XF5F and XP-50: how good they really were?

[pinsog]

Oh, I agree completely with Merlin's on a Whirlwind, I think they were too much engine on too small an airframe. I also like the Whirlwind.

I have a book at home that has British tests of some British, US and German fighters, Flying to the Limit. In their test the early Cyclone powered Martlet I only got up to 293 mph at 13,700 feet, the Martlet II did 298 at 21,000 feet, the Hawk 75 with a Cyclone did 302 at 14,000.

 

[MIflyer]

Well, based on the configuration in which it actually flew the F5F would not have been very useful in Europe. Its best speed at altitude, 380 mph, occurred at only 16,500 ft.

But in the Pacific it would be a different story. 380 mph was as fast as a Hellcat, and nobody was going to outturn a Zeke anyway. But the kicker was its climb rate, up to 4000 ft/min, a lot better than a F6F. It could have both out climbed and outrun a Zeke and that would have been enough to make it very valuable. The four .50 cal guns would have been fine for dealing with Japanese aircraft. Too bad they never got the landing gear to be strong enough. .

 

[Shortround6]

There is something of a disconnect in the climb figures.
How any plane that can climb at 4,000fpm takes 4.2 minutes to climb to 10,000ft is beyond me. Unless they were using a much lower power setting than even max continuous? (engines over heating on climb?)

 

[tomo pauk]

Well, based on the configuration in which it actually flew the F5F would not have been very useful in Europe. Its best speed at altitude, 380 mph, occurred at only 16,500 ft.

But in the Pacific it would be a different story. 380 mph was as fast as a Hellcat, and nobody was going to outturn a Zeke anyway. But the kicker was its climb rate, up to 4000 ft/min, a lot better than a F6F. It could have both out climbed and outrun a Zeke and that would have been enough to make it very valuable. The four .50 cal guns would have been fine for dealing with Japanese aircraft. Too bad they never got the landing gear to be strong enough. .

No 380 mph for the (X)F5F. 358 mph unarmed: linky

 

[pinsog]

No 380 mph for the (X)F5F. 358 mph unarmed: linky

Unarmed but at least ballasted for the weight of the weapons, 600 pounds normal, 900 pounds over load.

Can anyone guess the increase in speed by changing to smaller diameter P&W engines from the gigantic Wright's? (Use the same hp at same altitude, just reducing the drag)

There is also the turbocharged option that gives 1200 hp per engine at 25,000 feet. 2,400 hp at 25,000 should move the little fighter right along,

 

[MIflyer]

A turbo exploded on the XP-50's first flight and it was destroyed on 19 May 1941. It was equipped with two R-1820-67/69 engines rated at 1200 hp each with turbosuperchargers. Top speed was estimated to be 424 mph at 25,000 ft and time to 20,000 ft was 5 min. Service ceiling was 40,000 ft. Of course they never actually got any performance data.

But would that airplane really be faster than a P-38? I sure doubt it.

You know, Curtiss had a mock up of a P-40C with two V-1710.

 

[tomo pauk]

The R-1830 + turbo would've make it going close to the P-38F/G - so probably not all 400 mph, but probably well above 380 mph (provided the 'pointy nose' was installed).
However, I'd try to install the V-1710s on the Grumman.

 

[pinsog]

It has been reported that it would do 380ish. Of course we don't know which model, but the wrights only put out 1,000 hp at 14,000 feet.

Let's put some much smaller diameter P&W on it with turbochargers. Now we should already get a pretty decent increase in speed from the smaller diameter engines alone. But, in addition to that, we now have 1,200 hp per engine 9,000 feet higher! What did a non turbo Wright put out at 25,000 feet? 550hp? So instead of a total of 1,100 hp, we have 2,400 hp. It has 10 feet less wingspan than a P38, doesn't have the giant tail, (P38 also had the huge radiator scoops) and it weighed 3,900 pounds less than a P38.
Looking at all of that, 425 mph at 25,000 feet doesn't surprise me a bit

 

[pinsog]

Let's look at a P36 vs a P43.

A P36 would do 280 at 25,000 on a 560 hp P&W.
A P43 would do 356 at 25,000 on 1,200 hp.

75 mph faster. All of this technology was available in 1939. No magic, no speeding up the time line. It gave Hellcat performance on the wrights up to 18,000 feet or so when the single stage Wrights run out of wind. Even just using single stage P&W it should surpass a Hellcat by a good margin.

How could it not outclimb a P38 when the P38 outweighed it by 3,900 pounds, and that's a light version of the P38.

 

[tomo pauk]

The XF5F was lightweight. The F5F with R-1830 will weight more, with turbo & intercoolers much more. Weight increase will happen again when protection is added, both for pilot and fuel tanks. P-38 carried hefty load of guns & ammo, more than 1300 lbs with full ammo carried. Many guns = increase in drag.
The P-38 have had big scoops, the turbo F5F will also have scoops for oil coolers and inter-coolers, plus for cooling the turbo.

 

[pinsog]

The XF5F was lightweight. The F5F with R-1830 will weight more, with turbo & intercoolers much more. Weight increase will happen again when protection is added, both for pilot and fuel tanks. P-38 carried hefty load of guns & ammo, more than 1300 lbs with full ammo carried. Many guns = increase in drag.
The P-38 have had big scoops, the turbo F5F will also have scoops for oil coolers and inter-coolers, plus for cooling the turbo.

 

[pinsog]

900 pounds of weapons on overload XF5F would be a P38 without the 20mm cannon and ammo, 4 50's and a lot of ammo.

3,900 pounds leaves considerable room for a couple of turbos, armor and self sealing tanks.

 

[MIflyer]

You'd be better off to use the two stage supercharged R-1830's from the F4F-4. They would be less powerful than turbocharged R-1830's but also less likely to blow up. On the F4F they had to use all of the available cowling area for engine and intercooler air intake, and that led to oil coolers out on the wings. FM-1 shot attached.

Maybe they would have at least flush riveted the airplane? Well they didn't on the F6F.

 

[pinsog]

You'd be better off to use the two stage supercharged R-1830's from the F4F-4. They would be less powerful than turbocharged R-1830's but also less likely to blow up. On the F4F they had to use all of the available cowling area for engine and intercooler air intake, and that led to oil coolers out on the wings. FM-1 shot attached.

Maybe they would have at least flush riveted the airplane? Well they didn't on the F6F.

This is from earlier when Shortround was talking about weight increase of 2 stage P&W:

If you add the 860 pounds of extra engine (2 stage P&W) you talked about, 140 pounds of armor, that leave 300 pounds for self sealing tanks and the Hellcat and XF5F would weigh the same.

You would also have 2,000 hp at 20,000 to 21,000 feet using 2 stage P&W and the P&W are considerably smaller diameter.

Any guess on speed increase do to smaller diameter engines?