Westland Whirlwind revisited

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They changed engines on Hawks a lot though didn't they? Did the Mohawk IVs (Hawk 75 A4?) used in India still have the 1940 engines meant for France?
See the attached. I think this is the only case where they actually yanked the R-1820's and replaced them with R-1830's. It seems that not only were the R-1820's suffering from basic flaws such as poor lubrication but sitting around had not exactly improved matters. Presumably they had some fairly worn out R-1830 Hawks that could at least supply the cowlings.

Both the Hawk and the Buffalo had problems with the R-1820's, which were otherwise known as reliable engines. The 1820 had been around for a while, powering the F11C, BF2C, F3F, Lockheed Super Electra, and some models of the DC-3, among others. You have to wonder if Curtiss and Brewster were using rebuilt older model engines to handle the wartime surge of requirements.
And then they were replaced by Typhoons, the other RAF fighter bomber that had engines too unreliable to make it across the Channel.
Sorry. Complete brain fart! Still thinking Mohawks.

No Whirlwinds to India. About 90 Mohawks to India.

137 swapped its Whirlwinds for Hurricane IV in June 1943 and then converted to Typhoons in Jan 1944. 263 swapped its Whirlwinds for Typhoons in Dec 1943. By then the Napier Sabre's problems were largely solved. Before this pair converted there were at least 6 squadrons flying Typoon in 2nd TAF with more to come online before D-Day, all flying happily across the Channel and coming home safely.
Back to the whirlwind:

It was mentioned earlier that the Whirlwind should have had the XP-50 wing, but at what cost to performance?

From what I've read, the Whirlwind had a favorable roll rate. Putting a wing with a larger sg.ft. would have to have an impact in that regard.
Back to the whirlwind:

It was mentioned earlier that the Whirlwind should have had the XP-50 wing, but at what cost to performance?

From what I've read, the Whirlwind had a favorable roll rate. Putting a wing with a larger sg.ft. would have to have an impact in that regard.

Not necessarily - P-40 and P-36 had a fairly large wing (236 sq ft and 37' span) with a pretty low aspect ratio and they rolled very well, right?


Same for the Mustang (235 sq ft and 37').

I think a really long wing span is bad for roll, as is a lot of weight on the wings (putting cannon into the wings seemed to slow the roll rate on some fighters). The shape probably matters too but those are two types (above) which seemed to roll quite well.

I am not certain but IIRC the F4U had a good roll rate too, that was 314 sq ft and 41' span.

Whirlwind was 45' and 250 sq ft, so I would think they could increase the aspect ratio of the wing a bit.

How much a wider wing affects drag is something hopefully someone else with better knowledge of aerodynamics and physics can answer.
How many Whirlwinds did the RAF send to India?

Does sending Hawk 75s to India make them better than the Whirlwind?

Or worse?

In WW2 Britain tended to keep the better, more desirable, aircraft on the home front.

An example is the Spitfire and Hurricane. The Hurricane was sent to O/S commands before the Spitfire because the RAF wanted the Spitfires for home defence. Only when there were sufficient Spitfires were they sent to O/S commands.

That they sent Hawk 75s to India indicates that they had no need for them in Britain, and sending anything to India was better than sending nothing.
I don't think that is what he was getting at. Whirlwind was apparently 60 mph faster than a Hawk and much better armed to boot, I think it was a better fighter in many respects, certainly for combat against German aircraft.
That they sent Hawk 75s to India indicates that they had no need for them in Britain, and sending anything to India was better than sending nothing
The Hawk 75s that Britain had, were of limited number as well as having a limited reserve of parts.

The decision to send the Hawks to the far East was sound, since their service would buy time for Britain to build up enough fighter numbers (Hurri, Spit) that they could afford to send east.
All they had to do was fit 2 stage merlin's and Browning M2's into the Whirlwinds,
I don’t think fitting the larger and heavier Merlins onto the Whirlwind is that easy. Why not just put the Merlin’s two stage supercharger onto the Peregine?

  • Length: 73.6 in (1,869 mm)
  • Width: 27.1 in (688 mm)
  • Height: 41.0 in (1,041 mm)
  • Dry weight: 1,140 lb (517 kg)
Merlin (albeit the later 61)
  • Length: 88.7 in (225 cm)
  • Width: 30.8 in (78 cm)
  • Height: 40 in (102 cm)
  • Dry weight: 1,640 lb (744 kg)
If we can find some earlier or concurrent applications for the Peregrine where the Merlin was too large or heavy, we might have the scale to justify the project. Maybe a twin engined bomber? Peregrines on a Blenheim? The Hispano-Suiza 12Y, of similar size and weight to the Peregrine was used in several compact and twin engined combat aircraft.
  • Length: 2,137 mm (84.3 in)
  • Width: 764 mm (29.9 in)
  • Height: 945 mm (37 in)
  • Dry weight: 492 kg (1,085 lb)
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They should have put in Rolls Royce pelicans in it, those provided more than enough horsepower and weighed half as much as a merlin III.
o_O? I think I have lost track of the discussion.

Some number for comparison.

re the wings, BHP, and weights of the Whirlwind and F5F and P-38

____________________Whirlwind__________XF5F__________ P-38F
Wing Span___________ 45' 0"____________42' 0"___________52' 0"
Wing Airfoil_NACA___ 23015*___________23015* __________23016-4412
Wing Area (gross)______ 250 ft2___________304 ft2__________ 328 ft2
Aspect Ratio__________8.10_____________ 5.80_____________8.24
TOGW (clean)_______10,350 lbs________10,138 lbs**______15,000 lbs
Wing Loading _________41.4 lb/ft2________33.4 lb/ft2* ______ 45.7 lb/ft2
Horse Power_________ 1770 BHP________2000 BHP________2000 BHP (all at 15,000 ft)
Power/Weight ratio___ 0.171 HP/lb______ 0.197 HP/lb______ 0.133 HP/lb
Vmax at 15,000 ft***___~350 mph________~350 mph________~350 mph

*The NACA 23015 is the airfoil for the inner wing section for both the Whirlwind and the XF5F-1. I do not know if the outer wing panels used the same airfoil - they may have been a thinner airfoil. Does anyone have any info on the outer wing panel airfoil sections?

**It was estimated that the TOGW (clean) of a combat ready F5F-1 (ie 4x .50 cal, armour, SSFT, radios, etc) would have been about 11,100 lbs, which would give a wing loading of 36.5 lb/ft2, and a Power/Weight ratio of 0.18 HP/lb.

***The Vmax are for the equivalent of Normal power using 100/130 grade fuel and in temperate conditions. The seemingly slow~350 mph for the P-38F is due to field tests where it was found that the intercoolers and turbosupercharger could not sufficiently cool the charge at higher power settings, causing the V-1710 engines to experience detonation at said higher power settings below about 20,000 ft.

Some observations.

As far as Wing Loading goes, you could increase the TOGW of the Whirlwind by 1,075 lbs and end up with the same Wing Loading as the P-38F. The XF5F-1 is clearly the winner in terms of lower wing loading at 33.4 lb/ft2 for the prototype, and still clearly superior at the projected TOGW of the combat ready F5F-1 airframe at 36.2 lb/ft2.

As far as Power/Weight ratio goes, the XF5-1 is clearly the winner, followed by the Whirlwind, and then the P-38F. The combat ready F5F-1 is still superior - though not as much so - at 0.18 HP/lb.

As far as the Wing T/C ratio goes the Whirlwind and XF5F were the same 15%*, and the P-38 is an average of 14%. The P-38F is slightly superior in the T/C category and this combined with the high Aspect Ratio probably gives it the edge in Cd for the wings.

re a developed Peregrin II engine.

The Peregrin I was slightly more efficient than the Merlin III in terms of HP/in3. If it had been developed further and given the same tweaks as the 'Hookerized ' Merlin, there is (I think) no reason the power could not have been similar to the Merlin 45 in terms of HP/in3 at +9 lbs boost - ie 0.73 BHP/in3. So a 'Hookerized' single-speed Peregrin II should give about 950 BHP at ~15,000 ft. This increase would give the Whirlwind a Power/Weight ratio of 0.181 HP/lb, basically the same as the combat ready F5F-1, and clearly superior to the P-38F.

NOTE All of the above obviously ignores the superior altitude rating of the P-38F with its turbosupercharger system. Presumably, the P-38 would steadily reduce any performance differences as altitude increases above 15,000 ft and probably surpass the Whirlwind and XF5F-1/F5F-1 at any altitudes above about 20,000 ft. With the later intercooler/turbocharger arrangements the Vmax for the P-38F was about 370 mph at 15,000 ft.

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