WI/AHC: Improved Manchester and no Lancaster?

[NOMISYRRUC]

That's not counting the prospect of more Griffons making de-rated Merlins more-readily available for tanks, nor, indeed, de-rated Griffons turning up there...

That doesn't follow. The factories that were building Merlins IOTL will be too busy building Griffons ITTL.

If you want a better tank engine, "Don't take Liberties," by having HMG pay Rolls Royce to build a factory to make a Merlin-based tank engine instead of paying the Nuffield Organisation to build a factory to build Liberty tank engines.

A Merlin based tank engine can be developed in time to be built instead of the Liberty. Rolls Royce will have the design capacity to to it if it's concentrating on the Merlin and Griffon instead of the "Peregrine and Vulture interlude". If that's unacceptable on timing grounds have this RR factory build a tank engine based on the Buzzard or Kestrel instead of the Liberty and then re-tool to build the Meteor.

 

[NOMISYRRUC]

Big 2-engined bombers were being replaced by 4-engined bombers for good reasons.

That has no relevance to what I wrote.

 

[tomo pauk]

That has no relevance to what I wrote.

You are right. That comment was supposed to end up in the ALT Warwick thread.

 

[phx1138]

I case you've not worked it out yet, one of the "flutter of butterflies" is a Griffon-Warwick replacing the Wellington on the production lines at Blackpool, Chester and Weybridge at the end of 1940/beginning of 1941. IOTL the failure to find an suitable engine for the Warwick was only reason why the Wellington was built for as long as it was .

I honestly hadn't even thought of it. Thx. (Turn over the Wimpys to Coastal Command in Newfoundland? {Stop me when you're sick of hearing that. })

That doesn't follow. The factories that were building Merlins IOTL will be too busy building Griffons ITTL.

Duh... Give me a smack.

If you want a better tank engine, "Don't take Liberties," by having HMG pay Rolls Royce to build a factory to make a Merlin-based tank engines instead of paying the Nuffield Organisation to build a factory to build Liberty tank engines.

A Merlin based tank engine can be developed in time to be built instead of the Liberty. Rolls Royce will have the design capacity to to it if it's concentrating on the Merlin and Griffon instead of the "Peregrine and Vulture interlude". If that's unacceptable in timing grounds have this RR factory build a tank engine based on the Buzzard or Kestrel instead of the Liberty and then re-tool to build the Meteor.

Given no Vulture, I would suggest no Buzzard, Kestrel, or Meteor--unless it amounts to a detuned Griffon (per above), & honestly, if I've got a factory capable of building Griffons, I damn well want them for Manchesters, Griffon-Warwicks, Griffon Spits, & Griffon *Mustangs. Building a new factory? Tool up for something like Ford's GAA V12, or a Hercules DFXE, or something.

 

[NOMISYRRUC]

I honestly hadn't even thought of it. Thx. (Turn over the Wimpys to Coastal Command in Newfoundland? {Stop me when you're sick of hearing that. })

You're "double counting" again. There won't be any surplus Wimpys because the three factories that were building them IOTL (Vickers, Blackpool, Chester and Weybridge) will be making Warwicks from the turn of 1940/41.

Production might begin as early as the turn of 1939/40 because the Warwick was started a year before the Halifax, Stirling, Supermarine B.12/36 and whatever the Avro P.13/36 ends up being called ITTL.

10,152 of the 11,461 Wellingtons built IOTL (including the prototype) were completed after 1st January 1941 and 1,001 of them were completed in 1940. Wellington production could be as low as the 308 production aircraft completed in 1938 and 1939 plus the prototype.

 

[phx1138]

You're "double counting" again. There won't be any surplus Wimpys

I should just shut up.

Production might begin as early as the turn of 1939/40 because the Warwick was started a year before the Halifax, Stirling, Supermarine B.12/36 and whatever the Avro P.13/36 ends up being called ITTL.

10,152 of the 11,461 Wellingtons built IOTL (including the prototype) were completed after 1st January 1941 and 1,001 of them were completed in 1940. Wellington production could be as low as the 308 production aircraft completed in 1938 and 1939 plus the prototype.

You're entirely right.

However, I see 308 Wimpys...& that's 308 more than were present OTL. So, as they're replaced by Griffon Warwicks (& I presume they are)... Or is replacement entirely for losses, & those 308 have to be expended? In that event, I'm wrong again... (How about, "Advice to High Wycombe: don't bomb sub pens, it's not productive"? {Yeah, getting a bit OT... })

 

[Bougnas]

That doesn't follow. The factories that were building Merlins IOTL will be too busy building Griffons ITTL.

If you want a better tank engine, "Don't take Liberties," by having HMG pay Rolls Royce to build a factory to make a Merlin-based tank engines instead of paying the Nuffield Organisation to build a factory to build Liberty tank engines.

A Merlin based tank engine can be developed in time to be built instead of the Liberty. Rolls Royce will have the design capacity to to it if it's concentrating on the Merlin and Griffon instead of the "Peregrine and Vulture interlude". If that's unacceptable on timing grounds have this RR factory build a tank engine based on the Buzzard or Kestrel instead of the Liberty and then re-tool to build the Meteor.

Britain was supposedly working on a tank Griffon, but that was late in the war. That would be one hell of a powerful engine for transmissions to handle too.

 

[NOMISYRRUC]

Britain was supposedly working on a tank Griffon, but that was late in the war. That would be one hell of a powerful engine for transmissions to handle too.

Was it intended for the A45 tank that evolved into the FV200 family? Would it have been too big for the Centurion?

 

[Bougnas]

Was it intended for the A45 tank that evolved into the FV200 family? Would it have been too big for the Centurion?

The Griffon was substantially shorter than the Merlin, a tad narrower but some 6" higher, so it should fit but with a more pronounced bump at the back unless something above could be moved somewhere else, so in theory it should fit in a tank version. However the Griffon was purpose-designed with a supercharger in mind so I don't know if it could be easily converted in a naturally aspirated engine (should be possible IMO, but I'm not a specialist).

The Griffon had a more efficient layout which allowed it to increase its displacement by 10L without making the engine larger, so in theory would have been much more powerful. I calculated over 900hp without a supercharger at least, which is consistent with such a large displacement engine at the time, although considering it is fuel-injected maybe the difference between the fuel injected Meteor and a Meteorized-Griffon wouldn't have been high.

There are rumors that a Centurion was tested with a supercharged Meteor doing 900-1000hp. In any case cooling would have to be improved but considering the relative inefficiency of the Centurion's components it should have been possible to get a more powerful engine.

Unfortunately, development of the tank Griffon was supposedly cancelled and the FV 201, 221 and Conqueror went with a fuel-injected Meteor with 810-850hp, while eventually focusing on smaller but also less powerful engines, usually of the diesel type. This is more logical for a lighter vehicle and the aircraft engine roots of the Griffon and Meteor meant they were not fully satisfactory in tanks, but a fuel-injected, possibly supercharged Griffon (and even more insane, a dieselised version of it, a diesel Meteor was considered after all) would have been a sight to see in a late 50's British heavy tank.

 

[phx1138]

The Griffon was substantially shorter than the Merlin, a tad narrower but some 6" higher, so it should fit but with a more pronounced bump at the back unless something above could be moved somewhere else, so in theory it should fit in a tank version. However the Griffon was purpose-designed with a supercharger in mind so I don't know if it could be easily converted in a naturally aspirated engine (should be possible IMO, but I'm not a specialist).

Shouldn't be a problem. The issues for supercharging are about making parts strong enough to withstand the greater pressures & heat generated. Compression ratio is also a factor (lower for a blown engine), but that's easy enough to fix.

The big problems I see relate to strength of parts. Aircraft engines demand very light weight; tanks, not so much. That being so, very lightweight parts, like connecting rods, aren't essential in tanks: stronger (thus heavier) ones are, & that does absorb some power. Given the *Griffindore will be derated from peak aircraft power, that shouldn't be a hardship.

Heat rejection needs addressing, so the radiators might have to be bigger compared to the Meteor.

Let me say, a dieselized version would have been epic.

 

[Dupplin Muir]

So long as they can keep the tail plane from falling off in a dive.

The Typhoon's woes have been seriously overstated. About 28 were lost to the tail-plane breaking off, whereas a couple of hundred P51's crashed when a wing broke off - a problem that was never solved. Initially it was believed to be due to the rearming panels opening in flight, but the losses continued even after modifications were made.

 

[Bougnas]

Let me say, a dieselized version would have been epic.

The Canadians were apparently working on a dieselised version of the Ford GAA V8, and the Americans had plenty of tank radials that were diesels from the start or were converted to diesels on an experimental or production basis, be it the RD-1820 or the R-975 or the Guibersons. Generally everyone agreed that as long as you could restrict the horsepower loss going to diesel was better, especially for radials that have notoriously poor torque characteristics. However with the parent radials and existing diesel engines being prioritised by Navies and Air Forces, supply was too limited to even think about fully converting to diesel (the fuel supply itself can be an issue but is generally more flexible than engine production itself).

 

[Peg Leg Pom]

Concentration on the Griffon Engine rather than the Vulture and Peregrine has a large impact on the Fleet Air Arms Fulmar. A Fulmar able to do 290 - 300 mph is very different beast to the actual aircraft doing around 260 in 1940.

 

[phx1138]

The Canadians were apparently working on a dieselised version of the Ford GAA V8, and the Americans had plenty of tank radials that were diesels from the start or were converted to diesels on an experimental or production basis, be it the RD-1820 or the R-975 or the Guibersons. Generally everyone agreed that as long as you could restrict the horsepower loss going to diesel was better, especially for radials that have notoriously poor torque characteristics. However with the parent radials and existing diesel engines being prioritised by Navies and Air Forces, supply was too limited to even think about fully converting to diesel (the fuel supply itself can be an issue but is generally more flexible than engine production itself).

I won't say it would be practical in the circumstances, let alone necessary, but it would be cool.

 

[NOMISYRRUC]

You're entirely right.

However, I see 308 Wimpys...& that's 308 more than were present OTL. So, as they're replaced by Griffon Warwicks (& I presume they are)... Or is replacement entirely for losses, & those 308 have to be expended? In that event, I'm wrong again... (How about, "Advice to High Wycombe: don't bomb sub pens, it's not productive"? {Yeah, getting a bit OT... })

If you want better maritime patrol aircraft for the RCAF squadrons in Newfoundland in the first half of the war there are easier ways of doing it.

Option 1 - Build Short Sunderlands in Canada

IOTL the RCAF ordered a total of 40 Supermarine Stranraers from Canadian Vickers in four contracts. According to the Putnam's Supermarine Aircraft since 1914 the Canadian-built Stranraers had 960hp Pegasus X or 1,010hp Pegasus XXII engines.

The 3 Stranraers were ordered in November 1936. According to Canadian Military Aircraft Serials (C.M.A.S.) (http://www.rwrwalker.ca/) the first aircraft (RCAF Serial 907 and constructor's number CV.184) was launched on 19th October 1938 and made its first flight on 21st October 1938. The Putnam's book says it was delivered on 9th November 1938. According C.A.M.S. the second aircraft was delivered on 30th November 1938 and the third wasn't delivered until 11th May 1939.

Judging by the taken on charge dates and constructors numbers on the C.M.A.S. website the next batches were for 4 and 3 aircraft respectively. The 4 aircraft in Batch 3 were taken on strength between 30th May 1939 and 5th August 1939. The 3 aircraft in Batch 4 were taken on strength on 31st August 1939, 27th September 1939 and 12th November 1939. That meant a total of 8 aircraft had been delivered before war was declared.

Christopher Shores in The History of the Royal Canadian Air Force says that the RCAF had 8 Stranraers on charge in September 1939. They equipped Nos. 4 and 5 (General Reconnaissance) Squadrons, RCAF. No. 5 Squadron was part of Western Air Command and No. 5 Squadron was part of Eastern Air Command.

My guess is that the 30 remaining aircraft were all part of the fourth contract. According to Putnam's Canadian Aircraft since 1909 the difficulty in getting material from UK slowed production in 1940. According to C.MA.S. the last 30 Stranraers were taken on strength by the RCAF as follows:

• 3 between 23rd October 1940 and 28th November 1940. (Putnam's Canadian Aircraft says 2 were delivered in the fourth quarter of 1940.)
• 3 between 6th February 1941 and 19th March 1941.
• 3 between 27th May 1941 and 26th June 1941.
• 9 between 4th July 1941 and 16th August 1941. (Putnam's Canadian Aircraft says 2 were delivered in third quarter of 1941.)
• 12 between 7th October 1941 and 17th November 1941. (Putnam's Supermarine Aircraft says the last Canadian-built Stranraer was delivered on 26th November 1941).

Meanwhile the British Air Ministry ordered the first 11 Short Sunderlands in March 1936. Therefore, I think the Canadian Department of National Defence could have ordered 3 Sunderlands from Canadian Vickers in November 1936. The only problem is that first British order was an "off the drawing board" purchase because the prototype hadn't flown yet and wouldn't until 16th October 1937. The first Short-built production Sunderland flew on 21st April 1938 and the type entered RAF service in June 1938.

Therefore, Canadian Vickers probably delivered its first Sunderland a few months later than the first Stranraer, but I think it would have caught up with the OTL schedule by the outbreak of World War II. The first 10 aircraft would be built with Pegasus XX engines producing 1,010hp like the early British built Sunderlands, but difficulties in obtaining these engines would result in the last 30 would have P&W Twin Wasps producing 1,200hp which had the side-effect of extending their endurance.

However, I think we can do a lot better than that...

According to the Putnam's Canadian Aircraft book the Catalina was selected by the RCAF in December 1939, but negotiations did not start until the spring of 1940 and 731 were eventually built by Boeing Canada and Canadian Vickers as follows:

Air Britain's The British Air Commission and Lend-Lease says that 307 of the Catalinas were built on British account and 424 were built on Canadian account.

According to C.M.A.S. the RCAF received 55 Boeing Canada built aircraft that were taken on charge between 15th October 1942 and 15th July 1943. It also received 139 Canadian Vickers built aircraft that were taken on charge between 5th April 1943 and 3rd July 1944. The Putnam's on US Navy Aircraft says that the other 230 aircraft built by Canadian Vickers went to the USAAF as the OA-10A and the other 307 aircraft built by Boeing Canada went to the RAF, RAAF and RNZAF.

Meanwhile, the RAF had purchased a single Consolidated Model 28-5 to Contract 988730/39 that was delivered to the Marine Aircraft Experimental Establishment (MAEE) at Felixstowe in July 1939 with the British military serial P9630. The British Purchasing Commission ordered 30 Catalinas when war broke out and the total ordered before Lend-Lease was 174 aircraft in 5 contracts, which included 18 ordered for Australia, 50 for Canada and 40 for France. The first Catalina arrived in Australian on 2nd February 1941. The RAF received their first Catalina in March 1941. The RCAF received its first Catalina on 11th December 1941. According to the Air Britain book the RAF also received 275 Consolidated-built Catalinas via Lend-Lease along with 10 Consolidate Coronado and 5 Martin Maryland flying boats.

Quote from Air Britain's The British Air Commission and Lend-Lease

...the question of Canadian materiel support in war was discussed at the Imperial Conference of May 1937. However, due to a number of circumstances, progress prior to the outbreak of war was slow, primarily related to cost variation and the uncertainties of funding by the UK Government. Canadian industry remained interested, but in the event only one Canadian company (the National Steel Car Corporation) received an order, other than for aircraft, prior to the imminent outbreak of war (50,000 anti-aircraft gun shells).

It continued...

The Air Ministry, having kept a "watchful eye" on Canadian production of some "fifty-two" airframes of three types in British service for the RCAF (the Shark, Stranraer and Lysander II), and after protracted discussions/negotiations by "follow-up" British Air Missions to Canada (May-August 1938) led by Sir Samuel Hardman Lever, the Air Ministry placed direct contracts in November 1938, with Canadian Associated Aircraft Ltd. and the Canadian Car and Foundry Co. Ltd., for eighty Hapden and forty Hurricane aircraft respectively, together with a promised initial manufacture of 100 Stirling bombers. Sir Samuel Hardman Lever also led similar Air Missions to Australia and New Zealand.

However, ITTL the Canadians ordered Sunderlands in November 1936 instead of Stranraers. This led to the Air Ministry cancelling the Saunders Roe A.33 and Lerwick in December 1936.

The A.33 was the Company's rival to the Sunderland that had been designed to Specification R.2/33. The prototype flew on 14th October 1937 but was written off on 25th October 1937. This led to the cancellation of a production contract for 11 aircraft that had been ordered in March 1936.

The Lerwick was being designed to meet Specification R.1/36. The Air Ministry reserved serials for 22 aircraft in December 1936. The initial order 10 aircraft (including 3 to be used as prototypes) was increased to 21 aircraft in June 1937. The first aircraft was launched at the end of October 1938 and made its first flight early the next month. The 21 aircraft were delivered between March 1939 and June 1941.

Therefore, ITTL the Air Ministry places a direct contract for 10 Sunderlands from Canadian Vickers in December 1936 and this order was increased to 21 aircraft in June 1937. The Air Ministry would still buy the Consolidated Model 28-5 for evaluation, but the Air Ministry would order 30 Sunderlands from Canadian Vickers at the outbreak of World War II instead of the OTL contract for 30 Catalinas. These would be the first of 174 Sunderlands ordered from Canadian Vickers and Boeing Canada instead of the 174 Consolidated Catalinas ordered to British contracts. These would be followed by 290 Sunderlands instead of the 275 Catalinas, 10 Coronados and 5 Mariners obtained from the USA under Lend-Lease and the 731 Catalinas built in Canada IOTL.

Thus a grand total of 1,256 Sunderlands were delivered between October 1938 and the end of World War II and all because the Canadian Department of National Defence ordered 3 Short Sunderlands for the RCAF in November 1936 instead of 3 Supermarine Stranraers.

The other reason for cancelling the Saro A.33 and Lerwick was that the Air Ministry had subcontracted Walrus production to that Firm to allow Supermarine to concentrate on Spitfire production. This is what happened IOTL in the summer of 1940 . However, ITTL it happens in 1936. Therefore, the 285 Walruses that the Supermarine built 1936-40 IOTL were built by Saunders Roe ITTL. (Source: Putnam's Supermarine Aircraft since 1914)

 

[phx1138]

If you want better maritime patrol aircraft for the RCAF squadrons in Newfoundland in the first half of the war there are easier ways of doing it.

Option 1 - Build Short Sunderlands in Canada

....Air Ministry places a direct contract for 10 Sunderlands from Canadian Vickers in December 1936 and this order was increased to 21 aircraft in June 1937. The Air Ministry would still buy the Consolidated Model 28-5 for evaluation, but the Air Ministry would order 30 Sunderlands from Canadian Vickers at the outbreak of World War II instead of the OTL contract for 30 Catalinas.

Much as I like this idea, I doubt the Air Ministry is going to contract a Canadian company that early, without a greater sense of desperation. I'm also wondering if the Sunderland isn't actually beyond Canadian capacity at the time. (Maybe not; I know Lancs were built here only a bit later...but that was with a fair bit of help, & with a war on.)

My sense is, it makes more sense for Ottawa (or RCAF, whoever) to order PBYs from CanVic in '36 or '37: they're adequate for the job, a proven design (unlike the Sunderland), & quite a bit cheaper (& less complicated), while offering opportunities for Canadian aircraft & aeroengine production, still fairly nascent.

I'll acknowledge, I may be thinking too small & aiming too low, at Canada's expense. (I don't want to wank it, so I'm trying to curb by desire to have CanVic building W.1s in 1943. )

 

[NOMISYRRUC]

Much as I like this idea, I doubt the Air Ministry is going to contract a Canadian company that early, without a greater sense of desperation.

I did that because the Air Ministry selected the Lerwick in November 1936 and I wanted Canadian Vickers to deliver its first Sunderland to the RAF ITTL when Saunders Roe delivered its first Lerwick ITTL. What I wrote about the Lerwick in Post 35 was based on notes that I made from the Putnam's book on Saunders Roe aircraft. Here are the relevant parts of those notes in full.

The Air Ministry ordered the Lerwick "off the drawing board" in November 1936 and a batch of 22 serials (L7248-L7269) was allocated. Though the initial order was for only 10. This quantity was swiftly revised; a December 1936 minute records the decision to order 16-20 examples. Eventually, 21 were built, but only after grave misgivings, cancellations and reinstatements.

And then...

10 were ordered in April 1937, the December 1936 decision having been laid aside. In June 1937, this order was expanded to 21, of which the first 3 (L7248-L7250) would serve as prototypes. L7248 was launched on 31st October 1938 and flew for the first time during early November.

Based on that it aught be possible to have the Air Ministry cancel the 10 Lerwicks that were currently on order from Saunders Roe in June 1937 and replace it with an order for 21 orders for Sunderlands in June 1937, which would would fit in with what I'd already written in Post 35 about Canada building aircraft for the RAF being discussed at the Imperial Conference of May 1937.

Canadian Vickers aught to be able to deliver the first Sunderland to the RAF in March 1939 (which is wen the first Lerwick reached the A&AEE) in spite of receiving their order 6 months later than originally suggested because the Sunderland was ahead of the Lerwick in development. The prototype was under construction and would fly in October 1937 while the Lerwick was a "paper plane" that wouldn't fly until November 1938.

 

[NOMISYRRUC]

I'm also wondering if the Sunderland isn't actually beyond Canadian capacity at the time. (Maybe not; I know Lancs were built here only a bit later...but that was with a fair bit of help, & with a war on.)

There was also the plan to build Stirilings in Canada after Canadian Associated Aircraft had finished building the Hampden.

I suspect that the Supermarine Stranraers built IOTL were beyond Canadian capacity at the time and that that accounted for the first aircraft flying on 21st October 1938, which was getting on for 2 years after it was ordered (November 1936). I also suspect that Canadian Vickers had a lot of assistance from Supermarine. There is some evidence for this because the Putnam book on Canadian Aircraft which says that the difficulty in getting material from the UK slowed Stranraer production in 1940.

If that's correct I don't see why Short Brothers couldn't have provided Canadian Vickers with the necessary assistance to build Sunderlands ITTL instead of Supermarine providing the necessary assistance to build Stranraers IOTL.

 

[NOMISYRRUC]

My sense is, it makes more sense for Ottawa (or RCAF, whoever) to order PBYs from CanVic in '36 or '37: they're adequate for the job, a proven design (unlike the Sunderland), & quite a bit cheaper (& less complicated), while offering opportunities for Canadian aircraft & aero engine production, still fairly nascent.

I agree with that for all the reasons that you've provided.

The most important being that the Sunderland wasn't a proven design in November 1936. OTOH the Sunderland's cousin the Short Empire Flying Boat (which was similar to the Sunderland, but not the same) was a proven design so I think that Ottawa (or RCAF, whoever) could have ordered Sunderlands in November 1936 without reasonable fears of the type being a failure. (The E.F.B. first flew on 3rd July 1936, was delivered in 22nd October 1936 and made its first revenue flight on 6th February 1937.)

Furthermore, the Air Ministry ordered many aircraft into production "off the drawing board" in the second half of the 1930s in spite of expecting some of them to be failures. That was the price that had to be paid for getting new designs into production sooner. Two of these aircraft were Saro Lerwick and Short Sunderland. The first turned out to be a failure and the second was an outstanding success.

Additional advantages of building Catalians instead of Sunderlands are that it has two engines instead of four and it might require fewer raw materials & man hours to build (due to being lighter & less complicated). Those were the problems that I foresaw in building 731 Sunderlands instead in Canada instead of the 731 Catalians that Canadian Vickers built IOTL.

 

[NOMISYRRUC]

However, I see 308 Wimpys...& that's 308 more than were present OTL. So, as they're replaced by Griffon Warwicks (& I presume they are)... Or is replacement entirely for losses, & those 308 have to be expended? In that event, I'm wrong again... (How about, "Advice to High Wycombe: don't bomb sub pens, it's not productive"? {Yeah, getting a bit OT... })

I suspect that the survivors of the first 308 Wellingtons (that is the ones that hadn't that hadn't been shot down, damaged beyond repair or written off in accidents) were passed onto second-line formations like the operational training units when more advanced marks of the aircraft became available for the front-line squadrons.

The 305 of the 308 Wellilngtons built to the end of 1939 were built at Weybridge. They consisted of:

• 180 aircraft built to the first production contract (placed in October 1936) and delivered between October 1938 and August 1939.
• 120 aircraft built to the second Weybridge production contract that was placed in May 1938 and were delivered between 3rd November 1939 and 27th December 1939.
• 5 from the third Weybridge production contract for 100 aircraft placed in April 1939 and delivered from the end of December 1939 to April 1940.

The other 3 were the first of 100 aircraft built at Chester to its first production contract. According to the Putnam's book on Vickers aircraft they were delivered between 4th August 1939 and 27th June 1940.

Therefore, the logical time for Weybridge to switch from the Wellington to the Warwick was after the the 180th aircraft was completed. Chester (and Blackpool) wouldn't build any Wellingtons at all because they would have received orders to built Warwicks instead.

This is how I think it would be done.

IOTL The first Warwick prototype was ordered on 7th October 1935, but it didn't fly until 13th August 1939 and the second didn't fly until 5th April 1940 in spite of being ordered on 2nd February 1937. These aircraft should have been quick and easy to build because AIUI the Warwick was an enlarged Wellington and was designed to be built in the same production jigs. I think the huge gaps between their ordering and first flights (nearly 4 years for K8178 and nearly 3 years for L9704) were entirely due to the problems that Rolls Royce was having with the Vulture.

ITTL development of the Merlin and what became the Griffon began at the same time. However, the development of the latter engine was halted for several years so that resources could be concentrated on developing the former. If development of the Griffon continues using the resources used for the Peregrine and Vulture IOTL it would be possible to have a Griffon-powered Warwick prototype to be flying by August 1938 and the engine in production in the first half of 1939.

That would allow Vickers to terminate Wellington production in 1939 after completing 180th aircraft and start building Warwicks in 1939. If I'm right about the Warwick being an enlarged Wellington that could be built on the same production line the first production Warwick to be completed would be L4770 built at Chester (instead of its first Wellington) and it would be delivered to the RAF on 4th August 1939. The first Warwick built at Weybridge would be N2685 which would be delivered to the RAF on 3rd November 1939 and be built instead of the factory's 181st production Wellington.

IOTL Vickers built 11,461 Wellingtons and 845 Warwicks (including prototypes). ITTL the totals would have been 180 Wellingtons and 12,125 Warwicks ITTL. That is unless we also get a Griffon-Windsor sooner than the OTL Merlin-Windsor. And/or the Chester factory doesn't re-tool to build Avro bombers sooner. IOTL the factory had orders for 1,620 Lancasters and Lincolns, but only built 235 that were delivered between July 1944 and September 1945.