Originally posted by WestPoint23
I was being very conservative with the 650 mile combat range figure given the altitude and speed, total 1,300. So yes, all at Mach 1.8 and at
65K.
I'll shortly demonstrate how ludicrous that is.
Originally posted by WestPoint23
Those figures are so misleading it's not even funny.
Yes... because Lockheed are under-selling the aircraft.
Originally posted by WestPoint23
I'm going by inference from pilot comments, not undervalued government figures.
Lockheed figures... not government.
You can infer whatever you want from whoever you want. If it could do those range figures, Lockheed would be screaming it, and so would the USAF to
get more under purchase.
Originally posted by WestPoint23
Do you really want to pretend that one of the most aerodynamically clean aircraft with efficient engines and 20,650 Lb of fuel on it can only fly for
410NM in combat?
Do you
really want to start talking to me about L/D figures, fuel fractions and range?
The Breguet range equation (for turbofans) is as follows:
Range = 1/gravity * Speed * Lift/Drag * 1/Tsfc * ln(initial weight/final weight)
Tsfc is thrust specific fuel consumption (which is the amount of fuel consumed in an hour per unit of thrust produced). The F119 has *supposedly* a
Tsfc of 0.78 lb/lbf.hr at full mil power (thats just what I've picked up along the way, it could be a bit lower).
I'm gonna circumvent the equation a bit. The L/D will be under 10 (10 would be absolutely ludicrously high for a fighter) - but we'll use it anyway
to drop the 1/gravity term.
So:
Range = (1.8*660) * 1/0.78 * ln(64,500/(64,500-20,650))
Range = 590 miles
Or looking at it another way
Drag squares with speed (subsonically), and you know that the F119s in the F-22 produce approaching double the thrust of the F100s in mil power
(~15,000 vs. ~25000). Which of course means approx double the fuel consumption.
The F-100 has an sfc of 0.76 lb/lbf.hr (@ full mil).
Which means the F-15 consumes 22,800 lbs of fuel in an hour and the F-22 39,000 lbs of fuel in an hour using the 0.78 mentioned earlier (at full mil
thrust). Each aircraft does have 2 engines after all.
At that rate, the F-22 can go just over half an hour on full mil thrust. At Mach 1.8 that corresponds to a ground range of 630 miles or so.
So a supercruise
range of 590 or 630 does roughly tie in with the
radius of 300+100 [sub + supersonic], i.e ranges of 600 + 200 [sub
+super].
Either way, your 1,300 miles range is absolute rubbish. Unless the F119 has a Tsfc of the order of 0.4 - which would be near half all fighter engines
in the world - including the F135 which its rumoured has a Tsfc of 0.7 lb/lbf.hr.
Oh, and that would neglect the time taken to climb to 65K feet.
Originally posted by WestPoint23
There were two ATF goals with respect to fuel and range. The ATF was envisioned as having a 700-750 mile combat range under supercruise.
The ATF goal was 250+100. That is 250 sub + 100 super.
NOT 350 in + 350 out all supercruise. You speak as if cruising supersonically does not come at a cost in fuel consumption relative to cruising
subsonically.
Originally posted by WestPoint23
As I said before the F-22 has an internal fuel capacity of 20,650 lb (3,082 gallons), or roughly 10.3 tons. So far with the 4 external fuel tanks
certified for it is has a total fuel capacity of 36,515 lb (5,450 gallons) or roughly 18.2 tons. Or about 28,582 lb with two fuel tanks.
Anyone still think the F-22 has no legs?
Amateurs talk fuel loads, professionals talk fuel fractions.
F-22 = 20,650/66,470 = 0.31
F-15 = 14,400/44,500 = 0.32
Su-27 = 20,700/60,600 = 0.34
MiG-31 = 36,050/88,550 = 0.41
That is why the MiG-31 has the massive range it does.
When you bring fuel tanks into it, you are sacrificing your radar properties. You also then are sacrificing your clean aerodynamic profile.
I am comparing aircraft on internal fuel only.