AA757 Near Stall - Recovery Caused Injuries
You're missing my point. Not in any way excusing allowing airspeed to drop 64 kts before taking action - just wondering why that action was so aggressive that it injured people in the back - flinging the flight attendants into the ceiling.
Seems a gentle forward push along with advancing the thrust levers would have been more than sufficient to prevent the aircraft falling out of the sky.
Seems a gentle forward push along with advancing the thrust levers would have been more than sufficient to prevent the aircraft falling out of the sky.
I haven't flown the 757, but guess min clean would be around 210 ( based on Vref30 + 80 kts and Vref135kts, found on the internetz, FWIW).
I do think that when you get 25 knots below your minimum speed swift action might be required, so I still maintain the first part was the bigger problem.
Perhaps the poorly handling pilot (PHP?) was startled and reacted thusly?
I would hazard a guess and say the pilots were physically looking at the instruments but not actually 'seeing' or understanding what they were seeing. So it's a tad more complex than 'c0ck-up' fellas....
I would hazard a guess and say the pilots were physically looking at the instruments but not actually 'seeing' or understanding what they were seeing. So it's a tad more complex than 'c0ck-up' fellas....
The data is pretty depressing... the reports are abysmal to pitiful.
For a considerable time, the crew appear to have been preoccupied with tasks other than monitoring the performance of the aircraft relative to desired targets. The closest the aircraft got to an aerodynamic stall was in the middle of the inputs by the pilot which become pretty uncoordinated to the required aircraft attitude necessary to recover the aircraft from the low-speed case back to the desired speed. The aircraft was never in any particular danger, it was merely at an undesired speed, and the injuries were directly related to the excessive response by the PF.
Fatigue would add to the lack of recognition of the condition of the aircraft, and to the response being uncoordinated to the need of the situation. Presumably, this is an early morning departure ex Scotland, given the event occurred at 13:00 CDT. (16:47:30UTC, first response by crew). The crew rest before the flight may have added slightly to the actions, but 3, crew, daylight flight, after some form of local rest.... not directly a big red flag on fatigue risk management.
For a considerable time, the crew appear to have been preoccupied with tasks other than monitoring the performance of the aircraft relative to desired targets. The closest the aircraft got to an aerodynamic stall was in the middle of the inputs by the pilot which become pretty uncoordinated to the required aircraft attitude necessary to recover the aircraft from the low-speed case back to the desired speed. The aircraft was never in any particular danger, it was merely at an undesired speed, and the injuries were directly related to the excessive response by the PF.
Fatigue would add to the lack of recognition of the condition of the aircraft, and to the response being uncoordinated to the need of the situation. Presumably, this is an early morning departure ex Scotland, given the event occurred at 13:00 CDT. (16:47:30UTC, first response by crew). The crew rest before the flight may have added slightly to the actions, but 3, crew, daylight flight, after some form of local rest.... not directly a big red flag on fatigue risk management.
Last edited by fdr; 15th May 2022 at 07:03.
As DaveReidUK suggests, those (unrestrained) towards the rear of the aircraft are more likely to be thrown about due to the longer levering arm towards the rear of the aircraft. A similar incident occurred with Qantas around 5 years ago - this is an extract from the ATSB report...
In-flight upset involving Boeing 747-438, VH-OJU, 110 km SE of Hong Kong Airport, on 7 April 2017
Contributing factors
- After overwriting the hold speed in the flight monitoring computer , the flight crew did not identify the need to re-evaluate the hold speed for the higher than expected hold level.
- Prior to entering the hold, the aircraft’s speed reduced below both the selected and minimum manoeuvring speeds. The crew did not identify that the aircraft was operating below these speeds.
- The reduced speed coincided with the turn to enter the holding pattern and the level capture. These factors resulted in pre-aerodynamic stall buffeting and probable stick shaker activation.
- The pilot flying attempted to arrest the rate of descent prior to completing the approach to stall actions. The pilot monitoring did not identify and call out the incomplete approach to stall recovery actions. These combined actions led to pilot induced oscillations and further stick shaker activations.
- The operator provided flight crew with limited training and guidance in stall prevention and recovery techniques at high altitudes or with engine power above idle. (Safety issue)
- The passenger in seat 63C was not wearing a seatbelt at the time of the stick shaker activations.
The interviews with the crew are interesting to read - such a normal day for all three pilots and then it all went very wrong, very quickly.
What it makes me wonder is how often events just like this occur but the crew save themselves a whisker sooner and don't get the NTSB involved? Is it a one off or the tip of an iceberg of inattention?
What it makes me wonder is how often events just like this occur but the crew save themselves a whisker sooner and don't get the NTSB involved? Is it a one off or the tip of an iceberg of inattention?
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As DaveReidUK suggests, those (unrestrained) towards the rear of the aircraft are more likely to be thrown about due to the longer levering arm towards the rear of the aircraft. A similar incident occurred with Qantas around 5 years ago - this is an extract from the ATSB report...
In-flight upset involving Boeing 747-438, VH-OJU, 110 km SE of Hong Kong Airport, on 7 April 2017
Contributing factors
- After overwriting the hold speed in the flight monitoring computer , the flight crew did not identify the need to re-evaluate the hold speed for the higher than expected hold level.
- Prior to entering the hold, the aircraft’s speed reduced below both the selected and minimum manoeuvring speeds. The crew did not identify that the aircraft was operating below these speeds.
- The reduced speed coincided with the turn to enter the holding pattern and the level capture. These factors resulted in pre-aerodynamic stall buffeting and probable stick shaker activation.
- The pilot flying attempted to arrest the rate of descent prior to completing the approach to stall actions. The pilot monitoring did not identify and call out the incomplete approach to stall recovery actions. These combined actions led to pilot induced oscillations and further stick shaker activations.
- The operator provided flight crew with limited training and guidance in stall prevention and recovery techniques at high altitudes or with engine power above idle. (Safety issue)
- The passenger in seat 63C was not wearing a seatbelt at the time of the stick shaker activations.
Nah. Plane never stalled, nothing other than the cabin crew was harmed. It actually was no closer than 10 KCAS to the min speed alert (185.5KCAS min CAS recorded, min manoeuver 174.5KCAS...). It wasn't dangerous from an aerodynamics or dynamics aspect, but the response from the crew was pretty darn "biggly".... didn't need to be, but as an institution, we are pre-priming crews to respond too aggressively to what was otherwise just a bit embarrassing.
- If we cannot fly in instruments we have no place being in the sky with clouds;
- If we cannot cope with the annoyance of a stall, we have no place being in the air period.
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The ceiling encounter of the cabin crew, in the back of the airplane, seems to be due to an even more aggressive correction to "undo" the original pitch reaction.
To me, this whole suggests a "firm" reaction to a suddenly detected potentially dangerous situation (IE low airspeed), with a subsequent "relieve", "Oh, it's not that bad". And that relieve reaction got screwed up by a far too aggressive input.
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I am trying to understand what Gz stands for: Is this the vert (?) acceleration of the airplane's center of gravity, or the vert (?) acceleration in the back of the airplane ? The latter being the relevant item, judging about what would happen with non-fixed objects in the back of the airplane. Both accelerations can be significantly different, when pitch actions are involved.
I am trying to understand what Gz stands for: Is this the vert (?) acceleration of the airplane's center of gravity, or the vert (?) acceleration in the back of the airplane ? The latter being the relevant item, judging about what would happen with non-fixed objects in the back of the airplane. Both accelerations can be significantly different, when pitch actions are involved.
To get a picture of what's happening at the back end, you would need to factor in pitch data.
Gz in the fdr trace will be measured wherever the accelerometer is located. My guess is that it's located in the avionics bay. An abrupt pitch rate will produce opposing Gz rates at the ends of the aircraft.
Once the pitch rate goes to zero, unrestrained objects will tend to continue in the direction they have been accelerated, much like a catapult if in the rear during a pitch down. In front, unrestrained objects in negative Gz will head to the ceiling and drop back down when Gz rate returns to zero, as was demonstrated by an ashtray bouncing off the ceiling when I advised my instructor we were climbing into the path of another airplane on a converging course. He had been questioning my reducing our climb from a practice forced approach.
Once the pitch rate goes to zero, unrestrained objects will tend to continue in the direction they have been accelerated, much like a catapult if in the rear during a pitch down. In front, unrestrained objects in negative Gz will head to the ceiling and drop back down when Gz rate returns to zero, as was demonstrated by an ashtray bouncing off the ceiling when I advised my instructor we were climbing into the path of another airplane on a converging course. He had been questioning my reducing our climb from a practice forced approach.
Last edited by RatherBeFlying; 16th May 2022 at 01:44.
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I disagree that HOLD mode is moronic. What is moronic is the mis-handling or lack of awareness and understanding of the aeroplane systems operation.
On the B777 and B787 the HOLD mode software has now changed in that speed protection, i.e. Autothrottle Automatic Activation, now functions when in that mode. I presume the change applies to other models as well.
On the B777 and B787 the HOLD mode software has now changed in that speed protection, i.e. Autothrottle Automatic Activation, now functions when in that mode. I presume the change applies to other models as well.
I think there are different ways of looking at this. It is nice to say that it is moronic to have a lack of awareness or have mis-handling of a system function and there may be a valid argument for that.
But there is also the reality that it is well known that when there are thousands of pilots around the world flying the aircraft types, who are humans and make mistakes, where weak pilots inevitably will fall through the cracks somewhere, where fatigue will be an issue, where distractions happen, where even good pilots make mistakes, where language barriers result in incomplete knowledge, where instruction may not cover everything as well as it should, where a pilot is close to overwhelmed with knowledge in training........ that it makes sense for a design where autothrottle wake-up exists in most areas but not in another(in HOLD mode) is an incident waiting to happen because someone will inevitably it existed but did not.
It may feel good to yell "you are a moron" but it doesn't make things much safer(in terms of lack of awareness/forgetfulness of the lack of autothrottle wake-up in HOLD Mode). I suspect the modification did.
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Also, who selects LVL CHG to correct 100ft?V/S would be a lot more appropriate...
FLCH is easier.
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I think V/S works fine. Need to change 100 feet, one could put the V/S at 100 fpm and you would have a full minute to reach that altitude. Perhaps some aircraft have had software issues.
where:
Anyway,
This case, the aircraft had a mild pitch up approaching the min soeed case, as the AP was atttempting to respond to the commended mode of the crew, as speed reuduced. (forget about the fact that the plane had already been cleared to a lower level, so the vertical mode is pretty much irrelevent, it is just options). As it got to peak pitch of just under 10 degrees, at 184.5kts, it then started to pitch down, at around 6 degrees a second, 0.1rad, and recorded a Gz lowest of -.025g +/-, which would have an actual almost zero g loading at the aft galley... Thereafter there was a pitch recovery and a return of the Gz towards normal levels.
Last edited by fdr; 17th May 2022 at 17:12.
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Once the pitch rate goes to zero, unrestrained objects will tend to continue in the direction they have been accelerated, much like a catapult if in the rear during a pitch down. In front, unrestrained objects in negative Gz will head to the ceiling and drop back down when Gz rate returns to zero, as was demonstrated by an ashtray bouncing off the ceiling when I advised my instructor we were climbing into the path of another airplane on a converging course. He had been questioning my reducing our climb from a practice forced approach.
