An Allison V-1710 with a two-speed supercharger in 1942 (1 Viewer)

[MikeMeech]

The thing is, that is the apparently permanent assumption about WW2, but I really don't believe that it's true.

Let's examine this statement by Geoffrey to dig deeper:



The thing is, this is partly true, but there is a really important bit missing. What determines whether the air battle (e.g. involving fighters) goes up or down, or stays in the middle, is almost entirely dependent on where the bombers are. And this, in turn, depends on the type of target and type of fighting.

During the pivotal year of 1943, or you might extend that to 1942-very early 1944, most of the fighting is taking place on a series of battlefields around the world:

Spoiler: Theaters of active combat in the mid-war

MTO
North Africa
Middle East
Mediterranean Sea (including major convoys)
Sicily and Mediterranean Islands (Sardinia, Corsica, Malta, Crete, Pantelleria, Lampedusa etc.)
Italy
Balkans

PTO
New Guinea
Solomon Islands
Other South Pacific Islands
Philippines
Aleutians

CBI
China
Burma / India
Pacific Rim
Indian Ocean

Russia / Eastern European front
Russia
Ukraine
Balkans
North Atlantic (Convoys and Fjords)

In each of these Theaters, targets during 1943 were generally Tactical or Operational, not Strategic. The Strategic bombing campaign did not really get going until later in 1944.

Strategic day-time bombers (e.g., the US heavy bombers in this case) can fly at high altitude, how high depending on the exact type (B-24 not as high as B-17, B-17 not as high as B-29), but they are only really useful against Strategic targets at that 20,000' / 6,000m + ft altitude.)

Where the ground armies are fighting, Operational targets like airfields, bridges, ports, supply depots, large artillery positions etc. can be targeted including by heavy bombers, but they will typically do so from much lower altitude. Partly this depends on the Theater and prevailing weather, as well as the season, local air defenses etc., but generally speaking, against Operational targets combat is at lower altitude. 8,000 - 20,000 ft, usually on the lower end of that band.

Ships can be either Tactical or Operational, or even Strategic targets, but regardless - to target them you have to get down pretty low, as in below 5,000 ft. They tried hitting them by dropping bombs from altitude but that almost never worked.

Tactical targets are of course typically below 8,000 ft, usually down around 2,000 ft or less, assuming low ground / near sea level.

View attachment 873734

Fighters will often fight for high ground / altitude advantage well above the bombers, but in order to win this fight some of them will have to be right where the bombers are.

In North Africa, though the skies were usually clear, the fighting rarely got higher than about 20,000 ft, and most of the fighting was down around 5,000-10,000 ft or lower.

Russia saw even lower altitude, as did SW Pacific and Burma, often due to weather and cloud ceiling. Same in Italy. Same in Normandy and through the Low Countries into Germany once the fighting started in NW Europe.

But it's in this middle part of the war that the thread is focused. There is nothing inevitable about air war in WW2 that says fighting is going to be at 30,000 ft. In fact, usually it wasn't even close to that.

Hi
Before it is started to be believed that not a lot was going on in the air in North West Europe, lets look at some data on the subject, first from 'Fighter Command War Diaries, Part 3' by John Foreman:

Then from OH 'The Strategic Air Offensive Against Germany 1939-1945' Volume IV, by Webster & Frankland:

From OH on the Maritime war:

These ops do not include RAF anti-shipping strikes.
From 'The Defence of the United Kingdom' by Basil Collier, noting German ops:

I don't think it could be classed as a quiet theatre, certainly the RAF was fairly busy.

I Hope that is of interest.
Mike

 

[Steamed_Banana]

I don't think night attacks or defense, as important as they were in many ways, are relevant to the issue of engines for daylight fighters.

German fighter losses were rising in NW Europe by the second half of 1943, so in terms of attrition it was starting to matter, but being pushed out of North Africa, the loss of Italy as a partner in the war, and the series of major defeats in Russia were far more significant to the outcome of the war.

I'm not saying that NW Europe was irrelevant in 1943, it was starting to matter, and showed promise to help end the war, but it by no means outweighed the rest of the fighting going on in MTO, PTO, CBI etc., especially for the US. It was not even close.

 

[Shortround6]

If someone thinks that V-1710 - especially without a turbo attached - was a gee-whiz engine per the standards of the day, I have the Brooklyn bridge on sale, real cheap

Ok, let's look at the Allison V-1710 engines produced in 1937 and 1938.
1937 7 engines delivered.
1 V-1710-9 (D1 pusher engine type test. converted to a-7 engine for the C4 type test.
4 V-1710-9s for the Bell XFM-1 Airacuda without turbos.
1 V-1710-7 for the XP-37 (with turbo)
1 V-1710-11 (C-7) development engine for the 1150hp type test.

1938. 14 engines delivered.
2 V-1710-11s. One right hand engine for the XP-38 and one engine for the XP-37
1 V-1710-15, left hand engine for the XP-38
8 V-1710-21 (C10) engines for the YP-37
1 V-1710-19 (C13) first flight engine for the XP-40
1 V-1710-17 (E2) first flight engine for the XP-39
1 V 3420-1 (A1) 50hr army development test.

Deliveries were running a bit behind orders. Engines delivered often did not fly until months later.
Only 5 of the engines were supposed to fly without turbos. 4 of those were pusher engines and one remote gear box engine was supposed to have a turbo.

I would say that on whole they were Gee-Whiz engines. No Airline executive was going to order Allison engines. They had no interest in engines with extended drive shafts going in either direction and no interest in paying for R&D on experimental engines.

I will give you a buck for that Bridge with a clear title

1939 was not much better. out of 46 engines 31 were for the Bell YFM-1 pushers, with and without turbos. 12 were for the YP-37s with turbos.
One was a spare for the XP-39 and one was for the Airabonita
only 1 was a normal tractor engine without turbo for the XP-40.

 

[Shortround6]

Military requirements often went to excess.
French SNCAC NC.150 first flew in May 1939

Had a 690hp H-S X engine in the fuselage driving a large compressor feeding air to the wing engines. Ceiling of over 11,000 meters.
Soviets used a 5th engine inside the Fuselage of the prototype Petlyakov Pe-8
Germans used turbo diesels and pressure cabins on the Ju-86 which prompted not only stripped Spitfires but two different twin engined high-altitude fighters.
Diversion of resources may have totally overshadowed any actual bomb damage or photo intelligence gained.
And of course we have the Wellington.

And of course the American B-17s which in early British service turned out to just about useless due to lack of heat, frosted over windows/canopies, faulty oxygen equipment and so on. Desire exceeded the ability of all the rest of the things needed even if the engines actually worked for all nations.

The path to B-17s operating at high altitudes being escorted by turbo equipped fighters over Germany was a long and twisted path.
Not helped by the Air Corp acting as their own contractor. They were going to buy the Allison engines, and buy the GE turbos and contract for the turbo controllers from a 3rd company and then ship everything to Lockheed to be installed. Plenty of room for finger pointing when things did not go well.

Allison may have been trying to develop their own two stage supercharger to get them out the 3/4 way mess of the turbo. And again, Allison (and GM) were not going to stick their necks out too far on R&D costs after the Army burned them in 1939 for 900,000 dollars.

 

[MikeMeech]

I don't think night attacks or defense, as important as they were in many ways, are relevant to the issue of engines for daylight fighters.

Hi
I would have thought that the various threats faced from over the Channel were very relevant to engine development for daylight fighters. First the high level threats led to specialised fighters like the Spitfire VI and VII which not only had Merlins optimised for high flight but also pressurised cabins. The low threat led to the use of the Griffon powered Spitfire XII and also the use of the Sabre powered Typhoon (from late 1941) which was very fast at low level despite its problems. But maybe more to the point, because of the threats that were to be faced, taking the Spitfire as an example, development of engines led to different variants with engines optimised for different altitudes. This led to the Spitfire V in both 'F' and 'LF' versions, the Spitfire VIII in 'F', 'HF' and 'LF', the Spitfire IX in 'F', 'LF' and 'HF' versions etc. These types also served in MTO and Far East so having impacts there at their various performance altitudes so probably "relevant to the issue of engines for daylight fighters." Presumably this also shows the development flexibility of the Merlin as compared with the Allison in actual use during WW2?

Mike

 

[tomo pauk]

I would say that on whole they were Gee-Whiz engines. No Airline executive was going to order Allison engines. They had no interest in engines with extended drive shafts going in either direction and no interest in paying for R&D on experimental engines.

V-1710 was not a gee-whiz engine, despite the fancy ways of installation.
It was a conventional V12 supercharged engine. It was no H16, nor H24, nor W12, nor W18, nor it was one of the other types of multibank engines Not a 3- or a 4-row radial. There were no sleeve valves. No DOHC. No fancy throttle. Supercharger was with just one stage, and with just one speed.
That Allison company was of the opinion that the internal spur reduction gear was a good thing was a bug, not a feature.

 

[Shortround6]

V-1710 was not a gee-whiz engine, despite the fancy ways of installation.
It was a conventional V12 supercharged engine. It was no H16, nor H24, nor W12, nor W18, nor it was one of the other types of multibank engines Not a 3- or a 4-row radial. There were no sleeve valves. No DOHC. No fancy throttle. Supercharger was with just one stage, and with just one speed.
That Allison company was of the opinion that the internal spur reduction gear was a good thing was a bug, not a feature.

The C-7 that was tested in 1937 (test took almost 5 months) was the 14th Allison V-1710 built since 1932.
It was the first Allison engine that used the 6.65 compression ratio (needed new cylinder blocks) and used separate supercharger drive and accessory drive.
Engine was good for 1150hp at 38.6in at 2950rpm AT SEA LEVEL and used 6.23 supercharger gears. It depended on using a turbocharger to make power much above sea level.
The C-7 differed from the previous engine/s by...
1st engine to use induction hardened main and crankpin journals
Forged connecting rods with improved grain flow
Nitrited cylinder barrels
Heads that would accommodate long reach spark plugs.

Some other companies were already using some of these techniques. The Allison engine was not novel, it was very much a work in progress however, with at least 14 changes on the C-10 version before they were done. Including changes to the oil system, modified vibration dampers, modified pistons and piston rings. By the time Allison gets to the C-15 there were a number of other changes including using a 15 bladed impeller instead of a 12 bladed impeller, rotating steel inlet guide vanes, a 3 barrel carb instead of 2 barrel carb, modified supercharger diffuser. Hollow head sodium cooled exhaust valves instead of hollow stem design. And other smaller changes.

By 1938 Wright had built over 8000 Cyclone 9s and thousands of 5, 7 and 9 cylinder Whirlwinds. P&W had built 3 different 9 cylinder engines in large numbers (and 1 in small numbers) and two 14 cylinder engines in large numbers. These are engines that customers could buy with some assurance that they would work.
Airlines had not liked their experiences with Packard V-12s (mainly air mail in the 1920s and very early 30s) or with Curtiss V-12s (pretty much with Curtiss built airframes) and were not i a hurry to get back into the V-12 game. Granted 5-8 years was long time in the aviation industry in the 1930s but the Airlines that were still in business were run by men who were a combination of dreamers/visionaries and hardheaded businessmen. Cost per passenger mile flown or ton mile of cargo. Purchase price/maintenance/fuel costs and so on.
Lets remember that it was only in 1935 with the DC-3 that airlines proved they could make money without government subsidies (air mail contracts).

 

[tomo pauk]

The C-7 that was tested in 1937 (test took almost 5 months) was the 14th Allison V-1710 built since 1932.
It was the first Allison engine that used the 6.65 compression ratio (needed new cylinder blocks) and used separate supercharger drive and accessory drive.
Engine was good for 1150hp at 38.6in at 2950rpm AT SEA LEVEL and used 6.23 supercharger gears. It depended on using a turbocharger to make power much above sea level.
The C-7 differed from the previous engine/s by...
1st engine to use induction hardened main and crankpin journals
Forged connecting rods with improved grain flow
Nitrited cylinder barrels
Heads that would accommodate long reach spark plugs.

Some other companies were already using some of these techniques. The Allison engine was not novel, it was very much a work in progress however, with at least 14 changes on the C-10 version before they were done. Including changes to the oil system, modified vibration dampers, modified pistons and piston rings. By the time Allison gets to the C-15 there were a number of other changes including using a 15 bladed impeller instead of a 12 bladed impeller, rotating steel inlet guide vanes, a 3 barrel carb instead of 2 barrel carb, modified supercharger diffuser. Hollow head sodium cooled exhaust valves instead of hollow stem design. And other smaller changes.

Not to throw shade on the people at Allison, but the engineers and technicians in the other companies were also not seating idle. Upping the bar via the better and more modern materials and technology was the order of the day, and, whoever was satisfied with what they did "yesterday", was up for a rude awakening "tomorrow".

By 1938 Wright had built over 8000 Cyclone 9s and thousands of 5, 7 and 9 cylinder Whirlwinds. P&W had built 3 different 9 cylinder engines in large numbers (and 1 in small numbers) and two 14 cylinder engines in large numbers. These are engines that customers could buy with some assurance that they would work.
Airlines had not liked their experiences with Packard V-12s (mainly air mail in the 1920s and very early 30s) or with Curtiss V-12s (pretty much with Curtiss built airframes) and were not i a hurry to get back into the V-12 game. Granted 5-8 years was long time in the aviation industry in the 1930s but the Airlines that were still in business were run by men who were a combination of dreamers/visionaries and hardheaded businessmen. Cost per passenger mile flown or ton mile of cargo. Purchase price/maintenance/fuel costs and so on.
Lets remember that it was only in 1935 with the DC-3 that airlines proved they could make money without government subsidies (air mail contracts).

This does not remove the need that Allison makes the best product possible.

 

[Shortround6]

Not to throw shade on the people at Allison, but the engineers and technicians in the other companies were also not seating idle. Upping the bar via the better and more modern materials and technology was the order of the day, and, whoever was satisfied with what they did "yesterday", was up for a rude awakening "tomorrow".

This does not remove the need that Allison makes the best product possible.

This is true.
But the only likely customer was the US Army up until 1939.
The US Army, until May of 1939, was not buying enough engines to keep the doors open.
The Army wanted turbo superchargers. They might want two speed or two stage mechanical superchargers as a backup but they weren't willing to pay for the R&D or at least the bulk of the cost of the R&D and with Allison losing money for 5-6 years on the V-12 engine project pouring money into backup technology when they were (spring of 1939) a few months away from closing and locking the doors?
Navy might buy one or two engines, mainly to see if they were still making a good choice with the air cooled engines.
The Airlines didn't want them.
The US Army was forbidding foreign sales.

Wright and P&W had much larger R&D teams. They were selling to the Army and Navy and the Airlines (not all engines at all times)
Wright dissipated their effort into 4 different engines of different priorities at times in 1938-42.
P&W ditched their liquid cooled program, and the R-1535 and R-2180 programs. Once they had the R-2800 program on track they adopted and 3 prong approach in 1940-41.
Short term (The B series), long term (the C series) and really long term (use R-2800 cylinder to make a 28 cylinder engine).
We have seen the number of engines for Allison in 1938-39. P&W made
year.............R-1830.............everything else*
1938...............695.......................1155
1939.............1792.......................1184
1940.............3643.......................3515
* R-985, R-1340, R-1535, R-1690, R-2180 in 1939/40 a handful of R-2800s.
P&W was not doing much R&D on the five older engines but they were creating a very useful cash flow.

We are criticizing Allison for not equaling RR R&D in 1939-42. We are forgetting that if WW II had developed slower in 1938 and 39 (war didn't break out until the summer of 1940) and the army had not made that large order in May 1939 there may not have been any Allison engines in 1940 and later.



As couple of fun factoids. GM made almost 30% more money (gross) from building licensed P&W engines than they did building Allison V-12s.
Total revenues for GM from marine diesels (and tank engines?) was about the same as the licensed P&W engines.

 

[Geoffrey Sinclair]

Altitude attitude

Let's examine this statement by Geoffrey to dig deeper:

To repeat myself, It is a basic rule when air forces fight each other altitude goes up, if the army and/or navy are involved altitude tends to go down.

The thing is, this is partly true, but there is a really important bit missing. What determines whether the air battle (e.g. involving fighters) goes up or down, or stays in the middle, is almost entirely dependent on where the bombers are.

Actually no, "Height gives you the initiative". If you are in a fight with a viable hostile air force then operations include larger numbers of fighter sweeps and a higher ratio of escorts to bombers, enabling everything from high to close cover. The average altitude comes back to the altitude performance of your fighters, secondly the bombers. Complicating this is the size and defences of the average bombing targets, smaller means lower altitude, better defended means higher. A big factor in determining bomber altitude is the amount of ground defences and the size of the bomber, a B-17 covered a larger area than a B-26 making it easier to hit. A key height was the effective ceiling of the local light AA. Throw in bomber speed as a factor.

In each of these Theaters, targets during 1943 were generally Tactical or Operational, not Strategic. The Strategic bombing campaign did not really get going until later in 1944.

So in other words they are invalid examples when discussing pure air force versus air force operations. Also the area around Britain is omitted, yet Alaska is included in the active combat zones, where the USAAF reports 4,706 sorties for all of 1943. The Balkans had a lot of resistance activity but not a lot of allied operations. Similar for the Philippines.

In 1943 the RAF in the Middle East flew 164,325 Bomber, Fighter, Coastal, Tactical and Miscellaneous sorties, Fighter Command and 2nd TAF flew 159,832 sorties, in both theatres plenty of defensive sorties. USAAF was 169,594 MTO to 63,929 ETO sorties. Fighter Command flew more sorties than the RAF in the Middle East in both 1941 and 1942.

Strategic day-time bombers (e.g., the US heavy bombers in this case) can fly at high altitude, how high depending on the exact type (B-24 not as high as B-17, B-17 not as high as B-29), but they are only really useful against Strategic targets at that 20,000' / 6,000m + ft altitude.)

So what defines a strategic target in this case?

Where the ground armies are fighting, Operational targets like airfields, bridges, ports, supply depots, large artillery positions etc. can be targeted including by heavy bombers, but they will typically do so from much lower altitude. Partly this depends on the Theater and prevailing weather, as well as the season, local air defenses etc., but generally speaking, against Operational targets combat is at lower altitude. 8,000 - 20,000 ft, usually on the lower end of that band.

So when the allies targeted the German inland ports as part of the transport plan, they were hitting an operational target? Were marshalling yards strategic or operational?

Tactical targets are of course typically below 8,000 ft, usually down around 2,000 ft or less, assuming low ground / near sea level.

What size artillery concentration raises it from tactical to operational target?

The Germans simply used operational targets, the allies tried to split them into tactical and strategic. How much is really about size, the ability to put bombs on the target? The higher you go and the bigger the formation the worse the accuracy.

Fighters will often fight for high ground / altitude advantage well above the bombers, but in order to win this fight some of them will have to be right where the bombers are.

Some is far from all. It is the escorts above the bombers that have the best chances of interceptions.

But it's in this middle part of the war that the thread is focused. There is nothing inevitable about air war in WW2 that says fighting is going to be at 30,000 ft. In fact, usually it wasn't even close to that.

Especially when the army and navy were involved. The reality is decisions taken in 1940/41 gave the Air Forces the aircraft to fight with in 1943/44/45. As of the end of the Battle of Britain height was considered quite important. That was reinforced by Fighter Command operations over France in 1941 and 1942 plus the way Luftwaffe fighters in North Africa used their altitude performance advantages. Throw in the Ju86 high altitude versions, while the contract for the Westland Welkin prototypes was issued in 1940, first production examples in September 1943. The first of 5 Mosquito XV appeared in December 1942 and ignoring the prototype first Spitfire VI in December 1941, VII in September 1942.

Bomber Command reports 1941 day bomber sorties as 60 Belgium, 1,392 France, 474 Germany, 295 Netherlands, 33 Norway, total 2,254, plus 1,988 anti shipping. With 162 of the sorties to France on either 24 July or 18 December, the main attacks on the German fleet at Brest. According to Eagle in Flames by E R Hooton the RAF flew 20,495 offensive fighter and 1,406 offensive bomber day sorties in the second half of 1941, and 43,339 fighter and 1,794 bomber sorties in 1942. This clearly ignores the anti shipping sorties, while those to Germany at least were unescorted. Hooton notes the upswing in bomber operations in 1942 thanks to the USAAF 1,453 sorties from July plus another 1,081 fighter. The RAF in Britain did not have a viable day bomber force in 1941/42, it flew lots of sweeps as well as raids where the bombers were well outnumbered by a fighter force around and up to well above it, to the point when Spitfire VII were available they did go near or over 30,000 feet.

What the US called the ETO was where the USAAF regularly sent its latest and best first, 3 groups of P-38 in 1942, the P-47 then Merlin P-51 in 1943, remembering the P-39 groups were there for ground support of any 1942/43 invasion of France. The 8th Air Force was losing B-17G in early October 1943, the four 15th Air Force B-17 groups had 2 B-17G on strength end November 1943, 13 end December and 64 end January by which stage the 8th had lost 213 B-17G.

The 15th Air Force has 108,033 heavy bomber sorties where the altitude is given, anything with 50 or less sorties was probably a single raid, 14,273 sorties reported attacking from 25,000 feet or higher.

A/F	11,283​	21,399​
A/F & A/I	69​	22,739​
A/I	985​	22,001​
A/I & M/Y	35​	22,000​
A/I Messerschmidt	40​	22,000​
A/Iasy	325​	20,657​
A/Iasy He 219	205​	22,393​
A/Iasy Me 109	1,052​	22,198​
A/Iasy Me 262	78​	21,994​
A/Iasy Me 410	133​	22,373​
A/Icomp	592​	21,801​
A/Icomp Me 109	417​	22,119​
A/Icomp Me 262	125​	23,149​
A/Icomp Me 410	445​	21,653​
A/Icomp Me109	50​	20,940​
A/Ieng	1,017​	23,492​
A/Ieng Fw 190	167​	25,165​
AAA	42​	24,426​
AFV	1,109​	23,581​
AFV comp	67​	24,712​
AFV eng	202​	21,857​
AFV repair	52​	24,306​
Ammo Dump	254​	20,444​
Armaments	811​	23,109​
Bearings	642​	22,451​
Chem/P	291​	22,396​
City	953​	19,914​
Depots	24​	23,100​
F/Y	850​	26,186​
Ferry	54​	17,481​
Ferry Terminal	33​	21,576​
Fuel Dump	60​	22,247​
Gun Emplacements	856​	18,080​
Hy/Br	1,219​	20,885​
Hy/defile	26​	20,000​
I/A	971​	22,319​
I/A motor	41​	22,100​
Loco/Wrks	445​	23,008​
M/T	156​	21,617​
M/T Depot	82​	17,232​
M/Y	36,723​	21,615​
M/Y & A/I	39​	21,500​
M/Y & City	27​	21,900​
MT/Depot	27​	19,000​
MT/Repair	116​	20,816​
Naval Shops	39​	18,000​
O/Ben	2,624​	24,903​
O/PumpSt	136​	21,817​
O/R	10,423​	22,889​
O/St	3,377​	21,990​
O/Sy	3,158​	24,063​
Ord/D	697​	25,028​
P/A	3,643​	20,831​
P/A Drydock	83​	22,465​
Radar	41​	19,000​
Radar (FC)	35​	19,500​
RR	898​	20,854​
RR/Br	9,003​	20,954​
RR/Br & Via	45​	22,467​
RR/Junc	19​	23,589​
RR/Shops	301​	19,376​
RR/Sidings	23​	21,600​
RR/Sta	129​	24,066​
RR/Via	1,045​	20,211​
Steel	53​	22,445​
Steel Mill	33​	21,000​
Steel works	58​	22,000​
T/O	90​	18,111​
T/T	7,216​	19,872​
T/T artillery	597​	19,051​
Tele/Ex	25​	19,500​
Torpedo factory	28​	25,500​
Torpedo/P	21​	22,000​
UB/Base	929​	22,350​
UB/Pens	46​	21,957​
Wagon Works	28​	24,000​
Total	108,033​	21,738​

Lowest average height Motor Transport Depot, 17,232 feet, highest Freight Yards (Vienna) 26,186 feet. Tactical Targets, enemy ground positions, was 19,972 feet, the heavy bombers did not operate usually at the lower end of the 8 to 20,000 foot band when attacking enemy ground positions and the like.

A fundamental consideration in USAAF heavy bomber raids was the fighters were unpressurised, given the bombers were operating at around 22,000 feet that limited how much higher the fighters could be over the bombers without causing too many problems for the fighter pilots.

Bombing from 20,000 feet was very hard against small targets, but ports and airfields (like at Darwin, Port Moresby, Henderson field) it could be effective,

The Japanese choice of altitude when bombing Darwin was based on their understanding of the P-40 performance, pre war the "European" population of Darin was 944, how big does anyone think the port was? Benghazi was around 34,000 people. When you look at the area airfields covered they rank high compared with most factories.

In the MTO fights, the bombers were mostly down low, but the fighters went up above them, to 15, then 20,000 feet to get the high ground so to speak. Here, the Hurricane II was given a new lease on life by the Merlin XX. It arrived in Theater starting in Feb - April 1941,

Malta received its first Hurricane II as part of Operation Winch, 3 April 1941. Takoradi lists first mark II fly outs in May 1941. Britain exports of mark II starting March 1942 monthly to June, around 13, 26, 2, 82. The British were sent 150 P-40F, 21 were lost in transit.

Then again, how long did it take to convert the P-40 to the Merlin XX and get the V-1650-1 into production? That seems to have happened pretty fast.

Over a year for the first engine, nearly 2 years for mass production. First P-40F 5 months after first engine production. The British made their engine order before the Lancaster existed, the US on assumptions about when, where and with whom it would be at war amongst other considerations.

US Merlin cumulative production passed 1,000 in April 1942, 2,000 in June and 3,000 in July, so end July 1,043 V-1650-1 for US, for 575 P-40F produced so far, P-40F output running at about 130 a month.

Totally disagree- Chiang may well have had undue influence, but they did absolutely need them in Theater. The P-51B/C were a huge step up in outcomes. The P-40s were holding their own but lacked range for a lot of important missions in Theater. The British were still using Hurricanes well into 1944 and Spitfires only slowly trickled in. Neither the P-51A nor the small number of P-38s in Theater were making much of a difference.

Spitfire exports to India started in February 1943, by month for year 2, 0, 2, 1, 27, 50, 11, 58, 22, 13, 80, exports went up in 1944.

P-47s didn't do all that well initially in the MTO or in the CBI. Nor did the P-38s, though obviously in both cases this changed when the improved variants became available.

So what are the month by month numbers? How long did the improvement take? P-47 in 15th Air Force December 1943 to June 1944, 4,366 effective sorties, claims of 155-25-23 for 50 lost or missing, 42 damaged.

The Americans were doing daylight strategic bombing of Germany in 1943. This is when P47s shot down and killed experienced Luftwaffe pilots. Mustangs in late 1943 were the coup de gras (sp?).

No, ETO USAAF fighter pilots had claimed 458 enemy aircraft destroyed in the air to end 1943, then 1,431 January to April 1944 with the P-47 units making the most claims, the P-51 was more effective per sortie, the P-47 more sorties during the time.

Daylight strategic bombing started in NW Europe in 1943, but it was not yet effective or really significant to the outcome of the war, particularly in comparison to the very intense ground and naval combat going on in the various Theaters I listed.

Philippines, Balkans, Alaska for example. Also the air force alone is being compared to air + sea + land. The USAAF in the ETO made 3,865 claims, MTO 3,740, all theatres against Japan 3,232 (5th and 13th AF 2,366 of this). We know the ETO claims were the least accurate. What qualifies as "really significant"?

The partially escorted raids on the ball-bearing plants at Schweinfurt an Regensburg in August and October 1943, which resulted in losses casualties so severe (60 bombers in the first raid and ~80 severely damaged, 550 aircrew MiA or PoW; 77 heavy bombers lost in the second raid) that they forced a pause on unescorted missions.

Regensburg was Bf109 manufacture. The 17 August mission 60 B-17 missing, 4 write offs, for 14 October it was 60 B-17 missing, 8 write offs, including accidents. Various references have the serial number lists. For the lost aircraft crew casualties for 17 August were 111 KIA, 380 PoW, 37 evaded, 20 interned, 73 Returned to Duty, for 14 October it was 153 KIA, 394 PoW, 37 evaded, 7 interned, 102 Returned to Duty plus for both days those killed or wounded on damaged bombers.

As improved versions of the P-47 became available they became more capable at fighting at lower altitudes as well, and were brought into the Tactical and Operational fighting quite a bit more.

The main requirement for non heavy bomber escort operations came about because of Operation Overlord, what were the improvements to the P-47 and when? The 9th AF had 3 P-47 groups go operational in February 1944, then 2 in March and 3 in April, what P-47 versions did they need before being brought into non escort operations? Remembering for much of 1943 the USAAF was P-47 bomber escort, P-51 for Army support.

(25,000 feet and up)

Strategic bombing was still essentially a sideshow in 1943, and combat at those kinds of altitude remained rare until 1944, as I originally noted.

Concluded by using comparisons of air versus combined arms and dropping Britain as a combat zone. In 1943 the USAAF in the MTO flew 22,389 heavy bomber sorties, how rare was the bombers or fighters going to around 25,000 feet, similar for the 27,362 ETO heavy bomber sorties. In 1943 Germany had to cede control of airspace to just about everywhere else to maintain it over Germany.

The first major Strategic bombing raid against Japan was in June of 1944, but really ramped up after the capture of the Marianas in November 1944.

75 B-29 detailed, 63 effective, around 130 short tons of bombs. By that measure the 8th was doing major raids for most of 1943.

The major effect of the B-29 campaign against Japanese industry was the loss of production through dispersal to avoid possible losses to bombing. The mining campaign was the most cost effective. The major effects of the 1943 operations against Germany was the cost of increased ground and air defences, decisions to phase out bomber production in favour of fighter and the withdrawal of fighter units from the front to Germany.

I don't think night attacks or defense, as important as they were in many ways, are relevant to the issue of engines for daylight fighters.

Mosquito hunters would disagree. Ground fire was less accurate at night, it enabled lower bombing altitudes.

I'm not saying that NW Europe was irrelevant in 1943, it was starting to matter, and showed promise to help end the war, but it by no means outweighed the rest of the fighting going on in MTO, PTO, CBI etc., especially for the US. It was not even close.

By isolating a single component like that you can make such comparisons, say USN anti submarine operations, USN carrier operations, US army units in combat with Japan (hint diseases meant lots of time out of combat, as well as amount of land available made it hard to deploy troops, consider when the Army first needed Corps HQ). There was a time in 1943 when there were no US Army units in contact with Japanese. Compared any of the above to say total units in the Mediterranean for example and they are easily outweighed Tarawa had a negative significance, if that was to be the normal result of amphibious assaults on Japanese held islands the central Pacific drive could be shut down.

 

[Shortround6]

Actually no, "Height gives you the initiative". If you are in a fight with a viable hostile air force then operations include larger numbers of fighter sweeps and a higher ratio of escorts to bombers, enabling everything from high to close cover. The average altitude comes back to the altitude performance of your fighters, secondly the bombers. Complicating this is the size and defences of the average bombing targets, smaller means lower altitude, better defended means higher. A big factor in determining bomber altitude is the amount of ground defences and the size of the bomber, a B-17 covered a larger area than a B-26 making it easier to hit. A key height was the effective ceiling of the local light AA. Throw in bomber speed as a factor.

I mostly agree with this. It is a rather complicated subject. Going to your last sentence Throw in bomber speed as a factor. Things get real complicated really quick as I am sure you are aware. different countries had different criteria as to what "effective" range meant. Some countries might say that the gun had to be able to 'engage' the target for a minimum of 20 seconds. That meaning that the target aircraft could cross through the top of the hypothetical dome of the AA gun fire at a height that allowed the gun to fire for 20 seconds.
Obviously, a faster plane could fly lower than slower plane and get through the danger area.
However, this was for a plane flying pretty much directly over the AA gun/battery. Flying a few thousand meters off to the side reduced the effective range by hundreds of meters.
A lot of large AA guns had fuses that self-destructed somewhere between 20-30 seconds of flight, if the time fuse failed. Firing hundreds of large shells into the sky that were going to fall back down on your people and buildings was not a very good plan.
A lot of the "light" AA had very, very optimistic ranges. Getting hit by a single 37-45mm shell was effectively a mission kill even for a big bomber but the actual chances of getting hit were very small. Most light AA did not have very good fire control. "effective" range (on a slant) was around 3000 meters or less even for a 40mm Bofors. The 40mm could lob shells around 5000 meters (?) up but actually hitting the intended target and not a plane flying several hundred meters behind?
In some ways the purpose of light AA was to keep the bombers 'honest'. Make the bombers fly higher where the slower traversing heavy guns could deal with the crossing speed and fire a decent number of time fused shells under control of a fire director which could predict the future location of the bomber/s.
It was the lack of decent light/medium AA that really hurt the Japanese. The Allies did lose some aircraft to light AA but not enough to make them stop Low altitude attacks. In fact Japanese AA was pretty poor in general which can really affect combat heights in the Pacific.

 

[Steamed_Banana]

Real quickly, since I have to split, (I'll come back with more detail later)

1) Every discussion about aviation does not need to devolve into US vs UK prestige or bragging rights. In 1943, the Germans had no means of taking ground territory from the British, nor did the British (barring tragic experiments like Dieppe) have any means of taking territory from the Germans. Germany and the Anglo-Americans were fighting over territory in North Africa and later Sicily and Italy. This had major impact on the war, including the air war (not least because some of the best fighters, if not the best, available to the Axis, i.e. the '5 series' Italian fighters, basically fell out of production when Italy first capitulated in Sept 1943. Similarly the land and naval war in the Pacific had substantial impact on the outcome of the war. Needless to say major battles in the east like Kursk etc. were extremely consequential to the Germans and in fact spelled their doom more than anything else going on at this stage.

In 1943, (and also 1942) the fighting in what we might think of (or in some cases, even dismiss) as the "outer-Theaters" were what had the most Strategic consequences to the outcome of the war. The entire war was not won and lost across the English channel.

2) The day-time fighting in NW Europe i.e. out of the UK in 1943 was a gradually accelerating attrition war on it's way to becoming a serious strategic bombing campaign, but was not yet having any significant impact on the outcome of the war. This is not to denigrate Bomber Command or the huge risks taken by their crews, and events like the fire bombing of Hamburg were certainly very significant for the people on the ground living there, but it's just not something that day-fighters were involved in, and the actual Strategic significance to the German war-machine, while no doubt the possible subject of an interesting debate, just isn't germane to the thread about improving day time fighters. It's really that simple.

3) Night time bombing, while somewhat significant to the outcome of the war in 1943, is simply not relevant to the development of daytime fighters, Mosquito engines notwithstanding (this largely due to the fact that the Mosquito production pace was not yet that high compared to major fighter types, due to limitations imposed by it's construction medium).

4) "Air force vs Air force" in some kind of pure sense really doesn't mean anything in WW2. I think the British were actually under an illusion after the Battle of Britain that they could pick fights with the Germans and resume successful attrition warfare without involving bombers, i.e. various cross channel fighter sweeps etc., but the Germans seemed to be content to fight strictly on their own terms and let their integrated AAA systems impose losses on British fighters. To get a real attrition war of 'air force vs air force' they ultimately had to bomb targets of Strategic value. With very few exceptions, all fighter combat in WW2 boiled down to bombing your enemy or preventing them from bombing you. If there was no ground army or navy involved, this meant that Strategic targets had to be hit.

5) Improvements to the P-47 which made them more useful in lower altitude combat included the introduction of external fuel tanks to improve range (summer 1943), improved engine power starting with the P-47D-5 (mid to late 1943) the paddle-bladed propeller (first arriving in Jan 1944), improved MW water injection (spring of 1944), the bubble canopy (later spring 1944). I don't think these are much of a mystery..?

6) Higher altitude does not always equate to mission success. In the Pacific and CBI in particular, high cover often completely missed combat going on at lower altitude where the bombers or fighter-bombers were engaged. This also routinely happened (though somewhat less often, admittedly) in North Africa, Sicily, and Italy. In Russia, about 9-10 months out of the year, most of the fighting was essentially restricted to 15,000 or less, sometimes down to 5,000 feet, by the cloud ceiling.

7) All the fighting in the Pacific was somewhat incremental, with the denouement of the epic Guadalcanal campaign representing the biggest single event of Strategic importance, Bismark Sea represented US and ANZAC land based air power demonstrating the capability to destroy a sea based invasion force, landings like at Tarawa represented US effectively taking island after island from the Japanese, as part of an overall (and permanent) shift from defense to offense by the Allies. Aleutians, as precarious and small scale as it was, represented the check and then end of a Japanese attempt to take land in the North, and were part of the general trend of rolling back their spectacular gains in the early part of the Pacific War.

The point here is that in 1943, in most of the world and the most consequential battles of WW2, most of the combat did not in fact rise to 30,000 ft.

 

[MikeMeech]

Real quickly, since I have to split, (I'll come back with more detail later)

1) Every discussion about aviation does not need to devolve into US vs UK prestige or bragging rights. In 1943, the Germans had no means of taking ground territory from the British, nor did the British (barring tragic experiments like Dieppe) have any means of taking territory from the Germans. Germany and the Anglo-Americans were fighting over territory in North Africa and later Sicily and Italy. This had major impact on the war, including the air war (not least because some of the best fighters, if not the best, available to the Axis, i.e. the '5 series' Italian fighters, basically fell out of production when Italy first capitulated in Sept 1943. Similarly the land and naval war in the Pacific had substantial impact on the outcome of the war. Needless to say major battles in the east like Kursk etc. were extremely consequential to the Germans and in fact spelled their doom more than anything else going on at this stage.

In 1943, (and also 1942) the fighting in what we might think of (or in some cases, even dismiss) as the "outer-Theaters" were what had the most Strategic consequences to the outcome of the war. The entire war was not won and lost across the English channel.

2) The day-time fighting in NW Europe i.e. out of the UK in 1943 was a gradually accelerating attrition war on it's way to becoming a serious strategic bombing campaign, but was not yet having any significant impact on the outcome of the war. This is not to denigrate Bomber Command or the huge risks taken by their crews, and events like the fire bombing of Hamburg were certainly very significant for the people on the ground living there, but it's just not something that day-fighters were involved in, and the actual Strategic significance to the German war-machine, while no doubt the possible subject of an interesting debate, just isn't germane to the thread about improving day time fighters. It's really that simple.

3) Night time bombing, while somewhat significant to the outcome of the war in 1943, is simply not relevant to the development of daytime fighters, Mosquito engines notwithstanding (this largely due to the fact that the Mosquito production pace was not yet that high compared to major fighter types, due to limitations imposed by it's construction medium).

View attachment 873951

4) "Air force vs Air force" in some kind of pure sense really doesn't mean anything in WW2. I think the British were actually under an illusion after the Battle of Britain that they could pick fights with the Germans and resume successful attrition warfare without involving bombers, i.e. various cross channel fighter sweeps etc., but the Germans seemed to be content to fight strictly on their own terms and let their integrated AAA systems impose losses on British fighters. To get a real attrition war of 'air force vs air force' they ultimately had to bomb targets of Strategic value. With very few exceptions, all fighter combat in WW2 boiled down to bombing your enemy or preventing them from bombing you. If there was no ground army or navy involved, this meant that Strategic targets had to be hit.

5) Improvements to the P-47 which made them more useful in lower altitude combat included the introduction of external fuel tanks to improve range (summer 1943), improved engine power starting with the P-47D-5 (mid to late 1943) the paddle-bladed propeller (first arriving in Jan 1944), improved MW water injection (spring of 1944), the bubble canopy (later spring 1944). I don't think these are much of a mystery..?

6) Higher altitude does not always equate to mission success. In the Pacific and CBI in particular, high cover often completely missed combat going on at lower altitude where the bombers or fighter-bombers were engaged. This also routinely happened (though somewhat less often, admittedly) in North Africa, Sicily, and Italy. In Russia, about 9-10 months out of the year, most of the fighting was essentially restricted to 15,000 or less, sometimes down to 5,000 feet, by the cloud ceiling.

7) All the fighting in the Pacific was somewhat incremental, with the denouement of the epic Guadalcanal campaign representing the biggest single event of Strategic importance, Bismark Sea represented US and ANZAC land based air power demonstrating the capability to destroy a sea based invasion force, landings like at Tarawa represented US effectively taking island after island from the Japanese, as part of an overall (and permanent) shift from defense to offense by the Allies. Aleutians, as precarious and small scale as it was, represented the check and then end of a Japanese attempt to take land in the North, and were part of the general trend of rolling back their spectacular gains in the early part of the Pacific War.

The point here is that in 1943, in most of the world and the most consequential battles of WW2, most of the combat did not in fact rise to 30,000 ft.

Hi
The air fighting would take place where the 'threat' was, which is obvious, so in air attacks between fleets or on convoys the air fighting would be at low to medium level mainly as that is where torpedo and dive bombers would be. When you have aircraft involved in ground attack then the opposition would have to come down to deal with them, although they would also have to deal with any fighter cover, again all very obvious. However, looking at the CBI we can see low and medium level fighting but we also have many examples of engagements at higher altitudes, here are a few examples:

Source is 'Bloody Shambles' Volume One by Shores et al., there are other examples. These continue through the series, his 'Air War for Burma' includes on page 83:

And page 151:

Other books have examples of 'higher' altitude air fighting, this includes 'Hurricanes over the Arakan' by Norman Franks:

and also on page 205 below:

To do 'boom and zoom' (and avoid being jumped by Japanese top cover) on Japanese formations the defending fighters would have to get up to nearly 30,000 ft, that is not including air combat with high flying recce aircraft (which could be treated as a special case), there are more examples of course in these and other books. In the CBI Theatre at least the Japanese were not just involved at the lower altitudes. I hope this is useful in the discussion.

Mike

 

[Geoffrey Sinclair]

Real quickly, since I have to split, (I'll come back with more detail later)

When doing so could you include all the other things like finally keeping many month old promises on Blenheim losses in the Middle East and other topics.

1) Every discussion about aviation does not need to devolve into US vs UK prestige or bragging rights.

So what examples from the current topic are doing this, the pro British and the pro American?

(not least because some of the best fighters, if not the best, available to the Axis, i.e. the '5 series' Italian fighters, basically fell out of production when Italy first capitulated in Sept 1943.

Assuming the Italian government stayed pro axis how many of the latest Italian fighters would have been available to say mid 1944? Plus trained pilots? How much better were they than the P-51 and Spitfire XIV?

Meantime we have another summary that combined arms operations world wide taken together were far more important than air operations alone out of Britain.

In 1943, (and also 1942) the fighting in what we might think of (or in some cases, even dismiss) as the "outer-Theaters" were what had the most Strategic consequences to the outcome of the war.

Outer theatres would apply to the axis, not the allies, Britain had set up an economy that had significant interests in an open Mediterranean for example.

The entire war was not won and lost across the English channel.

So what examples from the current topic are claiming it was?

2) The day-time fighting in NW Europe i.e. out of the UK in 1943 was a gradually accelerating attrition war on it's way to becoming a serious strategic bombing campaign, but was not yet having any significant impact on the outcome of the war. This is not to denigrate Bomber Command

Bomber Command was operating almost exclusively at night, so no way day operations can denigrate it. The firestorm at Hamburg was estimated to cost 1% of 1943 production and delivered the biggest single shock of the bombing campaign. If the RAF could do such raids so could the USAAF and probably more often given the average bombing accuracy day versus night in 1943. This was combined with the costs and failures at Kursk and Sicily. "On July 28, 1943, during a meeting to evaluate the damage Germany had suffered Goering ordered Milch to give the defence of the Reich the "main emphasis" in Luftwaffe planning." That was quite a strategic move brought about by the trends of the air war the European Axis were fighting.

events like the fire bombing of Hamburg were certainly very significant for the people on the ground living there, but it's just not something that day-fighters were involved in, and the actual Strategic significance to the German war-machine, while no doubt the possible subject of an interesting debate, just isn't germane to the thread about improving day time fighters. It's really that simple.

So the area of the air war where the allies had a general rule of their best air power earliest had no impact on "improving day time fighters"? Is the idea the range improvements in US fighters asked for or actual from January 1942 or earlier were all to do with the ranges to targets around the world except Britain to Germany? That the US would commit major forces to the Mediterranean was a well into second half of 1942 idea.

The activities of armies and navies around the world are declared relevant, the results of 1943 fighting in Alaska, Balkans and Philippines are declared relevant Around Britain not relevant. Conclusions can then be constrained to preferred outcomes.

Air Forces are supply intensive. There are reasons the 15th Air Force set up around Foggia and stayed there, why the heavy bomber forces and their fighters, stayed in Britain instead of moving in bulk to France in 1944/45, despite the advantages of moving closer to the targets. The Desert War was dependent on the MBT, the Main Battle Truck, which is why there were so few days of major combat, looking at the various front lines in 1942/43 only in Britain was the infrastructure to support intensive air operations, with the result it was generating a very big percentage of allied air activities. On top of that like the allies it was where the Germans as a rule sent their best equipment first.

As an aside the night raids resulted in the formation of I, II and III/JG300, I, II and III/JG301 and I, II and III/JG302 July to October 1943. The limitations of using non radar equipped single seat fighters were acceptable in summer but exposed in winter. The units used lots of better Luftwaffe pilots as they were instrument certified. The growing day threat meant they converted to mostly day operations in 1944, meant to be able to fly in poor weather.

3) Night time bombing, while somewhat significant to the outcome of the war in 1943, is simply not relevant to the development of daytime fighters, Mosquito engines notwithstanding (this largely due to the fact that the Mosquito production pace was not yet that high compared to major fighter types, due to limitations imposed by it's construction medium).

This is the comedy relief, the supplied figures are British Mosquito production, which never used US Merlins. Canada made 74 Mosquito in 1943.

Now the title is getting a better supercharged Allison engine earlier with the subtext of using the Merlin instead. If the Vulture had worked and in particular the reports it was reliably putting out 2,000 HP in early 1942, the Lancaster might not have been built, or built in numbers.

Britain kept the use of single stage Merlin near totally confined to Lancaster and non British Mosquito, no Lancaster would mean pushing 90% of US single stage Merlin would be available for US use, call it 20,000 out of 24,053 built. Compared with 8,702 Allison P-40 from 1942 to 1944 and we have been told over and over how the Merlin P-40 was so successful, there would be plenty of engines available for a Merlin P-38 version (at least the P-322) or alternatively a Merlin P-39, or for that matter Merlin P-51 in 1942. The latter has the best sales pitch, going to the British anyway. The way around this is to issue a declaration night does not affect day.

Seen the German fighter developments in their attempts to catch Mosquitoes?

4) "Air force vs Air force" in some kind of pure sense really doesn't mean anything in WW2.

Think of this as declaring the colour of the day sky is silver, now here is the way to find gold...

I think the British were actually under an illusion after the Battle of Britain that they could pick fights with the Germans and resume successful attrition warfare without involving bombers, i.e. various cross channel fighter sweeps etc.,

Actually the British worked out quite quickly they needed bombers as part of the force mix but did not have many. One of the noted points in 1943 was the 8th Air Force doing pure fighter sweeps while the British were escorting the USAAF bombers (heavy and B-26) as they knew that had a higher chance of finding Luftwaffe fighters.

To get a real attrition war of 'air force vs air force' they ultimately had to bomb targets of Strategic value.

Actually they had to threaten targets the enemy worried about. For an air force that included airfields and radar stations. Strafing works quite well against both.

With very few exceptions, all fighter combat in WW2 boiled down to bombing your enemy or preventing them from bombing you.

So we have now switched to all war which helps the conclusion as allied air operations were very end weighted. We have diverged from the day bomber scarce days of 1940 to 1942 and the shits in force mix in 1943. The conclusions above do not have such time limits.

If there was no ground army or navy involved, this meant that Strategic targets had to be hit.

In simple terms no. Think of the how we fight document issued under Montgomery's name in 1943, how it talks about winning the air battle before committing the ground forces. Drive the enemy air force away. Attack airfields.

5) Improvements to the P-47 which made them more useful in lower altitude combat included the introduction of external fuel tanks to improve range (summer 1943), improved engine power starting with the P-47D-5 (mid to late 1943) the paddle-bladed propeller (first arriving in Jan 1944), improved MW water injection (spring of 1944), the bubble canopy (later spring 1944). I don't think these are much of a mystery..?

The D-5 was built May to July 1943, so are the above dates production or deployment or a mixture? Meantime Roger Freeman indicates P-47 engines were the 2,000 HP R-2800-21 until the 2,000/2,300 HP rating of the R-2800-63 of the D-11 block starting in September 1943. The D-22 and D-23 introduced the paddle blade propellers into production in January and February 1944, arriving implies at the front in January. Bubble canopies were with the D-25, built February to May 1944. What block number is defined as having improved methanol water injection?

The improvements to the P-47 are well known and tracked. The mystery is the claim "As improved versions of the P-47 became available they became more capable at fighting at lower altitudes as well, and were brought into the Tactical and Operational fighting quite a bit more." by indicating the improvements were a requirement before low altitude operations were possible and were the driver, not the approach of Overlord nor the switch of the P-51 to heavy bomber escort. You could look up the US Fighter Bomber Groups that were renamed fighter. The 8th Air Force P-47 started fighter bomber operations in November 1943. The 57th Fighter Group, 12th Air Force was a little later, using its P-47 as bombers even while transitioning from P-40 (The 325th Fighter Group was not dropping bombs)

Where is the data to back the claim "P-47s didn't do all that well initially in the MTO or in the CBI. "

6) Higher altitude does not always equate to mission success.

So where in this topic is the claim made? A general rule is if the enemy fighters are initially above you the chances of a losing that fight are greater.

In Russia, about 9-10 months out of the year, most of the fighting was essentially restricted to 15,000 or less, sometimes down to 5,000 feet, by the cloud ceiling.

An interesting statement, given the distance from Moscow to the Polish border and the Baltic to Black Sea, also the way forest in the north gives way to grassland in the south, indicating reduced average precipitation and therefore clouds. So what is the area of Russia that has this weather?

In Russia the Luftwaffe fighters there again used their altitude performance advantages as a regular tactic, but also knew the Red Air Force lacked radios, easier to work from back to front as no radio warnings could be made, add the Red Air Force was definitely army support and almost always stayed low.

8th AF targets in Germany percentage of visual bombing, 1944, 24.78, 54.14, 33.61, 77.34, 57.79, 59.38, 44.43, 89.41, 37.29, 22.81, 12.64, 34.65. Notes, good weather reserved for strikes supporting Overlord particularly in June, it took until August/September for all groups to have their own H2X equipped aircraft.

The 15th Air Force, just under 122,000 effective sorties which give target weather conditions, 28,477 had 5/10 cloud or thicker, for December 1944 to February 1945, almost 19,000 sorties, 9,532 saw 5/10 or more cloud, 5,058 reported CAVU.

7) All the fighting in the Pacific was somewhat incremental, with the denouement of the epic Guadalcanal campaign representing the biggest single event of Strategic importance,

Back to 1943. In any case how about Midway, the loss of 4 IJN fleet carriers and that effect on Japanese strategic options? Followed by Milne Bay where a Japanese landing was repulsed and the building myths about Japanese as jungle fighters was refuted?

Bismark Sea represented US and ANZAC land based air power demonstrating the capability to destroy a sea based invasion force,

Resupply/reinforcement convoy, no New Zealand units involved.

landings like at Tarawa represented US effectively taking island after island from the Japanese,

Not taken effectively, far too many casualties and missteps to allow repeats.

as part of an overall (and permanent) shift from defense to offense by the Allies.

Apart from the CBI, either side of the mountains.

Aleutians, as precarious and small scale as it was, represented the check and then end of a Japanese attempt to take land in the North, and were part of the general trend of rolling back their spectacular gains in the early part of the Pacific War.

The Japanese never intended to go beyond where they landed in the area.

So the effect on German deployments caused by the commando raids on Norway must rate as similarly important?

The point here is that in 1943, in most of the world and the most consequential battles of WW2, most of the combat did not in fact rise to 30,000 ft.

And that is obvious to everyone, as is the trying to ignore the numbers fighting above 20,000 feet and the problems labelling targets, especially strategic.

Here ends the analysis of the "I'm the only reasonable person here" message, made possible by ignoring everyone else.

 

[Steamed_Banana]

Hi
The air fighting would take place where the 'threat' was, which is obvious, so in air attacks between fleets or on convoys the air fighting would be at low to medium level mainly as that is where torpedo and dive bombers would be.

Yeah that's a safe bet

When you have aircraft involved in ground attack then the opposition would have to come down to deal with them, although they would also have to deal with any fighter cover, again all very obvious.

Yes I agree, very obvous

However, looking at the CBI we can see low and medium level fighting

The question is, where was most of the fighting

but we also have many examples of engagements at higher altitudes, here are a few examples:
View attachment 874130
Source is 'Bloody Shambles' Volume One by Shores et al., there are other examples. These continue through the series, his 'Air War for Burma' includes on page 83:
View attachment 874131
And page 151:
View attachment 874132

Worth noting that Spitfires, (and in 1944 for 136 Sqn I believe those were Spitfire VIII) were taking losses to Ki-43s

Other books have examples of 'higher' altitude air fighting, this includes 'Hurricanes over the Arakan' by Norman Franks:

View attachment 874133

and also on page 205 below:
View attachment 874134
To do 'boom and zoom' (and avoid being jumped by Japanese top cover) on Japanese formations the defending fighters would have to get up to nearly 30,000 ft, that is not including air combat with high flying recce aircraft (which could be treated as a special case), there are more examples of course in these and other books. In the CBI Theatre at least the Japanese were not just involved at the lower altitudes. I hope this is useful in the discussion.

Mike

There were cases in the Pacific and CBI where the Japanese and the US attacked ports or airfields from 18-20 thousand feet, even up to 25 or 27,00 (for example this was routine for G4M Bettys attacking Darwin while the US 49th FG was defending it, and there were many attacks against Port Morseby like this). There were good reasons to attack from altitude, as this put them out of effective range of most of the AAA.

But as I already noted and really IMO should be obvious - in most cases (again, depending on the nature of the target) your bombers cannot do much damage from such an altitude. The Japanese would fly tight formations and drop patterns of usually quite small (i.e. 60 kilogram) bombs from height, but these rarely had much effect against well prepared airfields, i.e. with dispersed aircraft and revetments. After the first few raids, airfields tended to get much better prepared for attack. They could sometimes do damage to port and dock facilities, towns with warehouses etc., but those were only a small part of the target list, and could only be attacked when the weather allowed bombers to see targets from 20,000+ feet, and when you had level bombers (Ki-21, Ki-48, Ki-49) available which could do that kind of bombing. Many attacks from airfields were conducted at much lower altitudes by planes like Ki-51 and strafing fighters, as you know since you have the book.

Having read Bloody Shambles and Air War over Burma, would you conclude that most of the fighting was done at altitudes above 20,000 feet or that there was an urgent need for high altitude fighters capable of good performance at 30,000 ft?

The most successful Allied fighter units in Theater up into 1944 (23rd FG, 51st FG) were mainly flying Allison-engined P-40s for the most part, with performance marginal above 16-18,000 ft depending on type. Did these have better or worse outcomes than the Hurricane units?

 

[Steamed_Banana]

When doing so could you include all the other things like finally keeping many month old promises on Blenheim losses in the Middle East and other topics.

Because there is no point. You would just write more endless posts like this, never conceding a point, never admitting an error, endlessly making veiled insults. Everyone here knows what happened with the Blenheim, and why it was left out of the fight while the Boston, Maryland, and Baltimore continued. What is to be learned by posting data that most people here already have available?

So what examples from the current topic are doing this, the pro British and the pro American?

That's the thing, your are ardently on one side, nobody is fighting on the other side, but you are once again very tediously tilting at windmills.

Assuming the Italian government stayed pro axis how many of the latest Italian fighters would have been available to say mid 1944? Plus trained pilots? How much better were they than the P-51 and Spitfire XIV?

Fiat G 55 and Re 2005 were deemed by the Germans themselves to be better fighters than their own. They took a deep look at the possibility of producing the G 55 but determined it took too many man-hours to complete them. I don't know exactly how many a fascist Italy would have produced by mid 1944, nor does anyone else, but it's a safe bet it would have been more than the handful which were produced before they capitulated. They produced relatively few Macchi 202s in time to see combat - roughly 1,100, but they had an impact on the air combat in North Africa. Presumably a few hundred far better MC 205, Fiat G 55 and Re 2005 could have helped the German war-effort. At the very least it would have meant less German fighters had to be committed to the defense of Italy.

Meantime we have another summary that combined arms operations world wide taken together were far more important than air operations alone out of Britain.

1943

There was no strategically significant ground-fighting in or around England in 1943.

Ground fighting (Kursk, Dnieper, Kharkov, Guadalcanal, Tunisia, Sicily) was having a major impact on the outcome of the war in 1943, in various Theaters other than England.

Air combat in those Theaters was therefore more consequential.

Which you seem to take as an insult against the pride and honor of the United Kingdom. Which is utterly ridiculous. Pointing out it wasn't the center of the most crucial fighting in the war during every moment in the war is not the same as 'denigrating' it.

The Soviets actually had far more to do with the destruction of the Nazi war machine than the UK or the US did. How is that for disturbing news?

Bomber Command was operating almost exclusively at night, so no way day operations can denigrate it.

Denigrate? Hmmm....

Think of this as declaring the colour of the day sky is silver, now here is the way to find gold...

Pot. Kettle. Black.

And for the record, I think most people here are very reasonable. I engage with them quite a bit, as I think is pretty clear reading this thread.

Some here are extremely cranky, probably due to age. and care more about some kind of perceived / phantasmic agenda than history. I'm interested in history, not in a virtual battle for the honor of one nation against another in all things, or one old man against another for very empemeral virtual pride. That is utterly meaningless to me.

So I limit my engagement with those people, for what I think are obvious reasons. Partly because I'm rather old myself and I want to spend my limited time on this earth somewhat productively, and in here that means, learning things about history, not getting into a sumo wrestling match with some cranky old man about nothing.

 

[ggiumarra]

Been away from this conversation for a while mainly because the discussion here made me try once again to find some more original source materials online and I hit something of a jackpot when I found a website with a large number of US Air Force Historical Research Agency (AFHRA) files in PDF format (https://www.generalstaff.org/DRA/DRA.htm). I've been downloaded quite a few and have gone through several thousand pages already (obviously, not reading them all since not all were relevant) and found some very interesting stuff. For instance, I was able to find much of what I asked about in this thread earlier: documentation regarding Arnold's aircraft range extension program of February 1942. Bottom line, whatever the original intent it quickly transformed (apparently under the influence of everyone's favorite AAF general, Echols) into an initiative focused on increasing the ferry range of US fighters, not their combat range. Yes, there was a mad scramble to address that later in 1943, but in the intervening time period little was accomplished.

Since my study includes the RAF as well I was interested to find a some details on Wright Field's project in 1944 to increase the range of the Spitfire. Since I already have docs related to the RAF's (very much belated) efforts in that direction a little later in the year, it makes for a complete story I didn't have before.

Anyways, since one of my main themes is the unacknowledged importance of fighter range apart from heavy bomber escort and since that is not really the theme of this thread, I won't continue too much more right here on that. I will add that I found a doc from May 1943 in which Doolittle praises the Allison Mustang's "long range, excellent fire power, and outstanding performance" that he maintains would be useful to his command, though he also adds that with a "two speed, two stage or other high performance supercharger" (emphasis added) it could "escort heavies". The foreshadowing aside, what else could he have been talking about with "other high performance supercharger" than the original subject of this thread?

It is a basic rule when air forces fight each other altitude goes up, if the army and/or navy are involved altitude tends to go down.

Right. I have been saying the same for a long time, though I think your formulation there is more succinct than the way I have been putting it. My point (and evidently this is where Steamed_Banana is coming from too) is that for much of the war, and (for me at least) especially for 1942 through at least early 1943, low to medium altitude is more important because there are multiple ground campaigns going on and also very important naval actions taking place (of course, we can always pick out exceptional cases where there was high altitude flying going on, but as others have already pointed out, how significant were their impact really?). Things worked out well enough in the Pacific (though a long-range fighter like the original P-51 should have been very helpful and potentially could have secured some significantly better results for the USN in certain situations), but not quite as well in the Med. (about which more below).

Malta needed fast climbing fighters.

Agreed, but more than that they needed long-range fighters to get the fuel there to get those fighters off the ground to begin with. It did not necessarily need to be Mustangs (though they were def. more suited to recon - yet another vital role often glossed over - than the PR Spits that were favored but which there never was enough of on the island), the RAF could have just gotten more Spitfire drop-tanks to Malta than they did otherwise (basically the only ones there from what I can tell are the ones the Spitfires flew in with). The results of Op Harpoon showed this pretty clearly, but the RAF ignored it and nothing was done to bolster that key capability for Pedestal.

The Western Desert operations needed a reason to force the Luftwaffe to fight...

That's what FC was trying to do across the English Channel with very poor results. If you pump up your air power on Malta, which what was done really accomplished little more than to keep it from starving out (the contributions of Malta based air in the anti-shipping operations post Op Pedestal, though certainly not non-existent, have often been exaggerated), by increasing your long-range fighter capability and keeping a decent sized anti-shipping strike force (there was an unfortunate tendency for the RAF to disperse those to less critical and even quiescent areas and not so long after Pedestal avgas on Malta ran low again) you have an excellent chance of forcing the Luftwaffe to engage in a long-term attritional battle which would not be good for them at that time (much less capability to replace losses in 1942 than later in the war) or risk having DAK even more starved for supplies than historically. There's a very good chance both could happen as would take place around Tunisia the following spring. To concentrate in the Med., where your main ground operations were taking place and where you were trying to score a strategic win by opening it back up to save shipping resources (the main bottleneck for the Western Allies) just makes good sense.

...a major defeat of the Luftwaffe fighter arm before the invasion causing it to lose quality even as numbers remained...

I congratulate you for getting this at least half right (more than I can say for most), numerically the Jagdwaffe was not seriously written down in the months preceding D-Day (actually higher available SE fighters in GAF on 31 May 1944 than 20 Feb 1944, just before Big Week). This is what I intend to make the subject of Part II of my study and I base it on figures I got from the German military archives in Freiburg. I will have something to say on the qualitative dimension as well, which I have considerable evidence there was no dramatic drop off in that either (the Allies just overwhelmed them with large numbers of good fighters with good pilots).

9th Air Force ETO report..."Combat losses immediately wiped out the excess fighter and reconnaissance aircraft, and insufficient replacements created a critical shortage which existed until V-E Day despite the fact that some groups were converted to aircraft models which had a larger replacement flow."

There were not enough Mustangs in the world for a lot of the time in 1944...

The obvious way to obtain more Mustangs is to replace the order for Curtiss P-47G to P-51...

There is no doubt many aircraft stayed in mass production well after they were no longer front line material or something obviously better was available...

All the more reason to build more Allison Mustangs rather than Allison P-40s (the production of which continued well into 1944) or P-39s, both of which could have been largely phased out in 1943 (excluding, of course, P-39s for the Soviets, which came to 192 in 1942 and 2,627 in 1943, though that probably does not count those passed on by the British). The NAA Inglewood P-51 line was working at 1/3 capacity in 1941, 1942 and early 1943 at which point they were preparing for simultaneous production of the Allison and Merlin Mustangs (up to a combined 20/day, much higher than what actually resulted in 1943), the output of which was going to be limited for many months by the Packard Merlins anyways. NAA had a pretty good track record in WWII for performing so if they thought they could do simultaneous production (which was what Curtiss was doing, I believe, with the P-40) it seems reasonable to believe they could have pulled it off.

Wartime [Allison] production, 1 stage + 2 stage by year, 1940 to 1945, War production Report as well as the CAA report.

1,141 + 0, 6,447 + 0, 14,904 + 1, 20,549 + 514, 17,324 + 2,867, 3,841 + 1,645 total 64,206 + 5,027

Factory acceptances in 1942 of US fighters with the Allison = 7,015 of which 1,265 were P-38, so just under 8,300 total engines in completed a/c. I am not sure what the requirement for spares were but I don't see it could have been anywhere near the 6,600+ difference (with the 1942 14,904 + 1 figures you cite). Since the Inglewood plant was operating well below capacity, it could have been that P-40 or P-39 production could have maintained at the same level even with a large increase in Mustang output resulting in overall more fighter produced in that year. I had always believed that the number of Allisons that could be produced rather than airframes was the limiting factor, but perhaps not.

Returning to the main theme here: your figures illustrate the main reason the AAF should have been interested in pushing for the development of a single-stage/two-speed s/c for the Allison: you are going to be producing lots of them regardless so why not make a "medium tech" upgrade to extend their usefulness further into the war? To me the P-51A is still world-class at the still important medium and low altitudes right up to the end of the war. Enhancing it with single-stage/two-speed s/c would have been very, very nice. While I am not saying it's automatic that an AAF initiative earlier in the war (or GM, it really comes down to who would push/finance it) would have produced a better s/c on the Allison (after all they apparently flubbed their attempt at a two-stage/two-speed s/c) it easily could have paid a large dividend in fighter performance as early as early 1942 on.

Could you pleas let me know where I can find the "War production Report" or "CAA" reports you refer to? That would be very helpful to me.

P-51A 1,200 HP available for take off, Merlin P-51 either 1,380 or 1,490 HP, that translates to several hundred feet lower take off runs for the same weight...

The P-51A was, I believe, lighter than the Merlin P-51. In any event all sources I am familiar with, incl. the RAF relative airspeed chart I posted earlier, put the low altitude speed of the P-51A (and even the Mustang I at increased manifold pressure) significantly higher than the P-51B. If you're lighter and moving faster with a nearly identical air frame, it's hard to see how the takeoff run would be longer.

The British were definitely trying to convince the Americans to build more P-51 for much of 1942, involving Churchill easily shows that, not sure whether there was a consistent line about what to cut back on, they knew the Americans had the final decision.

I have never seen that Churchill got involved. That would be interesting. Do you have a source for that?

Curtiss-Wright had been around a long time with many good designs, it had a bank of goodwill as a result...Given the breadth of the Curtiss-Wright group and the head start with P-40 production it is not surprising in 1942/43 it was one of the bigger suppliers. The trouble with going into conspiracies is absence of evidence can be treated as proof of two conspiracies, the original and the cover up.

I am not here shouting "conspiracy!" or "treachery!" or even "corruption!". At best what you have is favoritism (aka "a bank of goodwill") that influenced decisions in the wrong way.

In any event, in my written study I tread very lightly on such nefarious possibilities, because it is not really central to my overall themes.

Just about everyone in the US had at least one loved one in the military, it was a strong deterrent to systematic corruption.

So have a Congressional investigation to root it out (or give the current governing party a fig leaf to hide behind). Oh wait, they did! And one of its major findings was that Curtiss was given contracts to produce an inferior fighter to the (Allison) Mustang. So it's not at all critical to my major point, and maybe it was just about publicity for the man heading the inquiry (paid off pretty big, didn't it?) but it is still interesting, IMO. Again, I'm not going to live or die on the "corruption!" hill, but I think it's pretty clear there was favoritism (sorry, "a bank of goodwill") involved, the result being the procurement of an inferior warplane at the expense of a better one. But if I had to discuss corruption I would mention that one of Gen. Echols's main subordinates at Wright Field, Gen. Meyers, was apparently convicted postwar of 3 counts of suborning perjury in an investigation of his own corrupt practices during the war related to AAF a/c procurement. I believe it even made Time magazine. Again, I'm not going to spend more time on this side issue, but to dismiss the possibility that there was significant corruption going on in the US with military contracts during WWII because lots of families had loved ones fighting in it is a bit of a reach. The very fact that the Truman Commission got the attention it did was that many Americans at the time assumed that not everything was on the up and up.

 

[Shortround6]

Just a few things.

, though he also adds that with a "two speed, two stage or other high performance supercharger" (emphasis added) it could "escort heavies". The foreshadowing aside, what else could he have been talking about with "other high performance supercharger" than the original subject of this thread?

Some higher officers did not have a good grasp of technical details, some did.
Some did not have a good grasp of manufacturing.
High performance supercharger may very well mean turbo supercharger.

The US navy got their hands on a Curtiss P-40F on Jume 6th 1942 and used it for evaluation/testing for at least a few weeks. Comparisons to the F4F-4 were madein a number oof tings from performance to cockpit noise, ventilation and size of the cockpit (P-40 waws cramped).
This was just a few weeks before the 1st flight of the F6F and a few weeks before the first production F4U-1 flies. This is 6 months after Goodyear is brought in as the third F4U-1 production source.

June 21st, 1942 CinCPAC sends a memo stating "......it is believed that providing P-40 planes for all Marine fighting squadrons assigned to outlying bases of high importance is imperative, if the P-40 can be modified for carrier operation. "

I have no idea of what they (He?) meant by carrier operations. it is one thing to fly lightly loaded land planes off a carrier as part of ferry operations. It is another thing entirely to get several dozen fully loaded planes off a carrier deck, perform combat missions and return to the carrier deck with an acceptable accident rate. I have no idea what even prompted this memo, The only P-40s in the Pacific area were Alison P-40s. Did they think the Allison P-40s (P-40Ks were not in Pacific at this time but were on the way) were superior in performance to the F4F-4s? Were they expecting a shortage of F4F-4s and the P-40s were the next best thing (only thing that even came close to working, P-39s on carriers was not happening)

It is also instructive to look at the P-40F evaluation. The P-40F could carry the 52 gal drop tank and while the F4F-4 was being tested with two drop tanks they don't appear to be in service at that time.
If you are really looking at any P-40 as a replacement/supplement to the F4F-4 you really have to look at not just the expected performance but at how fast you can get them in large numbers and how fast you can actually change some factories around.

is that for much of the war, and (for me at least) especially for 1942 through at least early 1943, low to medium altitude is more important because there are multiple ground campaigns going on and also very important naval actions taking place (of course, we can always pick out exceptional cases where there was high altitude flying going on, but as others have already pointed out, how significant were their impact really?).

Again, we have the historical knowledge of how things actually worked out. For the US just getting fighter planes to North Africa in most of 1942 was long, hard process until Torch.
First P-40Fs had to taken to West Africa, unloaded (flown ashore from Ranger) and flown across central African and then north to Egypt.

The 77 P-40F were loaded aboard the Ranger July 1st 1942, 1st official combat mission was Aug 31st 1942. Planes that were sent in crates took a lot longer to get into service between slow freighters and have to assemble the aircraft and test fly them before leaving the Gold Coast.
Now what happens in September/October 1942 if you had loaded the wrong type (altitude capable) planes on the Freighters in June?

The P-51A was, I believe, lighter than the Merlin P-51. In any event all sources I am familiar with, incl. the RAF relative airspeed chart I posted earlier, put the low altitude speed of the P-51A (and even the Mustang I at increased manifold pressure) significantly higher than the P-51B. If you're lighter and moving faster with a nearly identical air frame, it's hard to see how the takeoff run would be longer.

The Allison Mustangs had lower drag. North American had to splice in about 7in (?) to the thickness/depth of the fuselage to fit the larger radiator/oil cooler and intercooler.

Other drag items on the P-51B?
take a look at the Spitfire Vs and IXs. The IXs were faster at higher altitudes. Not so much at under 5,000ft. The Spitfire Vs had a lot less drag from their smaller radiators/oil coolers.

Take-off runs are not always power to weight. It is thrust to weight and here the exact propeller configuration can make a difference. Diameter, number of blades, area of the blades, air foil and even exact shape and twist. Some things make a lot more difference than others but using a slightly diameter propeller with 4 blades and not 3 and using more power can make up for a lot of weight.
P-47 got shorter take off just by changing the blades.

 

[Steamed_Banana]

The US navy got their hands on a Curtiss P-40F on Jume 6th 1942 and used it for evaluation/testing for at least a few weeks. Comparisons to the F4F-4 were madein a number oof tings from performance to cockpit noise, ventilation and size of the cockpit (P-40 waws cramped).
This was just a few weeks before the 1st flight of the F6F and a few weeks before the first production F4U-1 flies. This is 6 months after Goodyear is brought in as the third F4U-1 production source.

June 21st, 1942 CinCPAC sends a memo stating "......it is believed that providing P-40 planes for all Marine fighting squadrons assigned to outlying bases of high importance is imperative, if the P-40 can be modified for carrier operation. "

There was a brief moment of infatuation by the US Navy / Marines with the P-40, also around this time in particular the P-40F which was not in Theater yet but had made the rounds of memos. P-40s had suddenly begun to emerge by mid 1942 as the fighter that was starting to hold it's own against the Japanese fighters. The F4F was as well but the F4F-4 in particular definitely lagged in some respects, and operating in the same areas, it was clear that the Army pilots in the P-40 and P-38 had some advantages. And there is no way you were going to fly a P-38 from a ship, not to mention there weren't enough of them around.

But I think this fever broke once the F4Us started arriving and word spread about the F6F. F4U needed a lot of tinkering and tweaks but it was obvious from the get-go it had much more potential than the Army plane.

I have no idea of what they (He?) meant by carrier operations. it is one thing to fly lightly loaded land planes off a carrier as part of ferry operations. It is another thing entirely to get several dozen fully loaded planes off a carrier deck, perform combat missions and return to the carrier deck with an acceptable accident rate. I have no idea what even prompted this memo, The only P-40s in the Pacific area were Alison P-40s. Did they think the Allison P-40s (P-40Ks were not in Pacific at this time but were on the way) were superior in performance to the F4F-4s? Were they expecting a shortage of F4F-4s and the P-40s were the next best thing (only thing that even came close to working, P-39s on carriers was not happening)

I would say that yes, the P-40K or F were considerably better performing than an F4F-4. About 40-50 mph faster, better acceleration, much better dive speed, much better roll, at least as good turn performance, and depending on exact configuration P-40F in particular (or P-40K / M and N at WEP) has about twice the initial climb rate.

I suspect the carrier operations thing was more along the lines of ferrying them to the front, but for a USMC as an island / land based fighter, I think it actually does make more sense than an F4F-4 in many respects. F4F-4 has slightly better range (considerably better with two drop tanks, once those are available in enough numbers) and better altitude performance, but it loses a lot in terms of just tangling with Japanese fighters, and getting pilots back to base alive. And that was widely known already in mid-1942, definitely so by 1943.

It is also instructive to look at the P-40F evaluation. The P-40F could carry the 52 gal drop tank and while the F4F-4 was being tested with two drop tanks they don't appear to be in service at that time.
If you are really looking at any P-40 as a replacement/supplement to the F4F-4 you really have to look at not just the expected performance but at how fast you can get them in large numbers and how fast you can actually change some factories around.

The drop tanks may have indeed been a factor.

As we know, due to the details of the famous engine contract with Packard P-40F was going to be in very limited numbers regardless. But they did get some into the Pacific, in fact 44th FS was flying them from Guadalcanal itself during some very difficult times for the US Marine Corps and USAAF squadrons there, and did very well in several of those highly fraught early months of 1943. It proved very useful during that year, but by 1944 F4U, P-38, P-47 and F6F were all arriving, P-51 not far behind. By then you don't need a P-40F any more, and the Wildcat keeps it's value thanks to the FM-2 flying from escort carriers.

 

[ColFord]

The Allison Mustangs had lower drag. North American had to splice in about 7in (?) to the thickness/depth of the fuselage to fit the larger radiator/oil cooler and intercooler.

Ouch. Another case where the old Squadron/Signal books got it wrong. The fixation that if it was an early Mustang it was a P-51A that persists to this day.

The top illustrations marked as "P-51A" actually are more representative of the radiator air intake arrangement for the NA-73 Mustang I, NA-83 Mustang I and NA-91 P-51 (no suffix) Mustang / Mustang IA. It had the moveable 'alligator mouth' front intake ramp. RAF introduced a modification in March 1944 for setting the moveable intake at one of two positions depending on the season - summer or winter, which removed the need for the pilot to vary the intake settings manually.

The NA-97 A-36A Mustang introduced a fixed radiator intake mouth and the same basic design, slightly revised carried through into the NA-99 P-51A Mustang / Mustang II. This is from the NAA P-51A E&M Manual.

The radiator air scoop assembly for the P-51B and onwards was notably deeper and larger, even the front fuselage section was deeper on account of the air intake contained with the lower front cowlings below the engine for the updraught carburettor on the Packard-Merlin, which in itself was heavier than the Allison V-1710. The depth of the fuselage from the cockpit sill to the top of the wing was increased by around 3 to 4 inches (exact figure eludes me at the moment), then the significantly deeper radiator housing below the fuselage.