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I dont think there can be any doubt now that you are just trolling. The maximum speed of the P-39N was about 375MPH, its cruising speed at 15,000ft cruising altitude was 250MPH, Your consumption in cruise at 62gph is only marginally less than your combat 25 gals in 20 mins that is 75gph. most engines used circa 3 times the fuel on max power that they used in cruise.
I've come up with similar before. Our friend is confusing allowances for reserves and seems to use parts of the charts that will give the aircraft the most range, ignoring the 30 minutes reserve for emergency. Great post!Your calculations are incorrect.
(1) The P-39N-0/1 consumed 147 gallons per hour at full military power. The usual rule for combat fuel allowance was 15 minutes at full military power and 5 minutes at war emergency power. The latter isn't listed on the charts, so let's just go with 15 minutes of full military power.
147 / 60 * 15 = 36.75 gallons
The combat fuel allowance is closer to 37 gallons, not the 25 gallons you stated.
(2) At a take-off weight of 8,000 lbs, the P-39N-0/1 consumed a total of 39.7 gallons of fuel to climb to 25,000 according to the climb data section of the Take-off, Climb, and Landing chart.
The fuel consumed in climbing to 25,000 feet is closer to 40 gallons, not the 20 gallons you stated.
(3) Reserve fuel allowance normally used in radius calculations is thirty minutes, not twenty. Using Column V (max. range) for 7,500 to 7,100 lbs weight, fuel consumption per hour is about 35 gallons per hour. Call it 17 gallons for half an hour.
The fuel reserve is 17 gallons, not the 10 gallons you stated.
(4) The combat radius is determined by how far the aircraft can fly back on internal fuel after deducting allowances for warm-up, initial take-off, combat, and reserve (assuming the cruise out can be done mostly on external fuel in drop tanks).
At 120 gallons full internal: 120 - 37 - 17 = 66 gallons left to cruise back to base.
(Note that the internal fuel remaining would actually be slightly less than 66 gallons, since warm-up, take-off, and initial climb are done on internal fuel before switching over to external fuel. But let's use 66 to be generous.)
Using your own figures of 62 gallons per hour at a TAS of 276 MPH for the cruise back yields the following:
66 / 62 * 276 = 293.8 miles
See the relevant charts on pages 26-28 of the PDF found here:
Pilot's Flight Operating Instructions -- P-39N-0 and P-39N-1 Airplanes
I've come up with similar before. Our friend is confusing allowances for reserves and seems to use parts of the charts that will give the aircraft the most range, ignoring the 30 minutes reserve for emergency. Great post!
I found that depending on the manual there is a IAS to TAS chart based on a what I believe is a lapse rate calculation (true airspeed is an additional roughly 2% higher than indicated airspeed for each 1,000 feet above sea level) which is the most inaccurate way to calculate this.He put in the reserve allowance, but underestimated it by using 20 minutes instead of 30 minutes. He also apparently has the aircraft carrying the drop tank out and back, which is odd.
The P-39 manual I referenced only has IAS figures for the cruising values, so there's the question of what exactly those convert to in TAS. Later USAAF manuals included a TAS column.
Perhaps if you paid attention to the mountains of information being provided (often given in intricate detail), you would better understand the Bell product that's the subject of "debate".I really don't understand what there is to debate.
Wasn't that the problem with Bader's Big Wing during the BoB?According to Parks instructions. a good squadron takes up to 4 minutes longer than a test pilot to reach 25,000ft. two squadrons take 10-12% longer than that and three squadrons 15-18% longer.
According to Parks instructions. a good squadron takes up to 4 minutes longer than a test pilot to reach 25,000ft. two squadrons take 10-12% longer than that and three squadrons 15-18% longer. There maybe good reasons why escort squadrons did not have the same experience but I doubt it is hugely different.
When in contact with a bomber formation, the speed is the ground speed of the bombers, escorts can cruise at a speed to conserve fuel or to be fast enough not to be bounced, fuel used is how much is consumed between RV points. Using an individual aircraft performance to compare operational combat radii doesnt work.
At 120 gallons full internal: 120 - 37 - 17 = 66 gallons left to cruise back to base.
(Note that the internal fuel remaining would actually be slightly less than 66 gallons, since warm-up, take-off, and initial climb are done on internal fuel before switching over to external fuel. But let's use 66 to be generous.)
Using your own figures of 62 gallons per hour at a TAS of 276 MPH for the cruise back yields the following:
66 / 62 * 276 = 293.8 miles
Exactly although the situation is different, his big wing weren't all at the same airfield and took an age to form up. To turn the big wing and keep formation meant very, very slow turns or those on the inside had to almost stall while those on the outside couldn't keep up.Wasn't that the problem with Bader's Big Wing during the BoB?
Groundhoggery is almost as difficult to fathom as Turingery and Banburismus.Based on the P-39N-0/1 original internal fuel load of 87 gallons:
87 - 37 - 17 = 33 gallons left for the cruise back to base.
Using the same 62 gallons per hour at a TAS of 276 MPH that P-39 Expert gave:
33 / 62 * 276 = 146.9 miles.
So increasing the internal fuel from 87 to 120 gallons (+33 gallons, which is 198 lbs of weight) results in the radius being doubled.
And you have to make a decision if people cant keep up. Oh and you only find out if your plane isnt performing as per the manual when your engine starts sputtering.Formation flying also consumes more fuel as the throttle is always being moved.
Formation flying also consumes more fuel as the throttle is always being moved.
Exactly! I've flown formation in GA aircraft, a T-34 with a Bonanza and Debonair and in an L29 with 3 other aircraft. I found the jet to be the hardest as it took a few moments for the jet to spool up and when once you got momentum it was tricky to slow down (speed brakes). To throw some gasoline into the fire, we haven't even brought up this fact during our range/ fuel calculations, let alone not flying in a straight formation, constantly making shallow turns within the flight while not only making yourself a harder target but scanning for enemy aircraft. Sorry chaps, I've might have added another week to Groundhog Day!That's my non-piloting understanding as well; it's the same reason my truck gets better mileage using cruise-control than it does when I'm throttling through traffic, right?