Early war fighters, what was supercharged and what wasn't?

[renrich]

Yardstick range of early F4U1 was 1596 miles. Combat radius would be about 1596 divided by 2 multiplied by around 75%. which would be around 600 miles. Yardstick range of P47C-early D was 895 miles. Same formula gives around 350 miles for combat radius. These were all on internal fuel.

 

[tomo pauk]

Check the ranges at speed and altitude. Many Navy planes were rated for range at low altitudes meaning they weren't using power (fuel) to turn the first stage of their two stage superchargers. They were also sometimes rated at a rather low speed which, while safe enough for long over water flights with no air defenses below might not work out so good over Europe.

See: http://www.zenoswarbirdvideos.com/Images/F4U/F4USEC.GIF

While the Corsair may be able to fly using under 50 gals an hour at low altitude a high speed cruise could almost double that and note that at MAX continuous power (no time limit) fuel consumption is 250 gals an hour at high altitude.

What was the combat radius of the planes in question at operational heights and speeds?

Do you have any figures/sheets that would cover the issue for P-47/38/51?

 

[Graham Boak]

Combat radius is more like range divided by three or more, not two, for it has to include a combat period at full power, extra fuel for operating at non-optimal altitudes or speeds, fuel for organising into formations, and reserves for landing. None of these are normally allowed for in maximum range calculation, which is why some surprisingly large numbers appear in manufacturer's quotations. These do not translate into anything useful in service without major factoring.

The extra efficiency credited to the turbocharger is largely lost in differences between aircraft, and they require major compromises in airframe design. My understanding is that Lockheed would have loved to get Merlins on the P-38, but the redesign would have been horrendous because of weight distribution changes. The two-stage supercharged Allison, with separate stages, might have fitted better. Plus there were major political problems with the Merlin in the US.

I agree that there is much confusion over the differentce between 2-speed and 2-stage engines, not being to certain about that myself until a few years back. On Sunday, I did catch the RAF Museum making the same mistake on a Merlin 23 underneath a Mosquito - this one did have 2-stage engines, but they weren't 23s!

 

[renrich]

If you will notice there is a factor of 75% in the equation to account for start up, takeoff, climb out , cruise, combat, cruise back and reserve. This is according to Dean, "America's Hundred Thousand." He actually says 75% to 80% but I used 75% to be conservative. The 75% works the same whether applied to the yardstick range or to half the yardstick range. You are absolutely correct though that combat radius was dependent on load, altitude, etc. There is a table in Dean's book taken from Bureau of Aeronautics data which shows the P47D with a radius of action with 305 gallons as 125 miles at 25000 feet and a ROA with 370 gallons as 225 miles. There are no comparable ROA tables in his book for Navy fighters, just yardstick ranges at various altitudes. The F4U1 with 361 gallons of internal fuel actually has more range at 5000 feet than at 1500 feet. However, there is little question that the F4U1 on internal fuel had a longer range than the P47-C-D on internal fuel.

 

[Shortround6]

I think you have summed up things rather well.
As a 'for instance' I have seen range figures quoted for the Corsair at 179mph, altitude unspecified, and also 'yard stick' ranges for the corsair with the speed unspecified but the note that it at was at 5,000ft. Now at 5,000 ft the supercharger system on a Corsair has not only disengaged the 1st stage of the supercharger so that it is not turning and using any power but auxiliary doors have been moved in the ducts so that the air flow doesn't even go through the supercharger but instead goes directly to the intake of the second stage of the supercharger.
A very efficient system for low altitude, low speed cruise but rather misleading if you what to know the range at 25,000-30,000ft at 300mph plus where the 1st stage would be engaged and operating in high gear.

The Merlin P-38 was looked at several times and estimates ranged from a 5%-30% loss in range depending on which Merlin vrs which Allison and what speed/altitude was being compared.

 

[Shortround6]

The F4U1 with 361 gallons of internal fuel actually has more range at 5000 feet than at 1500 feet. However, there is little question that the F4U1 on internal fuel had a longer range than the P47-C-D on internal fuel.

Less drag at 5000ft, thinner air

With 20% more fuel feeding the same engine the F4U1 should go further. The question is whither it goes enough further at the heights and speeds needed for European bomber escort to show a worthwhile advantage over the P-47.

Part of the 100 mile difference for the two P-47s with 65 gallons of fuel difference is that the "book" figures for the P-47 called for 45 gallons for warm-up, take-off and climb to 5,000ft. Subtract even more fuel for climbing to 15,000-20,000 ft while forming up (same for early and late P-47s) and then figure the combat allowance (same for both planes?) and a certain amount of reserve (same again for both planes?) and that extra 65 gallons suddenly becomes 50% or more fuel available for "cruising".

the Corsair gets the same sort of "bonus" for it's extra fuel but then we are trying to figure if the Turbo charger helps the fuel economy in cruising at 25,000-30,000ft over the gear driven supercharger and the relative drag of the two aircraft. drag at 25,000-30,000ft being a whole lot less than close to sea level.

 

[renrich]

Another table in Dean gives yardstick ranges for later model P47D and F4U1D
P47D Gross weight-14784 pounds,Weight of fuel-2232 pounds, Range-1135 miles, 1.97 pound of fuel/mile

F4U1D Gross weight-12289 pounds, weight of fuel-1422 pounds, Range-811 miles, 1.75 pounds of fuel/ mile