I've wondered about this. I've heard it go on while taxiing even and for quite a long time too. It's pretty weird.

this has got me thinking about a time when i was on a plane and before we began our taxi to the runway there was a mechanical noise like a dog barking. the pilot came up the back asked us if it sounded like a dog barking (was pretty good way to describe it). he got the engineer etc and after a small delay we were on our way and it was fine until we began our descent and the noise came back. please note this is not an attempt at humour, it was mechanical and there were no dogs on the flight. two questions regarding it, what was it? (the pilot obviously had experience of it as it was his words when asking if it sounded like dog), and was there any danger given that the noise had came back when we started our descent?

Starts at 2:30.



Heard this exact noise on lots of flights recently.

EDIT: Explained here: http://www.askthepilot.com/questiona...airbus-noises/

Yep, that's the sound. Thanks for the link!

Reminds me of another question that popped into my head the other day.

We all know that one engine gets fired up for taxi to conserve fuel. Is there some system used to determine which engine gets powered up first? Seems like if you always taxied with the starboard engine, it'd end up having a bunch more time on it than the other and wear unevenly.

Pilots choice flip a coin game theory thing?

I see that a link has been posted with the explanation, beating me to it.

I'm pretty sure this question came up much earlier itt, and I had identified the culprit as the PTU (Power Transfer Unit), which is what that link discusses. The original question was about a noise occurring just before pushback, and I agreed this this could be a cargo door being closed. During taxi, however, the sound has to be coming from the PTU.

From the Ops Manual:

It's almost always the left engine that gets started for single-engine taxi, at least on the fleets that I've been on (88, 757/767). On the 757 there was a very good reason: the PTU operates continuously when only the right engine is running. I've never heard any discussion by anyone in the training department about uneven usage of the engines.

On taxi in, we will usually shut down an engine after the required cool down time (three minutes on the 88). On the 757/767, we would pick the engine based on which way we had to turn the plane in the gate area. If there's going to be a 90 left turn, we'll shut down the left engine. On the 88 this is not a consideration since the engines are close to the centerline. It's pretty standard to shut down the right engine.

Guess I've flown at mostly physically small airports. I don't remember them ever not starting both engines at the gate.

Awesome. With the razor focus on being absolutely as efficient as possible in a ton of ways that seem almost nitty, I'm legit surprised that the engines ending up with a differing number of hours isn't a thing. You figure if its 10 minutes per flight leg (which might not be close to right), thats a ton of hours per year. You should totally put a comment card in the suggestion box and win Pilot of the Year!

What kind of planes?

737's mostly, but maybe a few DC-9's years ago, or whatever they're called now.

Most of the time I've flown, we've pushed back, taxied straight to the runway and took off, or maybe been second in line. Maybe if they know they're going to be flying right away they start both?

Yes, we start both if it looks like we will go right out. Other airlines may vary, but we need a minimum of five minutes warm-up on an engine for the first flight of the day, two minutes for successive flights. But the only time we actually start them at the gate is if our APU is inoperative. Maybe you remember them starting the engines during pushback? That's a common practice.

Yeah, for the purposes of my post, gate = pushback. They aren't really on the taxiway when they start up is I guess what I was trying to say.

Sorry W0X0F

Doesn't the horsey have to fit underneath the seat? How does the window seat passenger exit in an emergency?

She rides the horse to safety ldo

Rides the pony, obv.

edit: slow pony, literally

I always thought of that noise as the "handsaw sawing the wing off" noise. I have weird ways of amusing myself during flights.

Bad place to take a nap

http://www.foxnews.com/us/2015/04/14...in-cargo-hold/

Typical baggage handing?

Pretty much.

Sounds great in heavy turbulence, a ditching, or a crash: a 400 pound horse torpedoing around the cabin flailing and kicking.

W0X0F, what would happen if you (as PIC) told this guy he couldn't bring the horse for safety reasons? Would your company back you up?

I would have to be able to make a case for it really being about safety. The only scenario that I can imagine this working is if we were flying into known turbulence. Even then, I think I'd be opening myself and the company up to potential legal action.

Thoughts on pilotless planes? I read that the technology basically already exists & there are plans to trial it on cargo planes. Eventually if passengers are comfortable enough about it, introduce it there.

I am a baggage handler. They're being a little rougher than normal but that is still pretty standard.

WOXOF, I had something unusual happen the other month while pushing back an 88. As we pushed into position, the Captain asked if the left engine was turning. It was night. Obviously the agent couldn't really tell and had to get closer. The engine was not turning. The captain asks again. Same thing. Captain then clears the pushback and we disconnect &c. He rolls out with one engine turning.

What the **** was that? I asked a pilot about it the next day and he said the captain was messing with us. I think this is likely but, considering that it was about 40* and pouring down rain, that would make his little prank a dick move of unbelievable order. I remind you that most of us are more baggage handling types than aerospace engineering types, and we're generally a gullible lot.

Endnote: the aforementioned pilot who I asked the next day also asked if the engine was turning. It was beautiful out and we all had a good laugh.