Forum: F-22A Raptor

johnwill wrote:

Were 3.0 and 3.2 at the same altitude? Without specifying altitude, the comparison is meaningless.

On a similar vein, as someone mentioned in an earlier thread, we aren't given at what altitude the 410nm radius corresponds to. The operational altitude of the plane might be significantly higher than that to which 410nm corresponds. At 60000 feet, drag is low, and cruise ought to be more efficient than at, say, 40000 feet.

Another hint that 410nm might not reflect true capability is according to the Raptor team website http://www.f22-raptor.com/technology/data.html, the actual requirement was just 360nm including just a 100nm supersonic "dash" each way (recall that the original ATF spec was around 700nm to be able to access central Europe from bases in England). The point of supercruise is to be able to operate supersonically for extended periods of time. Now, 100nm at 800kts is just 6-7 minutes. Considering how integral supercruise was as part of the Raptor's design philosophy, I would guess that the 260+100nm requirement, hence the 310-100nm radius, is somewhat of an understatement.

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Yes the altitudes were the same for the Mach 3.0 vs Mach 3.2, at least initially, both planes climbed to maintain a contant speed profile as fuel was burned, but in the end the difference between their altitudes was very small.

checksixx wrote:

StolichnayaStrafer wrote:

I remember an article in Popular Science or Popular Mechanics from back in the early days of the ATF trials. It said that one of the main requirements, since it would be a "stealthy" aircraft, was to be able to carry an internal fuel load equivalent to the F-15Cs internal AND external fuel capacity. I assume they did not quite achieve those results.

F-15C with three bags: 3,560 Gallons
F-22 internal fuel only: 3,082 Gallons

I'd say they did pretty good.

You mean 11665 litres? or 14008L？

My figures are clearly in gallons...you do the conversion.

checksixx wrote:

My figures are clearly in gallons...you do the conversion.

Nice one.

strykerxo wrote:

It could be that it just gets somewhere so fast and covers such a great distance that they would like to have more. The fuel fractions can be misleading with the thirsty engines. It is hard to say whether it was an "I wish or it needs more".

In all likelyhood the F-22's engines have a lower specific consumption than those on f-15's, after all technology goes forward not backwards. Hence for the same ammount of thrust the F-22 would consume less. However in maximum thrust F-22's may or not consume more, simply because the F-15's engines will fall short of the raptors max thrust mark. But then again you wont pull afterburner for a cruise range measurement, and consider the fact that F-22 reaches dry thrust levels for wich the F-15 will have to afterburn to.

Elite 1K Joined: May 26, 2005 - 08:39 PM Posts: 1496

Exactly, TANSTAAFL.

The F119s may be more efficient than the F100s in an F-15, but I'm still guessing an F-22 in MIL is guzzling more fuel per hour than an F-15.

DarkDuke wrote:

checksixx wrote:

StolichnayaStrafer wrote:

I remember an article in Popular Science or Popular Mechanics from back in the early days of the ATF trials. It said that one of the main requirements, since it would be a "stealthy" aircraft, was to be able to carry an internal fuel load equivalent to the F-15Cs internal AND external fuel capacity. I assume they did not quite achieve those results.

F-15C with three bags: 3,560 Gallons
F-22 internal fuel only: 3,082 Gallons

I'd say they did pretty good.

You mean 11665 litres? or 14008L？

Don't ask accurate data, somebody here will only give you what they want you believe to, so never with source. Razz

end wrote:

DarkDuke wrote:

checksixx wrote:

StolichnayaStrafer wrote:

I remember an article in Popular Science or Popular Mechanics from back in the early days of the ATF trials. It said that one of the main requirements, since it would be a "stealthy" aircraft, was to be able to carry an internal fuel load equivalent to the F-15Cs internal AND external fuel capacity. I assume they did not quite achieve those results.

F-15C with three bags: 3,560 Gallons
F-22 internal fuel only: 3,082 Gallons

I'd say they did pretty good.

You mean 11665 litres? or 14008L？

Don't ask accurate data, somebody here will only give you what they want you believe to, so never with source. Razz

Data presented by posters on this site can't be worse than that on other sites....such as Key Publishing's AFM site where Russian govt propaganda sites, or "news" sites are always used as sources....

Don't forget the effective ground speed from a light super-cruise at over 60k ft.

The big question is “can the F-22 supercruise at 60Kft at M1.5”? If it can, it picks up a considerable amount of supersonic range. Even though he’s a critic, Stephenson’s slides on CDI have turned out to be mostly factual, even if taken out of context. He cites a specific range of 0.04nm/lb for M1.5/45Kft. Using an extrapolation (he cites from 30K to 45K) and assuming the F-22 can cruise at M 1.5 @ 60K ft that should give a SR of roughly 0.055nm/lb. Assuming 12,000-14,000lb for ingress/egress, that should give a rough SS radius of 250-290nm at 45Kft. At 60K, that goes up to 330 to 385 nm for the same amount of fuel.

He also gives SR for M 1.25 and again using an extrapolation, this indicates a SR of 0.049nm/lb at 45K and 0.061nm/lb at 60K assuming it get up there. So that’s roughly 295 to 345nm for 45K and 366 to 430nm for 60K. The big problem here is that this extrapolation may not be too accurate, the air density at 60K is about half at 45K and this impacts thrust (also fuel consumption), drag and lift.

BDF

Forum: F-22A Raptor

F-22 Raptor range