Just by curiosity: what is the loud mechanic noise on Airbus jetsafter landing?

It sounds a bit like a somewhat underpowered concrete drill, 4-5 five
times close to the center of the aircraft.

Who might explain me what just happens?

Thanks

Laszlo

"James Robinson" wrote in message
. ..
Lazlo Lebrun wrote:

It sounds a bit like a somewhat underpowered concrete drill, 4-5 five
times close to the center of the aircraft.

Who might explain me what just happens?

There are two hydraulic systems, each powered by one engine. When only
one
engine is running, there would only be hydraulic pressure in one system,
except the aircraft is equipped with a hydraulic transfer pump, which runs
using hydraulic pressure from the system that is working, and supplies
pressure to the system with the stopped engine. You are probably hearing
that pump running.

Or it could be speed bumps.

Lazlo Lebrun wrote:
It sounds a bit like a somewhat underpowered concrete drill, 4-5 five
times close to the center of the aircraft.

Who might explain me what just happens?

Thanks

Laszlo
I posted a similar question a few weeks back. You get a fairly loud
noise briefly on the airbus typically at engine startup, which I do
believe matches JR's explanation (hydraulics in one system pressurizing
the other system). It could be you hear that after landing when one
engine is powered down and the system is still draining power on that
side of the hydraulics. I can't say that I have noticed that, but it may
depend on individual aircraft procedures.

T.

A pilot told me it was a hydraulic pump.


On 3/31/08 12:47 PM, in article , "Tom P"
wrote:

Lazlo Lebrun wrote:
It sounds a bit like a somewhat underpowered concrete drill, 4-5 five
times close to the center of the aircraft.

Who might explain me what just happens?

Thanks

Laszlo
I posted a similar question a few weeks back. You get a fairly loud
noise briefly on the airbus typically at engine startup, which I do
believe matches JR's explanation (hydraulics in one system pressurizing
the other system). It could be you hear that after landing when one
engine is powered down and the system is still draining power on that
side of the hydraulics. I can't say that I have noticed that, but it may
depend on individual aircraft procedures.

T.

Jim Davis wrote:
"James Robinson" wrote in message
. ..
Lazlo Lebrun wrote:

It sounds a bit like a somewhat underpowered concrete drill, 4-5 five
times close to the center of the aircraft.

Who might explain me what just happens?
There are two hydraulic systems, each powered by one engine. When only
one
engine is running, there would only be hydraulic pressure in one system,
except the aircraft is equipped with a hydraulic transfer pump, which runs
using hydraulic pressure from the system that is working, and supplies
pressure to the system with the stopped engine. You are probably hearing
that pump running.

Or it could be speed bumps.


Thanks, but that explanation not really match the noise!
It is pretty irregular like somewhat shifting in and out over old gears.
A transfer pump should operate steadily, isn't it?

Laszlo

James Robinson wrote:

No, the transfer pump runs irregularly. It is sometimes described as
sounding like a barking dog, sawing wood, or a starter motor on a car
that is barely turning over.

Yes a a starter motor on a car that is barely turning over is a pretty
goosd match.
Thanks for the astonishing answer. I am a bit less stupid now and will
be able to tease the flight attendants... ;-)

Laszlo