View Full Version : Two questions

22nd Oct 2008, 22:25
Hello all, two questions, perhaps the wrong forum if so mods feel free to move...

1. I was in SFO a couple of days ago, and saw a ANA either a 767 or 777, as the gear was being retracted i saw "smokepuffs" from the maingear, is this the brakes being applied before stowage? is it made automaticlly or bye the crew?

2. where does inflight "moving maps/flightinfo (speed, alltitude, head/tailwind, ETA) system get its info from, is it a stand alone system or has it got a link to the FMS? I guess there is a lot of different systems for this but feel free to tell about the once you know about...


26th Oct 2008, 12:26
1. I can't answer for the 777, but on the 767 the brakes are applied automatically during the retraction sequence. But that should not produce puffs of smoke.

2. The pax display systems I know of take their position and flight data info from the FMS and other flight deck sources -e.g. air data computer for speed & altitude. As all the data required is already present, there's little point in adding an independent source just for cabin display.

26th Oct 2008, 13:22
1. Yes, the smoke comes from applying the brakes. It is actually carbon dust coming off the disks.

gas path
26th Oct 2008, 14:11
The puff of 'smoke' comes from the hydraulic system ADP as it cuts in to augment the electric pump. The turbine drive unit is located aft of the wing on the left hand side behind the wing/body fairing.

26th Oct 2008, 23:07
I've noticed a similar 'puff of smoke' from A330s as the gear is selected up.

The autobrakes apply when the gear is selected up to stop the wheels before the retraction sequence starts so there are no gyroscopic forces to deal with as the undercarriage legs rotate inwards.

Used to do the brakes on/off on the MB326 before gear up during my pilot training in the RAAF for the same reason.


keith smith
26th Oct 2008, 23:38
I have a couple of supplementary questions on pax nav displays:
1.Who chooses the place names to be included. For example I wouldn't expect St Peters Port Guernsey to be a major Hub.
2.The rather big aircraft(BA that is). I presume that the longitudinal axis represents heading, but where is the actual location on the map---s it the nose or at about the quarter chord point?

27th Oct 2008, 00:45
but where is the actual location on the map---s it the nose or at about the quarter chord point? That's an intresting one. Frankly, I do not know. The aeroplane travels at 200 m per second, why should I?:E