planemad_bk

Any A320 drivers help me out? Was sitting just over the wing and before starting the engines i hear this noise which sounded like a dog barking? What was it? I would have thought hydraulics?

Right Way Up

PMb,
If you put A320 & noise into the search engine you will find the answers you require.

wobble2plank

Just to save you the hassle of the search, the 'Dog Barking' is the Power Transfer Unit for the hydraulics. As you start up the #2 engine the PTU powers up the green hydraulic system as the #1 Hyd pump isn't working at that point. As soon as #1 comes online the PTU stops 'barking'.

Or as the Cabin Crew once told a passenger, 'don't worry, it's only a dog we couldn't catch, it's ok though it'll freeze at 38,000 feet'

W2P

Airbus_a321

Avionics Ventilation System

wobble2plank

Could also be a dodgy DV window seal, leaking upto altitude and then the differential pressure seals it up.

wobble2plank

Fair enough, tends to be prevalent on the older crates we fly so that's probably down to knackered seals being louder than the avionics vent

Airbus_a321

I guess there is not even one single engineer in this world who will know BY HEART which valve at what time and at what temperature or delta-temperature will open or close and in which sequence and so on and so on. This system, at least for me, is just a mystery. But most of the time it's working perfect - if not - don't worry and don't start thinking why and what and which - just do ECAM ACTION

Clarence Oveur

Are you then rewarded with a banana?

Dani

Finally somebody could tell me! Thank you VRSCSE2 (your avater is as complicated as AI's valvology...)

There are endless rumours where this noise is coming from. Just lately it was explained here in Pprune that it was the toilet

Dani

FS-chick

I think it's time to make a subforum of Tech Log called "Strange noises in an Airbus"

Cardinal

The PTU noise can be largely avoided procedurally if the organization has the will to do so. Airbus says start #2 first. My outfit starts #1 first, and taxis single-engine on #1 with the yellow electric hydraulic pump on. Presto, no PTU noise except for self-test.

Phil Hudson

Barking sounds from down below means on of two things:

1: Hydraulic power transfer unit performing a selftest

2: There's a dog loose in the cargo hold

UP and Down Operator

Can someone then please explain why it always sounds like someone is hitting the fuselage on the F/O side, low, when climbing through about 2500 feet??
It sounds like some-one knocking from the avionics bay, and I continue to look out to see if we still have the groundhandler hanging in his headset somewhere

Phil Hudson

Well i dunno, that sound seemes to go away when we clean up.
Could be aerodynamical snafu, also could be groundhandlers headset blowing of

Cardinal

Being on the receiving end of that particular noise, I'd sure like to know as well. It almost harkens back to an earlier type that had no gear uplocks, and would occasionally hit the landing gear with a shot of hydraulic pressure if it started to sag in the well. Doing some FCOM research, I see that hydraulic pressure is removed from the gear above 260 kts. That could potentially generate a "clunk." This being an Airbus, these things usually occur over more of a range than at a specific point. Just a possibility.

Aztec Kid

The most likely reason for the air leak noise that was described would be the keel beam drains. You will find approximately twenty drains located along the keel beam (several are located beneath the flight deck).They close during climb and open during descent at 2.0 PSID.
Best regards,
The Kid

ladyflyby

It sounds more like a saw than dog barking. The horror on passenger's faces when they hear it! Another airbus related question – during taxi on the A321, when sat at doors 3 there is a clonking sound coming from below; what on earth is it?

tubby linton

That is probably the brake master valve.The ptu can also be described as a sawing sound.

Aztec Kid

The purpose of the keel beam drain is to eliminate fluids from the bottom of the fuselage. Hopefully the fluids are merely water from condensation on the interior of the aircraft skin.
On the A320 series you will find a grate on the floor of the flight deck, just after you enter from the forward galley. Under this grate is a basin that collects fluids that may come from the galley area. The fluids could be due to leaks in the galley or more commonly, rain coming in the forward entry or service door when the aircraft is on the ground.
Since this basin leads to a keel beam drain, one may hear the air leak noise emitting from below this grate.
The engineers I have worked with over the years have patiently answered many of my questions regarding the Airbus. If you have the inclination to learn more about the Airbus, see if you can get them to share a copy of the Aircraft Maintenance Manual. It will provide you with more of the system details than even the most technically adept pilot would need. Try to get the AMM specifically for your company’s aircraft. There may be substantial differences in systems of aircraft within the same fleet, due to hardware and software upgrades.
Sincere apologies for the thread creep.
Best regards,
The Kid

Panman

Having had to clean the Cockpit Grid Collector Assembly or "basin" as you call it (AMM TASK 53-19-00-210-001). I would be very impressed if any moisture in there is indeed from rain entering through the forward entry/service door as you mention. Especially if the flightdeck door is closed.

PaNmAn