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TransAsia in the water?

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TransAsia in the water?

Old 8th Feb 2015, 11:24
  #481 (permalink)  
 
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Why the hurry to apportion blame to the crew when all of the facts are not yet available?

You may have seen some of the FDR data, and read a report stating that re-training will take place. You have not listened to the CVR, have no knowledge of what cockpit indications were displayed, and certainly don't know if other defects combined with this those so far reported.

If you are not a qualified investigator, and don't have access to all of the facts isn't hanging the crew out to dry a bit premature?

Remember the those who were endlessly banging on about VMCA wing drop earlier in this thread? They went awfully quiet, so please do the same and stop apportioning blame.
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Old 8th Feb 2015, 11:25
  #482 (permalink)  
 
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I'm going to reserve judgement on criticising the crew until more information is made available. I don't know if there is more detail being released in Taiwan that doesn't make it to the Western media but I do find the way that information appears to be being released to be a little odd. I am used to seeing a brief overview fairly shortly after an accident, with maybe some early recommendations/engineering procedures to counter any immediate risk highlighted, and then a delay before a full, considered, report is released. This accident seems to be producing a trickle of information that still doesn't seem to give any real description of what happened, and more importantly, why. The early press releases in the Western media, attributed to the investigating authorities, were less than clear. Each time a bit more information comes out it appears to change casual observers viewpoint as to whether the crew were heroes or villians (or perceivably both).


For instance, did the #2 engine 'fail' or was it a prop/engine control problem? Why has the FDR trace been released? Why have elements of the CVR been released? The #1 power lever appears to have been moved very quickly; who moved it? Was the captain immediately aware that the #1 power lever had been moved? Did the #2 prop feather correctly or was it windmilling? So many unanswered questions.


Most comments appear to criticize the 'crew' but it could be that one person made a mistake and the others on the flightdeck were victims as much as everyone else. It could be that the training the crew received wasn't sufficient to prepare them for what they were presented with; if so, would it be their fault if they can't deal with it?


My personal opinion is that 'number of hours on the flightdeck' doesn't prove competence and isn't a good indicator of ability to deal with abnormal situations (as an aside, I also think that airlines should rethink their recruitment minima that appears to be predominately based on hours). You can have a pilot with low hours with lots of recent relevant experience, or a pilot with 1000's of trouble-free hours with only the simulator training (which may be the same every scenario every time) to fall back on.


The Kegworth disaster mentioned is an interesting comparison as, on immediate appearance it looks like a stupid mistake to close down the wrong engine, but if you actually look more deeply into the facts you can understand why it might have happened, even if you can't excuse it.
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Old 8th Feb 2015, 11:26
  #483 (permalink)  
 
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they should have flown on the higher side of the drag curve instead
The flattest glide (ie minimum height loss per horizontal distance travelled) corresponds to the bottom of the drag curve (max L/D).

Fly any slower or faster and you will be draggier with a resulting steeper descent.
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Old 8th Feb 2015, 11:27
  #484 (permalink)  
 
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The moment and engine fails, you do nothing but fly the plane and climb to safe altitude. The screw-up here is in pulling levers while the PF was likely not yet able to monitor.
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Old 8th Feb 2015, 11:29
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Glide speed

Am convinced after having issued the MayDay call the crew were committed to force land/ditch..there was no time to calculate the weight and rfer to the QRH for the best glide speed in the 2 minutes they had...rather just regress to the last best known speed..the white bug speed and ensure enough visibility out of their windshieds to survey the flightpath and maneuvre away from obstacles whilst looking for the least damaging spot they could settle their plane onto.There must have ben quite a bit of cockpit chit chat
In that sweaty cockpit that day.Is the CVR out for us to hear?

Yeah yeah..they might have climbed to MSA before shutting down an engine...but remember "Flame out" was the indication they had.They might have attempted to relight before shutting down using Igntiers A/B.Certainly had they had the resolve to keep on climbing with engines producing some power without feathering or shutting down..perhaps perhaps...who knows...but their reaction was driven by their recognition of Engine flame out..even if as we have so far supposed..identifying the wrong engine.
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Old 8th Feb 2015, 11:33
  #486 (permalink)  
 
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Apart from shutting down the wrong engine, all the DFDR trace tells me is that #2 engine didn't fail...
The failure sequence isn't #2 eng fail, #1 eng uptrim, #2 eng autofeather. It is infact #1 eng uptrim, #2 engine autofeather, #2 engine roll back. #2 engine didn't flameout, it remained running until the end....




Both engines responded exactly as designed to the commands they were given.
Uptrim/Autofeather was commanded when there was nothing wrong...
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Old 8th Feb 2015, 11:46
  #487 (permalink)  
 
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DavidReidUK "The flattest glide (ie minimum height loss per horizontal distance travelled) corresponds to the bottom of the drag curve (max L/D).

Fly any slower or faster and you will be draggier with a resulting steeper descent. "
Quite correct.

But what is the effect on the drag curve of having one prop still spinning and one feathered? Its like flying a glider with the airbrakes stuck fully open on one wing only. (I have been in that situation and it isn't nice). The speed for best L/D is considerably reduced, and is close to what would have been minimum sink speed, at the same time stall speed is increased.

Additional speed is also required for safe manouvering and for a controlled flair.
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Old 8th Feb 2015, 12:16
  #488 (permalink)  
 
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It is infact #1 eng uptrim, #2 engine autofeather, #2 engine roll back. #2 engine didn't flameout, it remained running until the end....

Both engines responded exactly as designed to the commands they were given.
Uptrim/Autofeather was commanded when there was nothing wrong...
Clarification, please, for a non-multi pilot.

Aerplane climbing normally, then; Uptrim (of #1) and autofeather (of #2) was commanded when there was nothing wrong with #2. Was that a pilot-initiated command or a spurious fault? Or don't we know? In other words, what event kicked off the autofeather of one good engine (#2) and the pilot's shutting down the other good engine (#1)?

Wasn't #2 power lever firewalled at one stage during the decent? If #2 was running, why didn't it unfeather, wind up, and save the day? Was it just that it was firewalled too late to do that?
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Old 8th Feb 2015, 12:34
  #489 (permalink)  
 
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Clarification, please, for a non-multi pilot.

Aerplane climbing normally, then; Uptrim (of #1) and autofeather (of #2) was commanded when there was nothing wrong with #2. Was that a pilot-initiated command or a spurious fault? Or don't we know? In other words, what event kicked off the autofeather of one good engine (#2) and the pilot's shutting down the other good engine (#1)?

Wasn't #2 power lever firewalled at one stage during the decent? If #2 was running, why didn't it unfeather, wind up, and save the day? Was it just that it was firewalled too late to do that?
No indication yet of why #2 feathered - except that it did so simultaneously with the flameout warning- but wasn't flamed out.

#2 was firewalled early on in the proceedings. It began to unfeather at exactly the point the power lever was retarded, sadly too late in the day to affect the outcome...
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Old 8th Feb 2015, 12:39
  #490 (permalink)  
 
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How are you going to cancel the autofeather?
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Old 8th Feb 2015, 12:46
  #491 (permalink)  
 
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Drag curve

RaveRaidUK
The flattest glide (ie minimum height loss per horizontal distance travelled) corresponds to the bottom of the drag curve (max L/D).

Fly any slower or faster and you will be draggier with a resulting steeper descent.
Are You 100% sure thats right, Rave ?

Bottom of the drag curve, lovest foot per minute descent.
On the high speed side of the drag curve, where a straight line from origo(at zero winds) meets the drag curve, you would find the speed for best glide i guess ?
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Old 8th Feb 2015, 12:59
  #492 (permalink)  
 
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Given the wide margin for error in such analysis techniques, it appears feasible that the actual Alpha is high, but still flyable. I would expect a clean stall Alpha in the region of 15-ish degrees on a wing of that design?
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Old 8th Feb 2015, 13:15
  #493 (permalink)  
 
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Originally Posted by Shaggy Sheep Driver
Clarification, please, for a non-multi pilot.

Aerplane climbing normally, then; Uptrim (of #1) and autofeather (of #2) was commanded when there was nothing wrong with #2. Was that a pilot-initiated command or a spurious fault? Or don't we know? In other words, what event kicked off the autofeather of one good engine (#2) and the pilot's shutting down the other good engine (#1)?

Wasn't #2 power lever firewalled at one stage during the decent? If #2 was running, why didn't it unfeather, wind up, and save the day? Was it just that it was firewalled too late to do that?
It has been a long while since I flew the Dash-8-300 but this is what I remember. (ATR-72 shuld be similar but please correct any inaccuracies)

There probably was something wrong with #2.

#2 Autofeathered automatically when it sensed a reduction of Torque. The engine does not shut down automatically and will continue to run. The torque reduction is usually due to a problem in the engine which causes a reduction in the power output. The reason the prop is designed to autofeather is to reduce the workload at this critical phase of flight.

The next step after the autofeather would have been to confirm that the #1 engine has increased power form 90% to 100% (Uptrim) and then do nothing until the aircraft had climbed to the engine out acceleration height. This height varies but is often about 1000' above the ground. (AGL)

At 1000' AGL they should have momentarily leveled off, accelerated to a higher speed and retracted the flaps. Once the flaps are up they would have continued climbing to a safe altitude and then called for the engine out drill (memory items) or an engine out checklist. That would then require them to first identify the engine by pulling back the power lever of the #2 engine. Before doing this the non-flying pilot (NFP) would place his hand on the power lever and say "Confirm #2 power lever".

The flying pilot (FP) would then momentarily take his attention away from flying the aircraft to look and see which power lever the NFP had his hand on. If it was the correct power lever he would then say "Flight Idle" and then the NFP would SLOWLY bring the power lever back to idle. The reason you slowly bring it back is because you don't want to cause the aircraft to suddenly Yaw (turn) if you pulled back the wrong engine. If you pulled the power on the operating non-feathered engine there should be a substantial yaw and this also helps identify the correct engine before you proceed to the next step.

Once the power lever is at idle the NFP would then place his hand on the Fuel Condition Lever (FCL) and say "Confirm #2 Fuel Condition Lever". Again the FP would momentarily take his attention away from flying the aircraft to look and see which FCL the NFP had his hand on and say "Shut-Off". (or "Idle Cut OFF", "Cut Off", etc)

Providing all this was done correctly they should have been able to continue flying, climb to a safe altitude, and return to land.

Something went seriously wrong here and it looks like they just mixed up the #1 and #2 engines. Firewalling the #2 engine will not cause it to unfeather. I don't remember exactly how to un-feather but there is probably a position on the Condition lever.

Last edited by Lost in Saigon; 8th Feb 2015 at 14:13.
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Old 8th Feb 2015, 13:27
  #494 (permalink)  
 
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Originally Posted by AAKEE
Bottom of the drag curve, lovest foot per minute descent.
On the high speed side of the drag curve, where a straight line from origo(at zero winds) meets the drag curve, you would find the speed for best glide i guess ?
No, you seem to be confusing the drag curve with the power curve.

Maximum range is at the bottom of the drag curve, but on the power curve it's where it meets the tangent from the origin.
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Old 8th Feb 2015, 13:37
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Lost in Saigon~unfeathering

CL...FTR..FSO

Restart engine
CL...Feather....Auto (assuming it was relightable)

Don't assume the engine readings were consistent to what they were expecting to see..we still don't know why Engine #1 was shut down and #2 was left unfeathered(if indeed it was the culprit engine. All that was announced in the Mayday call was "engine flame out)...no mention which engine or if both had flamed out.

Last edited by Trackdiamond; 8th Feb 2015 at 18:19.
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Old 8th Feb 2015, 13:40
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investing the drag curves

This might be too hypothetical and pedantic excercise. In such case all that was expected of them was to fly the Vmlb0 Drift down speed..obtainable from the QRH perf section after reckoning their weight..which would have been just shy of the tako off weight 3 mninutes earlier.That speed assumes any dead engine is feathered and the plane is in a clean configuration..

Last edited by Trackdiamond; 9th Feb 2015 at 07:21.
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Old 8th Feb 2015, 13:45
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Dave is correct, and the bottom of the drag curve does give the best approximation of the point for best L/D.

I found a very good method for calculating it exactly for a clean ATR 72 in cruise, here :http://www.fzt.haw-hamburg.de/pers/S...n/TextNita.pdf

Page 32 for 3 different methods of calculating L/D and graphs on page 146. This confirms 17:1 as the correct practical value in clean configuration, with a theoretical value as high as 19:1

To get the best L/D in a glide it is neccessary to construct a vertical speed polar vs ISA, and then the best L/D is the ratio at the point where the tangent from the origin just touches the resultant curve. I would expect the 17:1 value to be still confirmed but the same AoA would occur at a much lower speed.
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Old 8th Feb 2015, 14:24
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Originally Posted by Trackdiamond
CL...ICO

Restart engine
CL...Feather....Auto (assuming it was relightable)

Don't assume the engine readings were consistent to what they were expecting to see..we still don't know why Engine #1 was shut down and #2 was left unfeathered(if indeed it was the culprit engine. All that was announced in the Mayday call was "engine flame out)...no mention which engine or if both had flamed out.
Thanks for the corrections.

From what I have read the right engine never "Flamed Out" and the left engine was shut down in error.

I would expect that there is some indication or warning when there is an un-commanded Auto-Feather that would tell you which engine was feathered. Is there not?

The "mayday, mayday, engine flameout" call was not really accurate for two reasons.

1) No engine actually flamed out. One was running at idle and the other was shut down on purpose.

2) When both engines are not producing thrust I would call "Double Engine Failure" not "Flame Out".
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Old 8th Feb 2015, 14:42
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Thanks for the clarifications, guys.

Wasn't the call "engine flame out" simply reporting the fault indication that lit up on the flight deck, rather than a confirmation that any engine had in fact flamed out?
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Old 8th Feb 2015, 14:43
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Originally Posted by TheInquisitor
Look at the time indicated by the red line I've added - just before the #1 is slotted

EDIT: Can't get img hosting to work, look at approx. time 53:20

With the exception of Np, all the other readings would have been similar at this point in time - possibly adding to confusion?
At 53.20, the #1 PL was already on the flight idle stop. This move of the #1 PL was initiated at approx 53.05. If there was any confusion about which engine was to be shut down, it started earlier than you reckoned.
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