B777 Questions.
Thread Starter
Joined: Jan 2006
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From: Brussels
B777 Questions.
Just talking to an airline 777 pilot who mentioned a couple of things.
1.Why do they call Alert Height at 200 Radio. On a CAT111 approach where as they dont on a CAT11 approach.
2. Does the TAC still operate with severe damage separation or does it cease to function.
I am preparing for airline interviews and any info would be helpfull.
1.Why do they call Alert Height at 200 Radio. On a CAT111 approach where as they dont on a CAT11 approach.
2. Does the TAC still operate with severe damage separation or does it cease to function.
I am preparing for airline interviews and any info would be helpfull.
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From: USofA
I cannot speak to the reason anyone would call "Alert Height" at 200 RA on a CATll approach. Alert Height is a term used in CATlll approaches. Sounds like an airline specific item. In the US the Alert height is usually a point at which the pilot flying states the intention to let the airplane continue the autoland, usually at 50'. Maybe someone else with a different perspective can chime in here?
"The TAC automatically disengages if engine thrust data is lost. Also, if the engine is damaged or surges, TAC disengages because ther is no accurate prediction of engine thrust. The TAC may still cause some rudder deflection in the appropriate direction, just before automatically disengaging". Straight from the Boeing Vol. 2 FCOM
"The TAC automatically disengages if engine thrust data is lost. Also, if the engine is damaged or surges, TAC disengages because ther is no accurate prediction of engine thrust. The TAC may still cause some rudder deflection in the appropriate direction, just before automatically disengaging". Straight from the Boeing Vol. 2 FCOM
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From: AMS
Alert height for the 747-400 is 200 ft and only applicable in cat III operations. (Don't know about the 777, but I think this is type related and could be different).
If below the alert height one autopilot (of three) disengages it is allowed to continue the approach. Annunciation is even inhibited on the PFD's and EICAS.
Mac74.
If below the alert height one autopilot (of three) disengages it is allowed to continue the approach. Annunciation is even inhibited on the PFD's and EICAS.
Mac74.
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From: sh!# hole
Alert height is only used for fail safe (Cat III) approaches. On the B777 any loss of redundancy above the alert height you may have to go-around if the failed equipment is required for the approach. You may also revert to a Cat IIIa approach from a Cat IIIb provided the wx and equipment allow.
Any further losses of redundancy below alert height will be inhibited (includes EICAS messages except for 4 specific ones) The approach can be then continued.
The TAC is designed not to give rudder inputs following an engine severe damage, or when inputs to the TAC are invalid. Turing the TAC off then back to AUTO may re-engage it.
Oz
Any further losses of redundancy below alert height will be inhibited (includes EICAS messages except for 4 specific ones) The approach can be then continued.
The TAC is designed not to give rudder inputs following an engine severe damage, or when inputs to the TAC are invalid. Turing the TAC off then back to AUTO may re-engage it.
Oz
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From: USofA
Well not to confuse the subject anymore than need be, here is the answer from the B747 side of the house. The B747-Classic was never certified for CAT lll so the DH would have been 100' "see to land", CAT ll, while the B747-400 is in fact a CAT lll certified aircraft with a 100' alert height (no see to land) FAA rules. As someone has said before this is a function of the autopilot design and certification. Again all of this may look a little different under someone else's certification rules so don't bet the farm on these answers.
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From: USofA
Well guys I'm here at Boeing and no one can recall the -200/300 as having been a CAT lll airplane. Two axis autopilot and the lack of redundant controls on the NW steering were the most frequently mentioned reasons for the missing component. I have not personally flown the Classic so I remain clueless as how this discrepency can exist.
Last edited by Spooky 2; 31st March 2008 at 23:09.
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From: EDDF
alert height?
Hi guys
here some infos about the philosophy of making automated landings on a B744 and the callout "alert height"
the 200 ft RA " alert height " callout is a part of CAT3 approaches WITHOUT a DH.
when you make an approach without DH, your minimums are according to your A/C type and operator and could be for example 0 ft - 75 m
at 200 ft RA, PNF/CM2 makes the call out "alert height" and if no failures, warnings or etc exist, PF/CM1 calls out "continue"
after this point a go around is mandatory only in very few cases
1. tower calls for go around
2. A/P disconnects
3. LOC or GS deviation are out of range, wich is indicated by flashing scales
even a lost of A/THR would not be a mandatory go around, CM2 would just call at 20 ft for "Retard" to remind CM1 to close the throttles.
when CAT3 without DH was introduced and we trained it in the sim, it was a kind of spooky. Even if you lost all your CRTs on CM2 side below "alert height" you were supposed to shut up and continue... but you get used to it...
lars
here some infos about the philosophy of making automated landings on a B744 and the callout "alert height"
the 200 ft RA " alert height " callout is a part of CAT3 approaches WITHOUT a DH.
when you make an approach without DH, your minimums are according to your A/C type and operator and could be for example 0 ft - 75 m
at 200 ft RA, PNF/CM2 makes the call out "alert height" and if no failures, warnings or etc exist, PF/CM1 calls out "continue"
after this point a go around is mandatory only in very few cases
1. tower calls for go around
2. A/P disconnects
3. LOC or GS deviation are out of range, wich is indicated by flashing scales
even a lost of A/THR would not be a mandatory go around, CM2 would just call at 20 ft for "Retard" to remind CM1 to close the throttles.
when CAT3 without DH was introduced and we trained it in the sim, it was a kind of spooky. Even if you lost all your CRTs on CM2 side below "alert height" you were supposed to shut up and continue... but you get used to it...
lars
