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

[Gabriel]

Sadly, your initial impression is more correct. But, hoping you might have a fun attitude and will liven the place up.

Evan and Gabe are a bit too serious- Gabe, especially on the credentials thing. In Gabe’s defense, occasionally, we have been told that as not_airline pilots, we didn’t know what the phugoid we were talking about…Maybe, there’s an elusive middle ground [Shoulder shrug emoji]?

Boeing Bobby is a huge ass and shows pictures of him flying his Cub, whenever us outsider ankle biters get overly stimulated.

ATLCrew is a quintessential professional, who will sneak win on rare occasions with a nuclear statement of truth, along with snide humour.

It appears you are/were a much-credentialed airline pilot, like BoeingBobbie- Thus I tried to force a nickname on you: Boeing Bertie. I also have an alternative nickname, that Evan or others will be glad to share.

What about Kent?

[BoeingBobby]

What about Kent?

You mean the legend in his own mind?

[Evan]

You mean the legend in his own mind?

Why are you always riding Kent? He's your peer, a retired airman with a lot of pre-magenta experience and a wealth of stories about the Good Old Days, back when piloting an airliner was like hunting mastodons and planes crashed more often than the markets. I think we made a poor impression on captain Olsen.

[BoeingBobby]

Why are you always riding Kent? He's your peer, a retired airman with a lot of pre-magenta experience and a wealth of stories about the Good Old Days, back when piloting an airliner was like hunting mastodons and planes crashed more often than the markets. I think we made a poor impression on captain Olsen.

Have you ever met someone known as a "one upper?"

Here is the scenario.

3 couples are having a nice dinner at a seaside resort. The sun is about to set and the tropical drinks and appetizers are on the table. One of the group starts to tell a story about how they had been here 15 years ago before all the resorts were built and most of the beach was vacant land. "Well my wife and I were walking down this very beach 15 years ago, there was absolutely no one on the beach but us. As the sun went below the horizon, the sky exploded into a thousand colors, and a flock of seagulls flew by and it was one of the most beautiful things I have ever seen in my life." Kent responds, "Well I was here with one of my girlfriends 16 years ago, there was less people, more colors, and more seagulls."

Get the point?

I also happen to have a bunch of old zoner friends, so his reputation precedes him!

[Evan]

Have you ever met someone known as a "one upper?"

Oh, that's nothing. I met a "two-upper" once.

Okay, okay. I thought he was legit.

[Gabriel]

A couple of things I forgot to mention:

]I am convinced that the steep turn we see at the onset of stall was intentional and accelerated the stall.

I am convinced that wasn't a commanded bank (let alone intentional) and that it wasn't an accelerated stall.

I intended to add, as a justification, that
a) The roll is too brisk and fas, I don't believe that the ailerons would have such an aerobatic authority at such a low airspeed and such a high AoA.
b) Again, rolling or a steep bank doesn't accelerate the stall. The nose drops almost immediately after the bank started. Even if the pilots were intentionally banking initially (which I don't believe they were), I don't think that they would be already pulling up. The way you turn is you bank and pull up, in that order. You don't pull up since the beginning of the banking motion, otherwise the nose would go up first. You can actually feel it in a commercial plane when it does a turn. You can see the plane banking and, towards the end of the roll, the G's build up (a bit).

That procedure, in order to align with the runway, required a significant left bank at low altitude, and was very unsafe by 21st century commercial aviation standards, even with two engines producing thrust.

In the part you say and I quoted, which I was relying to, you did not mention anything about the steepness of the turn. You mentioned that they were overshooting final in all the previous approaches (and also in the fatal one) and I said that there was room to start the turn earlier.

Second, a pilot doesn't need a landmark to start the turn early enough not to overshoot final. A downwind-to-base and a base-to-final turn is pretty standard flying.

Lastly, a 30 deg bank is pretty typical in base-to-final turns. That's normally the maximum bank angle allowable in a transport category airplane, that's the maximum angle you can set up the AP to use in turns, and that is pretty typically what is used both in manual flight and in AP. You have a 5-degree "tolerance" before the "bank angle" alarm will start to sound at 35 degrees in most modern transport category planes. A coordinated constant-vertical-speed 30-deg-bank turn increases the stall speed in some 7%.

The real problem here was that:
a) When flaps where called, the PM pulled both conditions lever instead.
b) The PM didn't check that the flaps actually moved to the commanded (or supposedly commanded) position.
c) The PF didn't check either (although that's more understandable)
d) The landing checklist was not correctly executed, so they didn't catch that the flaps were not set.
e) The PM eventually et flaps 30, without saying a thing (not only something like "strange, I thought I had set the flaps" but didn't even call what he did. You just don't change configurations without the PF asking or even knowing).
f) Neither the PF nor the PM noticed that the engines were not producing thrust until it was too late.
g) Neither the PF nor the PM noticed a warning light associated with the engines being feathered.
h) They actively stalled the plane by pulling up too much (bank or no bank). If they had crashed short of the runway at low speed and under control there is a very good chance that we would have had survivors.

Yes, a new visual pattern approach (not a circle-to-land approach) to a new airport surrounded by terrain was a workload increaser and distraction and certainly that was a big factor. But it is within the realm of things that pilots do routinely. Many things increase the workload and cause distractions. At the end of the day, it was a single "brain fart" type of error that went undetected what killed them. Would have they caught the mistake had it happened in a straight-in ILS approach? Maybe. I doubt it. We will never know. Pilots need to be able to fly visual aerodrome circuit patterns even to airports where they had never been before.

[Evan]

A couple of things I forgot to mention:



I intended to add, as a justification, that
a) The roll is too brisk and fas, I don't believe that the ailerons would have such an aerobatic authority at such a low airspeed and such a high AoA.
b) Again, rolling or a steep bank doesn't accelerate the stall. The nose drops almost immediately after the bank started. Even if the pilots were intentionally banking initially (which I don't believe they were), I don't think that they would be already pulling up. The way you turn is you bank and pull up, in that order. You don't pull up since the beginning of the banking motion, otherwise the nose would go up first. You can actually feel it in a commercial plane when it does a turn. You can see the plane banking and, towards the end of the roll, the G's build up (a bit).


In the part you say and I quoted, which I was relying to, you did not mention anything about the steepness of the turn. You mentioned that they were overshooting final in all the previous approaches (and also in the fatal one) and I said that there was room to start the turn earlier.

Second, a pilot doesn't need a landmark to start the turn early enough not to overshoot final. A downwind-to-base and a base-to-final turn is pretty standard flying.

Lastly, a 30 deg bank is pretty typical in base-to-final turns. That's normally the maximum bank angle allowable in a transport category airplane, that's the maximum angle you can set up the AP to use in turns, and that is pretty typically what is used both in manual flight and in AP. You have a 5-degree "tolerance" before the "bank angle" alarm will start to sound at 35 degrees in most modern transport category planes. A coordinated constant-vertical-speed 30-deg-bank turn increases the stall speed in some 7%.

The real problem here was that:
a) When flaps where called, the PM pulled both conditions lever instead.
b) The PM didn't check that the flaps actually moved to the commanded (or supposedly commanded) position.
c) The PF didn't check either (although that's more understandable)
d) The landing checklist was not correctly executed, so they didn't catch that the flaps were not set.
e) The PM eventually et flaps 30, without saying a thing (not only something like "strange, I thought I had set the flaps" but didn't even call what he did. You just don't change configurations without the PF asking or even knowing).
f) Neither the PF nor the PM noticed that the engines were not producing thrust until it was too late.
g) Neither the PF nor the PM noticed a warning light associated with the engines being feathered.
h) They actively stalled the plane by pulling up too much (bank or no bank). If they had crashed short of the runway at low speed and under control there is a very good chance that we would have had survivors.

Yes, a new visual pattern approach (not a circle-to-land approach) to a new airport surrounded by terrain was a workload increaser and distraction and certainly that was a big factor. But it is within the realm of things that pilots do routinely. Many things increase the workload and cause distractions. At the end of the day, it was a single "brain fart" type of error that went undetected what killed them. Would have they caught the mistake had it happened in a straight-in ILS approach? Maybe. I doubt it. We will never know. Pilots need to be able to fly visual aerodrome circuit patterns even to airports where they had never been before.

I'm willing to blame myself for not explaining this clearly enough. So very clearly;

- YES, THEY WERE PULLING UP. It's pretty obvious in the video. And the stick shaker tells the tale. They had no thrust and less than 400ft of altitude with the airport still a mile off. They were not in the mood to descend, despite the plane wanting to descend.

- YES, THE STALL OCCURRED FROM EXCEEDING CRITICAL AOA. This was brought about by pulling up and hastened by banking. Laterally, they had to bank at that point. Vertically, they had to pull up in the turn to preserve enough altitude. Aerodynamically, they weren't going to make it.

- YES, THEY COULD HAVE TURNED EARLIER. THEY WERE FOLLOWING AN UNSAFE, IMPROVISED COMPANY APPROACH PROCEDURE. Yes, they could have turned final earlier, but they didn't on any of the previous approach attempts either. The evidence suggests that they were navigating the approach using landmarks and entering the turn over the old airport threshold. So, under those circumstances, they would not have turned earlier.

- YES, GABRIEL CAN SAFETY NAIL THIS APPROACH - And, by all means, do it all day in a Tomahawk. Do it inverted for all I care. But never in a revenue flight on a large turboprop with 72 souls on board. Also, I must remind you that all pilots are not as infallible as you are. Transport category passenger flights must ALWAYS adhere to stable approach criteria whenever possible. This is because you, the pilots, work for us, the passengers, and the job is to get us safely from one place to another. It's a job, not a sport.

And finally...

Yes, a new visual pattern approach (not a circle-to-land approach) to a new airport surrounded by terrain was a workload increaser and distraction and certainly that was a big factor. But it is within the realm of things that pilots do routinely.

There was nothing routine about this, and that is why it happened. The distraction wasn't just "a big factor". It was the reason one pilot wasn't monitoring while the other was flying. One pilot was navigating while the other was flying, and neither were monitoring the cockpit and configuration. Nor, could we be surprised by this "brain fart", considering the demand this unsafe approach placed on the pilots in terms of navigation and time compression. In a nutshell, NEVER DO THIS ON A REVENUE PASSENGER FLIGHT.

That's really it. Reams of accident reports have taught us that brain farts happen when pilots are overwhelmed by tasks and urgency. How do we prevent this? Stabilized approach criteria. If you must fly a visual to RWY 12, break off at a much higher altitude and fly a wider pattern that leaves you lined up and stabilized above 500ft. Don't do this until the brand new aerodrome establishes the approach and you have practiced it in the SIM and don't do it at all unless it is actually safer than landing on RWY 30.

Sincerely,

Your passengers.

[3WE]

A couple of things I forgot to mention:

I’d like to mention a couple things:

It looks EXACTLY like a powerless ATR slowly plowing along with inadequate airspeed…

…to the point of where it looks EXACTLY like an approach to landing stall and wing drop EXACTLY the way non-forgiving airliners drop a wing.

Please, someone do a textbook power-off stall in an ATR on MSFS and send us a video view from the front left.

[3WE]

I try two links Gabe- I think they show the same video.

https://youtu.be/AuXH1htEhyc?si=4gD9kP4Id6_gunfI

https://m.youtube.com/watch?v=AuXH1htEhyc

[Gabriel]

This was brought about by pulling up and hastened by banking. Laterally, they had to bank at that point. Vertically, they had to pull up in the turn to preserve enough altitude.

That's not what I see. The bank was too brisk to talk about "pull up in the turn". There was no turn per se, not before they were falling out of the sky. And again, something you didn't address, I don't believe that the plane would have had so much aileron authority to execute such a quick roll at such a low speed and such high AoA.

GABRIEL CAN SAFETY NAIL THIS APPROACH - do it all day in a Tomahawk. Do it inverted for all I care... all pilots are not as infallible as you are.

Why do you have to make it personal and use me, a low time single-engine PPL, as the "example"?
These were 2 captains (ok, 1 captain and 1 almost captain that would have been captain if the captain hadn't mistaken the prop condition levers for the flap lever) with thousands of flight hours. The captain had thousands of flight hours ON TYPE and was a certified ATR flight instructor.

Transport category passenger flights must ALWAYS adhere to stable approach criteria whenever possible.

• Approaches shall be flown so as to be stabilized in accordance with the criteria below (next slide).
• Unique approach procedures or abnormal conditions that require a deviation from any of the elements of a stable approach described below require a special briefing, and shall be briefed in advance.

Stable Approach Criteria: An approach is considered to be stable when all of the following conditions are met:

1. All briefings and checklists have been actioned.
2. The aircraft is in the planned landing configuration.
3. The aircraft is on the correct flight path (Note).
4. The aircraft speed is not more than final approach speed+10KIAS and not less than VREF (Note 3).
5. Power settings appropriate for the aircraft configuration.

Note: An aircraft is considered to be on the correct flight path if it is within the approach path laid down in the fleet specific FCOM.

Many things to break down here. Will try to keep it brief.
Overall: Nowhere it is said that the plane has to fly a straight in. Nowhere it says that the plane has to be aligned with the runway by the stabilization height.
Top bullet: I wonder if the airline intended that the visual procedure they established was to meet the stabilized approach criteria. If not, second bullet would apply.
Second bullet: I wonder if such special briefing existed and was executed.
Bullet 1: Not done correctly since the flaps were not in the condition expected by the landing checklist.
Bullet 2: It wasn't and it wasn't detected.
Bullet 3: "The aircraft is in the correct flight path" doesn't mean that it is already aligned with the runway. While the verbiage is specific for each airline, I have seen cases where turns below the stabilization height are allowed, normally followed by "airplane must be aligned with the runway and wings must be level by [lower altitude].
Bullet 4: Unfortunately the FDR data in the final report is extremely scarce. I don't know how much before the final stall they were in violation of this point.
Bullet 5: Not met for a BIG LOT of seconds, and not identified.

So why do you focus so much in the visual pattern when there was so much that was off the stabilized approach criteria?

In a nutshell, NEVER DO THIS ON A REVENUE PASSENGER FLIGHT.

Never do what? Do a visual circuit pattern and turn to final at an airport you have never been there before (real or in a sim) in a non-revenue flight with an instructor? At each airport where you may end up executing a visual circuit pattern? That's crazy.

That's really it. Reams of accident reports have taught us that brain farts happen when pilots are overwhelmed by tasks and urgency.

Do you want me to start listing cases of brain farts not related with any particular "unusual" (in your view) approach strategy? Do you want me to start listing "wrong lever" or "wrong knob" such brain farts? Yes, sometimes in high workload like take off and landing. Let's never do that in revenue flights either? But sometimes also in cruise. Let's ban cruise too?

https://www.youtube.com/watch?v=p5m8kvZqwC4

(Add to the list the case of the 737 where the capt when to the bathroom and when he was returning to the cockpit the FO, instead of operating the door unlock witch he used the rudder trim knob sending the plane into a crazy roll, dive and overspeed).

How do we prevent this? Stabilized approach criteria. If you must fly a visual to RWY 12, break off at a much higher altitude and fly a wider pattern that leaves you lined up and stabilized above 500ft.

That's not the stabilized approach criteria. That's Evan wishes was the stabilized approach criteria.

Don't do this until the brand new aerodrome establishes the approach

Find me the visual circuit pattern for some airports, please. Normally all you will find, if anything at all, is an altitude for the downwind and a side of the runway if for some reason the pattern should not be always flown with left turns. Normally the path for a generic visual circuit pattern is defined in the FCOM. Example: (Yes, I see it says "500-700ft stabilized on profile" but that's for a 737. In the Tomahawk, the downwind leg is 1/4 the distance and 1/2 the altitude. I could not find one for the ATR but imagine it will be way above the Tomahawk but below the 737.)

https://imgv2-1-f.scribdassets.com/img/document/189329592/original/975b0832aa/1704188394?v=1

But even if it isn't. Even if they did not meet the company's stabilized approach criteria (which according to the report they didn't), we still have all the problems I mentioned before.
- The company prepared a procedure that put them under this scenario.
- There was no word on where there was a special briefing established for that and whether it was executed.
- If there was no such briefing and there was an expectation that the approach would result stabilized, the first crew attempting this approach should have identified the unstabilized condition, gone around, and reported that to the airline.
- The mistake and many of the other failures (like the miss in the landing checklist) happened well ahead of the stabilized approach altitude and in a period of relatively normal workload for an approach.

There was nothing routine about this, and that is why it happened. The distraction wasn't just "a big factor".

Again, not saying that the tight visual circuit pattern to a new airport was not a factor. I already said it was qualified it as "big".
But you saying that it was all due to the visual circuit pattern is way too much. Repeating again myself repeatedly again:
Would have they caught the mistake had it happened in a straight-in ILS approach? Maybe. I doubt it. We will never know.
But pilots (including transport category pilots need to be able to reliably fly visual aerodrome circuit patterns even to airports where they had never been before.

[Gabriel]

I try two links Gabe- I think they show the same video.

Nice! (thanks for the not_Bermudas link).

[Evan]

Why do you have to make it personal and use me, a low time single-engine PPL, as the "example"?

Sorry, didn't mean to make it personal. I meant that the approach can be flown, and that I'm not concerned with it being flown by recreational airplanes, but that it should never have been flown by a commercial transport plane.

Bullet 3: "The aircraft is in the correct flight path" doesn't mean that it is already aligned with the runway. While the verbiage is specific for each airline, I have seen cases where turns below the stabilization height are allowed, normally followed by "airplane must be aligned with the runway and wings must be level by [lower altitude].

So, specifically:

Yeti Airlines‟ SOP Issue 3 Rev 00 dated 24-05-2022 (3.25):
“…Stabilized means
1. The aircraft is in the correct landing configuration;
2. Flight Path and Speed appropriate (VAPP -0 kts, VAPP + 20kts) (Give a precaution call)
3. Only minor changes in heading and pitch are required to maintain correct flight path;
4. Rate of descent is not greater than 1,000 fpm or required by approach procedure;
5. Power setting is appropriate for the aircraft configuration as defined in the relevant
aircraft document FCOM/ AFM;
6. All briefings and checklist complete…”

I don't consider a steep change in heading to be a minor change, do you?

Never do what?

Fly a new visual pattern approach to a new airport surrounded by terrain at low altitude with tight maneuvering requirements that cannot meet stable approach criteria. Never do that.

Do you want me to start listing cases of brain farts not related with any particular "unusual" (in your view) approach strategy?

No, there are many scenarios that cause these errors. High stress, high workload and external (navigational) distraction is one we certainly recognize.

Find me the visual circuit pattern for some airports, please.

Here's what I'm talking about when I say 'established":

Since the airport was going to be operated only for VFR flight, the validation flight was supposed to be conducted under full VFR condition using both runways and both right hand and left hand visual circuits of RWY 12 for landings.

But no validation flight was ever conducted—and validated—for the visual approach to RWY 12. Instead, there was this:

The operator had developed a visual circuit pattern internally into VNPR and attempted for the
aircraft to remain clear of surrounding terrain and Pokhara domestic airport. This resulted in
an approach that required tight turns during the descent and would result in the aircraft being
at a lower altitude once aligned to RWY 12. This did not meet the requirements for a
stabilised visual approach.

But even if it isn't. Even if they did not meet the company's stabilized approach criteria (which according to the report they didn't), we still have all the problems I mentioned before.
- The company prepared a procedure that put them under this scenario.
- There was no word on where there was a special briefing established for that and whether it was executed.
- If there was no such briefing and there was an expectation that the approach would result stabilized, the first crew attempting this approach should have identified the unstabilized condition, gone around, and reported that to the airline.
- The mistake and many of the other failures (like the miss in the landing checklist) happened well ahead of the stabilized approach altitude and in a period of relatively normal workload for an approach.

All true.

Would have they caught the mistake had it happened in a straight-in ILS approach? Maybe. I doubt it.

Why do you doubt it? The mistake was made because the pilot monitoring was consumed with navigating a challenging, maneuvering exercise, with his eyes focused outside the cockpit. On a straight in final, I would expect that pilot (assuming he was competent, and I do) to be focused both inside and outside of the cockpit, checking everything in a relaxed, routine manner. I would also expect him to put his non-distracted eyes on the flap lever when he moved it

[Gabriel]

3. Only minor changes in heading and pitch are required to maintain correct flight path;

I don't consider a steep change in heading to be a minor change, do you?

I wonder how is that self-consistent when the correct flight path itself is curved, thus requiring a change in heading.
Unfortunately the final report only quotes this short section of the stabilized approach criteria. There are some things that are obviously missing in the report but that have to be in the SOP (like the stabilization altitude and the correct reaction if the criteria is not met by that altitude). There are other things that may be missing in the report OR in the SOP (like what to do with curved flight paths or exceptions).

In any case, given the obvious non-compliance not only in this flight but also in the previous ones, this looks to be more a box-checked item for the sake of regulatory approval than something that the airline intended the pilots to comply, so it was not being enforced.

Why do you doubt it? The mistake was made because the pilot monitoring was consumed with navigating a challenging, maneuvering exercise, with his eyes focused outside the cockpit.

You don't know that. I don't know that. The FO that turned the rudder trim instead of unlocking the cockpit door was happily coasting at cruise with about zero workload. The other cases mentioned in the video were routine take offs and landings.
If he just grabbed the wrong lever by mistake, the brain would have set off al kinds of alarms. The shape, vertical position, operation and number is just too different.
In my opinion, the mistake was not aiming for a handle and grabbing the wrong one. It was aiming for the wrong handle. The brain got the sensory input it was expected.
Another theory for the wrong handle was that this was a captain used to fly on the left seat and reaching with his right hand across the control pedestal to the furthest level when setting the flaps, while in this case he had to use his left hand to reach the closest lever not crossing all levers in the pedestal. Perhaps he just didn't expect the flaps lever to be so close. But I don't trust this theory for the same reason: If you expect a single short wing-shaped lever and find 2 tall square levers with triggers underneath instead, your brain would set off all kind of alarms. Kind of what you drink from a glass of water except it was Sprite.

I will give you that in a lower workload / less distracted environment it would have been more likely to either catch the mistake, or detect the lack of power / torque.
But again, in my mind Yeti is one of your "no fly" airlines, with a poor safety culture, as evidenced by previous accident history (and how these accidents happened) but also, more to the point of this accident:
- The airline not performing the validation flights to RWY 12.
- The previous crew not aborting the approach when it became unstabilized, and not informing the airline that this approach could not be safely flown in that particular way.
- This crew not doing the landing checklist, just reading it (that is, doing the formality but not the actual checks, as evidenced by "checking" that the flaps were set when in fact they weren't)
- This crew not caring about the stabilized approach criteria, as demonstrated that the wrong config and the lack of power (2 things that need to be checked as part of the criteria) were never called out.
- The PM eventually setting flaps 30 but not calling it out.
So given this lack of professionalism and discipline, I am not strongly persuaded that they would have caught the mistake either. As I said, we will never know. (we is I, you and everybody else).

[Evan]

I wonder how is that self-consistent when the correct flight path itself is curved

Perhaps you could argue that a broad, consistent turn radius is a constant minor change in heading. But what was flown here and on the previous visuals was nothing like a consistent circling turn.

So given this lack of professionalism and discipline, I am not strongly persuaded that they would have caught the mistake either. As I said, we will never know. (we is I, you and everybody else).

While the decision to fly this approach is definitely a lack of safe discipline, I don’t think this is necessarily revealing a lack of piloting discipline, but rather a breakdown of piloting discipline. I think it is revealing how, under high stress or urgency, piloting discipline can be undone by the human factor known as ‘tunneling’, in this case, tunneling on navigation with eyes fixed outside the cockpit and thoughts consumed with maneuvering. I think it is reasonable to expect that these pilots would have otherwise had eyes on the controls as well as the terrain and would have visually checked the levers and configuration. I think that is instinctive unless your attention is otherwise dominated, and it would not be on a stable, especially straight-in approach.

[3WE]

Nice!

There were a couple other things shown in that video, but I guess you didn’t notice.