Originally posted by 3WE
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ATR-72 crash at PKR, Nepal. Many fatalities feared.
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Originally posted by BoeingBobby View Post
You mean the legend in his own mind?
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Originally posted by Evan View Post
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.
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!
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A couple of things I forgot to mention:
Originally posted by Evan]I am convinced that the steep turn we see at the onset of stall was intentional and accelerated the stall.Originally posted by GabrielI 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.
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.
--- 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 PostA 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.
- 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.
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.
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Originally posted by Gabriel View PostA couple of things I forgot to mention:
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.Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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I try two links Gabe- I think they show the same video.
Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Originally posted by Evan View PostThis 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.
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.
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.Originally posted by Example from Emirates- 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.
- All briefings and checklists have been actioned.
- The aircraft is in the planned landing configuration.
- The aircraft is on the correct flight path (Note).
- The aircraft speed is not more than final approach speed+10KIAS and not less than VREF (Note 3).
- Power settings appropriate for the aircraft configuration.
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.
That's really it. Reams of accident reports have taught us that brain farts happen when pilots are overwhelmed by tasks and urgency.
(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.
Don't do this until the brand new aerodrome establishes the 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.
There was nothing routine about this, and that is why it happened. The distraction wasn't just "a big factor".
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.
--- 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 3WE View PostI try two links Gabe- I think they show the same video.
--- 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 PostWhy do you have to make it personal and use me, a low time single-engine PPL, as the "example"?
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].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?
Do you want me to start listing cases of brain farts not related with any particular "unusual" (in your view) approach strategy?
Find me the visual circuit pattern for some airports, please.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.
Would have they caught the mistake had it happened in a straight-in ILS approach? Maybe. I doubt it.
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Originally posted by Evan View Post3. 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?
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.
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).
--- 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 Post
I wonder how is that self-consistent when the correct flight path itself is curved
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).
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