Why does a jet engine chirp?

Question

I work near Luke AFB in Arizona right in the landing path. When the F-15's are landing I heap a distinct chirp and it sound like it comes from the engine. I am just curious what this is all about?

Answer 1

too powerful an aircraft to be called a female, it has the balls to get the job done, i will bet that the  noise that you are hearing is the wheels chirping when they make contact with the runway.

i was born where you work, kind of interesting.

i had a chance to talk to a former f15 mechanic and what he is telling me  that what you are hearing is the exhaust of the engine changing in order to decrease out put. the tires were just a guess, but that would not be heard over the engines.

Answer 2

I believe what you are hearing is the hydraulic driven landing gear coming down. Watch the gear the next time, and remember, the sound will hit you 1100 feet per second later.

Answer 3

the F-15 is female. It has a high pitched voice depending on your position in relation to it.

Answer 4

That chip you are hearing is the main landing gear wheel going from zero to landing speed in a slip second.  The chip is caused by the rubber abrasion and reverted rubber caused by friction between the wheel and the runway.

On wet or ice covered runway you will see steam come from the wheels again caused by friction.

Answer 5

Its rubber coming in contact with the ashaplt at over a hundred miles per hour. I think you might chirp a bit too.

Answer 6

It could be a lot of different things which change as the aircraft comes in to land. It could be landing gear, spoilers (speed brakes), or an adjustment in power which is causing a momentary turbine stall (or any number of other things). Watch what the plane is doing specifically, and consider emailing or calling the base Public Affairs Office (PAO) as they can probably get you an accurate answer.

Best Luck!

Answer 7

I think I remember the sound you're talking about (Luke AFB 61 FTS, 1996), though it sounds more like a "zip" to me than a chirp.  If I'm right, then it's the sound of the engine exhaust nozzles returning to fully open as the pilot throttles down to idle.  The nozzle actuators in Pratt and Whitney engines are s***w driven (if I remember correctly), so they sound alot like power drills when they spin rapidly.

Answer 8

the engine reversing thrust