RAF rejects the Whirlwind, but the FAA shows interest

[Admiral Beez]

The Whirlwind came about from Westland's P9 submission to Air Ministry specification F.37/35 (single-seat day and night fighter armed with four cannon, capable of 330 mph at 15,000 ft). In Feb 1937, the Air Ministry issued a contract for two P.9s, with expectations that these two prototypes be flying by mid-1938. The prototype first flew on 11 October 1938.

Now, let's change up things. The RAF pushes the AM to reject the Whirlwind in favour of more Spitfires and Hurricanes, along with a push to expedite the cannon-armed Spitfire. Westland, upon hearing that the FAA will soon be turned over to Royal Navy control presents its two prototypes to the FAA for consideration. The FAA shows interest, and asks the Whirlwind's designer Petter to modify one of the prototypes for carrier ops. The FAA requires the Whirlwind to be able to land on a 25 knot carrier with 10 knots WOD with a landing speed of about the same as the new Fulmar, and have a range of at least 1,000 miles. Lastly folding wings, with a max folded width of <22 feet.

With the Whirlwind's inherent high landing and takeoff speed, is this even feasible? Or would Westland throw in the towel, demand either funding for an entire new design, or forget it and just sub-contract its plant to make Spitfires, etc? What sort of modifications are needed? Would a return to the original P.9's twin tail be useful? Can Fairey's patented Youngman flaps be used? Though the Whirlwind already has some of the biggest flags on a fighter I've seen.

 

[GrauGeist]

Leading edge slats (Handley-Page slats) might be an option.
The Fi156 was a prime example of how well they offered low landing speeds that were well beyond other type's critical stall range.
Of course, the Fiesler's slats were fixed, but they performed well for the Bf109 and Me262 in an automatic configuration.

 

[tomo pauk]

Whirlwind have had both slats, and Fowler flaps.
Make the wing fold between the wing station where flaps join the ailerons, that is just outboard of fuel tanks and inboard to the slats.

 

[Admiral Beez]

Leading edge slats (Handley-Page slats) might be an option.

Doesn't the Whirlwind already have leading edge slats? What's in the photo below? How does the Hanley-Page variant differ, did any pre-war fighter use them?

However there is no mention of slats in the cockpit controls. #19 and #20 control the flaps, so perhaps the slats are linked automatically - but most pics of the flaps in operations don't show the slats deployed. Conversely, the aircraft above shows the slats deployed whilst the flaps are closed. I wonder if the slats were deleted in the production versions?

 

[GrauGeist]

I freely admit to not knowing the Whirlwind well enough, to know that it had leading edge slats.
It appears that it did and so I will assume they were automatic (Like the Messerschmitt's were equipped with), so they will extend automatically when the air pushing against them drops to a preset pressure.

 

[Admiral Beez]

It appears that it did and so I will assume they were automatic (Like the Messerschmitt's were equipped with), so they will extend automatically when the air pushing against them drops to a preset pressure.

Perhaps for carrier landings the auto slats could be hydraulically operated by the pilot.

Given its huge flaps and slats, why did the Whirlwind have such a high stall, landing and takeoff speed? And what more, if anything can be done to slow it down for carrier ops? Presumably wing loading is too high compared to a Sea Hurricane, Fulmar or Wildcat - so a new wing? But now we're getting to the point of tossing the original aircraft entirely.

 

[GrauGeist]

The higher stall speeds would be relevant to it's wing area.
The seafire had a comparable wing area, but weighed considerably less.

 

[Admiral Beez]

The higher stall speeds would be relevant to it's wing area.
The seafire had a comparable wing area, but weighed considerably less.

Well, if we need a new wing for folding we might as well make a wing with increased chord, something like the later Sea Hornet's wing. This may reduce top speed, but may also allow for more internal fuel.

I had a look at the wing loading and area of similarly sized twin-engined fighters. Interestingly, per Wikipedia the 11,000 lb. (gross) IMAM Ro.57 has the identical 250 sqft. wing area as the 10,360 lb. Whirlwind.

 

[Glider]

I think you will find that they did have leading edge slats but they were normally wired shut. For the life of me I cannot remember why

 

[Admiral Beez]

I think you will find that they did have leading edge slats but they were normally wired shut. For the life of me I cannot remember why

Per Wikipedia...

"Handley Page slats were fitted to the outer wings and to the leading edge of the radiator openings; these were interconnected by duraluminium torque tubes. In June 1941, the slats were wired shut on the recommendation of the Chief Investigator of the Accident Investigation Branch, after two Whirlwinds crashed when the outer slats failed during vigorous manœuvres; tests by the Aeroplane and Armament Experimental Establishment (A&AEE) confirmed that the Whirlwind's take-off and landing was largely unaffected with the slats locked shut, while the flight characteristics improved under the conditions in which the slats normally deployed."

It's unclear above if the slat's removal caused high landing speeds. However I might be misunderstanding the purpose of the slats, not as landing aids but as agility boosters.

 

[Glider]

Thanks for this. My memory must be getting better

 

[Admiral Beez]

Thanks for this. My memory must be getting better

Perhaps the best place to start is to reactivate the slats, but have a switch so they only deploy for takeoff and landing. Do this at the same time the wing fold is being added. Maybe that's all we need to achieve workable low speeds?

 

[Shortround6]

Ok guys, slats are not magic, no little fairies pop out with pixie dust to increase the lift.

What the high lift devices allow is a higher angle of attack before the wing stalls.

Please note that to get the effect in the charts FULL SPAN flaps or slats are needed, partial span flaps and/or slats will give a much reduced effect.

Most of the time in the 1930s Handley Page slots were fitted to retain alerion control at or near stall, NOT to increase lift or reduce landing speed. They made the airplane easier to control (less likely to crash) at speeds just above stall.

If you were not landing or taking off with an angle of attack exceeding 13-15 degrees the slats don't do much at all.
If you are descending on a 6 degree angle/glide slope and have the nose pointed 7 degrees high you have a 13 degree angle of attack. That is a rather steep decent angle and can lead to heavy landings. 3 degrees is common for land airports.

You don't really want to hit the runway tailwheel first.