[squak7600]

the fluid on the ground is most likely water, from underwing frost melting after the aircraft has been refuelled. -talking from experience.

airbiii make alot of strange noises on the ramp, dont ask me what they are tho, i can only assume hydraulic pumps and a/c packs.but as for the PTU ,totally normal yet unnerving sound! have also heard ptu operate on ground with both engines shut off.(thought it was unusual)

[stovepipe]

Hi there
The "barking" sound was the clutches on the pumps. They make a rrr-rrr-rrr sound when the blue and yellow pumps are running. Both pumps have to be "on" to close the gear doors or move the flaps. The 'Bus makes plenty of noise, from it's packs, its pumps and the actuation of doors.
Passengers routinely tell the cabin crew about strange noises they have heard and we invariably find nothing out of order when we check.
regards
S

[dowlingm]

When I hear people are going to travel on a BA 744 I always tell them about the bang and shudder that happens at/around rotate - the first time I heard/felt it I was a bit concerned!

[Parasite Drag]

Re 744 bang & shudder, I noticed that also many years ago when I first travelled on an EI 747. I think it's the main landing gear bogies swivelling down on their hinges - look at a pic of a 747 flying with gear down and you'll see how the outer pair are at a different angle after take-off.