Forum: Modern Military Aircraft

Does anyone know the maximum time limit on which an F-15 can engage it's afterburners?

F-16.net Sponsor

t3h_pr3t3nd3r wrote:

Does anyone know the maximum time limit on which an F-15 can engage it's afterburners?

Until it gets very quiet.

OL

t3h_pr3t3nd3r wrote:

Does anyone know the maximum time limit on which an F-15 can engage it's afterburners?

In the technical definition of 'how long' can an F-15 engage it's afterburners (augmentors)?

The aircraft limit would be Vne (Velocity Never Exceed) speed for the Eagle, once you reach it, you would have to reduce power accordingly. Not back to MIL power, but likely not MAX AUG anymore. (But still in afterburner)

The F100 engines have no timed limit for augmentation or MAX power (Full Augmentor). Modern "Afterburners" or "Augmentation" are not an all on/off thing, like old engines. In the F100 there are multiple 'zones' of augmentation; much like a step-up in power (and fuel consumption). So for simply saying "afterburners engaged" at MIN AUG, the Eagle would fly much longer than if at MAX AUG, which is also "engaged". Fuel flow at MIN AUG is much lower than MAX AUG. If the fuel supply (at 10s of THOUSANDS of pounds per motor per hour) is sustained the engines will continue providing the power requested.

Which brings us too OL's response:

outlaw162 wrote:

Until it gets very quiet.

There would be a few alarms, two VERY loud bangs (one from each motor as they suffer fuel-starvation induced compressor stalls from augmented power settings) and then more associated alarms. Quickly hit the 'Master Caution' reset...

Now it's quiet, too quiet! Shocked

Not a good thing Big No No

Keep 'em flyin' Thumb

TEG

PS - how long exactly? take the fuel flow (PPH) of both engines at the density altitude you're flying, add them together, divide by 60 for total lbs/min; then divide the total pounds of fuel remaining on your indicator that figure by lbs/min. IE - Not long! If both motors are using 40K PPH each and you have 10K lbs of fuel remaining, about 7 minutes.

If the eagle were at min aug would it still be able to mainatin top speed or even get to top speed. The F-15 could save a lot of fuel if could get to top speed in somwhere in
the middle of max aug and min aug

mustang65 wrote:

Sure a 6000 hr. fatigued F-15 would not be doing more than mach 2 for than 6 minutes to preserve airframe life. If you had a 1,000 hr, fatigued F-15 it should be able to do it and maintain it into the double digits.

It's not just the airframe life that limits the amount of time an F-15 could maintain that speed. It's the amount of fuel it'd burn doing it that would be the biggest factor.

outlaw162 wrote:

t3h_pr3t3nd3r wrote:

Does anyone know the maximum time limit on which an F-15 can engage it's afterburners?

Until it gets very quiet.

OL

With the Pratt and crapneys...they usually got real loud (compressor stall) then real quiet...Eagle guys could expect to blowout, shell a motor before that piece of FOD would run out of fuel...

All they would have to do is coast up with tanks get as fast as possible and then once they are exausted drop them get to top speed then maintain it. Or they could modify the engines and it could do it for much longer.

mustang65 wrote:

All they would have to do is coast up with tanks get as fast as possible and then once they are exausted drop them get to top speed then maintain it. Or they could modify the engines and it could do it for much longer.

Hell why not strap booster rockets to the F-15? Rolling Eyes

All I am saying is that the F-15 can maintain top speed into the double digits. They could also modify the engines and then it could maintain top speed for a long time.

mustang65 wrote:

All I am saying is that the F-15 can maintain top speed into the double digits. They could also modify the engines and then it could maintain top speed for a long time.

There's no modification that could be done to an F-15 that would allow it to maintain its top speed for a long time(whatever a long time means). It will maintain its top speed until it runs out of fuel. If you put more powerful engines on it, it will run out of fuel faster than it does now. If you put external fuel tanks on it, then its top speed is drag limited. If you put weapons on it, its top speed will be drag limited. And then there's airframe fatigue to consider....

You might be able to do some modifications that could give you a higher cruising speed(i.e. Silent Eagle conformal carriage, along with uprated motors).

I was not saying to do the speed run with tanks or missiles, all I was saying was the F-15 would use the tanks to get as fast as possible, and once they are exhausted drop them and then get to top speed and maintain it into the double digits.

mustang65 wrote:

I was not saying to do the speed run with tanks or missiles, all I was saying was the F-15 would use the tanks to get as fast as possible, and once they are exhausted drop them and then get to top speed and maintain it into the double digits.

In other words M2.5 for more than 10 minutes? The thing that you're not taking into consideration is the time it takes for the F-15 to accelerate from the speed it could reach with EFTs to M2.5(and the fuel burned doing that), and then having enough fuel left to get you back to an airbase and land safely.
An F-15C carries ~13,455lbs of fuel internally. On full afterburner, each engine is going through >900lbs of fuel per minute(or ~1800lbs/min). Do the math.

wrightwing wrote:

mustang65 wrote:

I was not saying to do the speed run with tanks or missiles, all I was saying was the F-15 would use the tanks to get as fast as possible, and once they are exhausted drop them and then get to top speed and maintain it into the double digits.

In other words M2.5 for more than 10 minutes? The thing that you're not taking into consideration is the time it takes for the F-15 to accelerate from the speed it could reach with EFTs to M2.5(and the fuel burned doing that), and then having enough fuel left to get you back to an airbase and land safely.
An F-15C carries ~13,455lbs of fuel internally. On full afterburner, each engine is going through >900lbs of fuel per minute(or ~1800lbs/min). Do the math.

Does that burn rate include a full weapons load???

wrightwing's fuel burn estimates are reasonable. At lower altitudes, try 1300 lb/min for each engine.

Open this document. It will give you a lot about how thrust and fuel flow varies with altitude and speed.

Forum: Modern Military Aircraft

F-15 max speed