What is that whining sound aboard an inflight 747?

Several times for the past few years, while on a transatlantic flight
aboard a KLM 747-400, I begin to hear what sounds like a turbine
spinning up, almost like an engine start, but higher pitch...
Anyone know what it might be?

Thanks

Alan wrote in news:350bbf41-1810-4363-8323-
:

Several times for the past few years, while on a transatlantic flight
aboard a KLM 747-400, I begin to hear what sounds like a turbine
spinning up, almost like an engine start, but higher pitch...
Anyone know what it might be?



It's the Captain whining about his perdiums.

Or it might be one of the electric hydraulic pumps.


Bertie

Alan writes:

Several times for the past few years, while on a transatlantic flight
aboard a KLM 747-400, I begin to hear what sounds like a turbine
spinning up, almost like an engine start, but higher pitch...
Anyone know what it might be?

At what point in the flight? And in which seat?

Mxsmanic wrote in
:

Alan writes:

Several times for the past few years, while on a transatlantic flight
aboard a KLM 747-400, I begin to hear what sounds like a turbine
spinning up, almost like an engine start, but higher pitch...
Anyone know what it might be?

At what point in the flight? And in which seat?


Why, you going to book next to him and whine the whole way?


Bertie

Bertie the Bunyip wrote:
Mxsmanic wrote in
:

Alan writes:

Several times for the past few years, while on a transatlantic flight
aboard a KLM 747-400, I begin to hear what sounds like a turbine
spinning up, almost like an engine start, but higher pitch...
Anyone know what it might be?
At what point in the flight? And in which seat?


Why, you going to book next to him and whine the whole way?

What's the difference between a jet engine
and Anthony?

On Jan 14, 10:26 am, Alan wrote:
Several times for the past few years, while on a transatlantic flight
aboard a KLM 747-400, I begin to hear what sounds like a turbine
spinning up, almost like an engine start, but higher pitch...
Anyone know what it might be?

Thanks

Might be the air cycle machine. See this:

http://en.wikipedia.org/wiki/Air_cycle_machine

Dan

Jim Stewart wrote in news:LpadncVg6P9-
:

Bertie the Bunyip wrote:
Mxsmanic wrote in
:

Alan writes:

Several times for the past few years, while on a transatlantic flight
aboard a KLM 747-400, I begin to hear what sounds like a turbine
spinning up, almost like an engine start, but higher pitch...
Anyone know what it might be?
At what point in the flight? And in which seat?


Why, you going to book next to him and whine the whole way?

What's the difference between a jet engine
and Anthony?


Umm, lessee.

Ah go on, I won't ruin it for you..

Bertie

wrote in news:b7f23917-54a3-4227-a8cf-
:

On Jan 14, 10:26 am, Alan wrote:
Several times for the past few years, while on a transatlantic flight
aboard a KLM 747-400, I begin to hear what sounds like a turbine
spinning up, almost like an engine start, but higher pitch...
Anyone know what it might be?

Thanks

Might be the air cycle machine. See this:

http://en.wikipedia.org/wiki/Air_cycle_machine


Mm, they sort of hum more than whine, and the fans for the heat exchanger
are off when the flaps are up anyway.

It's either the hydraulic pumps, or if they're coming on and off in flight,
he probably means the flap motors.
In cruise nothing would be going on or off, though.


Bertie

On Jan 14, 11:05*am, Mxsmanic wrote:
Alan writes:
Several times for the past few years, while on a transatlantic flight
aboard a KLM 747-400, I begin to hear what sounds like a turbine
spinning up, almost like an engine start, but higher pitch...
Anyone know what it might be?

At what point in the flight? *And in which seat?

Do you have the seat schematics for different airlines?

-Robert

Good questions..

With these additional important details, someone may be able to offer
good suggestions...

Dave




On Mon, 14 Jan 2008 20:05:26 +0100, Mxsmanic
wrote:


At what point in the flight? And in which seat?