Originally posted by Evan
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Cargo airplane collapsed in Kyrgyzstan
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Originally posted by Evan View Postand GPWS is inhibited in landing configuration
"Sink rate", 'terrain", "woop woop pull up" and even "don't sink" (with a high power setting) all work in landing configuration (not if you are smoothing approaching the middle of the ocean in a landing-like profile, though, so they would not have sounded in this case). "Glide slope" of course is also active in landing config (what would be the point if not), but I don't know what is the criteria that "arms" this mode. This plane crossed the (false) glideslope and obviously deviated from it. [EDIT: Found it: "The mode is armed when a valid signal is being received by the capts glideslope receiver and the radio altitude is 1000 feet or less." I am not sure how this applies in this case, perhaps the GS was not being received anymore when the airplane crossed 1000ft]
Too low flaps and too low gear are not inhibited but will never be heard in landing config for obvious reasons.
Feel free to prove me wrong though.
Well, apparently it didn't, and it's safe to say that this 2003-build 747 had EGPWS (TAWS) installed.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Evan View PostBB, Can you tell us what happens on the 744 if the vertical mode goes to GS CAP and then loses the glideslope signal? Does it then transition to V/S by default? This flight transitioned to ALT HOLD when it reached 3400 with no glideslope capture, then flew level until it traversed the mirror glideslope at 9°, which activated GS CAP but of course it flew right through that. Yet it descended on autopilot. Why does it not remain in ALT HOLD in that scenario?
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Originally posted by Gabriel View PostIt is not. This one I know for sure.
"Sink rate", 'terrain", "woop woop pull up" and even "don't sink" (with a high power setting) all work in landing configuration...
from any airport in the terrain database." And of course it would have to be inhibited within airfields where the aircraft is expected to go below that safe altitude (in landing config) to land.
This is my assumption of how it works, and it explains why EGPWS didn't save this crew:
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Originally posted by Evan View PostAre you sure about "TERRAIN"? The first terrain warning is "TOO LOW TERRAIN" which my 747-400 FCOM indicates as "Descent below unsafe altitude while too far from any airport in the terrain database." And of course it would have to be inhibited within airfields where the aircraft is expected to go below that safe altitude (in landing config) to land.
Note GPWS without an initial E. The GPWS will not know where the airplane is in relation with the airport.
So "terrain" would be available, not "too low terrain".
"Terrain" is a ground closure rate warning (i.e. RA vertical speed), which can be caused by you descending toward the terrain or the terrain raising under you.
"too low terrain" is a ground closure warning (without "rate") that sounds when you are too close to the ground but not in landing configuration.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Gabriel View PostI was responding to you and quoted you saying "and GPWS is inhibited in landing configuration".
Note GPWS without an initial E. The GPWS will not know where the airplane is in relation with the airport.
So "terrain" would be available, not "too low terrain".
"Terrain" is a ground closure rate warning (i.e. RA vertical speed), which can be caused by you descending toward the terrain or the terrain raising under you.
"too low terrain" is a ground closure warning (without "rate") that sounds when you are too close to the ground but not in landing configuration.
https://www.boeing-727.com/Data/systems/infogpws.html
TERRAIN does not apply here because the closure rate was not excessive.
(With GPWS the TOO LOW TERRAIN warning is ALWAYS inhibited in landing configuration regardless of where the airplane drops below the safe altitude, so I'm not talking about GPWS.)
FYI: DON'T SINK is also inhibited in landing configuration (gear and/or flaps out) since it is intended for take off or go-around, not landing.
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Originally posted by Evan View PostIf I am correct about that, it would seem logical, and not too difficult, to fix that.
FYI: DON'T SINK is also inhibited in landing configuration (gear and/or flaps out) since it is intended for take off or go-around, not landing.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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How many posts dissecting "if-then" logic, when "watch the needles when doing an ILS in genuine IMC" is the failure here?
Great to have back-up checks, but instead of redesigning a plethora of XGPWS modes and logic trees, how about the I-pad depicting the view out the window, some boxes to fly through and maybe a flashing red light and a beep for "off course".Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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I am thinking... probably the crossed bars of the Flight Director where nailed in the center of the PFD. Some pilots tend to rely and focus too much in the FD, above other instruments like the ILS or even the attitude indicator.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Gabriel View PostI am thinking... probably the crossed bars of the Flight Director where nailed in the center of the PFD. Some pilots tend to rely and focus too much in the FD, above other instruments like the ILS or even the attitude indicator.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Exactly!
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Originally posted by Gabriel View PostI am thinking... probably the crossed bars of the Flight Director where nailed in the center of the PFD. Some pilots tend to rely and focus too much in the FD, above other instruments like the ILS or even the attitude indicator.
...still, the $ to rework all of the XGPWS logic vs. the I-pad app (and you know the I-pad comment is largely sarcasm, but with the genuine statement that we are pretty darn rich when it comes to data and computing power to provide some hellacious synthetic vision for a good ole cross check).Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Originally posted by Gabriel View PostI am thinking... probably the crossed bars of the Flight Director where nailed in the center of the PFD. Some pilots tend to rely and focus too much in the FD, above other instruments like the ILS or even the attitude indicator.
Essentially we have a perfect storm of:
- a complacent crew
- a delayed arrival at the FAF crossing altitude (3,400') preventing glideslope capture
- a false glideslope signal causing G/S CAP to initiate continued descent to the runway
- hard IMC, a lack of visual ground reference
- no automated warning alerting the crew that something isn't right
Remove any one of those conditions and this crash would not have happened. Guess which of those conditions is easiest to remove...
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