View Full Version : Question for the QF 747-400 guys
bugsquash1
27th Feb 2011, 11:28
Saw a QF 744 on the bay in HK doing a control check before pushback, is this normal if you have a pushback delay or would it be a problem, no engines running.:confused:
Just of interest it was morning of 24/2 if crew see this.
Bullethead
27th Feb 2011, 11:53
G'day bugsquash1,
Unlke the older B747s the B747-400 can pressurise all four hydraulic systems before engine start and complete the control check before pushback. This is standard procedure for QF. There is a combination of engine driven pumps, air driven pumps and electric pumps to pressurise the various systems.
Regards,
BH.
bugsquash1
27th Feb 2011, 12:16
Thanks
It just seemed strange to do it before start, but I suppose on the bus we wait for the computers to screw up on start before the control check :E
Fly by wire :mad:
rmcdonal
27th Feb 2011, 20:19
Do you complete a second control check prior to T/O? Or just the one on the bay?
regitaekilthgiwt
27th Feb 2011, 21:30
Just one on the bay
blueloo
27th Feb 2011, 22:55
I don't know why you bother on the bus... who knows what input they will send to the flying controls from one second to the next! :}:}
(FWIW the 767 does the same - preflight procedure is to get a clearance to pressurise the hydraulics and do a control check)
Why on the bus do you need to do a brake check when you taxi (like a cessna 172) - is it because you are checking the hydraulics ? Or you are checking the computers are sending a signal to the brakes?
esreverlluf
28th Feb 2011, 00:24
. . . and what happens if the brake test fails?
Is it a bit like, :ok:if at first you don't succeed, so much for skydiving.
caneworm
28th Feb 2011, 01:19
Blueloo
The check is done to ensure there is no residual pressure in the brake system that may cause a dragging brake.
. . . and what happens if the brake test fails?
esreverlluf
If the test fails, ie, you have a dragging brake, you will know pretty much the moment the wheels turn.
cheers 'n beers:ok: