767 HDG
Thread Starter
Joined: Mar 2004
Posts: 110
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From: Farnham
767 HDG
Hi All,
Might be something obvious that I'm missing, but does anyone know why the HDG on the 767 packs up on touchdown?
(e.g. scenario is L AC fail, R AC fail, APU gen fail, so you're operating on HDG alone)
Many thanks in advance,
NW3
Might be something obvious that I'm missing, but does anyone know why the HDG on the 767 packs up on touchdown?
(e.g. scenario is L AC fail, R AC fail, APU gen fail, so you're operating on HDG alone)
Many thanks in advance,
NW3
Joined: Dec 2005
Posts: 95
Likes: 1
From: uk
Well, it's not just instrumentation that the HDG runs.
In addition to the Capt's Flt Inst Bus, it also runs
L AC Tfr Bus
R AC Tfr Bus
Stby AC
Stby DC
Batt Bus
Hot Batt Bus
So if, as you say, it packs up on landing, you would be left with only the Hot Batt. Hardly ideal for taxying and unlike Boeing's usual logical approach.
I guess you've seen this in the Sim rather than the plane, so my guess would be that this is a Sim quirk; I'll check in the Sim next time I'm in.
In addition to the Capt's Flt Inst Bus, it also runs
L AC Tfr Bus
R AC Tfr Bus
Stby AC
Stby DC
Batt Bus
Hot Batt Bus
So if, as you say, it packs up on landing, you would be left with only the Hot Batt. Hardly ideal for taxying and unlike Boeing's usual logical approach.
I guess you've seen this in the Sim rather than the plane, so my guess would be that this is a Sim quirk; I'll check in the Sim next time I'm in.
Thread Starter
Joined: Mar 2004
Posts: 110
Likes: 0
From: Farnham
AJD -
The battery will still power the full Standby system (HBB, BB, AC Sby, DC Sby), so it's no different to landing off a e.g. standby instruments approach in a non HDG aircraft... I just thought it was a bit strange that it shut down on touchdown!
Thanks for your reply though.
NW3
The battery will still power the full Standby system (HBB, BB, AC Sby, DC Sby), so it's no different to landing off a e.g. standby instruments approach in a non HDG aircraft... I just thought it was a bit strange that it shut down on touchdown!
Thanks for your reply though.
NW3
Thread Starter
Joined: Mar 2004
Posts: 110
Likes: 0
From: Farnham
Apologies - my fault for using some UK 'slang'!
In the simulator, the observed behaviour is for the HDG to stop generating power on touchdown. The L INSTR XFER bus, and I presume both transfer buses, lose their power, leaving only the standby power system.
NW3
In the simulator, the observed behaviour is for the HDG to stop generating power on touchdown. The L INSTR XFER bus, and I presume both transfer buses, lose their power, leaving only the standby power system.
NW3
Joined: Jan 2011
Posts: 780
Likes: 89
From: Seattle
The HDP is shut down by air/ground logic to preserve center system hydraulics for the alternate brake system (and other stuff powered from the center system). The ADP capacity could be restricted due to reduced bleed air flow and it is better used for brakes and other controls once on the ground. There is more than enough battery/static inverter capacity for electrical loads still needed at this time.
At least, that's the way I remember it.
At least, that's the way I remember it.
