Forum: F-22A Raptor

Several years ago (well after the rollout of the EMD F-22s) numerous sources listed the F-22A's internal fuel capacity as 25000 lb whereas now the Air Force states the number as along the lines of 18000? Do we know what accounts for this change?

F-16.net Sponsor

mil_hobbyist wrote:

Several years ago (well after the rollout of the EMD F-22s) numerous sources listed the F-22A's internal fuel capacity as 25000 lb whereas now the Air Force states the number as along the lines of 18000? Do we know what accounts for this change?

The 18,000 lb. figure is flat out wrong. Where did you get it?

Members of this forum have reported 18400 or 20650 and used them in combat radius and engine efficiency estimations. For example, see

http://www.f-16.net/f-16_forum_viewtopic-t-5999-start-0.html

or

http://www.f-16.net/f-16_forum_viewtopic-t-5474-start-15.html.

20,650lb is the correct figure. It was in safety doc released by the AF a while ago.

Active Member Joined: Nov 22, 2004 - 09:20 PM Posts: 134

mil_hobbyist wrote:

Several years ago (well after the rollout of the EMD F-22s) numerous sources listed the F-22A's internal fuel capacity as 25000 lb whereas now the Air Force states the number as along the lines of 18000? Do we know what accounts for this change?

The 25000 lb figure has been around since the YF-22 rolled out (AvLeak), and the 18000/18400 lb figure probably came from its critics (at least that's where I first saw it). The F-22 has always had less internal fuel than originally planned, with its slimmed-down aft fuselage, and presumably some more fuel capacity was lost when the engineers decided to further reduce drag by tightening the F-22's skin around its internal components as their volumes became better defined.

I don't have any inside knowledge, but it seems as though a conscious decision was made to sacrifice some fuel capacity for lower weight and better power/drag ratio--in general, better efficiency. I imagine that there must have been an overall gain for this tradeoff, namely better flight performance with minimal impact on range (since lower drag and higher supercruise speed on the same power would obviously help). It is also quite possible that a larger fuel load would have required a stronger, heavier structure than anticipated, making that design less optimized than the current one.

JCSVT wrote:

20,650lb is the correct figure. It was in safety doc released by the AF a while ago.

I came across the figure of 9500 kg several years ago (don't remember where, unfortunately), which is very close, so that's one more point of corroboration, not that the safety document--Technical Order 00-105E-9, REVISION 11--needs it. On the other hand, maybe it does because there is an inconsistency in the figures. The units of volume are given in both gallons and litres, and according to the relevant diagram, the F-22 has 13031 L of internal fuel, which weighs approximately 23064 lb (JP-8 ). The funky conversion factor used between gallons and litres in this document does not correspond to any two units of volume with which I'm familiar, liquid or dry. The question is: which is correct? I suspect that the figures based on gallons are the most accurate, giving the F-22 a nominal internal fuel capacity of 3082 gallons or close to 20650 lb. That's not bad considering that it can perform to its full specifications with this much fuel, unlike some fighters (cough...Flankers...cough Razz

).

Forum: F-22A Raptor

F-22 Fuel