A320 noise
Hello all! this is my first post......a question!
Took a Jetstar A320 LST-SYD recently. As the ship left the gate there was a tremendous noise similar to flap extension that went on for at least a minute. All pax looked nervous (including myself and I fly A320 fairly regularly), however the cabin crew were as calm as... The noise was so loud all must have heard it including the flight crew. I had never heard that noise before and I can say that the noise was not flap extension as I could see that they were not! The flight was uneventful (flight crew must not have been perturbed by the noise) but I wondered what the noise could have been? Perhaps pressurisation pumps?
Do aircraft pressurise immediately on departure or is it done while on climb-out?
I thought there may have been a thread on this subject many moons ago, but I can't find it. My apologies if I'm repeating old stuff.
Anyone have any ideas?