Westland Whirlwind revisited

Not difficult to see why they kept breaking their tail wheels!

Edit: I thought I'd take a closer look at the tailwheel issue. Here is a list of Whirlwinds which suffered tailwheel collapses.

P6996, P6970, P6979 (x2), P6968, P7035, P7096, P7041, P7051 (x2), P7002, P7110, P7056, P7046 (x2), P7048, P7005, P6987, P7058, P6993, P7011.

That's 21 tailwheel collapses. There were only just over 100 Whirlwinds built. Westland never solved the issue, the last collapse was in June 1943.

In addition there were other problems with the tailwheel.

P6973 failed to lower, P6998 failed to lock down, P7004 burst tyre, P7036 failed to lower, P7096 failed to lower, P7110 failed to lower and a stern frame failure, P7043 stern frame failure, P7092 failed to lock down.

Almost 1 in 5 Whirlwinds suffered tailwheel issues or collapses, imagine if that was the Hurricane or Spitfire; that would be thousands of collapses! No wonder Fighter Command didn't want them too far away from Yeovil.

Apologies if this is already here, I can't read all 25 pages from the office But very interesting piece below on the aerodynamic thinking that went into the Whirlwind.

Whirlwind Fighter Project: July 2015

stona said:

During the rearmament period there were no engine shortages and the Air Ministry focussed on the airframe sector. Orders for all aero-engines fluctuated, it was the slow development of airframe production that led to Merlin orders for 1938 being progressively reduced from 2220 to 1470, an output which did not absorb R-R's maximum current production capacity, while at the same time the company was being asked to expand this capacity!

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Fascinating. I always assumed the opposite - that Merlin production was a binding constraint on prewar rearmament.

Therefore my Whirlwind (or Gloster G.39) fantasy was producing it two years sooner with standard Kestrels/Mercuries, to increase the number of useful fighters at the outbreak of war without cutting into Hurricane or Spitfire production.

But if there was more Merlin capacity than good airframes to put them in, designing a new airframe to use inferior engines seems a waste of time.

(Sorry for late reply, but this thread was already necroed once, so what the hell.)

hobbes154 said:

Fascinating. I always assumed the opposite - that Merlin production was a binding constraint on prewar rearmament.

Therefore my Whirlwind (or Gloster G.39) fantasy was producing it two years sooner with standard Kestrels/Mercuries, to increase the number of useful fighters at the outbreak of war without cutting into Hurricane or Spitfire production.

But if there was more Merlin capacity than good airframes to put them in, designing a new airframe to use inferior engines seems a waste of time.

(Sorry for late reply, but this thread was already necroed once, so what the hell.)

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If I had spare Merlins, I would have but the in the Gloster twin. Lots more wing area to cope with higher weights.

Admiral Beez said:

Whirlwind's issue will be ammunition, since with only 60 rounds per gun, you'd better shoot sparingly and with utmost accuracy. Would under wing .303 mg pods be a quick add-on? Like on this Potez POTEZ 63/11

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There were circular cut-outs in the underside of the wing for the drum magazines POTEZ 63/11

You either need a much larger pod to accommodate the ammunition, or you need to figure out where you can cut into the wing and fit ammunition inside. Of course, the MACs on the Po63.11 were easy to reload: refill the drum and bolt the pod back on. If you're putting a belt feed into the wing, you need access hatches in the top of the wing to reload. More complexity, not necessarily impossible.

Remember that the belts can fold the belts back over themselves, but they have to lie directly spanwise from the feed. You can't twist them through 90 degrees to run back along the chord If the ammunition is in the pod, the pod is going to be so much larger that the drag will we intolerable, unless you can put the ammunition on top and also make a really big cutout in the wing so that the ammunition fits into it. At that point, you're back to a lot of the space problems I already mentioned.

What if you make the guns longer-barreled and put the gun itself and the ammunition behind the cockpit, stagger them. Should be able to fit 120 round cans anyway.

Schweik said:

What if you make the guns longer-barreled and put the gun itself and the ammunition behind the cockpit, stagger them. Should be able to fit 120 round cans anyway.

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You can see from the cutaway in this post that it won't work. The fuselage isn't tall enough. You can't just lengthen the barrels for a whole bunch of reasons, but you can use blast tubes, but I wouldn't want to be sitting on top of one of them ...

You can see that there's no place to put partially-internal gun pods. The radiators are in the inner wings and there are fuel tanks in the middle wings. You can't load the outer wings (not strong enough).

The nail in the coffin is that the props simply block the inner and middle wings (see below).

At least on the H.S.404s, the 60 round drums couldn't be fully-loaded without inevitable jams. Some units only loaded 30 rounds in the magazines. With a 120-round drum, the variation in spring pressure would be so large that I can't image maintaining any sort of reliability. That's why belt feeds were so desirable. (The Bf109Es were not immune to the problem, and I believe it was the Swiss Bf109s that had serious problems with jams.)

This post shows the actual projects to increase armament, which involved lengthening the nose, or using a weapon pod with 12(!) .30 MGs. Westland Whirlwind It managed 120rpg for the HS Mk.IIs. I doubt that the CG changes were much fun ...

How about two 20mm with 120 round belts in the fuselage, using blast tubes. Too much weight?

Schweik said:

How about two 20mm with 120 round belts in the fuselage, using blast tubes. Too much weight?

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Sorry, I apparently left out the first link to a post of a cutaway. I don't think there's space to gun the barrels under the fuselage. The breaches would have to be behind the cockpit. The original question was about whether "a quick modification." This would be a major structural modification.

Is your plan to leave the two upper guns in the nose and move the lower guns back? That's taking a lot of weight out of the nose and moving it way behind the CL and CG. If you wanted to eliminate the nose guns completely and just have two cannon with 120rpg in the rear fuselage, you'd want to move the cockpit well forward, shorten the nose, bulge the lower fuselage, and end up with an undergunned Westland Welkin with shorter wings.

I'm not convinced it would be quite that difficult to fit two guns in the nose somehow with 120 rounds. They did it on a lot of other planes. Looking at them side by side the nose and fuselage of the Bf 110 isn't much bigger diameter than the Whirlwind (it's a much bigger plane but it's fairly slim in the fuselage). And they managed to fit four .30 cal and two 20mm, which is plenty. I think two x 20mm with 120 rounds is better armament than four x 20mm with 60 rounds (or even less if the drums are unreliable at full capacity).

Let's also keep in mind that the Whirlwind was in action / available for a fairly long time, from 1940 through almost the end of 1943. That is a pretty wide window in which to figure out how to improve the gun layout a little bit. I don't believe it's so hard to sort it out, similar changes were done to dozens of other aircraft in less time.

If you had a 2 cannon Whirlwind with a few other incremental improvements in say, 1942, I think that would have been very helpful for the DAF for example.

The cannon on the Bf 110 were not really in the nose. Under the cockpit, firing via blast tubes through the underside of the nose would be more accurate. The breeches were behind the pilot.

I'm well aware. That is what I was just suggesting, right? I think you could fit a couple of LMG in the nose and two x 20 mm beneath or behind the pilot, belt fed. That would be plenty of firepower and better than four x 20mm with the 60 rd. drums.

This was nowhere near as hard as people are making it out to be.

There were two different four 20mm cannon set ups with more ammo than the 60 drums.
While looking for a solution to the 60 round drum problem and while waiting for the belt feed some unsung hero (and it is good that he/they remain anonymous) developed an air powered magazine system. When test fired one gun exhausted the air supply (air bottle) well before the ammo was used up, let alone trying to power four guns.

Some of the experimental set ups are shown back on page 10.
Westland Whirlwind revisited

They did full mock ups of magazines holding 110-120 rounds per gun plus three .303 guns.
There was also an alternative cannon layout with all four guns in row with the outer guns further back than the inner guns.

The room for more ammo existed. The engineering capacity almost existed. The will or manpower to actually manufacture the new nose sections and install them on existing aircraft (or make a MK II on the production line) did not.

If it didn't there sure wasn't the manpower or will to go cutting holes in wings or trying to scab on .303 guns under the wing.

Replace the air powered magazines with the same belt feeds used the Beaufighter or Hurricane IIs.
Problem solved.

Well we know they didn't do it historically so that kind of puts a limit on how far is speculation can run. But that seems like within the realm of what would be a good idea at least in retrospect. I also think they could put in some more redundancy on a couple of systems without too much pain for added weight. and for that matter it's a cinch they could have gotten a little more power out of those peregrine's.

Schweik said:

I'm not convinced it would be quite that difficult to fit two guns in the nose somehow with 120 rounds.

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I agree. If the P-39 could run a drive shaft between the pilot's legs I don't see why an ammunition belt could be run from behind the pilot to the Whirlwind's guns in the nose.



AIUI, the belts didn't yet exist for the Whirlwind's guns, so drums were settled for.

all I was saying was if you can't fit the guns in the nose with the ammunition then put the guns behind the pilot but it's probable that you could fit them in the nose. Especially if you dropped it from four cannon to less

If you won't go back and look at the photos here they are again.

Upper left, four 20mm guns with 110-120 rounds apiece depending on source, this one says 120rpg. Plus three .303 guns.
There is at least one photo of the Prototype P.9 fitted with the guns (or mock ups), I don't know if it was flown that way.

Since the Hurricane only carried 90rpg and the Typhoon 140rpg a Whirlwind with 110-120rpg wouldn't have been that far off.

Several armament installations were tested on L6844: four belt fed cannon in a row, four cannon and three Browning machine guns, a 37-mm cannon, and the Martin Baker Company produced a twelve gun nose pod. None of these versions went into production.

The cannon were cocked on the ground prior to take-off and fired hydraulically on aircraft up to P6969, and pneumatically on all subsequent aircraft.

It obviously wasn't 'easy' to adopt a different system, because the British tried and failed. It was also not practical to introduce a new system, even when it worked, at the end of a short production run.

The first attempt was the 121 round Hydran magazines. These were initially tried in a single gun installation and there were issues with negative 'g' and firing short bursts, both of which resulted in stoppages. Hydran modified the magazine and a full four gun installation was tested, revealing further problems, the ammunition boxes were too fragile and too heavy (the magazine weighed 35lbs empty and over 100lbs when full, very difficult to lift and fit in the nose of the Whirlwind). More seriously, the magazine consumed pneumatic pressure so quickly that after a single long burst it had dropped to a level lower than that required for it to function. The Whirlwind had no pneumatic pump, the only source of air was a fixed bottle in the nose. Clearly a plan B was needed.

The French had realised the limitations of drum fed Hispano and Manufacture National d'armes de Chatellerault (MAC) had developed a belt feed that looked far more promising than any of the British projects. A model of the feed and drawings were brought to England in May 1940. On 8 October 1940 it was decided to abandon the Hydran system and accelerate the development of the Chatellerault feed. Westland had already been instructed to develop a trial installation and was constructing a new nose for the aircraft. L6844 turned up at the A&AEE in September for trials. The belt feed installation was technically cleared, but it was decided not to introduce it into production because it would only be possible for the last few aircraft of the Whirlwind's limited production run. It was not considered worth retro-fitting the installation and new nose to aircraft already in service.

The Whirlwind soldiered on with its unreliable '60' round drums, and for very good reasons. No. 263 squadron, did look at the possibility of mounting the four cannon vertically (they were inclined slightly outwards to allow clearance for the magazines) but this was deemed impractical. The squadron was lucky to have S/L Munro, who was charged with the task of 'persuading the cannon to fire without continual stoppages'. The Hispanos had a habit of stopping after just a few rounds, and when they did fire, the blast wave buckled the nose cone. This fairing was initially made from aluminium sheet over duralumin formers, but thicker sheet and the addition of duralumin blast tubes quickly solved this problem. The stoppages took a little longer. S/L Munro was the ideal man for the job as he had written the original armament installation specification for the aircraft, and it was on his instructions that P6970 and subsequent aircraft fired their cannons pneumatically not hydraulically as originally designed. Munro eventually moved on and took command of the Air Gun Mounting Establishment (AGME) at Duxford.

Probably repeating myself from other posts; given the number of Perseus Westlands used up in pointless Lysanders, to me the obvious POD for a Whirlwind would have been to use Perseus instead of Peregrines. Lighter, allowing wing roots to hold fuel instead of radiators, and leaving an option to upgrade to the Taurus later. An alternative would be Mercuries. Someone will say 'but the Taurus was unreliable'. So it was, when pushed, but the OTL production Taurus went into over ocean flying Beauforts and Albacores. So OTL the Peregrine Whirlwind has 1,650 bhp, the Perseus 1,800bhp and the Taurus has just over 2,000 bhp. No new engines and all in production.

Someone will also say 'Twin Wasp' as was projected for the Beaufort. However they had a bad habit of dropping to the sea bed courtesy of the German Navy.

yulzari said:

to me the obvious POD for a Whirlwind would have been to use Perseus instead of Peregrines. Lighter, allowing wing roots to hold fuel instead of radiators, and leaving an option to upgrade to the Taurus later. An alternative would be Mercuries.

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I like it, and a Bristol radial will free up RR to make their Merlins. From certain angles it would look like the Iman Ro.57. This person modeled one, looking sharp, IMO.



Our resident contrarians will tell us why it shouldn't, couldn't or wouldn't have happened, but a Bristol Whirlwind redesign also presents opportunities to swap in Curtiss and P&W engines if Whirlwinds we're produced offshore, by CAC alongside their Beaufort line (shown below at Fishermen's Bend, Melbourne, Australia in 1943), for example. P&W Australia were already making the R-1830 Twin Wasp for the Beauforts.


Fishermans Bend Aerodrome