1937-45: Doubling down on the 2-engined 'day fighters'

[Admiral Beez]

Enthusiasm overcame common sense.

Someone should have told Bristol's head office when the sleeve valve idea came for funding.

 

[Geoffrey Sinclair]

As of June 1939 Britain still had 1,270,000 registered unemployed out of 19,750,000 working population, in June 1940 it was still 645,000 out of 20,676,000, there was talk of scandal the number was still so high, when it comes to late 1930's aircraft output Britain was definitely limited by trained manpower but also factory space, overall still a lot of chances to increase production but money had to be available in 1936/37/38 to allow the system to build extra capacity, things like more factories and training. Unemployment was 60,000 out of 22,285,000 in June 1943. Female working population was 5,094,000 in June 1940, 7,253,000 in June 1943.

To have the Browning 0.50 inch in production would require purchase of the patents along with the 0.303 inch version and then set up a small production base say for example bomber guns, so production could be expanded to mass production but more likely see the US help expand production to support the USAAF in Britain.

Hurricane was switched from using Merlin I to II in December 1936. "It was decided to install the "Merlin II" engine since the "Merlin I" was not being put into production. Owing to difference in the cylinder blocks, the cowling shape and fairing lines were considerably altered. Other units affected were the air intake, airscrew, engine controls, engine mounting, hand starter gear, header tank and header tank mounting. Note - There is no doubt that this engine change slowed up production contract very much more than was at first anticipated."

Nothing to do with Battle engines.

Defiant guns could fire directly forward if the crew was willing to risk propeller damage. Production officially began in September 1939 with 5 for the month, switch to mark II in August 1941 except for 5 laggard mark I delivered August 1941 to January 1942, mark II production ended in May 1942, 1 target tow in January 1942, then from May 1942 to March 1943

1939, 16 mark I
1940, 266 mark I (5 in January and again February, steady rise to 56 in July then a decline)
1941, 330 mark I, 122 mark II
1942, 1 mark I, 85 mark II, 124 TT
1943, 16 TT

No.	contract	requisition	note
87​	622849/37	176/37	L serials
202​	751807/38	176/37	1st N serials
161​	751867/38	176/37	2nd N serials
150​	B34864/39	1/E1/39	T serials
50​	B34864/39	1/E1/39	V serials
270​	B34864/39	1/E1/39	AA serials, 30 more cancelled
0​	B34864/39	1/E1/39	AV serials, 300 cancelled
140​	B34864/39	2/E1/41	DS serials, Target Tow, 10 more cancelled on 30 November 1942

Once war came the normal procedure was to add further requisitions against the current contract but that did not exactly happen for the Defiant. The Contract summary cards have lots of changes, B34864/39 had up to 800 fighter versions on order at one time. When it came to paying Boulton Paul the blocks were
87 out of 87 aircraft off 622849/37
200 out of 363 aircraft off 751867/38 (2 more used as mark II development aircraft under B28069/39)
161 out of 363 aircraft off 751867/38
No further price information

In 1940/41 Defiants seem to have been useful night fighters for their time, which was one of their design requirements, faster than Blenheims, more available than Beaufighters, two pairs of eyes instead of one in a Hurricane or Spitfire.

Battle, from Merlin I to II in April 1938, Austin production switched to Merlin III in February 1939, Fairey in March, Austin switched to trainer versions in February 1940, Austin to target tow in April, 1,039 Battle built in 1939, for 1940 233 bomber, 200 trainer, 266 target tow.

When it comes to aircraft costs the airframe is far from the full cost.

Date	Model	Airframe	total cost	%Airframe	Note
28-Feb-43​	P-39	$24,866​	$50,685​	49.06​	Costs based on final production contract
31-Jul-44​	P-39	$32,824​	$64,293​	51.05​	Costs are weighted average of all Army contracts from 1939 to date
31-Aug-44​	P-39	$26,471​	$52,784​	50.15​	Costs based on uncompleted contracts
28-Feb-43​	P-40	$26,709​	$44,676​	59.78​	Costs based on final production contract
31-Jul-44​	P-40	$29,515​	$55,968​	52.74​	Costs are weighted average of all Army contracts from 1939 to date
31-Aug-44​	P-40	$26,352​	$47,583​	55.38​	Costs based on uncompleted contracts
28-Feb-43​	P-43	$54,907​	$82,923​	66.21​	Costs based on final production contract
28-Feb-43​	P-47	$47,796​	$87,852​	54.41​	Costs based on weighted average of uncompleted contracts
31-Jul-44​	P-47	$61,699​	$105,508​	58.48​	Costs are weighted average of all Army contracts from 1939 to date
31-Aug-44​	P-47	$55,783​	$98,406​	56.69​	Costs based on uncompleted contracts
30-Nov-44​	P-47	$49,420​	$89,296​	55.34​	Costs based on uncompleted contracts
28-Feb-43​	P-51	$23,583​	$52,215​	45.17​	Merlin Versions. Costs based on weighted average of uncompleted contracts
31-Jul-44​	P-51	$28,984​	$58,844​	49.26​	Costs are weighted average of all Army contracts from 1939 to date
31-Aug-44​	P-51	$27,889​	$57,415​	48.57​	Costs based on uncompleted contracts
30-Nov-44​	P-51	$25,795​	$53,481​	48.23​	Costs based on uncompleted contracts

The P-43 shows the cost of short production runs. Tooling is an important factor as Ford showed at Willow Run but production runs were usually too small to allow extensive tooling. The B-26 engines cost about 50% more than the B-25 ones as another non airframe choice. Profit margins were reduced in wartime. Early Spitfire costs were increased by the need for expansion, the size of the initial order and the use of new construction techniques, payment to Supermarine dropped to 4,425 pounds per Spitfire in 1941.

Just calculating the costs of an aircraft has uncertainties, comparing different countries is even harder, what is exactly being included, especially sub contractors, company overheads?, while different countries had different wages, and the German aviation industry had a lot of SS supplied "workers". Are calculations done for just the airframe or ready to fly? When in the production run? The US dd a lot of research and for example Eastern making FM-2, aircraft 20 used 15 manpower hours per pound of aircraft weight, aircraft 600 used 3 hours, aircraft 1,600 around 0.9 hours. P-51H at Inglewood, aircraft 10 used 4 hours, aircraft 450 used 0.9 hours. "On Site and direct Off Site man hours" For production speed what is the usual elapsed time between the first appearance on the production line and roll out?

Year	Bf109	Spitfire
1939​	1,540​	435​
1940​	1,868​	1,253​
1941​	2,628​	2,519​
1942​	2,664​	4,134​
1943​	6,418​	4,276​
1944​	14,212​	4,918​

the USSBS notes 7 different Bf109 production lines, including the one in Hungary, the three German production lines output 1943/44 Regensburg 2,164/6,329, Erla 2,015/4,472, WNF 2,200/3,141.

As we know the answers, start with
Beaufort proposal in 1936, Beaufighter end 1938, replace the fort with fighter in 1936, thereby cancelling Taurus, Beaufighter comes with the ability to fit wing stations for bombs or fuel tanks, under fuselage ability for torpedo, mine, bomb, fuel. Hercules production was about half Taurus mid 1939 to mid 1940. There were 251 Beaufort now fighter built to end June 1940, to be distributed 2 squadrons Coastal Command rest Fighter. Blenheims not converted to fighters available to replace Battles but really in performance terms the Blenheim was a longer range Battle, but that releases Battles into the training system. It should be noted the replacement of Battles with Blenheims had already begun, from 10 to 8 Battle squadrons in France between 1939 and May 1940, more were planned. By end 1940, 385 Beaufort and 112 Beaufighter built.

Westland cancel Whirlwind in 1938 and given task of creating and building Seafire, cancel Peregrine

Boulton Paul given task of helping design and building Merlin powered Barracuda instead of Defiant, no need for Albacore, or Taurus, or Exe engine.

Vulture engine cancelled, thereby allowing another 200 Lancasters instead of Manchesters. And simplifying Hawker's Typhoon design issues, 4x20mm mandated, no argument, also thin wings, yes they build the Tempest from the start, then with resources freed from the Taurus the Centaurus appears in 1943 to end Sabre production.

Speed up Castle Bromwich opening.

GR Stirling only (better performance and cheaper than Sunderland) or bust.

Botha and Fulmar become Barracuda.

Henley gone.

Austin only built 15 Hurricanes February to August 1941, though they were starting up Stirling production at the time, Battle to Hurricane at the same time as Gloster starts perhaps.

Albemarle, use strategic materials, transport, rear fuselage loading ramp, medium range transport with self sealing fuel tanks, a definite improvement over the C-47 on many missions.

Up Wellington production earlier to enable phase out of Whitley for Albemarle production with the Whitley VII GR version instead of the V bomber version built from end 1939, to be replaced by Wellington GR.

More Lancaster lines than Halifax, including one for York, fuselage as per new Albemarle, again a major improvement in many ways for long range transport. Britain staying in the wartime transport aircraft business helps the industry cope better post war.

Indulge the de Havilland days of yore dreams about wooden aircraft when first proposed in 1938, not 1939.

All the above to be well advanced in mid 1940 thereby evading the production freeze orders.

All this apart from dumping a pile of money on top of Whittle in the mid 1930's plus secondment of various engineers from British engine etc. producers to help build prototypes.

Hindsight is quite easy really.

 

[Howard Gibson]

I am forever baffled by the idea that twin engine fighter (with a pair of under 1000hp engines)was too expensive or used too much fuel but a single engine fighter of 2000hp was just the thing that was wanted

How much more expensive was a Rolls Royce Griffon than a Rolls Royce Merlin? You require the same number of parts because they are both V12s. The Griffon uses a bit more material, and requires a bit more machining. Double the power requires a more efficient supercharger presumably a bit bigger than the one mounted on the later Merlins, and 130 octane fuel. The 2050HP Griffon actually was technologically equivalent to a Merlin 63 that put out 1710HP.

I like to think that the P-38 Lightnings and the P-47 Thunderbolts show us how Clarence Kelly Johnson and Alexander Kartveli got 2000HP out of the USAAF''s favoured Allison V-1710. The Bristol Beaufighter was a heavy fighter constructed from Bristol Beaufort parts, and brought into service as quickly as possible. A fighter built from a ground up around a pair of Bristol Hercules engines would be interesting, but if you think about it, the big Beaufighter performed some useful missions.

The twin-engined P-38 and de Havilland Hornets had relatively long ranges compared to most single-engined fighters. A really small twin-engined fighter should be able to out climb a single engined fighter, and carry heavier armament. Prior to the war, the heavy fighters all were perceived as multi-place.

 

[Howard Gibson]

Someone should have told Bristol's head office when the sleeve valve idea came for funding.

Napier had problems with sleeve valves, eventually solved by Bristol. Bristol solved their problems in the thirties. As far as I know the Pegasuses and Hercules engines were reliable workhorses in WWII. It would have been nice to have gotten the Centaurus engines into service, but I don't think anybody was pushing for them. It might have helped to light fires under Napier's butts. Apparently, three-speed two-stage superchargers were more important than making the thing run for more than twenty four hours.

A point a bit off topic is a single Bristol Hercules powered fighter. It would have to be a small aircraft, as the Hercules was small for a WWII radial fighter engine. The Nakajima Homare was smaller though.

 

[Geoffrey Sinclair]

In the what if, amend Fairey from Barracuda to Beaufighter, replacing 159 Fulmar built to end 1940 with half that of Beaufighters instead of its production at Fairey beginning in February 1941.

Centaurus IV entered production October 1942, ended July 1944, 732 built, mark VII from August 1943 to January 1945, 997 built, mark V and XI entered production October 1944, 668 and 410 built by end 1945, mark IX entered production in February 1945, 143 built to end 1945.

1941 to 1945 there were 2,967 Centaurus and 4,939 Sabre built. Centaurus by year 1942 to 1945, 8, 497, 1,401, 1,061

Posted before, AVIA 15/2389 covers the sale of RAF aircraft to France in 1945/6, including serial numbers, one point is the prices (costs) quoted, in pounds, completed aircraft,
37-40,000 Lancaster I
40,000 Halifax
15,000 Mosquito VI
16,000 Mosquito 30
16,000 Mosquito PR XVI
16,300 Mosquito PR.34
10,000 Spitfire IX
9,700 Spitfire XIV
13,650 Typhoon
26,000 Wellington XIII
25,000 Wellington XIV
55-65,000 Sunderland III

Spare engine prices,
1,530 Merlin 22
1,460 Merlin 24
3,830 Hercules 100
1,480 Merlin 25
1,840 Merlin 76
1,840 Merlin 67, 72 etc.
1,900 Merlin 114
1,800 Merlin
2,300 Griffon
5,550 Sabre II
3,180 Hercules XVII
1,596 Pegasus XVIII

 

[Admiral Beez]

A point a bit off topic is a single Bristol Hercules powered fighter. It would have to be a small aircraft, as the Hercules was small for a WWII radial fighter engine.

A twin-engined, single-seat fighter powered by the Hercules would be interesting. Sort of a mini Beaufighter or Tairov Ta-3.

 

[Reluctant Poster]

There maybe something to be said for the stopping the Defiant production.

The Battle production gets a lot iffier. It is not quite a zero sum game.
Battle production started in late 1936/very early 1937. First operational squadron (No 63) got their first planes in May 1937.
Early Battle production used Merlin Is, Prototypes had used a Merlin C and a Merlin G.
There were a lot of problems with the Merlin I and after 136 planes had been built they switched production to the Merlin II.
This did affect Hurricane production but in the end the Hurricanes got the better engines.

There is also the problem that Hurricanes and Spitfires could not do the job the Battle was supposed to do. In Sept 1939 15 bomber squadrons were equipped with Battles.
Yes the Battle was not a good bomber in Sept 1939 but if you don't build them then you have 15 bomber squadrons flying around with Hawker Hart biplanes (or slightly newer versions)
using overhauled engines. Maybe Vickers could build a few more Wellesley bombers? Or maybe Fairey could have figured out how to stick a Pegasus in the nose of the Battle instead of the Merlin for a truly slow bomber.

Battle bomber operations in France make for depressing reading, but a lot of that has to do with poor doctrine, tactics and training (they were not training enough for the job they were called upon to do). But 10 Hurricane squadrons in April/May of 1940 were not going to slow down the German army much better than the Battle squadrons. Attacking the Bridges with .303 guns wasn't going to work.

I would argue that the Battle should never have been ordered in the first place. It was in part a product of wishful thinking, being originally designed to the weight limit for bombers of 3 metric tonnes proposed at the1932 Geneva Disarmament Conference.
Colin Sinnott's excellent book "The Royal Airforce and Aircraft Design 1923-1939" in the chapter "Bombers to Attack France" gives an in depth accounting of the debates on the merits of single vs twin engine designs. A lot of thinking seems to have been skewed by the success of the Hawker Hart, as well as the need for an easy to transport aircraft to protect the Empire. One of the problems common to most single engine bombers of that time was the perceived need for a three man crew resulting in a significant size over the two man Hart.
Incidentally Dowding thought the single engine bomber should have the proposed Roll Royce Griffon to give it better performance.

There were doubts about the effectiveness of the what became the Battle even before the design had begun.
Specification P.27/32 was issued in April 1933. In July 1933 Ludlow -Hewett (the new DCAS) wrote:
"This specification will produce an aircraft which will certainly not fulfil the need for a light high performance day bomber. It is questionable whether it will meet any particular requirement."

 

[tomo pauk]

How much more expensive was a Rolls Royce Griffon than a Rolls Royce Merlin? You require the same number of parts because they are both V12s. The Griffon uses a bit more material, and requires a bit more machining. Double the power requires a more efficient supercharger presumably a bit bigger than the one mounted on the later Merlins, and 130 octane fuel. The 2050HP Griffon actually was technologically equivalent to a Merlin 63 that put out 1710HP

Fellow member was comparing the Merlin of the day with the 24 cyl engines of the day (+ Centaurus?)

I like to think that the P-38 Lightnings and the P-47 Thunderbolts show us how Clarence Kelly Johnson and Alexander Kartveli got 2000HP out of the USAAF''s favoured Allison V-1710. The Bristol Beaufighter was a heavy fighter constructed from Bristol Beaufort parts, and brought into service as quickly as possible. A fighter built from a ground up around a pair of Bristol Hercules engines would be interesting, but if you think about it, the big Beaufighter performed some useful missions.

A more 'fighterish' fighter powered by two Hercules engines would've certainly been a very interesting thing IMO. Talk ~350 sq ft wing etc to the ratio, and a couple of thousands of lb lighter than the Beau.
If/when needed, arm it with rockets, a torpedo or two, make a night fighter out of it etc.

 

[tomo pauk]

The twin-engined P-38 and de Havilland Hornets had relatively long ranges compared to most single-engined fighters. A really small twin-engined fighter should be able to out climb a single engined fighter, and carry heavier armament. Prior to the war, the heavy fighters all were perceived as multi-place.

P-38 was conceived as an 1-seater, so was the Whirly and the Gloster's twin. Same for the Fw 187.
From the RAF's point of view, an over-performer with the heavy weapons' battery is right up their alley past 1935.

 

[Admiral Beez]

A twin engined fighter, if well designed to eschew anything but necessary weight gain and extra crewmen should be faster than a single engined fighter. For example, is there any fighter powered by a single Allison V-1710 that's faster than a P-38 powered by two? The only twin engined, single-seat fighter powered by the Merlin is the post-war DH Hornet. If we made the DH Hornet in 1939 using the early Merlin, can we outpace 1939's Spitfire or Hurricane? Otherwise I don't see the point. As the P-51 shows, if you want longer range, you needn't add an engine.

 

[Howard Gibson]

A twin-engined, single-seat fighter powered by the Hercules would be interesting. Sort of a mini Beaufighter or Tairov Ta-3.

I agree that it would have been cool. The problem is that the Beaufighter was easy to develop, and it turned out to be very useful. The guy in the rear could navigate, operate radios and radar, and who knows what else.

It appears that development of the de Havilland Hornet started in 1942. This would have been an excellent time to investigate Hercules engines, but they were into Merlins.

 

[Reluctant Poster]

I like to think that the P-38 Lightnings and the P-47 Thunderbolts show us how Clarence Kelly Johnson and Alexander Kartveli got 2000HP out of the USAAF''s favoured Allison V-1710. The Bristol Beaufighter was a heavy fighter constructed from Bristol Beaufort parts, and brought into service as quickly as possible. A fighter built from a ground up around a pair of Bristol Hercules engines would be interesting, but if you think about it, the big Beaufighter performed some useful missions.

Johnson and Kartveli didn't have any input into the design of the V-1710, in fact Kartveli didn't use the V-1710 in his aircraft. The 2,000 HP V-1710G series were a post war development that was never installed in a P-38.
The USAAF actually preferred the V-1650. The V-1710 was the only major US engine that that saw a reduction in production in 1944 when all the others showed increases. The V-1710 was cancelled shortly after VE day while the V-1650 remained in production until after VJ day

 

[Reluctant Poster]

A twin engined fighter, if well designed to eschew anything but necessary weight gain and extra crewmen should be faster than a single engined fighter. For example, is there any fighter powered by a single Allison V-1710 that's faster than a P-38 powered by two? The only twin engined, single-seat fighter powered by the Merlin is the post-war DH Hornet. If we made the DH Hornet in 1939 using the early Merlin, can we outpace 1939's Spitfire or Hurricane? Otherwise I don't see the point. As the P-51 shows, if you want longer range, you needn't add an engine.

You are comparing apples to oranges. Two stage supercharging vs single stage. A P-51J, if it ever worked properly, would blow the doors off any P-38.

 

[Reluctant Poster]

I am forever baffled by the idea that twin engine fighter (with a pair of under 1000hp engines)was too expensive or used too much fuel but a single engine fighter of 2000hp was just the thing that was wanted

Why use 2 engines when 1 can do the job? One propeller to purchase and maintain. This can be extended to all the auxiliary systems such as fuel. Double the maintenance. Less pilot training, very important when your air force is expanding at a breakneck pace. The number of pilots qualified to teach how to fly a high performance twin in the 1930s was tiny. A smaller, more agile aircraft, rate of roll of twins is slower.

 

[tomo pauk]

Why use 2 engines when 1 can do the job?

It was often a thing of mass production, availability & reliability of two smaller engines, vs. dubious availability of the big engine that is not debugged and it exists in ones and twos.

 

[Howard Gibson]

A twin engined fighter, if well designed to eschew anything but necessary weight gain and extra crewmen should be faster than a single engined fighter. For example, is there any fighter powered by a single Allison V-1710 that's faster than a P-38 powered by two? The only twin engined, single-seat fighter powered by the Merlin is the post-war DH Hornet. If we made the DH Hornet in 1939 using the early Merlin, can we outpace 1939's Spitfire or Hurricane? Otherwise I don't see the point. As the P-51 shows, if you want longer range, you needn't add an engine.

The DH Hornet used laminar flow wings, and Merlin engines modified for low frontal area, and it was expected to systematically use 150 octane fuel. Figure half the power, and significantly more drag in 1939. Power is a function of velocity cubed...

octave:1> 485/2000^(1/3)*1000^(1/3)
ans = 384.94
octave:2>

This calculation accounts for power only. The 1939 Hornet would not be as aerodynamic. The real Hornet was conceived as a long range escort fighter. In 1939, it was obvious that bombers did not need escort, so this would have been seen as less critical.

The P-38 and the Whirlwind were conceived as single-seat fighters. Most twin engined fighters from the late thirties were perceived as heavy fighters with at least one extra crew. The heavy fighters were not capable of dogfighting, which made them useless for air superiority, and for intercepting escorted bombers. They were effective at nightfighting, with the second crewman operating the radar, and they made effective fighter-bombers.

 

[Admiral Beez]

I agree that it would have been cool. The problem is that the Beaufighter was easy to develop, and it turned out to be very useful. The guy in the rear could navigate, operate radios and radar, and who knows what else.

Oh yes, to me a fast, multi-seat twin-engine strike aircraft like the Beaufighter and Mosquito makes far more sense than a twin engined fighter. Unless you're seeking an interceptor to face unescorted level bombers, if you can't mix it up with the opponent's single engined fighters, you're doing it wrong.

 

[tomo pauk]

The heavy fighters were not capable of dogfighting, which made them useless for air superiority,

We can recall that Bf 110 have had a positive exchange (kills/loses) during the BoB. Despite being big and heavy, bigger and heavier than needed.

 

[Howard Gibson]

We can recall that Bf 110 have had a positive exchange (kills/loses) during the BoB. Despite being big and heavy, bigger and heavier than needed.

The Germans claimed something like 3,600 of the 950 aircraft the British lost during the Battle of Britain.

 

[tomo pauk]

The Germans claimed something like 3,600 of the 950 aircraft the British lost during the Battle of Britain.

I'm talking about what can be read in the most recent publications, not just dividing the claims with losses.