Curiosity. I’m sitting on an A319 during a ground stop. There is an extremely annoying repetitive noise going on that sounds somewhat like an air wrench taking off a lug nut. I seem to recall this happening after landings, too, on Airbuses - but don’t recall hearing it on Boeing products. Any of you ‘bus experts have any idea what I’m talking about - and what it might be? Many thanks...

hydraulics

http://www.askthepilot.com/questionansw ... us-noises/

There you go. Thanks!

I'm a Boeing guy but I feel Airbus is doing very well. Have you noticed the Airbus cabin is always warm even at 37K? I have to bring a sweater when I'm flying my beloved Southwest or any other Boeing.

AG

Its the Power Transfer Unit (PTU) that connects the Green and the Yellow systems in case of pressure loss on one side. When it detects a difference of ~500psi it will activate using the pressure from one system to power the other. Typically you leave No. 1 running during SE (powers the Green system) and are supposed to have the electric pump powering the Yellow system (No.2 powers the Yellow normally). Sometimes guys will shut all the way down during a delay and leave the electric pump running on the Yellow system and thus you'll have the PTU powering the Green system. IMO the Yellow electric pump and the PTU are super annoying to the pax so it's important to do a "Parking checklist" after corking both engines to ensure we shut off the damn hydros from making a racket in the back (can't hear them on the flight deck.) Its required to anyway at my company so CYA on both ends.

Hydraulics PTU is correct. Hearing it at the gate after shutdown is most likely due to an incomplete shutdown ‘flow’. Departing crew may have left the Yellow (right) electric hydraulic pump on pressurizing the Yellow system and the PTU is trying to use Yellow system pressure to power the Green (left) hydraulic system. Annoying but not detrimental.

Do people still wear sweaters!!

Do people still wear sweaters!!

Sometimes they kind’a sound like a barking dog. Whenever a FA wanders by I ask if they could do something to calm the stressed/starving/dying puppy.

Already answered.

I thought it was the mule hauling more coal over for the next flight.




I’ve always wondered what that sound was. I figured it was the hydraulic system. It sure is funny watching passengers get that odd look at the end of the flight and the Airbus starts he-hawing.

I’m no Airbus expert, as I only fly them.

But as already explained above, the barking dog is the PTU. When I was an FO, I always tried to wait until the #1 engine spooled down before I turned off the yellow hydraulic pump to keep the ptu from operating if we taxiied in on one engine.

The 757 does this too for a similar reason. If you sit just behind the wing, you will hear it on taxi in.

PTU in action https://youtu.be/9ffJgk1-tCA

That’s is the cleanest airliner I have ever seen in my short life... not just inside the wells but the belly too.