Question for the QF 747-400 guys

[bugsquash1]

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.

Just of interest it was morning of 24/2 if crew see this.

[Bullethead]

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]

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

Fly by wire

[rmcdonal]

Do you complete a second control check prior to T/O? Or just the one on the bay?

[regitaekilthgiwt]

Just one on the bay

[blueloo]

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]

. . . and what happens if the brake test fails?

Is it a bit like, if at first you don't succeed, so much for skydiving.

[caneworm]

re, A330

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