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TransAsia in the water?

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TransAsia in the water?

Old 5th Feb 2015, 21:37
  #221 (permalink)  
 
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That wing should glide fairly well - I just read somewhere that the ATR has a L/D of around 17:1.

Not sure of how valid or relevant this may be, but some (very) approximate calculations from those traces suggest in the minute between 03:53:30 and 03:54:30 they descended approximately 600', and taking a stab at an average speed of say 90KIAS, this represents 450' / nm, equating to an L/D of around 13.3:1 (assuming no thrust).

Do the ATR's props decouple under high neg tq?

Maybe someone far cleverer than I could say if anything can be inferred from this?
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Old 5th Feb 2015, 21:51
  #222 (permalink)  
 
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They are free turbine engines so they are never coupled.

The L/D ration only works with both engines secure and your at the best speed.

The only thing that can be inferred is they had substantially less effective power than they required for flight.

The reason for that lack of effective power be it high drag or low power on the live engine we will have to wait for the report.

I am pretty sure though its high drag due to low speed and an unsecured failed engine or one that is producing some power but not above the zero thrust level.
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Old 5th Feb 2015, 22:05
  #223 (permalink)  
 
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fish

It's all getting very technical and a bit off the mark for specific ATR ops.

Put simply the ATPCS system automatically arms during the takeoff roll, part of the takeoff procedure is to check it is active. If an engine fails the system up trims the live engine from 90% TQ to 100% (RTO PWR) and feathers the failed engine. Technically from that point the engine is secure! After acceleration altitude (min 400ft depends on second segment restrictions etc) memo items at carried out that confirm the ATPCS has functioned correctly and manually confirm the failure (PL, CL to FTR and FSO, bleed if live engine isn't within limits and performing). Form this point the engine is well and truely secure, the only way to unfeather the prop is to attempt a relight which I highly doubt occurred here, not enough Alt or SPD or time to go to QRH.

Now if they had already gone through accel alt and moved the PWR MGT to CLB the ATPCS function would have been disarmed requiring prompt action from the crew to identify and feather the engine. If not done quickly performance can be serverly degraded.

In a glide at VmHB the ATR does approx 2nm per 1000ft altitude, compared to other TP I've operated it glides quite well but from 1300ft you don't have much time to get on top of it.

For those interested Vmcl is 98 for F15 and F30 config.
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Old 5th Feb 2015, 22:10
  #224 (permalink)  
 
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VMCL, the minimum control speed during landing approach with all
engines operating, is the calibrated airspeed at which, when the critical
engine is suddenly made inoperative, it is possible to maintain control of
the airplane with that engine still inoperative and maintain straight flight
with an angle of bank of not more than 5 degrees. VMCL must be established
with--
(1) The airplane in the most critical configuration for approach with all
engines operating;
(2) The most unfavorable center of gravity;
(3) The airplane trimmed for approach with all engines operating;
(4) The maximum sea level landing weight (or any lesser weight necessary to
show VMCL); and
(5) Maximum available takeoff power or thrust on the operating engines.
(g) For airplanes with three or more engines, VMCL-2, the minimum control
speed during landing approach with one critical engine inoperative, is the
calibrated airspeed at which, when a second critical engine is suddenly made
inoperative, it is possible to maintain control of the airplane with both
engines still inoperative and maintain straight flight with an angle of bank
of not more than 5 degrees. VMCL-2 must be established with--
(1) The airplane in the most critical configuration for approach with the
critical engine inoperative;
(2) The most unfavorable center of gravity;
(3) The airplane trimmed for approach with the critical engine inoperative;
(4) The maximum sea level landing weight (or any lesser weight necessary to
show VMCL-2);
(5) The power or thrust on the operating engines required to maintain an
approach path angle of 3 degrees when one critical engine is inoperative; and
(6) The power or thrust on the operating engines rapidly changed,
immediately after the second critical engine is made inoperative, from the
power or thrust prescribed in paragraph (g)(5) of this section to--
(i) Minimum available power or thrust; and
(ii) Maximum available takeoff power or thrust.
(h) The rudder control forces required to maintain control at VMCL and
VMCL-2 may not exceed 150 pounds, nor may it be necessary to reduce the power
or thrust of the operating engines. In addition, the airplane may not assume
any dangerous attitudes or require exceptional piloting skill, alertness, or
strength to prevent a divergence in the approach flight path that would
jeopardize continued safe approach when--
(1) The critical engine is suddenly made inoperative; and
(2) For the determination of VMCL-2, the power or thrust on the operating
engines is changed in accordance with paragraph (g)(6) of this section.
I don't think Vmcl is appropriate as they didn't have the gear down. Gear down reduces it. And I don't think they had both engines working



It's all getting very technical
I don't think it is, in fact I think it should be required knowledge for all multi engined prop drivers.

And what's your Vs ? For VR its 1.3Vs or 1.1 Vmca which ever is higher. So Vmca is more likely before stall.

Last edited by mad_jock; 5th Feb 2015 at 22:29.
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Old 5th Feb 2015, 22:35
  #225 (permalink)  
 
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Mad Jock, apologises

I thought I read further back someone wanted the Vmcl. I just gone back and it was Vmca as you have pointed out. 1.1 Vmca based on ISA conditions and SL is 108kts so approx 98kts.

Stall speed is obviously variable given config and weight but a rough guide for 23T clean airframe is about 117 CAS (ATR don't offer any other charts)

Last edited by BO0M; 5th Feb 2015 at 22:41. Reason: Pressed post before finishing
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Old 5th Feb 2015, 22:38
  #226 (permalink)  
 
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Its the higher of 1.3 Vs or 1.1 Vmca

So it could be less than 98 and the Vr is limited by the Stall speed.

They way you can tell is if the Vr decreases with temp above ISA its Vmca limited.
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Old 5th Feb 2015, 22:54
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2nm per 1000' - correlates reasonably with the plots.

It's also feasible that 80-odd kts GS correlates to nigh-on 98 KIAS.

So it seems we're not that far from the mark - they could well have been gliding with little-to-no thrust available - possibly not even stalled?

I've been trying to examine the vids & stills to determine rudder position, but can't make it out. One would expect that if there was any appreciable thrust on that right donkey, the rudder would have been hard over right...

Edit: Not sure if I'm seeing it correctly, but on the video the right aileron appears to go from a neutral position to up in the last moments before impact - I would expect a good degree of 'right hand down' to already be applied with asymmetric thrust...

Last edited by TheInquisitor; 5th Feb 2015 at 23:33.
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Old 5th Feb 2015, 23:00
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If it was 1.3 Vs that would give it a stall speed of about 85 knts.

I presume it has a stick shaker at 1.1 Vs and push at 1.05 Vs ?
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Old 6th Feb 2015, 02:32
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TAIPEI CRASH: CAA dismisses engine problems

The Civil Aeronautics Administration (CAA) yesterday denied that pilots of the TransAsia Airways Flight GE235 that crashed on Wednesday had identified problems with their aircraft’s engines before they took off from the Taipei International Airport (Songshan).

The airlines ground crew also did not let the flight leave with a bad engine to avoid government penalties for a flight delay, the agency said.

The comments came in response to a story in yesterday’s Liberty Times (the Taipei Times’ sister newspaper), which cited information provided by an alleged TransAsia Airways pilot, who said that the aircraft, serial number B-22816, had completed one round-trip from Taipei International Airport (Songshan) to Kinmen.

The person told the Liberty Times that Flight GE235 pilot Liao Chien-tsung (廖建宗) had identified problems with the engines in the technical log book after the flight returned from Kinmen to Songshan.

The story also quoted the source as saying TransAsia’s ground crew workers feared that a delay in Flight GE235’s departure would cause the company to be penalized by the government, and so they decided to let the flight take off with a problematic engine and conduct a more thorough inspection of the engine when the aircraft returned from Kinmen.

The CAA displayed the aircraft’s technical logs, which showed that the plane had been used to conduct flights GE231 and GE232 before Flight GE235. No engine problem was entered in the log book.

The administration said that the log book for Flight GE235 was on board the airplane when it went down, adding that it was impossible that the aircraft could be cleared to take off with engine problems.

Aviation experts have been puzzled over the fact that the aircraft stalled less than two minutes after takeoff.

Some CAA flight instructors have looked at a video captured by a car’s dash camera and questioned why the aircraft appeared to operate stably until it experienced a stall, which caused its body to tilt before crashing into the river.

TAIPEI CRASH: CAA dismisses engine problems - Taipei Times
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Old 6th Feb 2015, 03:04
  #230 (permalink)  
 
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Taiwan aviation regulator has ordered Airline to conduct engine/fuel system checks

Taiwan's aviation regulator has ordered TransAsia and Uni Air, a subsidiary of EVA Airways Corp 2618.TW, to conduct engine and fuel system checks on the remaining 22 ATR aircraft they still operate.
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Old 6th Feb 2015, 03:25
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The only way I know of to prevent the roll over when you get below VMC is to reduce the power on the operating engine RFN.
With both engines out, a reduced airspeed lower energy emergency landing can be achieved in your new glider.
1.1 VSO for 50 foot ref, slowing even more if ground effect can be used to slow down in ground effect where the stall speed is reduced. Although this would require excellent skills beyond that would elude the four landings a month crews. Those guys should continue to fly it on to the chosen landing area/spot.
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Old 6th Feb 2015, 05:04
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Some CAA flight instructors have looked at a video captured by a car’s dash camera and questioned why the aircraft appeared to operate stably until it experienced a stall, which caused its body to tilt before crashing into the river.
Seems they need to read Tims prose as well.

Or maybe they only have experence of turbo fans.
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Old 6th Feb 2015, 05:04
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The CAA displayed the aircraft’s technical logs, which showed that the plane had been used to conduct flights GE231 and GE232 before Flight GE235. No engine problem was entered in the log book.
Well, yes, but that does not mean that the pilot did not bring to the attention of the mechanics faults with the engine. Obviously, something written in the tech log with regards to abnormal engine parameters would instantaneously ground the aircraft, or at least, require further troubleshooting before release for flight.

I would be more interested in the conversation between the pilot and engineer, especially if it was captured by the CVR and took place onboard the aircraft.

I'm not saying this is what caused the crash, or that it even happened. I'm simply pointing out that this report by the CAA does not rule out the possibility of a known malfunction prior to takeoff.

In fact, them coming out and denying it so soon makes me think the opposite.
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Old 6th Feb 2015, 05:47
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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?


And with those hours quoted for the jump seat pax I am wondering if it was an authority "instructor" in the jump seat. Which if it was is going to make the whole thing more political.
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Old 6th Feb 2015, 05:47
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I flew the original ATR72 in the nineties and had an engine failure on takeoff.
I don't know about the -600 and it is a long time ago now but on the original it would have auto feathered the prop and up trimmed the power on the good engine (before you did the climb sequence).
In my failure there was a problem with water getting into the electrics somewhere in the prop control system (where I think the signal came from for the auto feather and up trim) so neither auto feather or uptrim happened for me. Aircraft performance was not exactly great until we feathered the prop...
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Old 6th Feb 2015, 07:18
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MadJock
I have done a feather failure only a couple of times in 10 years and never on departure below 1k in the sim. Its not required as part of the LPC.
I've heard of some who train for feather failure with a V1 or just above, engine failure. So there are some who do train for this. Perhaps dependent on type.
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Old 6th Feb 2015, 07:33
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Type and which authority your under I suspect.

In fact I think I will add into my lots next sim cycle.

Might as well use a similar profile to this.

Gear up through acceleration and fail it as they bring the power back to climb rpm or just before.

Straight ahead with wings level for the FO's and give the Capt inside engine during a turn starting at 600ft.
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Old 6th Feb 2015, 07:37
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Information released today 06th...

quote

On Feb 6th 2015 Taiwan's ASC reported that the investigation so far determined from flight data and cockpit voice recorders: the aircraft received takeoff clearance at 10:51Z, in the initial climb the aircraft was handed off to departure at 10:52:33Z. At 10:52:38Z a master warning activated, at 10:52:43Z the left hand engine was throttled back and at 10:53:00Z the crew began to discuss engine #1 had stalled. At 10:53:06Z the right hand engine (engine #2) auto-feathered. At 10:53:12Z a first stall warning occured and ceased at 10:53:18Z. At 10:53:19Z the crew discussed that engine #1 had already feathered, the fuel supply had already been cut to the engine and decided to attempt a restart of engine #1. Two seconds later another stall warning activated. At 10:53:34Z the crew radioed "Mayday! Mayday! Engine flame out!", multiple attempts to restart the engines followed to no avail. At 10:54:34Z a second master warning activated, 0.4 seconds later both recorders stopped recording.

unquote
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Old 6th Feb 2015, 07:40
  #239 (permalink)  
 
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multiple attempts to restart the engines followed to no avail
Engines or engine????
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Old 6th Feb 2015, 07:43
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UK media reporting just now double engine failure from investigators
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