Westland Whirlwind revisited

[Wild_Bill_Kelso]

You missed a couple dates for Tempest: Laminar flow investigation - March '40, Specification March '41, Contract Nov '41, 1st flight Sept '42, 1st production Jun '43, Introduction to service Jan '44. Almost 48 months from investigation to in service.

Dates for Welkin are almost same: Requirement F.4/40 March '40, Approval to Design Jan '41,1st flight Nov '42, 1st production approximately Oct '43, Introduction to service May '44. 52 months from requirement to in service.

One of the items Petters said he learned from Whirlwind was the delay from 1st flight of prototype to in service - 18 months.

None of us are saying that Westland could build a Merlin powered twin, just the amount of change => time of delay, would it still be front line.

You need to keep Whirlwind (Mk.II)/Peregrine(Mk.III) production in tact for that length of time (Jan 42 to June '43) it takes for Whirlkin to come on line. But will it be better than Typhoon/Tempest?

Aside: 8" circular radiator has frontal area of ~50 in^2; x3 = 150 in^2; rectangular radiator of 8 x 24 has 192 in^2, almost exactly the 25% increase needed for Merlin (and rectangular radiators are more efficient?)

Weren't many if not most of the delays with the Welkin and the Typhoon due to engine issues?

And weren't many if not most of the delays in getting Tempest into action due to the engine as well? Was that 18 months all due to the wing?

With the benefit of hindsight, I think we can say that a merlin powered "Whirlkin" may well have been better than a Typhoon. Not a Tempest though. So there is your time limit. Ideally I think you want it to be available at least in small numbers in 1943.

I think the delay would have been the engines though. Petters says he's already considering new versions with the newer generation of engines. We can also say in hindsight that a merlin XX still looks like a pretty good power plant well into 1943, but there is no way they would know that.

 

[EwenS]

Wasn't it Air Ministry that initially cancelled the Peregrine? Only to request RR resume for Whirlwind to be long range PR aircraft (early PR Mosquito. Then the DH propellers rob it of altitude performance.

Add outer wing and fuselage fuel tanks (interconnected with existing tanks) with Rotol propellers and Whirlwind is long range PR airplane when RAF wants every Hurricane & Spitfire for Fighter Command. Gives us critical role that keeps Whirlwind and Peregrine rolling.

RR's problem was every engine: Peregrine, Merlin, Griffon and Vulture needed a complete redesign to handle power that was being developed with 100 octane.
Griffon I was easiest to start over as no production tooling existed yet. Merlin was critical all over the place. Loss of the Vulture really hurts RR later in war/immediate post war - yes they develop Eagle, but a little late.

I think Wyvern is pretty airplane too. Pretty lucky too seeing RR canceled planned engines both piston and turbine.

The other RR engine that ended up being canned in 1939/40 was the Exe or Boreas intended for the Barracuda - a c1,000hp with potential to increase to c1,500hp, 24 cylinder, air cooled, X engine which was already at the flight test stage. Hives ar RR wanted this cancelled as he believed producing 275 of these would cost 1,200 Merlins being produced.

Rolls-Royce Exe (Boreas) and Pennine Aircraft Engines

From the late 1930s to the mid-1940s, Rolls-Royce developed two air-cooled X-24 aircraft engines: the 1,200 hp (895 kW) Exe and the 2,800 hp (2,088 kW) Pennine. Neither engine entered production.

oldmachinepress.com

 

[z42]

RR's problem was every engine: Peregrine, Merlin, Griffon and Vulture needed a complete redesign to handle power that was being developed with 100 octane.

The solution, as mentioned above, was to cut down the number of engines in development, and intense engineering focus on the remaining ones. And that, ultimately, was the war-winning recipe - not flailing around trying all kinds of more or less exotic concepts like X or H layouts, slide valves and whatnot. Merlin and Griffin were, in a way, both fundamentally quite boring and unremarkable, but had tremendous resources applied to improving them.

Loss of the Vulture really hurts RR later in war/immediate post war - yes they develop Eagle, but a little late.

Not sure about that. By the end of the war Griffon still had some legroom left (looking just at power/displacement vs the Merlin), and by then it was clear that jets were the future. Vulture and Eagle could have been useful if the jet age had been delayed for one reason or another, and I guess they had reason to be nervous about it at the time.

The success, to the extent one can call it that, of the Sabre was I think as much due to the ministry not wanting to see a RR monopoly, so in that way it didn't really matter that RR had Vulture and Eagle, Sabre was going to be deployed anyway as long as it wasn't an outright disaster.

 

[EwenS]

What I fail to understand in this whole Whirlwind v Welkin debate is how anyone can seriously consider the Welkin as some sort of improved Whirlwind fighter. Not only was it a completely separate design (we have already done that aspect to death in this thread) but when you go back to its origins it had an entirely different role.

1940 an emerging threat was seen to be the Ju 86P high altitude recce aircraft and later (1942) bomber. But this threat never amounted to much of a problem in practice, although the 1942 bombing campaign (if it can even be called that given the few sorties flown by single aircraft dropping a handful of bombs) was something the RAF was determined to stop.

Look at the requirement set out in the Spec F.4/40

"To meet Operational Requirement OR.81, the aeroplane is to be of the Pressure Cabin Type, the pressure in the cabin being chosen to maintain conditions appropriate to 25,000 feet when the aircraft is above that height up to 45,000 feet."
The British Aircraft Specifications File

AIUI the main problem with the Welkin was that of compressibility at the high altitudes it was to operate at and the propellers rather than the engines themselves. The props were non-feathering, so if an engine required shut down the windmill effect from the prop caused overheating and fires. Add to that, they found prop tip speeds approaching the speed of sound with the DH props.

One aircraft, DX340, was later fitted with Merlin 113/114 engines. As part of the radiator was displaced by the wing intakes for the downdraught carbs fitted to these engines, this had to be made up by installing additional radiators in a bearded chin intake under the engine. This change had little or no effect on handling or performance.

The Welkin is maybe best summed up as follows:-
"...The Westland Welkin was for its time an ambitious and very advanced aeroplane, but its role and the need for it eventually disappeared. Nevertheless, it did fly higher than any previous British production aircraft and helped to uncover some of the secrets of compressibility. It also broke new ground in the development of pressure cabins which would become so important in the jet age, but the type never fired its guns in anger and quickly faded from the scene."
British Experimental Combat Aircraft of World War II. Prototypes, Research Aircraft and Failed Production Designs by Tony Buttler published by Hikoki Publications (now part of Crecy Publishing) in 2012

As for the high altitude threat, Supermarine developed the high altitude pressure cabin Spitfire Mk.VI (100 built Dec 1941-Nov1942) and then the Spitfire Mk.VII (140 built late 1942-early 1944).

In response to Ju 86P raids in Aug/Sept 1942, when even the Spitfire VI & IX struggled to intercept at the high altitudes (36,000-42,000 feet), De Havilland hastily (in less than a week!) took the prototype pressure cabin Mosquito bomber, MP469, replaced its nose with that from a NF.II, fitted 4 blade props, smaller wheels and extended wingtips and took out as much weight as possible. It was recorded as reaching 45,000 feet albeit with a reduced fuel load on a ferry trip, some 300 feet more than the Spitfire VII had then recorded.

In Oct/Nov 1942, in response to the potential threat of Ju 86P night raids (something that never materialised) MP469 was further converted to become the prototype NF.XV with radar in the nose and the 4x0.303 MG in a blister under the fuselage. 4 further Mosquito NF.II were converted to a similar standard as NF.XV with Merlin 77 engines. Between March & August 1943 these of these operated with the Fighter Interception Unit and a special high altitude C flight in 85 squadron. They reached heights up to 44,600 feet. Without any "trade" these operations ceased in Aug 1943.

Over in the Middle East, as discussed in other threads, stripped down Hurricane II and Spitfire V were used to intercept, and on occasion shoot down, the Ju 86P recce aircraft flying over Egypt.

Coming back to the Welkin, from early 1943 development of a night fighter version was undertaken (Westland Project No. P.14/2 becoming the Welkin NF.II). A fuselage mock up was viewed on 13 May 1943. Then in Nov 1943 Spec F.9/43 was issued to cover it. Welkin I DX386 was taken from the production line, given a new nose containing a radar set and a second seat for the operator, before flying again as PF370 in Oct 1944. Re-serialled again as WE997 postwar, it continued to be used by Westland as a trials aircraft until May 1950 and was not scrapped until 1953/54. So ended the tale of the Westland Welkin.

 

[EwenS]

You missed a couple dates for Tempest: Laminar flow investigation - March '40, Specification March '41, Contract Nov '41, 1st flight Sept '42, 1st production Jun '43, Introduction to service Jan '44. Almost 48 months from investigation to in service.

Weren't many if not most of the delays with the Welkin and the Typhoon due to engine issues?

And weren't many if not most of the delays in getting Tempest into action due to the engine as well? Was that 18 months all due to the wing?

Well one question is which version of the Sabre and therefore which version of the Tempest.

The plan originally was to build the Tempest I with the Sabre IV engine. Then came the delays. Tony Buttler in his book on the Tempest notes:-

1. "In fact the first investigations into the new wing (or rather at that stage, more thorough research into high speed wing sections as a whole) had been put in hand in 1940, but full development of what later became the Tempest wing was, because of the demand for Hurricanes, not started until September 1941."
2. The new wing (for what initially was thought of as a Typhoon II) "resulted in alterations to every major unit in the aircraft with the exception of the rear fuselage monocoque", which caused the name change to Tempest.
3. The same month as the prototype was ordered, Nov 1941, the Air Staff decided they wanted a 6 cannon armament, for which there was no room in the Tempest wing. That led to design work on a Universal wing able to take various combinations of cannon & MG. It was Oct 1942 before the Universal wing idea was dropped.
4. Then Hawker forgot to order certain wing root end forgings which held up work.
5. It was also noted in May 1942 that there was a "lack of drive" over the project which had to be addressed with night shift and 7 day working in bottleneck areas.
6. More significantly the Sabre IV engine, was expected to be ready by Dec 1941. But that date kept slipping back. That resulted in the search for replacement engine to keep the project moving. That engine was the Sabre II with its chin radiator from the Typhoon. But fitting that called for further airframe changes (most notably elimination of the wing root radiators).

So the Tempest prototype that first flew in Sept 1942, HM595, was not the aircraft originally envisaged. But it served as the basis of the first production version, the Tempest V.

Development of the Tempest I continued and the prototype of this version, HM599, flew on 24 Feb 1943. But as the Sabre IV engine kept failing its type testing, orders for this version were switched to other marks. The sole airframe was used for development work.

As development of the Tempest V got underway it was found other changes needed made. Changes were made to the Typhoon radiator bath to combat compressibility problems (a side effect of the changed wing and its interaction with the shock waves from the radiator). Also to the tail (tail fillet & tailplane of greater span & chord), in part because of the greater side area of the chin radiator compared to the intended leading edge radiators of the Tempest I.

Buttler notes that when Tempest V series production started in Oct 1943, it had slipped by about a year from the late 1942 date originally envisaged for the Tempest I due to all the changes and delays that had to happen along the way.

The tale of what originally began life as a thin wing Typhoon II and the changes needed to arrive at the operational Tempest V simply reinforces what others have said already about proposals to re-engine and/or re-wing the Whirlwind. You end up with such a different aircraft that Sydney Camm recommended the change of name to Tempest in Jan 1942 (although it took the Air Ministry until Aug that year to approve it)

This site is worth looking at for those unfamiliar with the various Tempest marks.

The Hawker Tempest Page

www.hawkertempest.se

 

[Wild_Bill_Kelso]

very interesting and thanks for posting. Due to my own insanity no doubt, I draw different conclusions from the same data you present here. It sounds like they had the wing sorted out rather quickly. Most of the delays were due to the changing (and somewhat optimistic) requirements for armament, production for the Hurricane, and the saga of the engines.

 

[yulzari]

I remain convinced that the best base was the existing airframe. Yes it needed assorted bits in it rearranged etc. but the basic airframe was fine. What it offered was both early war production and late war power given another step in the Peregrine or a suitable alternative. It does not need to be bigger. Heavier were needed. After all the Spitfire pretty well doubled in weight during the war.

Now the change would need to be pre war in place of the Spitfire and future engines, in the Vulture/Sabre power levels, might be the developed Peregrine, Exe or possibly Dagger. I don't know what might clash with the undercarriage with these. The simplest choice is the developed Peregrine. Two of these would be a good match for the Vulture/Sabre with less risk and earlier introduction. Imported engines are not a sound strategic choice.

 

[buffnut453]

very interesting and thanks for posting. Due to my own insanity no doubt, I draw different conclusions from the same data you present here. It sounds like they had the wing sorted out rather quickly. Most of the delays were due to the changing (and somewhat optimistic) requirements for armament, production for the Hurricane, and the saga of the engines.

Quickly relative to the problems faced by the engines...but the fact remains that the wing change "resulted in alterations to every major unit in the aircraft with the exception of the rear fuselage monocoque."

The Tempest's major issues with engines had nothing to do with the complexity of changing the wing from the one used on the Typhoon to that of the Tempest. Changing the wing was a major redesign that, in the mind of the designer, was sufficient to justify an entirely different name for the aircraft.

At the end of the day, "quickly" is dependent on the resources applied to the problem. Much of the Typhoon development was slowed because it was deemed that production of the existing Spitfire and Hurricane took priority. Yes, a re-winged Whirlwind was feasible but it was not deemed a priority. Even Petter's idea for shoehorning Merlins into the Whirlwind was not taken up. None of that has any relevance to the complexity involved in putting a larger wing (as opposed to a wing of longer wingspan) on an existing airframe.

Putting a bigger wing on an existing airframe will drive a redesign of pretty much everything...and that increases risk which is part of the decision calculus on whether to accept a manufacturer's proposal.

 

[Wild_Bill_Kelso]

Quickly relative to the problems faced by the engines...but the fact remains that the wing change "resulted in alterations to every major unit in the aircraft with the exception of the rear fuselage monocoque."

The Tempest's major issues with engines had nothing to do with the complexity of changing the wing from the one used on the Typhoon to that of the Tempest. Changing the wing was a major redesign that, in the mind of the designer, was sufficient to justify an entirely different name for the aircraft.

At the end of the day, "quickly" is dependent on the resources applied to the problem. Much of the Typhoon development was slowed because it was deemed that production of the existing Spitfire and Hurricane took priority. Yes, a re-winged Whirlwind was feasible but it was not deemed a priority. Even Petter's idea for shoehorning Merlins into the Whirlwind was not taken up. None of that has any relevance to the complexity involved in putting a larger wing (as opposed to a wing of longer wingspan) on an existing airframe.

Putting a bigger wing on an existing airframe will drive a redesign of pretty much everything...and that increases risk which is part of the decision calculus on whether to accept a manufacturer's proposal.

I don't disagree with any of that necessarily - it just seems like redesigning the wing and at least most of the other cascading changes were accomplished pretty quickly. This is the sort of thing that WW2 era aeronautics engineers seem to have been quite good at. The tricky parts are the engines and of course, the capricious changes to requirements from their customer.

We know with the benefit of hindsight that they probably should have ditched the Typhoon and switched to the Tempest as soon as the latter became a possibility. What's the earliest they could have started making Tempests? Could you make a Tempest with merlin XX while they are sorting out Saber etc.? Then you could ditch the Hurricane too and probably wouldn't need any P-40s in the Middle East.

We can see how extraordinary the Whirlwind was for it's time, and speculate that it could have been the basis or inspiration for a truly great aircraft for the mid-war and maybe later, but of course that was a roll of the dice as any significant change brings in the random element. There is really no way of knowing how it would have turned out.

 

[Wild_Bill_Kelso]

I remain convinced that the best base was the existing airframe. Yes it needed assorted bits in it rearranged etc. but the basic airframe was fine. What it offered was both early war production and late war power given another step in the Peregrine or a suitable alternative. It does not need to be bigger. Heavier were needed. After all the Spitfire pretty well doubled in weight during the war.

Now the change would need to be pre war in place of the Spitfire and future engines, in the Vulture/Sabre power levels, might be the developed Peregrine, Exe or possibly Dagger. I don't know what might clash with the undercarriage with these. The simplest choice is the developed Peregrine. Two of these would be a good match for the Vulture/Sabre with less risk and earlier introduction. Imported engines are not a sound strategic choice.

You are probably right in the short term, you would just likely end up with a high(er) wing loading aircraft, which has some downside, but it's the sort of thing pilots seem to have eventually figured out how to deal with during the war. I still think a wider chord wing would have been better but that is much more of a roll of the dice.

I think it's like Shortround6 noted, they thought they had their four cannon aircraft for the 'cost' of one engine, in Hurricane II and (certain variants of) Spitfire VC, even though these didn't turn out quite as expected.

 

[Glider]

I think it should be remembered that the Welkin was designed for a specific task and was never meant to try and take on fighters or any of the most common types of combat.

To try and just add engines that have a combined weight of at least 1,000lb, and the associated larger radiators, again with the additional weight. Then add fuel which would be needed for the extra consumption, adding I don't know how much extra to the TO weight. Throw in the extra strengthening needed in the structure to maintain the integrity of the airframe, again pick your own figure. This will also significantly increase the drag of the aircraft, something that is often forgotten

Can you imagine what it would do to your wing loading, agility, acceleration, range and climb.

No, the only way to correct this is if someone had said to the designers before they started. Give us a four 20mm cannon armed fighter with one pilot and powered by two Merlin or Hercules engines.

 

[Wild_Bill_Kelso]

It's also true that other fighter aircraft were modified for basically the same (fight at high altitude) task during the war, seemingly without that much trouble. For Spitfires, wing extensions and a different impeller helped a lot. Ta-152H was a successful innovation 'in the family' of the Fw 190

Many, in fact almost all aircraft that were used long enough in the war gained weight equivalent to 1,000 lbs (or close to it). Spitfire did, P-40 did, Bf 109 did.

 

[Shortround6]

Could you make a Tempest with merlin XX while they are sorting out Saber etc.?

No.

Maybe you could have stuck a Merlin XX engine in the air frame and with a few (or more than a few) hundred pounds of ballast gotten it to fly with less than an expert pilot but it would have been a crap warplane.

I don't have the weight figures for the Tempest. The weight figures for the Sea Fury MK II are from here,

http://www.wwiiaircraftperformance.org/Fury/Sea_Fury_Hawker.pdf

Weights for the American planes are from AHT.


component........................................Fury II............................................P-51B/C...................................P-40F............................................P-47D
Mainplane........................................1854lb.............................................1066lb.....................................1132lb.........................................1460lb
Fuselage..............................................757lb...............................................509lb........................................418lb.........................................1443lb
Tail unit................................................231lb...............................................183lb........................................154lb............................................250lb
Landing gear.....................................718lb...............................................781lb........................................552lb..........................................1123lb
Flying controls....................................84lb...............................................108lb (?).....................................98lb (?)...................................137lb (?)

Total Structure................................3,644lb..............................................2647lb........................................2254lb.....................................4413lb


Note, fuselage does not include cowl or engine mounts. add 859lbs but change as needed for the Merlin. American planes do not include the Cowl/engine mounts/engine section.
Note, the "flying control" weights are from a listing for "surface controls" on the US planes and may refer to the internal control linkage/cables?

If you design a plane to use a big engine you cannot stick a smaller engine in it and get combat performance without totally redoing the entire structure.
A Tempest is going to be lugging around roughly 1000lbs of extra weight just for the structure vs a plane designed for the Merlin XX or something of close to that size.

 

[Wild_Bill_Kelso]

Yeah true good point, I should have looked at my 1/72 Tempest next to a Spitfire

R-2600 then...

 

[Shortround6]

Many, in fact almost all aircraft that were used long enough in the war gained weight equivalent to 1,000 lbs (or close to it). Spitfire did, P-40 did, Bf 109 did.

The Spitfire gained over1000lbs going from prototype to just the MK V.
P-40 gained around 1500-2000lbs from the long nose planes to the F.
109 gained well over 1000lbs from the C/D to the late Gs.

However the P-40s gained just over 100lbs of wing weight. Other weights moved around. Accommodations for the six .50s or beefing up the wing to handle going from an under 7000lb plane to over 8,000lb plane?
109 got a new wing and new tail, weight was????
Spitfires got modified main spars and new Longerons.

seemingly without that much trouble.

Define trouble.
The un pressurized Spitfires worked, but only just.
Even a pair often could not stay in formation at the higher altitudes. Armament had to be reduced, and flights had to be of limited duration because using oxygen masks alone was not healthy/safe for flights of several hours.
Pressure cabins that could not jettison the canopy in case of emergency are not really long term solutions either.

Being able to see out was also considered a plus. Fogged (or frosted) windscreens/canopies were not a good thing for general flying let alone combat.

 

[BarnOwlLover]

We also might consider these Supermarine proposals and if they could've been any better than the Whirlwind or the Typhoon (since they were largely designed to the requirement that prompted the development of the latter):

The challenge to replace the Spitfire and Hurricane: Supermarine twin fighters

When the time came to replace both the Hurricane and Spitfire, the Air Ministry had a very hard act to follow...

www.key.aero

 

[Wild_Bill_Kelso]

The Spitfire gained over1000lbs going from prototype to just the MK V.
P-40 gained around 1500-2000lbs from the long nose planes to the F.
109 gained well over 1000lbs from the C/D to the late Gs.

However the P-40s gained just over 100lbs of wing weight. Other weights moved around. Accommodations for the six .50s or beefing up the wing to handle going from an under 7000lb plane to over 8,000lb plane?

Hold on, something doesn't quite add up there. Going from 4 .30 caliber M1919 machine guns and ammo, to 6 .50 caliber M2s with ammo, I would think that would be more than #100

109 got a new wing and new tail, weight was????
Spitfires got modified main spars and new Longerons.


Define trouble.
The un pressurized Spitfires worked, but only just.
Even a pair often could not stay in formation at the higher altitudes. Armament had to be reduced, and flights had to be of limited duration because using oxygen masks alone was not healthy/safe for flights of several hours.
Pressure cabins that could not jettison the canopy in case of emergency are not really long term solutions either.

Being able to see out was also considered a plus. Fogged (or frosted) windscreens/canopies were not a good thing for general flying let alone combat.

Very high altitude was a challenge for the recon planes too obviously. HF spitfire worked well enough until Gloster Meteors were available

 

[Wild_Bill_Kelso]

We also might consider these Supermarine proposals and if they could've been any better than the Whirlwind or the Typhoon (since they were largely designed to the requirement that prompted the development of the latter):

The challenge to replace the Spitfire and Hurricane: Supermarine twin fighters

When the time came to replace both the Hurricane and Spitfire, the Air Ministry had a very hard act to follow...

www.key.aero

That sounds interesting but that site is always tricky to browse, can you summarize?

 

[EwenS]

Very high altitude was a challenge for the recon planes too obviously. HF spitfire worked well enough until Gloster Meteors were available

There was only 1 operational Meteor squadron in WW2 starting operations at the end of July 1944 against V1 Flying Bombs. Initially with the Mk.I it transitioned to the Mk.III in Jan 1945 when it moved to the Continent for low level work. By the time the Meteor arrived very little manned Luftwaffe traffic of any sort was appearing in the skies over Britain in daylight.

There were never many Spitfire VII equiiped units. The last gave up the type in Nov & Dec 1944.

 

[Wild_Bill_Kelso]

I'm pretty sure the Ju-86R weren't flying by then, though there were some Arado jets.

Ju 86 were shot down by field modified Spits and I think even a Hurricane on one occasion in North Africa.