2025-06-16T23:23:00
permalink Post: 11903868
I do not wish to speculate on the cause of this horrible accident but
this vey situation happened to a good friend of mine, former Tornado pilot with 25 years on airliners, as a captain and PF on a B777. In his words he was initially totally confused why the aircraft stopped climbing. He engaged the autopilot and quickly realised the problem but they came very close to stalling.
I would not like to place money on how quickly I would recognise the, highly unusual, situation of flaps being retracted with the gear remaining down and react appropriately.
The Air India flight was circa 30 seconds from lift-off to crashing.
I am sure an initial report will soon publish the basic facts.
Except for the initial conversation about mistakenly retracting flaps instead of landing gear, which eventually was dismissed in favor of engine failure as there has been an almost unanimous agreement that even if such mistake was made, it was recoverable.
I would not like to place money on how quickly I would recognise the, highly unusual, situation of flaps being retracted with the gear remaining down and react appropriately.
The Air India flight was circa 30 seconds from lift-off to crashing.
I am sure an initial report will soon publish the basic facts.
Subjects: Engine Failure (All) Gear Retraction
2025-06-18T00:23:00
permalink Post: 11904796
In any case the autopilot wouldn’t have been in at such a low altitude and the PF would have been hand flying. Most of the min engagement altitudes for autopilots is 400’ AGL.
767 pilot here, on the 767 it would capture the altitude, but more importantly, it would freeze the airspeed at whatever speed the alt capture occurred at. So the thrust levers would retard to maintain the much slower speed at the point of capture. This could be a possible scenario, especially if the crew was slow to realize what happened, AND the 787 has a similar low altitude capture issue.
Subjects: Flap Setting Flaps (All) VNAV
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2025-06-18T12:59:00
permalink Post: 11905219
Assuming then that VNAV in the 78 engages at 200` AGL vice the 400` of the 777 ?
Subjects: VNAV
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2025-06-18T15:50:00
permalink Post: 11905350
VNAV hasn\x92t engaged yet in that scenario. So do I get SPD LNAV ALT ?
At that point the FMAs read:
At 50' LNAV engages and the FMAs change to:
At 400' VNAV engages and the FMAs change to:
The height is referenced to a barometric snapshot taken during the take off roll at 100kts.
If an altitude is captured before VNAV engagement (totally bizarre to capture an altitude of less than 400') then the FMAs would change to:
SPD | LNAV | ALT
Subjects: Takeoff Roll VNAV
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2025-06-18T17:40:00
permalink Post: 11905419
A mate tried gear/flap scenario in the sim earlier. Selecting flaps up (all the way) instead of the gear did not predjudice the flight path at all. They selected flaps up at normal gear retraction height and punched the AP in. The Slats remained out until 225kts (as per my post about 50 pages ago) and the aircraft climbed happily away clearing all obstacle by a good margin.
Subjects: Flaps (All) Flaps vs Gear Gear Retraction
2025-06-19T14:25:00
permalink Post: 11906063
It then automatically re-engages at 400ft AGL (though I am not sure how the altitude is measured), and begins to operate as requested by various human and computer systems.
Subjects: Takeoff Roll VNAV
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2025-06-19T15:10:00
permalink Post: 11906101
A question to those familiar with Boeing and the 787: are the thrust levers physically moved by Autothrust or does Boeing use them only to stake an upper thrust limit as Airbus does with active A/T?
Subjects: None
2025-06-20T22:29:00
permalink Post: 11907367
he autopilot would NOT be engaged below 400’ (or 200’ in the 78–although I doubt anyone engages it that low. The autopilot and autothrottles are separate systems but do interact. The autothrottles typically WOULD be engaged from the start of the takeoff roll; using the TOGA levers to set takeoff thrust).
I am guessing because although I flew the 777 I never tried a low altitude capture before VNAV engaged — and it`s been a few years). But think it probably would. As one goes through 50’ LNAV engages; VNAV is normally armed prior to the EFIS check if it`s to be used (which it usually is). So in this scenario LNAV would have been engaged but since VNAV is armed but never engages my guess is that the automatics would engage in SPD/LVAV/ALT.
HOLD is present in many other regimes of flight; all it means is that the auththrottle (right now) is not controlling the throttles and they stay where they are—and the PF can move them if desired at will. Fr` instance, when descending in FLCH or even VNAV SPD the throttles will usually be in HOLD. (To me this usually meant `hold` the throttles—and tweek them in descent as required). Thrust can be modulated to adjust rate of descent (the throttles become vertical speed levers). On altitude capture in the case of FLCH or path capture in the case of VNAV SPD (in descent) the auththrottles kick in and it becomes SPD/xxx/ALT (or VPTH or VALT as the case might be).
Most everyone knew the autothrottles would not engage below 400` and that FLCH in descent at very low altitudes was not an appropriate mode — and they did not activate providing low speed protection in the case of Asiana.
Since the Asiana accident many airlines prohibit use of FLCH below 1,000' and the lowest altitude setting when using FLCH is then, of course, 1.000'
IIRC our throttles went into HOLD at 60 knots and stayed there until VNAV activated (THR REF—takeoff thrust). It was also possible that the autothrottles under some environmentals wouldn`t fully achieve takeoff thrust setting (EPR or N1 depending on which engines) and they could be manually moved in HOLD to achieve it. Although I don`t remember that as ever happening.
Subjects: Engine Failure (All) TOGA Takeoff Roll VNAV
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