Nepal Plane Crash
Almost all of the controls in an aircraft can have fatal consequences if moved incorrectly. To put an oral announcement on each of them would result in a continuous series of alarms going off.
On a previous post by 'Discorde'. The engine numbering scheme could also have problems..
Should we shut both engines down..?
No, just shut down One..
On a previous post by 'Discorde'. The engine numbering scheme could also have problems..
Should we shut both engines down..?
No, just shut down One..
If it is the plane's response and the pilot calls for "FLAPS 15" and the plane responds "FEATHER 1 FEATHER 2" the pilot will know that something is immediately wrong.
Almost all of the controls in an aircraft can have fatal consequences if moved incorrectly. To put an oral announcement on each of them would result in a continuous series of alarms going off.
To add to the issue, most pilots will probably note a 'caution' alert as not critical, especially on base/final. So look up, meh its an AC gen tripped, keep going we'll deal with after landing, nothing that affects landing performance, type response. Would you immediately tie it to a feathered prop?, probably not, unless you really had a point of view from the 'what's the worst it could be' angle. On the flip side a master 'Warning' in a similar position will get your attention very fast, especially if there are enunciated lights saying props are feathered.
Last edited by 43Inches; 18th Mar 2023 at 00:33.
How different can two types of levers be? The flap and condition levers look and actuate in completely different ways. As an airline pilot you are meant to know what each do. It is impossible to train for complete human irrationally.
Compare the DASH-8 and SAAB 340 throttle quadrant and you will see a big difference in how the levers are aligned and the sharp edges of the prop/condition levers.
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The knob shape is deliberate, and required for design compliance for certification. It's up to pilots to be aware of the knob shape. More importantly, its up to every pilot to "select - identify - confirm and move" any given control. Fast hands are trouble. Pause, and think about what you're doing. Last week's flight testing involved selecting and moving a specified toggle switch for the test. The wrong switch would shut the engine down instantly. Another wrong switch might cause costly damage to the engine. In each case (and reminding myself about this accident) in each case it was: " XX switch identified (as I held it), XX switch confirmed (while I thought about it) and XX switch [on/off], observing for the intended effect (which had never before been tested). It all worked out fine.
We professional pilots should be stepping up to the true responsibility of no fast hands, identify/confirm/move to prevent accidents so that bad things don't happen because of our mistake, and designers don't keep thinking of new ways to complicate systems to prevent errors which we should not be making!
Think: What do I want to happen next? What control do I have to move to make that happen? Is my hand on that control, and going to move it the correct direction? Have I confirmed that? Now, did moving the control produce the result I expected? If you're not doing that, you're not doing it right! Don't blame the airplane!
We professional pilots should be stepping up to the true responsibility of no fast hands, identify/confirm/move to prevent accidents so that bad things don't happen because of our mistake, and designers don't keep thinking of new ways to complicate systems to prevent errors which we should not be making!
Think: What do I want to happen next? What control do I have to move to make that happen? Is my hand on that control, and going to move it the correct direction? Have I confirmed that? Now, did moving the control produce the result I expected? If you're not doing that, you're not doing it right! Don't blame the airplane!
It should not happen, but we all err at some point. I know even the best pilots have made mistakes, and cockpit design should be focused on reducing or eliminating anything that can be misidentified. I know of a number of unintentional feathers, one where a crew was activating a fuel pump due to a failed auto switch, where directly above is the manual feather selector (backup for the feather through the CL movement), they went slow, and even identified the PNFs hand was on the switch and proceeded to feather a live engine. The PF just identified that the PNFs hand was on 'a switch', not reading the switch lettering. The CVR sounded like it was methodical and deliberate as mentioned here, they just did not pick up the error until the prop feathered. At least in that case they realized immediately what went wrong and rectified it.
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It should not happen, but we all err at some point. I know even the best pilots have made mistakes, and cockpit design should be focused on reducing or eliminating anything that can be misidentified. I know of a number of unintentional feathers, one where a crew was activating a fuel pump due to a failed auto switch, where directly above is the manual feather selector (backup for the feather through the CL movement), they went slow, and even identified the PNFs hand was on the switch and proceeded to feather a live engine. The PF just identified that the PNFs hand was on 'a switch', not reading the switch lettering. The CVR sounded like it was methodical and deliberate as mentioned here, they just did not pick up the error until the prop feathered. At least in that case they realized immediately what went wrong and rectified it.
That is the missing sauce. We routinely respond to a call and then realise that it was an automatic response without verification, or the other pilot does, so the first part of the process is often problematic, of verifying a change of a system. The final part of the process is the verification that the system behaved as expected. There is an expectation bias that as systems become more reliable, what you select is what you will get, and that is quite true until the system doesn't behave as expected, or when the selection was inadvertently of the wrong system as appears to have been the case in this sad occasion. It is up to the instructors to drum into students the survival instincts that provide a basis for all operations. It is up to the crew member to continue to maintain personal discipline to maintain SA of the system they are interacting with.
The older designs have numerous examples of features that would be unacceptable to the flight crew, where the control was not observable to the crew member, and the actuation had to be confirmed by the response of the system. Often that ended badly... the F-111 bleed selector comes to mind... almost everything on British designs, a lot of soviet jets.... thankfully Part 25 generally gives a good outcome now, but, SA can still be lost.
The older designs have numerous examples of features that would be unacceptable to the flight crew, where the control was not observable to the crew member, and the actuation had to be confirmed by the response of the system. Often that ended badly... the F-111 bleed selector comes to mind... almost everything on British designs, a lot of soviet jets.... thankfully Part 25 generally gives a good outcome now, but, SA can still be lost.
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Very interesting discussion on human factors and ergonomics. Just a small reminder that the misidentification of the condition levers has not yet been proven/confirmed, we all think we know what happenned, but there is still a small posibility there is something else to it .
On the ergonomics, I have flown many aircrat types, mostly GA nowadays , and I am always amazed of the different use that a " standard" switch or lever may have depending on the type. For instance the basic push/ rotate lever/screw used on US GA aircraft for throttle is also used for mixure ( Cessnas) or even Prop pitch ( Super Dechatlon)
The most confusing example , is the gear lever on the Fouga Magister CM-170 that was my first jet trainer in the Air Force. The gear lever is a small wing shaped flat lever moving between 2 walls, excatly the same switch used on many other types of GA aircraft as the electric flaps switch.. Not really an issue if you move from that jet to a GA later , but a serious one when you do the opposite. I have not seen the report but I would bet that this was the cause of an early gear retractation during a touch a go of a civil historic CM-170 in Netherlands that led to a crash in 2013..
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On the ergonomics, I have flown many aircrat types, mostly GA nowadays , and I am always amazed of the different use that a " standard" switch or lever may have depending on the type. For instance the basic push/ rotate lever/screw used on US GA aircraft for throttle is also used for mixure ( Cessnas) or even Prop pitch ( Super Dechatlon)
The most confusing example , is the gear lever on the Fouga Magister CM-170 that was my first jet trainer in the Air Force. The gear lever is a small wing shaped flat lever moving between 2 walls, excatly the same switch used on many other types of GA aircraft as the electric flaps switch.. Not really an issue if you move from that jet to a GA later , but a serious one when you do the opposite. I have not seen the report but I would bet that this was the cause of an early gear retractation during a touch a go of a civil historic CM-170 in Netherlands that led to a crash in 2013..
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I was fortunate in being allowed to fly an early Beech Bonanza which had identical knobs for u/c and flaps -- beside each other on the right of the throttle, if I remember right. You can guess the rest without consulting the early Bonanza accident stats. The poor owner's hand was actually twitching as I landed and selected flaps up. Lovely aeroplane otherwise.
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In the more recent design standards, knob shape and relative position in the cockpit are prescribed. For an airplane approved and designed in recent years, there will be an excellent control knob, motion and location layout. For older airplanes, or somewhat newer planes still made to a very old design, the knob shape and relative position may not be as we expect from a newer airplane.
I was test flying a deHaviiland Beaver a week ago. It has the original throttle control (the prop and mixture have been removed). The original DHC throttle knob is black (correct) and exactly the shape a landing gear knob should be (not ideal). As a wheel plane, not a big deal, but the airplane will be put on amphibian floats this spring - and I know that the knob shape for the landing gear for those floats is more like a throttle knob shape than a wheel shape! Amphibian airplanes have additional landing gear selection disciplines, so I'm not really worried about this, but it's noteworthy. In the mean time, when engine controls are being changed as a part of a deign change, I will not approve them unless they are compliant with the latest design requirements, regardless of the airplane's certification basis - just to harmonize an older plane with the new requirements.
the regulators and airplane builders do their best to reduce human factors risks in the cockpit, but the pilot still has some responsibility for Select/Identify/Confirm/Move/Check for intended outcome......
I was test flying a deHaviiland Beaver a week ago. It has the original throttle control (the prop and mixture have been removed). The original DHC throttle knob is black (correct) and exactly the shape a landing gear knob should be (not ideal). As a wheel plane, not a big deal, but the airplane will be put on amphibian floats this spring - and I know that the knob shape for the landing gear for those floats is more like a throttle knob shape than a wheel shape! Amphibian airplanes have additional landing gear selection disciplines, so I'm not really worried about this, but it's noteworthy. In the mean time, when engine controls are being changed as a part of a deign change, I will not approve them unless they are compliant with the latest design requirements, regardless of the airplane's certification basis - just to harmonize an older plane with the new requirements.
the regulators and airplane builders do their best to reduce human factors risks in the cockpit, but the pilot still has some responsibility for Select/Identify/Confirm/Move/Check for intended outcome......
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Very interesting discussion on human factors and ergonomics. Just a small reminder that the misidentification of the condition levers has not yet been proven/confirmed, we all think we know what happenned, but there is still a small posibility there is something else to it .
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Would the levers survive the impact ?
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Could CVR differentiate the sounds of pulling the Flaps vs the Condition lever?
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One would think that the pilots would have heard(and possibly felt) the engines feathering. It is certainly very noticeable on the ground, although I suppose it is starting from a different blade angle.
As for differences in noise, the gates and clicks of the flap vs CL movement should be identifiable if the recording is clear enough.
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They probably felt the feathering props and assumed it was the flaps travelling...again expecting a certain feel, rather than crosschecking indicators (not the PFs job until the checklist). When you take flap you expect a little nose up and speed to reduce, which is probably what happened, and at that point what the PF was expecting and wanting to occur. It wasn't until; later when she realized power lever movement was not resulting in increased IAS that they started to comment on it.
As for differences in noise, the gates and clicks of the flap vs CL movement should be identifiable if the recording is clear enough.
As for differences in noise, the gates and clicks of the flap vs CL movement should be identifiable if the recording is clear enough.
I can't remember how much or little sound is made by movement of these levers. Perhaps a current ATR pilot can let us know. We shouldn't assume that it makes a sound audible above the sound of the engines.
The cabin video audio didn't cover the time that the condition levers were apparently moved, the primary acoustic signature was of the turbine, there was also another odd line that may have been a blade rate of the feathered propellers, it didn't tie in with an AC fan or blower or other obvious sound source.
I would suspect that the last few seconds, the RHS pilot may have comprehended that the engines had been feathered, and selected the condition levers to normal. The LHS Pilot, having already stated twice there was no power, had pushed the power levers to max TLA, at 57:11, and nothing happened apparently to the Nh at that time. A click was heard at 57:16 and 1 second latter, Nh on both engines increased from 73% flight idle (to avoid over torque) to 77%. 2 seconds later the LHS hands over to the RHS pilot, 57:18, at 57:20, the RHS pilot now flying states there is no power, and 4 seconds later the stick shaker goes off, at 57:24. 2 seconds later, at 57:26, another stick shaker sounds, and that is around the time that the aircraft has commenced a roll to the left that it never recovers from, at 57:32 it impacts well nose down, and inverted. At the point where the aircraft departed to the left, it became irrecoverable, whether thrust was applied or not. It sounds like there may be a chance that the condition levers are found in normal, the ECUs would presumably record the change of the commanded operating state, the FDR may not. There is a high probability that the simultaneous loss of torque on both engines, without an audible click when the flaps 30 config was commanded came from the condition levers being moved in error. Something else changed to both engines at 57:17, 1 second after a click sound in the cockpit, and 7 seconds before the stick shaker. How long does an ATRs prop take to come out of feather?
Last edited by fdr; 21st Mar 2023 at 20:56.
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Seasoned ATR pilot Fly with Magnar answered to my questions on youtube:
Q: How could they not hear and feel the prop mushing / RPM drop?
A: When the propeller is feathered in flights, the change in sound is more subtle than when feathering the propeller on the ground. And ANR headsets remove almost all sounds from the propellers and engines.
Q: How long would it have taken the prop regulator to unfeather once the pilots would have recognized the mistake?
A: It's faster than on the ground. So around 15 seconds sounds reasonable.
Q: How could they not hear and feel the prop mushing / RPM drop?
A: When the propeller is feathered in flights, the change in sound is more subtle than when feathering the propeller on the ground. And ANR headsets remove almost all sounds from the propellers and engines.
Q: How long would it have taken the prop regulator to unfeather once the pilots would have recognized the mistake?
A: It's faster than on the ground. So around 15 seconds sounds reasonable.
Seasoned ATR pilot Fly with Magnar answered to my questions on youtube:
And ANR headsets remove almost all sounds from the propellers and engines.
And ANR headsets remove almost all sounds from the propellers and engines.