Before/During Taxi Noise...

[bowler_man]

In real life before or during the taxi, sometimes I hear a loud high-pitched whizzing noise that sounds like a drill drilling in bolts. What is that noise?

Thanks
--Jimmy

[Ashton Lawson]

ya, that's the engines starting up.  not only does the pushback truck push the plane back, but a link supplies power to start up the engines, whilst the plane is pushed back.  so if u want to get things real and proper, start at the gate with ur engines off, then whilst ur pushing back, start them up.

[bowler_man]

Well, if at that point the engines haven't been started yet, what is the engine-sounding noise I hear before the whizzing noises? Is it just the jet's generators?

Someone else said it might have been the pilot turning on the autopilot pump...whatever that is...

[Mobius]

Someone else said it might have been the pilot turning on the autopilot pump...whatever that is...

Please refer to my previous post about the autopilot pump.

http://www.simviation.com/cgi-bin/yabb2 ... 667013/0#5

[bowler_man]

Oooh, okay. Haha, actually, Airplane! is my favorite movie. I just thought the picture was your signature, and I didn't even see the "Maybe not"


Okay, everything makes sense now  ;D

[Nexus]

[quote]ya, that's the engines starting up.

[DizZa]

Definitely sounds like the PTU (Hydraulic Power Transfer Unit). It runs between the first and second engine starts.

[Nexus]

Definitely sounds like the PTU (Hydraulic Power Transfer Unit). It runs between the first and second engine starts.

There is a possible reason, definetely. At least if you're in an Airbus  :)

[bowler_man]

The APU is a small jet engine located back in the tail.

So, this may be a noob question, but is that the APU?

[ATI_7500]

Yep.

[bok269]

If I am not mistaken, doesnt the APU power the lavatories?

[reider]

If I am not mistaken, doesnt the APU power the lavatories?

No, you must be thinking of the Ablution Power Unit  used in cases where a number 2 is excessive

Short Definition of the APU....

An aircraft APU is a relatively small, self-contained generator used to start the jet engines, usually with compressed air, and to provide electricity, hydraulic pressure and air conditioning while the aircraft is on the ground. In many aircraft, the APU can also provide electrical power in the air.

Reider

[loomex]

this may be a noob question, but is that the APU?

Auxiliary power unit. It runs a small generator to provide power when the engines are not on and the aircraft is not "Plugged" in