The RAF, just that little bit better in 1940

Vickers were committed to their geodesic construction. Hence still churning out Wellingtons to the end of the war.
That might might be overstated. The Wellington was built in three Vickers factories, Blackpool, Chester and Weybridge. In chronological order, the first Weybridge built Wellington was delivered in July 1938, the first Chester built Wellington was delivered in August 1939 and the first Blackpool built Wellington was delivered in August 1940.

However, the Chester factory also built 235 Lancasters out of 1,620 Lancasters and Lincolns that were ordered from that factory. Therefore, it might have been possible to abandon geodetic aircraft sooner had something better been available.
 
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Vickers were committed to their geodesic construction. Hence still churning out Wellingtons to the end of the war. The Warwick was a Wellington contemporary. Put 4 Pegasus on a 4 engined Warwick to replace the smaller Wellingtons. Perhaps Hercules or Merlins later on.
AIUI the Warwick built to Specification B.1/35 was intended to replace the Wellington which designed 3 years earlier to Specification B.9/32. However, that didn't happen because the RR Vulture was a failure.

It aught to be possible to design the Warwick as a 4-Merlin or 4-Hercules aircraft from the beginning by changing Specification B.1/35 in the same way that we could have had the Lancaster 18-months to 2 years earlier had Specification P.13/36 been for an aircraft powered by 4-Merlins or 4-Hercules engines.

Handley Page designed an aircraft to Specification B.1/35 and a prototype was ordered. However, it was cancelled in favour of the Halifax built to Specification P.13/36 issued a year later. Had B.1/35 been for an aircraft with four Merlins or four Hercules engines we might have had the Halifax in service a year earlier.
 
Can Napier do even that right?
Although I'm not a Barnetite I do think he was write in saying that the interwar British aircraft industry was fragmented and would have benefited from some rationalisation. That is provided the result was aviation equivalents to ICI rather than more firms to match British Leyland.

One of them would have been for Rolls Royce to take Napier over in 1931. IOTL Napier was bought by English Electric in 1942 and Rolls Royce acquired the aero engine side of the company in 1961.

I want the result to be that the Napier factory stops building the existing Napier designs by the middle of the 1930s and from then on to only build the parent company's engines. At the same time it stops the development of its own engines and the design team is broken up. The redundant engineers go to work at Derby to strengthen Rolls Royce's design department (which is the result I want) or go to work for other aero engine firms.

That aught to stop all of Napier's sleeve-valve engines happening in the first place. That is unless Rolls Royce either puts Frank Halford and his team on developing sleeve-valve engines them, which the unfortunate consequence that the Dagger and Sabre are still developed but have bird of prey names. Though the result I want is that the former Napier engineers are used to strengthen the design teams working on the OTL Rolls Royce engines, preferably the Merlin and Griffon.

The other alternative is that Rolls Royce makes Napier its diesel engine division to develop diesel aero engines from the Junkers Jumo 204 that it acquired a licence on. In that case we might have had maritime reconnaissance aircraft fitted with Napier diesel aero engines derived from the Jumo 204 during the war and the Deltic marine diesel sooner.
 
The Bolton Paul Defiant did quite well before the Germans found out that it had no forward firing guns. So have a Merlin XX cut down the number of guns in the turret, but make them more than .303 and two guns in the wings?
 
The whole thinking behind the turreted fighter concept was flawed from the start as at its core was the assumption that it would be used to attack un-escorted bombers.
As soon as a turreted fighter is working in contested airspace where it will meet single seat interceptor style fighters there can only be one winner. That fundamental constraint was ignored by the RAF and AM planners in the 1930's.
 
The whole thinking behind the turreted fighter concept was flawed from the start as at its core was the assumption that it would be used to attack un-escorted bombers.
As soon as a turreted fighter is working in contested airspace where it will meet single seat interceptor style fighters there can only be one winner. That fundamental constraint was ignored by the RAF and AM planners in the 1930's.
To be fair to the planners they did not ignore that constraint. They looked at contemporary and expected ranges of potential escort fighters and concluded that Germany was too far away to escort bombers over Britain. It was an uncontested assumption that France would not fall. That was reasonable, looked at in the period. Given the assumptions and the doctrine that the speed of fighters would limit the quantity of fire in a pass (hence as many as 8 guns) the Turret Fighter would be able to place it's fire on the target for much longer so half the firepower would have much more than twice the time. Also the target could be switched without re engaging for another pass. What they can be accused of is failing to develop a contingency tactical doctrine were they to face single seat fighters and to fit the sights and training to use the turret guns by the pilot in a fixed forward manner. When one squadron did have a local tactical doctrine to defend themselves, the circle of a squadron of Defiants could, in principle, bring up to 80 guns to bear on any attacker above or abeam them. The Defiant was a failed concept but not one without careful reasoning.
 
The whole thinking behind the turreted fighter concept was flawed from the start as at its core was the assumption that it would be used to attack un-escorted bombers.
As soon as a turreted fighter is working in contested airspace where it will meet single seat interceptor style fighters there can only be one winner. That fundamental constraint was ignored by the RAF and AM planners in the 1930's.
It was also based on the performance of severall 2-seater fighters of WWI, that did very well even in fightervsfighter combat. But, but the late 30s, air combat had changed radically...
 
Both the RE8 and the Bristol FE2 had fixed forward firing guns as well as the flexible mounts in the aft cockpit. That lesson from WW was forgotten by the Whitehall warriors in the 1930's.
 
In defence of the Boulton Paul Defiant (and Hawker Hotspur)... which I don't do very often.

When Specifications F.5/34 (which led to the Spitfire and Hurricane) and F.9/35 which produced the Defiant and Hotspur were written the job of British fighters was to shoot down unescorted bombers crossing the North Sea. Nobody expected Germany to occupy northern France half-a-decade later. At worst they would occupy the Low Countries.

However, I've seen Air Ministry files (parts of which have been posted here) from 1936 showing that 9 squadrons of Hotspurs were to be sent to France with the Air Component of the British Expeditionary Force. Meanwhile, the 7 Spitfire and 14 Hurricane squadrons planned at the time were to remain in the UK. That's what I think is bonkers. It should have been keep the Hotspurs in the UK and send 9 Hurricane squadrons to France.

That was part of Expansion Scheme F, which included 420 fighters in 30 squadrons of 14. That is 9 Hotspur, 14 Hurricane and 7 Spitfire squadrons. 389 Hotspurs were ordered from Avro in 1936 to equip the 9 squadrons and provide the approved scale of reserves. However, the order was cancelled and it was decided to put the Defiant into production instead.

Edit. I wrote that before I saw Post 186 by @yulzari. He explained it better than I did. That is...
To be fair to the planners they did not ignore that constraint. They looked at contemporary and expected ranges of potential escort fighters and concluded that Germany was too far away to escort bombers over Britain. It was an uncontested assumption that France would not fall. That was reasonable, looked at in the period.
And...
Given the assumptions and the doctrine that the speed of fighters would limit the quantity of fire in a pass (hence as many as 8 guns) the Turret Fighter would be able to place it's fire on the target for much longer so half the firepower would have much more than twice the time. Also the target could be switched without re engaging for another pass. What they can be accused of is failing to develop a contingency tactical doctrine were they to face single seat fighters and to fit the sights and training to use the turret guns by the pilot in a fixed forward manner. When one squadron did have a local tactical doctrine to defend themselves, the circle of a squadron of Defiants could, in principle, bring up to 80 guns to bear on any attacker above or abeam them. The Defiant was a failed concept but not one without careful reasoning.
 
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I am a fan of the Whirlwind but I think in OTL 1940 is way to late to make the change. The Bristol Beaufighter is available, the Mosquito is in the pipeline and is a merlin Whirlwind really worth two Spitfires or even two Hurricanes, There was not a glut of Merlin XX'a at that time so it is one or other IMVHO.
There's a more interesting option.

The Hispano-Suiza 12Y - available off the shelf at that time, and the subject of several licensing deals, including becoming the Klimov VK series which powered many Soviet designs. The numbers are fascinating.
PeregrineMerlin (mk II)Hispano 12Y
Capacity (L)212736
Power (HP)
885​
1035​
1000*​
Weight (dry) (Kg)
517​
744​
515​
Length (M)
1.87​
2.25​
1.72​
Width (M)
0.69​
0.78​
0.76​
Height (M)
1.04​
1.02​
0.94​

(12Y -51 of 1939)

So, postulate setting up a shadow factory / alternate engine supply channel - or just buying them in from the French pre-war. You have a viable Whirlwind (indeed, probably some performance improvement) with minimal rework. And the design certainly had improvement potential. Klimov produced variants with up to 1360 hp.

 
The numbers are fascinating.
No Replacement for Displacement, and the 12Y as a SOHC with two valves, and single speed, some had single stage blower, so acted like the Allison as per altitude

W.Allies missed the boat on bigger engines turning slower(2400rpm), and having lower stressed components after France threw in the towel, until the Griffon

Also, for early war 1000hp class engines
P&W R1830AllisonMerlin (mk II)Hispano 12Y
Specific Fuel Consumption0.49 lb/(hp•h )0.46 lb/(hp•h )0.50 lb/(hp•h )0.54 lb/(hp•h)

'Thirsty' radial wasn't so thirsty, it seems
 
In defence of the Boulton Paul Defiant (and Hawker Hotspur)... which I don't do very often.

When Specifications F.5/34 (which led to the Spitfire and Hurricane) and F.9/35 which produced the Defiant and Hotspur were written the job of British fighters was to shoot down unescorted bombers crossing the North Sea. Nobody expected Germany to occupy northern France half-a-decade later. At worst they would occupy the Low Countries.

However, I've seen Air Ministry files (parts of which have been posted here) from 1936 showing that 9 squadrons of Hotspurs were to be sent to France with the Air Component of the British Expeditionary Force. Meanwhile, the 7 Spitfire and 14 Hurricane squadrons planned at the time were to remain in the UK. That's what I think is bonkers. It should have been keep the Hotspurs in the UK and send 9 Hurricane squadrons to France.

That was part of Expansion Scheme F, which included 420 fighters in 30 squadrons of 14. That is 9 Hotspur, 14 Hurricane and 7 Spitfire squadrons. 389 Hotspurs were ordered from Avro in 1936 to equip the 9 squadrons and provide the approved scale of reserves. However, the order was cancelled and it was decided to put the Defiant into production instead.

Edit. I wrote that before I saw Post 186 by @yulzari. He explained it better than I did. That is...And...
I would add that just a few years later 'Schräge Musik' would prove very successful at shooting down British bombers at night and that system is not a million miles away from the Turret fighter concept
 
I would add that just a few years later 'Schräge Musik' would prove very successful at shooting down British bombers at night and that system is not a million miles away from the Turret fighter concept
But that system only worked against one specific kind of target (RAF bombers) in one specific situation (night bombing), so not really the same. Any german fighter trying it against a USAAF bomber would get a shower of belly mounted .50"...
 
But that system only worked against one specific kind of target (RAF bombers) in one specific situation (night bombing), so not really the same. Any german fighter trying it against a USAAF bomber would get a shower of belly mounted .50"...
Exactly Defiant was supposed to intercept un-escorted twin engined bombers over the UK in 1940 attacking off beam or directly underneath were they could not be engaged.

A box formation of B17s in 1944 with a chad fighter escort would make short work of a Messerschmitt Bf 110G-4 trying to do the same thing in broad daylight!
 
Exactly Defiant was supposed to intercept un-escorted twin engined bombers over the UK in 1940 attacking off beam or directly underneath were they could not be engaged.

A box formation of B17s in 1944 with a chad fighter escort would make short work of a Messerschmitt Bf 110G-4 trying to do the same thing in broad daylight!
AIUI it made a half-decent night fighter. Not as good as the Beaufighter, but a step up from the Blenheim.

Boulton Paul did propose developments of the Defiant with the Griffon and Sabre engines with (IIRC) six 20mm forward firing cannon with the turret retained or replaced by an observer. It looked formidable in the artist's impression in the Putnams Bolton Paul Aircraft book. However, it wasn't developed because the Beaufighter was coming into service and the even better night fighter version of the Mosquito was expected at the same time. That's also why the proposed developments of the Gloster Reaper with Merlin or Hercules engines weren't built.

Edit - Replied to the wrong post. Sorry!
 
I would add that just a few years later 'Schräge Musik' would prove very successful at shooting down British bombers at night and that system is not a million miles away from the Turret fighter concept.
AIUI it made a half-decent night fighter. Not as good as the Beaufighter, but a step up from the Blenheim.

Boulton Paul did propose developments of the Defiant with the Griffon and Sabre engines with (IIRC) six 20mm forward firing cannon with the turret retained or replaced by an observer. It looked formidable in the artist's impression in the Putnams Bolton Paul Aircraft book. However, it wasn't developed because the Beaufighter was coming into service and the even better night fighter version of the Mosquito was expected at the same time. That's also why the proposed developments of the Gloster Reaper with Merlin or Hercules engines weren't built.
 
That's also why the proposed developments of the Gloster Reaper with Merlin or Hercules engines weren't built.
Had the 12Y been in production in Britain instead of Rolls trying to reinvent the wheel with the Peregrine then the Gloster Reaper would have been more likely to enter service instead of the Beaufighter,
 
What was the rationale for the Peregrine? A development of the Kestrel and the Merlin a private venture for a greater capacity? They are so close at 21 and 27 litres. Was it a hope for some development crossover with work on the Vulture?
 
What was the rationale for the Peregrine? A development of the Kestrel and the Merlin a private venture for a greater capacity? They are so close at 21 and 27 litres. Was it a hope for some development crossover with work on the Vulture?
It's more a direct follow up of the kestral (21 and 22 litre).

The kestral had run the end of its development potential but the developers saw a lot of small changes they could do that would make it a better engine at a similar size.

Also they felt that the Merlin was a little large for a fighter (they didn't realise how fast speed improvement was needed at the time).
 
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