Aer Lingus Flight - Identify The Sound Pls :-)

djsim101

Hi All,

Long time follower, not much of a poster :-) I was deleting some video's from my phone, when I came across this video I took from a flight to Italy. The Aer Lingus flight originated from Dublin so I assume it was on a A320.

The video itself is 14 seconds long, but the noise went on for a least double that. Out of curiosity, can ye experts tell me what is was?

https://youtu.be/37Y7PESe0b0

Thanks.

ShanE90

Ah the aul airbus barking dog...as far as I know it's hydraulic fluid being pumped from one tank to another

Psychlops

PTU ( Power Transfer Unit )

http://www.askthepilot.com/questionanswers/the-barking-dog-airbus-noises/

"What you hear is a device called the power transfer unit, or PTU, which is designed to ensure adequate hydraulic pressures during single-engine operations. To conserve fuel, it’s fairly routine for two-engine planes to taxi with an engine shut down. Each engine normally pressurizes its own hydraulic system, but with a motor not running, that leaves one system without a power source. That’s where the PTU comes in, helping left power the right, or right power the left. Since it is activated only when the pressure falls below a certain level, the PTU cycles on and off, on and off, on and off. Due to pressure fluctuations, the noise will sometimes continue even after both engines are up and running. It also does a self-test when the starboard engine is started, so you’ll hear it then as well. Some Boeing aircraft also employ a PTU, but the operation is slightly different and it doesn’t bark like a dog."

djsim101

Thanks for the explanations guys.

@ Psychlops - probably a silly question, when this procedure occurs, and one engine is shut down to safe fuel, will be always be a left or right engine that will be shut down , or would it be up to the pilot to pick one?

Thanks

Deatr

I may be wrong but I don't think EI do single engine taxi!

Brennus335

It also runs a self test during engine startup.

Lustrum

djsim101 wrote: »

Thanks for the explanations guys.

@ Psychlops - probably a silly question, when this procedure occurs, and one engine is shut down to safe fuel, will be always be a left or right engine that will be shut down , or would it be up to the pilot to pick one?

Thanks

In my place it's up to the pilots what engine to shut down. However you'd take into account things like direction of turns, wind direction as fumes could be blown into APU inlets for example, a and sometimes it's purely because the off-side engine shut-off is further away from you than the on-side one, and you're feeling extra lazy!