but had good enough training that fought on near equal terms. Reading about New Guinea and Guadalcanal. We actually did an outstanding job against the Japanese. The P-39 was an effective dive bomber and low altitude fighter. Credited for saving Guadalcanal strafing Japanese positions. They did a lot more than shoot down planes.

Did an evaluation of Pearl Harbor and Philippines. Just a 15 minute warning before Japanese planes struck. Enough of our combat planes would have created a different result. They were trained enough to do substantive damage, just based off what few fighters got off the ground. Battle of Midway was another good example despite losing most of our Fighters. They still caused a good 20+% loss or out of action of Japanese aircraft.

But then again most pilots perished in all countries with a good percentage becoming aces. So the Training process in all countries typically recruited the ones that were quick learners. The Education systems at the time in the US recruited heavily from the Colleges and noted brilliant High School students. In 1940 the US Army became our largest public education system, Navy not far behind. US had the option of bringing back experienced combat pilots back to the states to help the training processes. Something that none of the other combatants had. Japan tried a bit of that with their surviving combat pilots. Biggest issue with the Axis opponents they had little fuel for training but somehow managed to train a good batch of new pilots into competent flyers.

You don't think there is a bit of patriotic chest thumping there?

Comparing parts counts between the Allison and the Merlin has to take into account the fact that Rolls-Royce used a multitude of small fasteners in places where Allison used a smaller number of large fasteners.

Packard Merlins were all 2 speed engines (apart from the experimental -11), compared to most V-1710s which were single speed. That meant extra gears, clutches, shafts, fasteners.

The statement "Just the task of converting all of the measurements from metric imperial to US Standard units was daunting enough" shows that the article is not entirely accurate. They originally stated metric, but changed it to imperial, which means they are saying it was a difficult job for Packard to convert the drawings from inches to inches.

If you read further...and other material....most everything was being moved to SAE standards. Rolls Royce did not want to go that route. Hense since there were no US suppliers to provide them all the fasteners were made in-house at Packard. As for engineers most of us have egos but fascinated how other engineers come up with solutions. US and Brits worked very hard on agreeing to the many upgrades, improvements and changes to the Merlin. Allowing a 1000hp Designed engine to exceed 2000hp. When a upgrade was approved both sides implemented the change. It was amazingly smooth.

In fact Rolls Royce engineers gave Allison some good solutions for their supercharging issues they were having and thumbed their noses up. But that was the Allison Management not the engineers.

The Allison was a much better stronger cost efficient platform than the Merlin...dominated the low mid Altitude combat scene.

 

[wuzak]

If you read further...and other material....most everything was being moved to SAE standards. Rolls Royce did not want to go that route.

Most everything of what was going to SAE standards? The British aero engine industry before and during WW2?

The fact is that the Merlin was designed in Britain and was in production in Britain prior to Packard making a single Merlin. To change to SAE threads to suit one factory over sevaral others does not seem like a war winning production strategy.

They had to maintain the same fasteners so there was interchangeability with UK built engines.

Packard Merlins for US consumption used SAE spline output shafts to fit with US propellers. UK engines all had SBAC spline output shafts.

Remembering that it was 1942 before Packard started making engiines in any sort of quantity.

Hense since there were no US suppliers to provide them all the fasteners were made in-house at Packard.

Yes, they had to make their own fasteners, which I doubt was a big deal.

US and Brits worked very hard on agreeing to the many upgrades, improvements and changes to the Merlin. Allowing a 1000hp Designed engine to exceed 2000hp. When a upgrade was approved both sides implemented the change. It was amazingly smooth.

Pretty much all the major upgrades were developed by Rolls-Royce and then implemented across the factories.

In fact Rolls Royce engineers gave Allison some good solutions for their supercharging issues they were having and thumbed their noses up. But that was the Allison Management not the engineers.

When did Rolls-Royce engineers have anything to do with Allison? And why would they?

The Allison was a much better stronger cost efficient platform than the Merlin...dominated the low mid Altitude combat scene.

Yes, the Allison V-1710 was a good, solid design.

Don't know about it being more "cost efficient" and I doubt it could be claimed that the V-1710 "dominated the low mid Altitude combat scene".

 

[Shortround6]

Nope.

Miles M20

The Merlin XX was pretty much the same engine as the V-1650-1 used in the P-40F.
Granted shifting 306lbs worth of radiator and coolant to the rear of the plane vs the chin helps balance the longer heavier Merlin 61 engine.

The plane as it stood was slower than a Hurricane II using the same engine, it was a lot slower than the P-40F using the same basic engine.
Wiki says 154 imp gallons of fuel which is not double what the Hurricane carried but a bit over 60% , Wiki could be wrong.
A P-40f carried about 123 IMP gallons of fuel in the internal tanks.

The Miles M 20 was designed so fast because they used a Lancaster (and Beaufighter) "power egg". change the engine and change the radiator location (and add retracting landing gear) and you are changing things considerably.

 

[Shortround6]

US and Brits worked very hard on agreeing to the many upgrades, improvements and changes to the Merlin. Allowing a 1000hp Designed engine to exceed 2000hp. When a upgrade was approved both sides implemented the change. It was amazingly smooth.

Actually RR had a very good idea that the basic engine would survive power in the high teens (1500-1800hp) due to work on the engine for the Speed Spitfire record attempt plane.
That power level was achieved using a special racing fuel but they did it at time when the Allison was lucky to break 1000hp (late 1938 and early 1939)
Yes a few minor tweaks were needed to really get the reliability RR wanted but over 10 hours on the test stand at those power levels and peak output of over 2000hp showed there were no fundamental flaws in the Merlin engine.

It would have been stupid for Packard to try to make the Merlin to SAE standards when the main customer (the British) wanted as much intercanagbility as possible with the British built engines. And indeed in North Africa the British gave the US up to 600 engines (many used) to help the US overhaul the engines in the P-40F & L, something that would not have worked had the engines been built to different standards.
It also would have been stupid for the US to try to redesign the Merlin in 1943 to SAE standards with the hit to production that would have entailed or the problems of setting up 2nd production line with the British still getting British standard engines and the US getting the SAE engines.

Please note that the lead in fuel swapped back and forth just a bit. British using 87 octane (rich number unknown but quite possibly higher than US 87 octane or even 91 octane?)
US went to 100 octane first but the Under 2% aromatic fuel had no rich rating or no improvement in rich response while the British 100 octane not less than 20% aromatic fuel offered the performance of 100/115-120 in the later rating numbers. The US specified a 125 PN number fuel but quickly changed to a joint specification of 100/130 with the British.

It was this fuel that allowed much higher pressures (and temperatures) inside the cylinder that allowed the engines to make so much more power than when they started.

 

[wuzak]

Actually, I was being half serious, if you look at that power egg on the M20, it doesn't provide much extra boost from the engine exhaust. So, replace it with a Merlin 61 with individual exhausts and put a Mustang style radiator underneath to take advantage of the Meridith effect. Now would we then have a fighter with twice the internal fuel of a Hurricane and the speed of a Spitfire? Any takers on this idea?

What makes you think the radiator doesn't gain from some of the Meredith Effect?

So, you take a Merlin 61 and put it into the Miles M20 and get the speed of a Spitfire V? IX? XIV? I'm going to go with the speed of a Spitfire V.

Meanwhile, you are taking a Merlin 61 away from an actual Spitfire IX.

Where's the advantage in that?

 

[wuzak]

Actually RR had a very good idea that the basic engine would survive power in the high teens (1500-1800hp) due to work on the engine for the Speed Spitfire record attempt plane.
That power level was achieved using a special racing fuel but they did it at time when the Allison was lucky to break 1000hp (late 1938 and early 1939)
Yes a few minor tweaks were needed to really get the reliability RR wanted but over 10 hours on the test stand at those power levels and peak output of over 2000hp showed there were no fundamental flaws in the Merlin engine.

It would have been stupid for Packard to try to make the Merlin to SAE standards when the main customer (the British) wanted as much intercanagbility as possible with the British built engines. And indeed in North Africa the British gave the US up to 600 engines (many used) to help the US overhaul the engines in the P-40F & L, something that would not have worked had the engines been built to different standards.
It also would have been stupid for the US to try to redesign the Merlin in 1943 to SAE standards with the hit to production that would have entailed or the problems of setting up 2nd production line with the British still getting British standard engines and the US getting the SAE engines.

Please note that the lead in fuel swapped back and forth just a bit. British using 87 octane (rich number unknown but quite possibly higher than US 87 octane or even 91 octane?)
US went to 100 octane first but the Under 2% aromatic fuel had no rich rating or no improvement in rich response while the British 100 octane not less than 20% aromatic fuel offered the performance of 100/115-120 in the later rating numbers. The US specified a 125 PN number fuel but quickly changed to a joint specification of 100/130 with the British.

It was this fuel that allowed much higher pressures (and temperatures) inside the cylinder that allowed the engines to make so much more power than when they started.

Just to add that when Packard were struggling to get the V-1650-3 into volume production in 1943 Rolls-Royce were developing the 65/66 (which would become the V-1650-7 in US production) and by mid 1943 were attempting to run the Merlin 66 at +18psi boost for 100 hours continuously, succeeding in late 1943. This was part of the development of the 100 series, a version of which would become the Packard V-1650-9.

By early 1944 Rolls-Royce were working on the RM.17SM, which was rated at 2,200hp in MS gear and 2,100hp @ 15,000ft in FS gear. Notably this was without ADI, which the V-1650-9 used to get similar ratings. The RM.17SM was flight cleared for 2,380hp.

 

[Kevin J]

Correction. The M20 had twice the fuel of the Hurricane after take off, climb to height and forming up for combat. The objective is to have in service by 1943 a single seat, single engine fighter escort for the USAAF for the Schweinfurt raids. So first individual exhaust ejectors should bring the speed up to 350-360 mph for the 1941/42 timeframe and 2x 62.5 IG drop tanks should bring range up to 1840 miles. For 1942/43, install Merlin 61/63/66, shift the radiator a la Mustang under the fuselage, 33 IG rear fuel tank, 2x 75 IG underwing drop tanks, range 2210 miles, speed a la Spitfire. So fuel load and performance should be sufficient for Schweinfurt raids. For 1944/45, put second 33 IG fuel tank in rear fuselage, use 90 IG tanks and range goes up to 2650 miles, so Iwo Jima to Tokyo and back so that we can help the Yankees out again as they would never have built the Mustang.

 

[wuzak]

You're expecting 20-30mph from the ejector exhausts?

 

[Kevin J]

You're expecting 20-30mph from the ejector exhausts?

I'm expecting a performance 3% down on the P-40F/L because of the fixed undercarriage, or 5% up on the prototype M20.

 

[Kevin J]

Correction. The M20 had twice the fuel of the Hurricane after take off, climb to height and forming up for combat. The objective is to have in service by 1943 a single seat, single engine fighter escort for the USAAF for the Schweinfurt raids. So first individual exhaust ejectors should bring the speed up to 350-360 mph for the 1941/42 timeframe and 2x 62.5 IG drop tanks should bring range up to 1840 miles. For 1942/43, install Merlin 61/63/66, shift the radiator a la Mustang under the fuselage, 33 IG rear fuel tank, 2x 75 IG underwing drop tanks, range 2210 miles, speed a la Spitfire. So fuel load and performance should be sufficient for Schweinfurt raids. For 1944/45, put second 33 IG fuel tank in rear fuselage, use 90 IG tanks and range goes up to 2650 miles, so Iwo Jima to Tokyo and back so that we can help the Yankees out again as they would never have built the Mustang.

The Canadians build the M20, the Americans end up building the P-38K and the P-40Q.

 

[wuzak]

The Canadians build the M20, the Americans end up building the P-38K and the P-40Q.

Still don't know why you'd build the P-40Q. You already have the P-51B/D/H and P-47D/M/N (and the P-38K in your scenario) by that time.

 

[Kevin J]

Still don't know why you'd build the P-40Q. You already have the P-51B/D/H and P-47D/M/N (and the P-38K in your scenario) by that time.

The Brits by building the M20 have built the perfect army cooperation fighter with its fixed undercarriage so the Mustang never gets built.

 

[wuzak]

The Brits by building the M20 have built the perfect army cooperation fighter with its fixed undercarriage so the Mustang never gets built.

The Mustang was not designed for army cooperation.

 

[Milosh]

The Canadians build the M20, the Americans end up building the P-38K and the P-40Q.

They did???

 

[Kevin J]

They did???

They would have had to without the Mustang.

 

[PAT303]

40 IG and a slipper isn't going to get you there and back over hostile territory. If we could flood out the entire North German plain first than that would help. The La Palice raid was 370 miles radius, the East Timor raid was 445, both were over water with little chance of interception.

96G main, 66 or 75G rear, 26G wings, 50 or 90G dropper, fixed.