Forum: F-35 Lightning II

Corsair1963 wrote:

Really, considering the vast amounts of fuel that the F-35 carries. (i.e. 15,000 - 20,000 lbs) Is the range being purposely underestimated???

I agree with you.
I think that F-35B's range is as about 1,300nm, similar with F/A-18F without drop tanks. AND F-35A/C 's range is about 1,800nm or more, similar with F/A-18E/F with 3*480 gallon tanks.

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As for radius the CTOL will do about 750nm on a max range air-to-air combat profile on internal. LM did a comparison some time ago (printed in JanesDW), all except Flanker with three droptanks:

* F-35A 751nm
* Super Hornet 816nm
* GripenC 502nm
* Eurofighter 747nm
* Rafale 896nm
* Su-30MKI 728nm

Bear in mind that these were estimates. Also consider that all performance metrics on the F-35 is based on combat weight, and end-of-life engine performance with 5 percent degradation in fuel economy and 2 percent in thrust.

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the data seems abnormal.
It may use defferent methods to calculate each plane.

1--
http://morisson.thomas.free.fr/Eurofigh ... bility.pdf
EF-2000's ferry range is about 2,000nm with 2 drop tanks.

2--
* F-35A 751nm
* Eurofighter 747nm

if they use the same method to calculate the range and radius, F-35A's range is over 2,000 nm?

(No Weapons: Internal Fuel) {Fuel Fraction} [L/D] Thrust (mil/ab/mil t/w / ab t/w)

F-35A: (23 tons) {39%} [Assume 9.5] ( 14 /21.5 /.61 /.93)
Tiffy: (17 tons) {29%} [Assume 10] (13.5/20.2 /.79 /1.19)
(F-35A is 35% heavier) {F-35A has 34% higher Specific Fuel}( Tiffy has 27-29% higher T/W)

5K weapon load

F-35A: (25.5 tons) {35%} [Still 9.5] (.55 / .84)
Tiffy: (19.5 tons) {26%} [likely closer to 9] (.69 / 1.03)
(F-35A now 30% heavier) {and 35% more Specific Fuel} ( only 23-25% higher T/W)
For any given TSFC the F-35A will have up to 34% more range when clean, while Tiffy will be far more powerful.
So concider this, the F-35A can carry up to 2.5 tons of ordnance (10% specific load) while maintaining L/D, as soon as Tiffy carries bombs or missiles it loses L/D and thus range. It can increase its Fuel Fraction with Drop tanks at the expense of L/D, but will still be hard pressed to reach the fuel fraction of the F-35.
Also, because the F-35A is heavier it takes a higher payload to adversely affect its fuel fraction and T/W ratios. The F-35 can also be expected to have a lower fuel consumption due to the higher BPR and newer design. So for a practical combat load the F-35 can be expected to have phenomenal range/endurance.

The f135 probably uses a lot of fuel to get its thrust. You cant compare different engines because each has different fuel consumption, there are many variables to determent range. But they are trying to make F135 more fuel efficient to increase range.

yes, its call Thrust Specific Fuel Consumption, the TSFC listed in my post. By comparing Fuel Fractions, L/D, T/W, and TSFC (all fairly unitless ratios) I have taken away the need for weights and Thrust ratings themselves. Two EJ200s have a TSFC of .81 in Mil power while F135s have a TSFC of .89. So for the Mil thrust ratings above, Tiffy burns 10.9 tons of fuel per hr, F-35 burns 12.5 tons per hour. That leaves the Tiffy with 27 minutes of fuel at that thrust rating, while the F-35 has 43 minutes. Tiffy would have to travel 60% faster to have the same range. So an F-35 traveling at 620 (0.94 Mach, reasonable) knots would have a range of roughly 444 miles at sea level (where these thrust numbers are based), to match the range the Tiffy would have to travel 992 knots or Mach 1.47 in mil thrust at sea level. Not happening. Tiffy is faster, but not that much faster.

'Greater Than' Range 'Facts' from LM August 2010: http://www.f-16.net/f-16_forum_download-id-13653.html (40Kb PDF)

Forum: F-35 Lightning II

F-35 Range Greatly Underestimated???