ATR-72 crash at PKR, Nepal. Many fatalities feared.

[Evan]

They stalled because they pulled up

YES!

(we at least agree that there is no way around that), and they pulled up before the bank.

YES!

At 10:57:24 when the aircraft was at 311 feet AGL, the stick shaker was activated warning the crew that the aircraft Angle of Attack (AoA) increased up to the stick shaker threshold

I believe that's the obvious pull-up we see in the video. Note that the report does not indicate a stall here, only a stall warning. Then the stall warning ceases. WHY?

At 10:57:26, a second sequence of stick shaker warning was activated when the aircraft banked towards the left abruptly. [/QUOTE]

That precedes the stall. Ask yourself why a wing drop stall would occur at the moment of stick shaker activation? If it did, we would be missing the stall margin. The wording is unfortunately somewhat vague, so it remains a mystery and I could certainly be wrong, but, it seems to say that the bank activated the stall warning (at a margin above stall, thus unstalled), and that would support the speculation that the bank was intentional and triggered an immediate accelerated stall.

It's also consistent with a plane that has lost power and must land immediately. That was the last moment where a turn needed to happen in order to make the runway.

I'm sorry if my impertinence wears on you, but it is a legitimate speculation based on what we know so far. Calling it delusional and stupid and hanging up is unwarranted.

[Evan]

METAR:

VNPR METAR 0430Z 17003KT 070V190 6000 FEW025 14/09Q1016 NOSIG
VNPR METAR 0500Z 12005KT 080V160 6000 FEW025 14/09 Q1015 NOSIG

3-5kt tailwinds on the stabilized ILS approach to RWY 30.

[Evan]

Regarding the danger inherent in the new RWY12 visual approach:

1.8.4 From the retrieved FDR data, the investigation team was able to recover the flight path of the event flight and another flight on 12 Jan 23, where another set of crew landed on Runway 12 of VNPR.

1.8.5 Due to the shortened final approach leg for runway 12, in both the flight the stabilization criteria for a visual approach could not be stabilized at the height of 500ft AGL.

Not good.

3 INTERIM SAFETY RECOMMENDATIONS

3.1 The Aircraft Accident Investigation Commission has recommended the following interim safety recommendation: The CAAN should conduct a comprehensive study to determine the appropriate flight path that allows the criteria for a stabilised visual approach to be met, taking into consideration of the simultaneous operations at both VNPK and VNPR airports before resuming visual approach on Runway 12 of VNPR.

They seem to consider it unsafe as well.

[Gabriel]

What happens if the stickshaker AoA is 10 degrees, the critical AoA is 12 degrees, and you pull up at once from from 9 degrees to 13 degrees? Just a hypothetical question, of course.

[Gabriel]

it seems to say that the bank activated the stall warning

I think that it was the cloud that activated it. What? Clouds don't activate stall warnings? Exactly.

[Evan]

What happens if the stickshaker AoA is 10 degrees, the critical AoA is 12 degrees, and you pull up at once from from 9 degrees to 13 degrees? Just a hypothetical question, of course.

That certainly could have happened. It just defies explanation after recovering from a stall warning moment earlier. I would expect the pilot to be riding the stall warning threshold very carefully at that point. You, see, what I am trying to find here is logical motive by a skilled pilot. We've seen pilots, even instructor pilots, do inexplicable things, so it's possible. It's just as possible, but less inexplicable, that the pilot neglected to factor in maneuvering load while riding the stall warning threshold.

[Gabriel]

I hope that the FDR records flight control positions.

[Gabriel]

That certainly could have happened. It just defies explanation after recovering from a stall warning moment earlier. I would expect the pilot to be riding the stall warning threshold very carefully at that point. You, see, what I am trying to find here is logical motive. We've seen pilots, even instructor pilots, do inexplicable things, so it's possible. It's just as possible, but less inexplicable, that the pilot neglected to factor in maneuvering load while riding the stall warning threshold.

You are trying to fit the data to your narrative, rather than the other way around. First figure out the facts, only then start investigating the motives. Understand what happened. Only then start to try to understand why.

Watch the video and tell me in what frame you would place the first stickhaker and in what frame the second stickshaker. They have to be 2 frames more or less 2 seconds apart.

I have 2 hypothesis (reference: the video posted in AvHerald)

1) The first stichshaker just before the video starts, the second stickshaker is around end of second 1 and beginning of second 2 in the video, when we see the pull up. Then the wing drops.
2) The first stickshaker happens around end of second 1 and beginning of second 2 in the video, when we see the pull up. They lower the nose a bit but it is too little too late, the plane is already stalling and rolling. Then second stickshaker happens when they pull up hard in desperation when the plane is already way overbanked and the nose going way down (because that's 2 seconds after the pull up). At that point it doesn't matter what they do anyway.

I cannot envision a scenario where a stickshaker was not associated with the pull up. Add, given that and the ~2 seconds difference between stickshakers, I cannot envision a scenario that fits your narrative, where a second stickshaker happened because they pulled up as part of a "normal" turn before losing control.

[Evan]

You are trying to fit the data to your narrative, rather than the other way around. First figure out the facts, only then start investigating the motives. Understand what happened. Only then start to try to understand why.

That's not true. I'm working with the facts we have, the interim report and trying to understand why.

Watch the video and tell me in what frame you would place the first stickhaker and in what frame the second stickshaker. They have to be 2 frames more or less 2 seconds apart.

I have 2 hypothesis (reference: the video posted in AvHerald)

1) The first stichshaker just before the video starts, the second stickshaker is around end of second 1 and beginning of second 2 in the video, when we see the pull up. Then the wing drops.
2) The first stickshaker happens around end of second 1 and beginning of second 2 in the video, when we see the pull up. They lower the nose a bit but it is too little too late, the plane is already stalling and rolling. Then second stickshaker happens when they pull up hard in desperation when the plane is already way overbanked and the nose going way down (because that's 2 seconds after the pull up). At that point it doesn't matter what they do anyway.

I can also envision either of those scenarios (although, based upon the ATR research I've done, I'm not convinced that a wing would drop as the first sign of stall). I just can't understand why. But, of course, there is a history of this inexplicable stuff...

I cannot envision a scenario where a stickshaker was not associated with the pull up. Add, given that and the ~2 seconds difference between stickshakers, I cannot envision a scenario that fits your narrative, where a second stickshaker happened because they pulled up as part of a "normal" turn before losing control.

I understand that you can't envision a stall occurring when a pilot riding the edge of stall warning neglects to factor in maneuvering load when making a do or die turn to final. That is understood.

Enough about that until we see (or hear about) some FDR plots.

What do you think about the nature of the constrained approach pattern with consideration to stabilized criteria and safety? Do you see fail to see it as a significant causative factor?

[Gabriel]

I understand that you can't envision a stall occurring when a pilot riding the edge of stall warning neglects to factor in maneuvering load when making a do or die turn to final. That is understood.

Oh my goodness...

I CAN envision that. but I can't envision what I SAID that I can't envision.

Again, please tell me where you would place the first stickshaker and the second stickshaker in reference to the video posted in AvHerald. Because whatever else happened in that flight, what we can see in the video did happen. So any narrative NEEDS to be consistent with the video, or it is false.

What do you think about the nature of the constrained approach pattern with consideration to stabilized criteria and safety? Do you see fail to see it as a significant causative factor?

Could be a factor, but that's not the decision to make the visual pattern but how they executed it. Who told them to turn where they did? Apparently "not overflying the old airport" was not the reason, because they overflew it.

By the way #1. It is not clear to me that the outcome would have been any different had they done a longer downwind before turning base and "selecting flaps 30".
By the way #2. The stabilized approach criteria is a generalized concept, but there is no industry standard for the specific criteria. Different entities (manufacturers, operators, industry organizations, governmental agencies) use different criteria. And an operator can make and use their own. For example Boeing says that the criteria is that by 500 ft the airplane is in the correct flight path and only minor control inputs are needed to keep the plane in said flight path, and that in visual approaches the wings must be level by 500 ft except in circling approaches where they must be level by 300 ft.

[Evan]

Oh my goodness...

I CAN envision that. but I can't envision what I SAID that I can't envision.

Again, please tell me where you would place the first stickshaker and the second stickshaker in reference to the video posted in AvHerald. Because whatever else happened in that flight, what we can see in the video did happen. So any narrative NEEDS to be consistent with the video, or it is false.

The first stickshaker during the pull up we see preceding the bank, which is followed by a slight nose down moment that I think could be a correct pilot reaction to that warning.

(I think the pilot would be expected to adopt this strategy when faced with a power deficit and critically low altitude. I mean, you once did.).

The second stickshaker, as stated in the report, at the onset of the bank, which the continuing steepness of the bank (while holding altitude) immediately accelerates into a stall at around 15-20deg of bank.

Could be a factor, but that's not the decision to make the visual pattern but how they executed it. Who told them to turn where they did? Apparently "not overflying the old airport" was not the reason, because they overflew it.

Of course I have no clue who laid out the pattern or if it was total effing improv. It might have been driven by the VOR of the old airport if they were practicing an instrument approach. But there are terrain constraints everywhere. They have to thread the space between Bhadrakali Temple and the neighboring hillside, then get to a base leg before reaching the hills directly in front of them. In any case, that's not going to leave more than 1.5-2 miles of final. But they certainly could have turned base further afield than what they did here. I'm wondering it it wasn't force of habit for landing at the old airport.

BTW: It appears that a nice stable straight-in approach to RWY 12 is possible, maybe with ILS or backcourse.

[3WE]

Gabriel…it’s on the CVR…”let’s land on the other runway so we can make a really steep bank which will increase our load factor because it goes against the ATR-72-212A FCOMPOHQRH because we are improvisational cowboys and like to ride bicycles.”

[3WE]

…and being serious, we need the thought recorders. They were aware of the need for more power and moving the power levers appropriately.

[Gabriel]

[Evan]

You can see in that photo the trigger levers under each condition lever. To move from AUTO to FTR, you must first lift the trigger levers and then pull the levers into the FTR detent.

The flaps lever requires you to lift the entire lever out of the detent and then move it into the next detent.

Both levers require lifting and then moving, but a pilot has to be quite out of the game to not notice the difference.

Or quite distracted.

It's also puzzling how at least the PF realized that there was a power issue but didn't notice either the CL levers or the amber LO PITCH indications on the engine control panel (and I think there's also a master warning). There is plenty of SA there.