Westland Whirlwind revisited

Our man Brown had this to say about the Whirly (again, not the last word, but where else can we find a good recounting of flying it):

"The Manoeuvrability of the Whirlwind was brought into question by the tendency to buffet badly in tight turns, and with a wing loading of 40lb/sq ft this was a crippling restriction. Also in dives from 25,000ft above 350 mph a longitudinal pitching set in, and if speed was allowed to increase there was a distinct loss of elevator effectiveness at 400mph at 15,000ft and a very strong pull-force was required for recovery. These characteristics made the Whirlwind a poor bet as a fighter, and so it was given a fighter bomber role in service and proved less than effective in that form."

"The aircraft was not easy to land because speed had to be kept up to provide suffient elevator control for hold-off, and this therefore gave a long run-out - not the best characteristics for all-weather operations..."

"Certainly I must confess to profound disappointment at its handling qualities in all but single-engine flying. it's just as well that it had the latter blessing, for the Peregrine engine had its fair share of problems."

wuzak said:

The Hercules, in use in existing types, was an even higher priority.

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I am certainly not saying the Hercules wasn't higher priority, and the Hercules did need a lot of tinkering with. From prototypes in 1930s to last production engines post-war it went through 7 different (?) cylinder heads in a constant battle to improve cooling as one example.

The Centaurus benefited from much of the work being done on the Hercules, it did not spring into being as a 2300- 2500hp engine.

Am I right to understand that the issue with the Peregrine isn't a lack of power, just at HA. Instead of putting in much heavier and larger Merlins, how hard is it to adjust the supercharger for HA?

Admiral Beez said:

Am I right to understand that the issue with the Peregrine isn't a lack of power, just at HA. Instead of putting in much heavier and larger Merlins, how hard is it to adjust the supercharger for HA?

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The easiest way is to change the supercharger drive gear ratio.

But then you sacrifice low end performance.

So you add a 2 speed drive. one with a lower ratio and one with a higher ratio. You improve slightly at high altitude and low altitude, and lose in the altitude around the gear change.

Making a 2 speed drive would be a lot of extra work.

Another alternative, which probably wasn't feasible, would be to adapt the Merlin 2 speed supercharger to the Peregrine. That would be even more work than designing a 2 speed drive.

Admiral Beez said:

Am I right to understand that the issue with the Peregrine isn't a lack of power, just at HA. Instead of putting in much heavier and larger Merlins, how hard is it to adjust the supercharger for HA?

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There is a lot of 'low tech' ways to improve Peregrine's altitude capabilities, and with that Whirlwind's performance. 1st, don't mess big time with carb air intake, go KISS like it was done on the Gloster's twin. Less convoluted intake = better use of ram effect = better altitude power. Also use a better exhaust stacks layout, the inboard stacks need to clear the radiators. A better carb will also help.
I don't know whether Peregrine used the cleaned-up intake as it was the case with Merlin XX vs. earlier Merlins.

tomo pauk said:

There is a lot of 'low tech' ways to improve Peregrine's altitude capabilities, and with that Whirlwind's performance. 1st, don't mess big time with carb air intake, go KISS like it was done on the Gloster's twin. Less convoluted intake = better use of ram effect = better altitude power. Also use a better exhaust stacks layout, the inboard stacks need to clear the radiators. A better carb will also help.
I don't know whether Peregrine used the cleaned-up intake as it was the case with Merlin XX vs. earlier Merlins.

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I've read somewhere that a better propeller would have increased altitude performance too.

Admiral Beez said:

Am I right to understand that the issue with the Peregrine isn't a lack of power, just at HA. Instead of putting in much heavier and larger Merlins, how hard is it to adjust the supercharger for HA?

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wuzak said:

The easiest way is to change the supercharger drive gear ratio.

But then you sacrifice low end performance.

So you add a 2 speed drive. one with a lower ratio and one with a higher ratio. You improve slightly at high altitude and low altitude, and lose in the altitude around the gear change.

Making a 2 speed drive would be a lot of extra work.

Another alternative, which probably wasn't feasible, would be to adapt the Merlin 2 speed supercharger to the Peregrine. That would be even more work than designing a 2 speed drive.

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Wuzak is quite right with his post but some of the gain in high altitude performance rather depends on the gears the original supercharger was using and the design of the supercharger itself. If we assume for instance that the Peregrine supercharger was very similar in design to the original Merlin supercharger (MK III Merlin) the the supercharger is going to max out at around 17,500-18,000ft even with different gears as it did on the Merlin X engine. Changing gears on the Peregrine might have gained 2-3,000ft as Wuzak says at the cost of take-off and low altitude performance.
Hookers redesigned inlet (a more efficient supercharger) allowed for several thousand feet of altitude performance gain using the same gears over the original supercharger.

I don't know why but for RR the supercharger drive or at least the housing for it was part of the crankcase casting, you cannot add the two speed drive in the field and in fact some Merlin factories only built single speed engines while others built two speed engines (and two stage which also were two speed) which certainly indicates (but does not prove) that adding a two speed drive is considerable work. At least the way RR did it. Wright claimed you could retro fit certain R-1820s in the field with their 2 speed drive. I have no idea if it was ever done.

As is the Whirlwind/Peregrine combination had 2-3 things going against for high altitude work, in no particular order they are
1. A lousy air intake for the carb.Air was taken from the radiator/oil cooler inlets in the wing roots and ducted to the top of the engine nacelle and then into the downdraft carburetor, a lot of turns with pressure loss and a lot of joints to keep tight. Less RAM air boost than some other designs? especially in service?
2. Shrouded exhausts, great for night flying, but lousy for getting exhaust thrust from. due to the lower air pressure at higher altitudes the thrust from the exhaust gases is best at near critical altitude or a bit above. Highest mass of gas flow with the greatest pressure differential.
3. (?) one modern article says the airfoil used in the propeller blades on the Whirlwind lost efficiency at the higher altitudes which cost thrust. Take that one as you will. Many other planes went through a number of propeller experiments at this time. WWII AIrcraft Performance has tests of both British and American planes with up to five different prop blades being tested in one test. Propeller design was a much art as it was science in 1939/40.


Peregrines on the Gloster F.39/7
Is it just me or do those look like counter rotating propellers?

None of these or even all three is going to turn the Whirlwind into a MK V Spit but the difference wouldn't have been as great. The new inlet on the Supercharger itself might have been much easier to do than a two speed drive.

Then figure out if you want the Whirlwind as a high altitude interceptor or a low altitude interceptor/ground pounder and fit the appropriate supercharger gear.

Shortround6 said:

Peregrines on the Gloster F.39/7
Is it just me or do those look like counter rotating propellers?

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Seems they were counter-rotating indeed: link
Every day is a learning day.

None of these or even all three is going to turn the Whirlwind into a MK V Spit but the difference wouldn't have been as great. The new inlet on the Supercharger itself might have been much easier to do than a two speed drive.

Then figure out if you want the Whirlwind as a high altitude interceptor or a low altitude interceptor/ground pounder and fit the appropriate supercharger gear.

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Even if we get a 5 mile per each improvement (intake, exhausts, carb, change of gearing), there is a 380 mph fighter with 4 cannons.
On the other hand, a Spitfire V with a bit nip & tuck will be doing 380-390 mph, on just one engine...

Shortround6 said:

View attachment 559804
Peregrines on the Gloster F.39/7
Is it just me or do those look like counter rotating propellers?

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tomo pauk said:

Seems they were counter-rotating indeed: link
Every day is a learning day.

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The first Whirlwind prototype also used counter rotating propellers.

The engines were handed, unlike the Merlin 131 on the Hornet which had an idler gear in the propeller reduction gear in order to reverse rotation.

I believe there was a comparison made between the handling qualities of the Whirlwind with handed engines and without which found little difference, resulting in production Whirlwinds getting the same engine on both sides.

Now that you mention I believe you are correct.

I was looking at my little model collection and noticed how similar in size the Whirlwind and the Ki-46 were. Both quite small for twin engined birds, probably something like half the size of say a B-25. Both very streamlined. Both fast for their era.

Ki-46 looks like it has small engines too so I looked those up. Interesting...

Mitsubishi Zuisei - Wikipedia

from the wiki: "The Mitsubishi Zuisei (瑞星 Holy Star) was a 14-cylinder, supercharged, air-cooled, two-row radial engine used in a variety of early World War II Japanese aircraft. It was one of the smallest 14-cyl. engines in the world and the smallest diameter Japanese engine. "

This Ki-46 perhaps looks like a template for a successful path for the Peregrine powered Whirlwind. Ki-46 was just a recon plane but in that role it was quite successful for quite a while, and I think the Whirlwind could have done even more. But it also (to me) demonstrates the validity of the "smaller is better" design ethos for early to mid-war military aircraft with a need for speed, i.e. before the big engines come out, and in fact in this example using a small engine to solve that exact problem.

A low drag design with 2200 hp is potentially a very effective weapon.

While Wiki is very handy to copy and paste from (especially for the typing challenged like myself) it is always a good idea to double check Wiki with one or more sources before doing so.

Mitsubishi Zuisei engine = 1710 cu in (?) (1695 by my math but inches are rounded off from metric)
Nakajima Sakae engine = 1700 cu in (?) (1686 by my math but inches are rounded off from metric) listed as 1 in greater in diameter.
Bristol Taurus engine = 1550 cu in, diameter 2.2 in bigger than the Zuisei?
P & W R-1535 engine = 1535 cu in (surprise!) diameter 0.12 inches bigger?
Gnome-Rhone 14M =1149 cu in with a diameter 6.6 in less than the Zuisei
Hispano-Suiza 14AB=1593 cu in with a diameter 4.2 in less than the Zuisei, not used very much.

to be fair the last two are 700hp engines. the R-1535 is about an 825 hp engine but development stopped pre war using 97 octane fuel.
The non-Japanese engines never got more than single speed, single stage superchargers.

we can argue about what the total number of different 14 cylinder engines there were and where being the 5 or 6th smallest on the whole list puts the Zuisei but the wording does give a somewhat misleading impression.

Well it is small - for a 14 cylinder. Maybe not as tiny as a Gnome Rhone 14M but that is as you noted, almost too small. With a mere 44" diameter and a dry weight of 1200 lbs it is definitely a lot smaller than an R-2600 (55" diameter, 2,600 cu in, 2,045 lbs) or a BMW 801 (2,560 cu in, 51" diameter, weight 2,231 lbs). And it's even smaller and 100 lbs lighter than a Bristol Taurus. Wikipedia looks wrong on their claim of smallest in the world, but I think that qualifies as a small engine. Considering they were able to get 1,100 hp and later put a two stage supercharger on it, that's pretty good for the size.

The Nakajima Sakae is small too but it is also 100 lbs heavier.

Weight is very similar to Peregrine (1,140 lbs) and the Peregrine at 41" x 27" is comparable in size, albeit slimmer as inline engines usually are. Merlin is also comparable in size but 200-400 lbs heavier depending on the type.

Importantly for a fighter like Whirlwind, aside from weight, the frontal diameter is what matters, not so much how many cylinder rows there are. The Zuisei was small and light enough to solve the problem for the zippy Ki-46 anyway. (It wasn't enough to save the Ki-45 but that plane was too big).

My point is that the Ki-46 was a successful small plane built around what I would certainly call a small engine, and thereby another good example of how smaller can be better, and how relatively small engines could have been worth producing.

Why was the Mitsubishi Ki-83 a twin seater? It wasn't a night fighter needing a radar operator and didn't have a rear gun. Strip out the weight of the second man and the Ki-83 looks like an ideal candidate for a Japanese Whirlwind, Hornet or P-38.

there could be at least 3 reasons, all are supposition on my part and there could be more or different reasons.
Since it was designed as a long range and/or long endurance fighter
1. 2nd crewman was to assist in navigation.
2. 2nd crewman operated a radio of longer range and more complexity than they thought a pilot could operate while flying.
3. They knew radar was coming, but they didn't know when. they allowed for extra crewman and space for extra equipment should it become available during the planes development.

Schweik said:

My point is that the Ki-46 was a successful small plane built around what I would certainly call a small engine, and thereby another good example of how smaller can be better, and how relatively small engines could have been worth producing.

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The Ki 46 was successful plane designed to do one mission and for the most part, employed on the mission it was designed for. This was not as common as we might expect with many aircraft forced into different roles than originally designed for.

The Ki-46 was essentially an unarmed (or sketchley armed) flying fuel tank with a camera or two. A lot of things were sacrificed for low drag and high speed and that worked well for a reconnaissance plane. the Ki-46 II carried 365imp gallons internal and the Ki-46 III carried 417 imp gallons internal and 101.2 imp gallons in a drop tank.
The Ki 46 didn't do High G maneuvers and didn't climb particularly well. no armor, no protection for the fuel, some early planes had a Lewis gun out the back, later ones got rid of it.

Low powered engines can work in some circumstances for a specialized aircraft, but even the Ki-46 IIs losses mounted when P-38s and Spitfire Vs showed up resulting in the Ki-46III which used 1500hp engines, the same engines used in the Ki-100 fighter, the last two Zero prototypes (A6M-8) the D4Y-3 Suisei and others, while not a large engine it was 1970 cu in and 48 in in diameter according to one source, so it wasn't small either.

Shortround6 said:

The Ki 46 was successful plane designed to do one mission and for the most part, employed on the mission it was designed for. This was not as common as we might expect with many aircraft forced into different roles than originally designed for.

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You are missing the point. Even if it ended up as a one trick (short or long range recon) pony, if it was as successful as the Ki-46 it would have been of immense value to the RAF at least until the Mosquito became available in sufficient quantities. Do you know how many Tac-R Hurricanes got shot down in North Africa? F-4 (P-38s) didn't do much better. An untouchable recon aircraft would have been quite an asset.

The Ki-46 was essentially an unarmed (or sketchley armed) flying fuel tank with a camera or two. A lot of things were sacrificed for low drag and high speed and that worked well

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I know the history very well thank you. It was a 'flying fuel tank' because being based in the Pacific. To be a useful recon plane in that Theater it needed to be not only high speed and high altitude, it also needed fantastic range. So that plane had a 1,500 mile range. You could make a faster, more agile, armed version of the same plane with half as much fuel and it would still be useful to the RAF to fly recon trips over the Channel and the front line in Tunisia.

Low powered engines can work in some circumstances for a specialized aircraft, but even the Ki-46 IIs losses mounted when P-38s and Spitfire Vs showed up resulting in the Ki-46III which used 1500hp engines, the same engines used in the Ki-100 fighter, the last two Zero prototypes (A6M-8) the D4Y-3 Suisei and others, while not a large engine it was 1970 cu in and 48 in in diameter according to one source, so it wasn't small either.

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I already specified, by the mid war the really heavy duty engines started coming into their own. You had 1,500 - 1,800 hp inline engines and the 2,000-2,800 hp double row radials, you had MW /50 and NO2... all making it more practical for the medium sized and bigger planes to begin to realize their potential. The niche for the smaller planes was in the early war, when you really needed low drag to be able to get that high speed. Similar to how the Bf 109 was the speed demon until the Merlin 60 and the R-2800 started butting in.

But back in 1941 when it came into action, and all the way through 1942 I would say, the Ki-46 was a damn effective recon plane. A far sight more effective than the Blenheims and PBY's we were using for that role. And that is one of the most important missions the Air Forces do. The Ki-46 may have been limited into it's specialist niche if it was unmaneuverable, but that wouldn't have been the fault of the engines. The Whirlwind in fact was a maneuverable aircraft by all accounts and we know was already capable of success as a fighter early on even with not fully developed engines..

Shortround6 said:

there could be at least 3 reasons, all are supposition on my part and there could be more or different reasons.
Since it was designed as a long range and/or long endurance fighter
1. 2nd crewman was to assist in navigation.
2. 2nd crewman operated a radio of longer range and more complexity than they thought a pilot could operate while flying.
3. They knew radar was coming, but they didn't know when. they allowed for extra crewman and space for extra equipment should it become available during the planes development.

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1 and 2 were pretty standard for a number of navies around the world. It seems probable that the Japanese Army would have adopted a similar principle for a long range reconnaissance aircraft.

stona said:

1 and 2 were pretty standard for a number of navies around the world. It seems probable that the Japanese Army would have adopted a similar principle for a long range reconnaissance aircraft.

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Maybe. You can see the window in the fuselage for the rear crewman, plus his downward window for ground observation. Certainly the RAF used the de Havilland DH.98 Mosquito for fast two man recon, but for the Japanese, facing an onslaught of heavy high altitude bombers, using a 440 mph, land-based heavy fighter for two-man reconnaissance seems wasteful. Given that it was first flown in Nov 1944 when inland reconnaissance is less a priority, I would have ditched the second man, reduced the weight and made the Ki-83 a HA interceptor.

Schweik said:

You are missing the point. Even if it ended up as a one trick (short or long range recon) pony, if it was as successful as the Ki-46 it would have been of immense value to the RAF at least until the Mosquito became available in sufficient quantities. Do you know how many Tac-R Hurricanes got shot down in North Africa? F-4 (P-38s) didn't do much better. An untouchable recon aircraft would have been quite an asset.

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How many TAC-R Hurricanes got shot down is rather imaterial. You are also confusing missions. The Ki-46 was pretty much for high (or high considering the theater and time) strategic missions. Not low level tactical recon of front lines. Untouchable recon aircraft are always an asset but part of being untouchable depends on the opposition.

Schweik said:

I know the history very well thank you. It was a 'flying fuel tank' because being based in the Pacific. To be a useful recon plane in that Theater it needed to be not only high speed and high altitude, it also needed fantastic range. So that plane had a 1,500 mile range. You could make a faster, more agile, armed version of the same plane with half as much fuel and it would still be useful to the RAF to fly recon trips over the Channel and the front line in Tunisia.

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I would note that the Mosquito flew it's first recon missions in Sept of 1941. In early 1942 a Mosquito recon plane had flown over Poland and one had done a round trip to Murmansk.
as for " a faster, more agile, armed version of the same plane with half as much fuel and it would still be useful to the RAF to fly recon trips over the Channel"

Gee sounds like a Allison powered Mustang
Unfortunately for your comparison, better planes for the jobs in the other theaters existed, the British just were not deploying them to those theaters. and trying to modify bombers or photo recon planes into fighters doesn't work well because they were never built to withstand high G maneuvers (even if the control authority allows it) and beefing up the structure to withstand High G maneuvers can add lot of weight. The P-38 carried about 3/4s of ton worth of armament and perhaps that is too much (500rpg of .50 cal ammo seems a bit excessive) but pulling around 940lbs of fuel out of the Ki-46 doesn't really give you enough weight for both guns/ammo and a slight bit of protection.

Schweik said:

I already specified, by the mid war the really heavy duty engines started coming into their own. You had 1,500 - 1,800 hp inline engines and the 2,000-2,800 hp double row radials, you had MW /50 and NO2... all making it more practical for the medium sized and bigger planes to begin to realize their potential. The niche for the smaller planes was in the early war, when you really needed low drag to be able to get that high speed. Similar to how the Bf 109 was the speed demon until the Merlin 60 and the R-2800 started butting in.

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Well, the 109E was hardly a speed demon, that took the 109F. ANd the 109F had a few problems, like lack of range and lack of fire power.

Schweik said:

But back in 1941 when it came into action, and all the way through 1942 I would say, the Ki-46 was a damn effective recon plane. A far sight more effective than the Blenheims and PBY's we were using for that role. And that is one of the most important missions the Air Forces do. The Ki-46 may have been limited into it's specialist niche if it was unmaneuverable, but that wouldn't have been the fault of the engines. The Whirlwind in fact was a maneuverable aircraft by all accounts and we know was already capable of success as a fighter early on even with not fully developed engines..

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The QUestion on the Ki 46 is what would take to make in maneuverable?
larger wing and tail control surfaces means more drag. More weight means already poor climb gets worse. ANd since you bleed off speed in maneuvers a low powered plane is at a disadvantage.