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TransAsia in the water?

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TransAsia in the water?

Old 6th Feb 2015, 09:53
  #261 (permalink)  
 
Join Date: Feb 2015
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HOTEL MODE??

I just read the early reports / translations/news articles and it says the planes right engine went into IDLE MODE. Still having oil pressure.

COULD the right prop somehow gone into HOTEL MODE (which as many of you know puts a ''brake'' on the right prop to allow the engine to be used to run a generator, while on the ground instead of an apu)?


The translation is the thing I guess. And what do they mean by idle mode. And do they mean if for the prop? There is Beta Mode, Alpha mode, HOTEL mode.

Could the crew have thought that the left engine was producing too much power when in reality the right engine/prop was reversing? Could that be why they shut the left down?

And yet the video shows the left engine/prop turning so slowly if at all. could they have suddenly gotten the right engine back but were below vmca?



So many questions.
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Old 6th Feb 2015, 09:53
  #262 (permalink)  
 
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It's not just you.

The presence of an experienced, authoritative 3rd person on a 2-man flight deck is bound to increase overall stress levels and put everyone outside their comfort zone, including the 3rd person.

The check captain is sitting in the jump seat: not the normal position from which to fly the aircraft. A serious event happens and quite naturally he (unconsciously) thinks "I'm not going to let these two inexperienced clowns kill me" and intervenes, interrupting the *normal and practiced* 2-man rhythm.

Things can then get forgotten, as in the BOAC 707 at Heathrow; or in deferential societies the crew doesn't immediately question the check captain's wrong initial analysis of the situation, which we've seen many, many times.

Put that into a tightly coupled, complex, highly time-critical situation as was the case here and there is very little time to rectify early cognitive mistakes.

(In less deferential societies the outcome can be rather different, as with the Qantas A380, although there was less immediate time pressure in that incident.)

I've just finished reading 'Normal Accidents" by Charles Perrow, which whilst written in the early 1980s is still highly relevant. He has a lot to say about complexity and coupling. Recommended.
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Old 6th Feb 2015, 09:53
  #263 (permalink)  
 
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mad_jock:
...does it have a noise procedure?
No, no restrictions

Plates (scroll down)
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Old 6th Feb 2015, 09:55
  #264 (permalink)  
 
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Someone has to fly the aircraft and keep it within the envelop. Had they not stalled although a crash was inevitable more people would have survived
Big words, bigpants. It looked to me they were stretching the glide to avoid an even worse outcome. Doing a nice descent at best glide speed isn't much good if you smack into a highrise or into the middle of a bridge.
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Old 6th Feb 2015, 10:04
  #265 (permalink)  
 
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Had they not stalled although a crash was inevitable more people would have survived had a pilot maintained control of the aircraft and ditched in the river.
watching the video it looks like someone was watching, otherwise they would have hit the building and everyone would have been killed and people in the building, the stall might have occurred from trying to get over that building
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Old 6th Feb 2015, 10:05
  #266 (permalink)  
 
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By looking at the diagram it's clear that:

Eng2:
Master Warning
Beta2 increase from 30 to 90
ITT, FF, NP, NL, NH all go down

Eng1:
Bleed Closes
Objective Torque increases from 90% to 100%

All that is consistent with ENG2 failure and UPTRIM kicking in.

ENG1 doesn't seem to indicate problems and, as per investigators info, ENG1 throttle was moved back which seems to agree with the diagram where gradual reduction of FF and ITT is seen (not nearly as drastic as what happened to ENG2).

Only when Fuel SO is operated in ENG1 you see similar behaviour to that experienced by ENG2 (more drastic ITT, NP, NL, NH and BETA2).

But just because ENG1 doesn't seem to have drastic problem, it doesn't mean it couldn't have some problem that lead the crew to identify it as the problematic one.
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Old 6th Feb 2015, 10:09
  #267 (permalink)  
 
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Seems like there is confusion about flame out actions even when not in the air with the emergency happening around you. Appreciate this is a -500 not -600 but assume not much difference. Can only assume the engine problem, presence of 3rd person in cockpit, pre-knowledge of faulty engine and emergency happening in a densely populated area may have been information overload for the crew.
Standard departure seems to be a right hand turn and from the flightpath graphics, it started but then deviated from that and commenced a left hand turn before turning right again to its final position. Could the pilot have been attempting to return to the airport but on seeing they were unlikely to make it, aimed for the open space of the river?

http://www.pprune.org/tech-log/44625...-take-off.html
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Old 6th Feb 2015, 10:21
  #268 (permalink)  
 
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Not blaming anyone...

When the problem occurred and they were at 1300 feet why not turn back towards the airport, they were closer to it.

Also looking at the flight path they could have ditched it in the river way before their impact point.

I think Iron Duck as valid points too.

Of course it is easy to say now while sitting behind a key board.
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Old 6th Feb 2015, 10:33
  #269 (permalink)  
 
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Any clues so far as to why the RH engine failed? That still seems to be the trigger event starting the chain leading to this accident?
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Old 6th Feb 2015, 10:35
  #270 (permalink)  
 
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The 'wrong engine shut down' theory does join up some dots to my interpretation.

I've been wondering about the change of heading. This suggests to me either RH engine failure or over-correction of LH engine failure. It looks more like the former from all the simulator plots I've seen.
But why would they over-correct the yaw but do nothing about the speed/pitch?

I'm tempted to suggest a short circuit in the engine management system. The failure appears to have occurred about the point at which the engine management would be selected to Climb power.

The ATR will fly on one engine with an unfeathered prop but if below V2 it takes ages to accelerate especially with the gear down (V1 cuts).

(3000 hours on ATR mostly -72-500).
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Old 6th Feb 2015, 10:43
  #271 (permalink)  
 
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Am I right in saying that they did restart Eng1, as ITT1 had risen ten seconds prior to the end of the recording?
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Old 6th Feb 2015, 11:01
  #272 (permalink)  
 
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False master caution - Flameout?

Since no one else has done it here is a timeline of what appear to me to be the key events.

From posted FDR trace.
@olasec - post presently #243
http://www.pprune.org/rumours-news/5...ml#post8856151

#1 Solid line, Green
#2 Dotted line, Blue
False "Flameout master caution" and consequent autofeather?

52:00 (-38s)
Gear up

52:38 (0s)
Altitude 1350ft
#2 Master Caution - Flameout - but engine was still running, oil pressure NH, NL all not zero.
#2 Feathered
#2 Fuel flow to 250
#2 NL 50%
#2 NH 70%
#2 Oil pressure unchanged
LH Eng Bleed valve closed
#1 Fuel flow rises slightly

52:43 (+5s)
#1 Fuel flow slowly drops to take-off value

52:46 (+8s)
#1 fuel flow slightly below take-off value and stabilises

53:06 (+28s)
#1 Fuel flow rapidly reduces to 500

53:10 - 53:22 (+32s -> +44s)
Altitude 1500ft - Maximum.
#1 Fuel flow smoothly reduces to near ZERO then cuts off.

54:19 (+1m 41s) - A minute later.
#1 Fuel flow +ve but low
#1 ITT rises to near take off value

54:31 (+1m 53s) In the last few seconds - about 4s
#2 Master Caution Flameout OFF
#2 unfeathering
#2 fuel flow rising
LH Bleed valve still closed
#1 oil pressure just below normal
#1 NL rising through 20%
#1 NH rising through 60%

Close but no cigar? Tragic.

Last edited by jimjim1; 6th Feb 2015 at 11:04. Reason: Quoted #2
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Old 6th Feb 2015, 11:17
  #273 (permalink)  
 
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What I find interesting is that if you look at FF, NL and NH in ENG2 they seem to be at Idle values (~200 and 60% respectively), not Off. And they stay that way for the entire period. Also the oil pressure never indicates problems.

It's Prop RPM that drastically reduces as the PROP is Feather to 86Degrees (or thereabouts).

All of them happen at the same time (within the same second I would say) so they don't look like manual ID and feather procedures on that engine (#2).

Could it be that something caused the prop to feather but not the actual turbine to fail? Any ATR/TP expert that could shed some light if this theory makes sense?
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Old 6th Feb 2015, 11:29
  #274 (permalink)  
 
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Shocking when you look at the level of experience of the crew, especially the F/O: TransAsia Airways Flight 235 - Wikipedia, the free encyclopedia
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Old 6th Feb 2015, 11:42
  #275 (permalink)  
 
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Found this report, seems exactly the same problem that happened in this flight, although at a different flight phase:

autofeather with good engine

I can see autofeather kicking in way before any TQ going below 18% or any other engine problems.

We can clearly see in the diagram that ENG2 is unfeathering and starting to spool up just before impact (and so shows the video).

And Eng 1 turbine starting up (ITT spike) and other params increasing but Prop still very much feathered (or close to it). This would take longer because unlike the ENG2 that was never off, this was completely secured.

It looks like a few more feet, a few more seconds and they would have come out of it with two engines running normally.
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Old 6th Feb 2015, 11:44
  #276 (permalink)  
PBY
 
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This is from wikipedia:

On 6 February, investigators revealed that there had been no engine flameout; rather, the right engine, for which the warning had sounded, was operating normally. Subsequently, the pilots commanded the right engine to produce idle thrust and cut power to the left engine.[8][21]

Does it mean, it was a false warning for the right engine?
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Old 6th Feb 2015, 11:48
  #277 (permalink)  
 
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Shocking when you look at the level of experience of the crew, especially the F/O:
Cockpit gradients in Asia, forget experience. The Taiwanese have a long history of aviation accidents related to cockpit gradients.......unfortunately a legacy from the military.
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Old 6th Feb 2015, 12:06
  #278 (permalink)  
 
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It would seem that the drag of the #1 prop un-feathering is what caused the wing drop... What a bugger.
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Old 6th Feb 2015, 12:17
  #279 (permalink)  
 
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Originally Posted by jfkjohan View Post
Mad Jock: Does anyone have plates for the airport?

If so does it have a noise procedure?

Or is it SOP for the company to always fly one?

--

When an engine fails, NADPs no longer apply.

@jfkjohan
I found this on a Boeing website: http://www.boeing.com/commercial/noise/sungshan.html#ns

Noise Abatement Departure procedures:
Jet planes
(a) Before reaching 1,000 ft above airport level (AAL)

Take-off Thrust
Speed: (V2+10 to 20kt)

(b) From 1,000 to 3,000 ft AAL

Climb Thrust
Speed: (V2+10 to 20kt)

(c) After passing 3,000 ft AAL

Accelerate and retract flaps/slats to normal en-route climb speed.

Turbo-propeller planes:
(a) Before reaching 1,000 ft above airport level (AAL)

Takeoff power
Speed:: (V2+10 to 20kt)

(b) From 1,000 ft to 3,000 ft AAL

Climb Power
Speed: (Vzf+10 to 20 kt)
Retract flaps/slats.

(c) After passing 3,000 ft AAL

Accelerate to normal en-route climb speed.

These noise abatement departure procedures are applicable in normal conditions only. While in abnormal conditions, the respective aircraft operation manual shall be followed.



This Jeppesen chart 10-4 say only for jets, but it is as per the SID.









Last edited by Lost in Saigon; 6th Feb 2015 at 15:18.
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Old 6th Feb 2015, 12:19
  #280 (permalink)  
 
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On the FDR readout that has been linked previously, it shows that the Master Warning for an Eng 2 flameout was correctly triggered upon the drop in ITT, fuel flow and torque on #2.

Unless there was a serious miswiring in the warning system or a mistakenly swapped lens read "Engine #1" instead of the correct engine on the annunciator panel, I think it is improbable that the crew was presented the wrong indication.

What surprises me quite a bit about the graph is the change in PLA #1 at about 2:52:43 that comes together with the #2 engine failure and the consequent systemic demand for uptrim (that can be seen on the objective TRQ curve). I would not exclude the following scenario: the crew felt the yaw from the #2 failure, looked at the engine indications to find the unusually high #1 torque indication and consequently were at least tempted to apply the "Unscheduled Prop Feather" checklist to #1. #2 power lever seems to have never been moved in consistence with a shutdown procedure, and even seems to have been increased in search for an uptrim.
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