TN486
Topic Author
Posts: 431
Joined: Mon Jul 28, 2008 11:08 am

### JQ A320's - Engine Noise On Approach

I am strictly an amateur guys so please all you techies dont give me stick, I just wish to learn!!
I live immediately below a S-SW approach to MEL, this approach is normally flown by all ac incoming from TASMANIA, for arrival runway 27. The point they fly over my home is normally 17-18 minutes to touch down. At this point JQ A320's sound as if the engine/engines are "winding down" momentarily then almost immediately they are "winding up" again. In some cases it happens a second time, then everything then goes back to normal. Any thoughts please.
remember the t shirt "I own an airline"on the front - "qantas" on the back

Ceph
Posts: 104
Joined: Tue Jun 12, 2007 1:29 pm

### RE: JQ A320's - Engine Noise On Approach

Jet engined planes need to cross the threshold at a certain percentage N1. The throttles need to be adjusted to maintain that and the approach speed.

Correct me if I'm wrong, all the jet pilots out there.

AAH732UAL
Posts: 242
Joined: Sun Mar 30, 2008 9:41 pm

### RE: JQ A320's - Engine Noise On Approach

 Quoting TN486 (Thread starter):The point they fly over my home is normally 17-18 minutes to touch down. At this point JQ A320's sound as if the engine/engines are "winding down" momentarily then almost immediately they are "winding up" again. In some cases it happens a second time, then everything then goes back to normal. Any thoughts please.

Probably leveling off. If you say they are that far out from the airport, they are probably just finishing up their crossing restriction and are leveling out for further descent.

 Quoting Ceph (Reply 1):Jet engined planes need to cross the threshold at a certain percentage N1

Not really, just at or above Vref and at or around the TCH(Threshold Crossing Height) for the type of approach.
DME/DME RNP0.3 NA -Escalators don't break---- they just become stairs!

TN486
Topic Author
Posts: 431
Joined: Mon Jul 28, 2008 11:08 am

### RE: JQ A320's - Engine Noise On Approach

Thank you, but I should have added that this does not happen with the QF/DJ 737/738 that ply the same route. Still a mystery!
remember the t shirt "I own an airline"on the front - "qantas" on the back

AAH732UAL
Posts: 242
Joined: Sun Mar 30, 2008 9:41 pm

### RE: JQ A320's - Engine Noise On Approach

They probably do a continuous descent to save more fuel
DME/DME RNP0.3 NA -Escalators don't break---- they just become stairs!

airbuster
Posts: 328
Joined: Fri Mar 30, 2007 12:43 am

### RE: JQ A320's - Engine Noise On Approach

Maybe there is a level restriction right above your place, that would mean they have to try and make it, say for example they all have to be at or below FL150. If they are getting on the high side, they may spool down to have a greater descent rate, and once made the restriction spool up again for a slower descent.....

but hey, i'm sitting at the other side of the world so don't know the procedures.....just my thoughts.

ab
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