Jet noise?

nocturnalaviator

Family Man
So I live above the pattern at McGuire AFB (JBMDL) and see the c17s/10s/135s over flying my house regularly. Tonight I noticed a sound I've never heard before. It sounds like they're rapidly throttling back like a mid to low pitch moaning sound. Is this right? I've only noticed it when they do their night ops. Can someone enlighten me as to what I'm hearing? So far I've only noticed this with the 17s

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///AMG

Well-Known Member
Sometimes motors sound funny at certain throttle settings in cooler/denser air. I've heard this moaning noise from Hornets with certain environmentals and/or airspeeds.
 

nocturnalaviator

Family Man
Sometimes motors sound funny at certain throttle settings in cooler/denser air. I've heard this moaning noise from Hornets with certain environmentals and/or airspeeds.
Yeah it's really strange a few months ago I saw 5 17s doing night ops they were about 3000ft no lights and I guess doing tactical descents they were coming down in a hurry and each one of them let out that sound before descending.

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///AMG

Well-Known Member
Yeah it's really strange a few months ago I saw 5 17s doing night ops they were about 3000ft no lights and I guess doing tactical descents they were coming down in a hurry and each one of them let out that sound before descending.

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Yeah, the Hornet will make a weird howl with pretty high airspeed at or around idle. I'm guessing it has to do with back-pressure on the compressor side at high IAS (350+). It is noticeable in the cockpit and from the ground. I'd bet they might have some of the same, if at lower A/S
 

nocturnalaviator

Family Man
Yeah, the Hornet will make a weird howl with pretty high airspeed at or around idle. I'm guessing it has to do with back-pressure on the compressor side at high IAS (350+). It is noticeable in the cockpit and from the ground. I'd bet they might have some of the same, if at lower A/S
sounds reasonable thanks bud!

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SteveCostello

My member is well-known.
None of this is any good without audio/video ;)

I have no idea why, but one of my favorite aircraft sounds is the span of time when a C-5 between short final and reverse thrust. An example:

I just love the sound of the throttles getting jostled on approach, going completely idle before touchdown, then into a full scream for reverse. Love it. Could listen to that soundtrack all.day.long. That is just a seriously eerie howling sound being behind a C-5 going into reverse. It's deliciously creepy.
 

Matt13C

Well-Known Member
None of this is any good without audio/video ;)

I have no idea why, but one of my favorite aircraft sounds is the span of time when a C-5 between short final and reverse thrust. An example:

I just love the sound of the throttles getting jostled on approach, going completely idle before touchdown, then into a full scream for reverse. Love it. Could listen to that soundtrack all.day.long. That is just a seriously eerie howling sound being behind a C-5 going into reverse. It's deliciously creepy.
That is sweet! It is amazing how slow of an approach and landing distance they can make with such a large jet.

I personally love the sound of the Rolls Royce engines on the 757. I love how it sounds like a saw as it approaches then goes into high pitch scream as it goes passed. My understanding is it air coming of the front fan and hitting the stator vanes, but I've never received a definitive answer.

 

SteveCostello

My member is well-known.
That is sweet! It is amazing how slow of an approach and landing distance they can make with such a large jet.

/snip crazy 757 climb rate video...
Wow... I know that airliners are not nearly as nimble as, well... anything, but pulling off maneuvers in something like that has got to be a blast. Similar I would imagine to tactical takeoffs/landings with the military cargo aircraft.
 

Hacker15e

Dunning–Kruger Observer
ugh reverse thrust to back the aircraft up on the ground while taxiing. The thrust reversers can also be used in flight at idle-reverse for added drag in maximum-rate descents. - wiki
Saved by wikipedia again. :rolleyes:

I wasn't saying the airplane was not capable of it.

I was saying that this is probably not responsible for the sound that the OP is talking about while C-17s are in the pattern at McGuire AFB at night.
 

nocturnalaviator

Family Man
I'm still trying to find a solid explanation of the sound, heard it again yesterday and it's driving me nuts now. The way to describe it better is its like listening to a nascar or speed bike racing by. It's that kind of sound but coming from the engine. Maybe it's a rapid throttle change? No idea but I'm still researching..

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