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TransAsia in the water?

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TransAsia in the water?

Old 4th Feb 2015, 14:50
  #101 (permalink)  
 
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Once you have past the acceleration altitude and set the power management from TO to Climb you do not have anymore the protection of the ATPCS.
On the -600 you just move the rotary switch from TO to Climb and that's it the climb sequence is over.
Should you loose an engine just at this moment it can be very tricky as you need to recognise it quickly enough to have time to feather it manually.
Furtermore the -600 has in my opinion some interface ergonomy can be confusing and with stress I am not sure if the crew could not be confused by some PFD indications instead of reverting to "basic airmanship".

We will see what it comes out from the inquiry....

The ATR is quite underpowered, single engine in optimum conditions is as requested for certification.
In actual OEI conditions, especially with a windmilling prop, I have some doubts if it can maintain level flight and speed.
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Old 4th Feb 2015, 15:03
  #102 (permalink)  
 
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Tracking shows the aircraft climbed to at least 1250 feet.

On the initial takeoff it was still on rwy heading and by the end of the rwy at 300 feet and 113kts.

At one point after the rwy end it makes a sharp right turn while climbing to 1250 feet where the speed is now at 83kts!

It further drops to 81kts while descending and eventually gets to 85kts before the impact.

For those familiar with the ATR 600, what is the Vmca, flaps up or in takeoff position?
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Old 4th Feb 2015, 15:39
  #103 (permalink)  
 
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The wing stalled....that seems pretty obvious to many here. It was certainly not a deliberate roll to the left, the aircraft simply isn't capable of such a rate of roll.

For those who favour the VMCA theory I strongly disagree. Reducing IAS through VMCA would never produce such a high rate of roll. For certain one wing stalled, and quite likely very shortly after so too did the other one.

A tragedy, and for those fortunate enough to survive, also miracle.
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Old 4th Feb 2015, 15:51
  #104 (permalink)  
 
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@ deefer dog...

Well a Vmca departure could also lead to a wing stalling if you try to keep the nose up and try to counteract with ailerons plus spoilers.

I know that with full power on one engine only if you allow the speed to go below Vmca on a Dash 8 it will roll into the dead engine pretty fast.

Of course if you keep bleeding the speed back then the wing will stall most likely the one with the failed engine first because of the prop wash on the other wing.

In this case it could be that they initially thought they could make the opening on the other side of the highway but at the last minute saw they could not and added power (if it wasn't always at max power) and were too slow and hit Vmca.

Anyway with the black boxes retrieved, they will know.

Obviously an aircraft not under control both in direction, speed and altitude.


Last edited by Jet Jockey A4; 4th Feb 2015 at 16:13. Reason: Bigger picture added.
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Old 4th Feb 2015, 17:32
  #105 (permalink)  
 
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I am trying to find online that article of Tim Allan's. Some is asking for it.

I think everyone up north was pushed towards reading by a certain exam callsign and Flight ops inspector.

It really is a superb article for all multi engine prop pilots.

It was in the operator safety magazine and it was written when Tim was still a test pilot for them which I reckon was maybe around the 1995-2000 period.

Now the perfect thing would be someone nice from BAe regional that reads this to get authorized for public viewing and online somewhere. It really is a superb training document and would aid flight safety to all.

I think my copy of it went to the wind a few years back with a hard drive failure. And anyway I wouldn't post it on line as understandably its copyrighted.
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Old 4th Feb 2015, 17:50
  #106 (permalink)  
 
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I have been on the ground for most of the day at the crash site. I'm not going to offer any speculation as to what caused the accident, but I'd like to say that the Taiwanese emergency services have done an absolutely stellar job today with the rescue and recovery operation.
It has been a bad 12 months, particularly for Asia, for aviation. I am hoping that this year will see an end to this peculiar run of aviation related tragedies.
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Old 4th Feb 2015, 18:03
  #107 (permalink)  
 
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MJ,

copy of the article here. It should be compulsory on each type rating. Starts pg 9

http://www.availableaircraft.co.uk/I..._-_Issue_1.pdf
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Old 4th Feb 2015, 18:36
  #108 (permalink)  
 
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https://www.facebook.com/video.php?v=1053519784674205

USe that video on HD and full screen. Its not feathered and still turning.
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Old 4th Feb 2015, 18:39
  #109 (permalink)  
 
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Regarding the screen shots on page 1:

Is it perspective/elevator position, or is there a piece missing from one of the horizontal stabilisers?

If so: debris from failed engine taking out control surfaces?

EDIT: it's most visible on the first, the second has contamination from the impact and light gantries, making it artificially appear that the lower side is longer.
EDIT2: I suspect the length difference is a perspective issue due to the position of the stabilisers on the T-tail. Not sure if this totally accounts for the difference in shape though?

Last edited by papershuffler; 4th Feb 2015 at 19:21.
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Old 4th Feb 2015, 18:42
  #110 (permalink)  
 
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Here we go again. The company are going to review their safety procedures. What about a total review of training procedures and experience of crew reviews.

The authorities and companies don't seem to have any idea of dealing with the issue. Just awaiting more stringent and regular medicals and university degrees as a remedy,

Where is ICAO when you need them??
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Old 4th Feb 2015, 18:53
  #111 (permalink)  
 
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The article isn't the full article about the dangers of trying to nurse a engine home when its delivering less than zero thrust ie not feathered.

It looks like the time period 1995-2000 is correct though.
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Old 4th Feb 2015, 19:22
  #112 (permalink)  
 
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"The wing stalled....that seems pretty obvious to many here. It was certainly not a deliberate roll to the left, the aircraft simply isn't capable of such a rate of roll.

For those who favour the VMCA theory I strongly disagree. Reducing IAS through VMCA would never produce such a high rate of roll. For certain one wing stalled, and quite likely very shortly after so too did the other one.

A tragedy, and for those fortunate enough to survive, also miracle."

I'd have to disagree with you on this one, Asymmetric roll over happens pretty quickly

https://www.youtube.com/watch?v=YqmomTUVsAw
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Old 4th Feb 2015, 20:08
  #113 (permalink)  
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Look at the graph in the post #104. I think there is some answer. They lost an
engine, but managed to climb to 1300 feet in one minute. That seem to be an excessive climb rate. It seems some quite excessive pitch for being on one engine. It seems the speed for single engine was not taken care off. I am not sure, what is the single engine climb rate in an ATR. But 1300 fpm seem to be high. They went below the safe speed and it goes downhill from there. Of course it is just a theory. Who knows, what else could cause all this. But if it was not a control difficulty problem, than it seems to be overcontrolled.
Sad day.
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Old 4th Feb 2015, 20:26
  #114 (permalink)  
 
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Originally Posted by Livesinafield View Post
Interesting thanks, but in all my OPC's LPC etc i have never been taught to lower the nose, I am more interested in my speed

Only time i would consider lowering the nose is if i was at a very high pitch angle and even then i am going to keep some of that while i slow towards V2, if i simply lower the nose as you say and its low level i suspect we will loose height

I guess it all varies what type your flying...
In the climb phase, especially initial climb, there will inevitably be a lowering of the nose to accelerate. This is what the level off height or third segment is all about. Lower the nose, accelerate, clean up. Even for enroute climb, if you want to maintain the same airspeed, what are you going to do. Cruise altitude and you need to drift down, how are you going to do initiate the drift down. If you are more interested in airspeed(which is the important thing) how else are you going to maintain it or increase it when required.

Originally Posted by Massey1Bravo View Post
Interesting, I didn't expect the overuse of ailerons would have such a major impact on performance to the point where the aircraft cannot maintain altitude, especially for a large turboprop. I mean this isn't an MU-2 with roll spoilers.
The ATR does have roll spoilers to augment the ailerons. While not nearly as significant as an MU-2 which has no ailerons, adding significant amount of roll input will raise the associated spoiler reducing lift on that wing. Same with many large jets. I have seen someone in the sim use lots of aileron(with spoiler deflection) in a multiple engine out scenario and it just contributed a continual loss of airspeed(for that type and scenario).

If there was an engine failure with no autofeather in this accident, six-bladed props might make things worse as compared to the older 4 blade engine aircraft.
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Old 4th Feb 2015, 20:42
  #115 (permalink)  
 
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go123.
That manoeuvre in the video is a spin, not a Vmca loss of control.
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Old 4th Feb 2015, 21:24
  #116 (permalink)  
 
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The video initially shows a wings level descent which indicates the a/c was under control, but seriously short of power over hostile terrain.

Fuel not getting to the engines would be more likely than two near simultaneous
mechanical failures.

I can understand the crew desperately needed at least one engine back, but may have been too slow to maintain control if an engine suddenly produced thrust.

One can understand why they would stretch the glide as the terrain was as hostile as it gets.
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Old 4th Feb 2015, 22:09
  #117 (permalink)  
 
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All plausible scenarios, Vmca excursion, Dual flameout, or incorrect securing of a non-failed engine.

I'm tending to think they had lost power on both power plants, because if you look at the speed/graph posted, when the aircraft stopped climbing, it was in a very steady descent, with mostly constant speed.

Seems to me that badly mishandled asymmetric flight would at least provide mostly level flight, or at least a shallower descent. That last minute pull was an automatic reaction to the pilots seeing that they were gonna hit the bridge or power lines. I don't think it was a Vmca roll, it just doesn't seem to have enough yawing and the wing drop looks more as a result of a stall.

Either way, the recorders look in great shape so we should have all the data soon and I'm sure the preliminary report will be quite expedient due to this airline's safety record. This will be a very politically charged event no doubt.
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Old 4th Feb 2015, 22:25
  #118 (permalink)  
 
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As a boy, I saw the Breguet Atlantique crash at Farnborough in September 1968. It looked very similar.
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Old 5th Feb 2015, 01:16
  #119 (permalink)  
 
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The altitude reached in the graph suggests that the engine failure may have occurred after the after take-off checks were commenced, one of which (on the turboprop I fly) is to turn off the autofeather (is it the same on the ATR?). After that the prop will windmill, and when instructing in the sim I occasionally see pilots forget or mis-handle the windmilling prop. they still expect the prop to feather.

The graph suggests that the pilot maintained the best speed he could to avoid the stall after the failure. In the final moments he was left with no option but to pull the control column aft to avoid the buildings / bridge and reach the river. The 'g' and speed reduction from this action likely caused a stall and Vmca at the same time.

We do exercises in Vmca in the sim on initial courses. We set up the conditions under which the aircraft Vmca speed is certified; MAOM, aft CG, critical engine failure, take-off flap, gear up, 5,000ft PA. If a gentle descent is maintained for demonstration purposes to allow a slow speed reduction towards Vmca then it can be docile maneuver, but the real world is never like that. If the pilot concentrates on maintaining altitude during the exercise then at Vmca the aircraft will roll very rapidly to the failed engine.

Vmca is generally close to the stall speed. Maintaining aft control column and max rudder deflection at this speed has a name: Full pro-spin action.
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Old 5th Feb 2015, 01:27
  #120 (permalink)  
 
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Originally Posted by George Potter
Is it known for certain that it didn't contact the power lines? It appears to me that the right horizontal stabilizer is breaking up before any of the empennage contacts the bridge. Makes me wonder if they snagged the powerlines.
As mentioned at #109, I was studying the horizontal stabilisers ("h/s") earlier and thought there was a section missing on the port side.

Bearing in mind the t-tail design which distorts perspective, it's not so much the length, rather than the shape.

BBC News - Taiwan TransAsia plane crashes into river

On the third clip (taken by the car in the right lane) at 18-20s, have a look at the port side. I confirmed with a bit of modelling tonight, that the end of the stabiliser should graduate away bearing in mind perspective and the angles the plane travels through. Instead, it's 'blunter' than it should be; the tapered end part appears to be missing.

So, if part of the h/s had gone, some down force would be lost, the nose would go down, and the AOA of that wing would lower, possibly creating a spin. Does this fit the scenario?

Last edited by papershuffler; 5th Feb 2015 at 01:51.
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