Yes new addition on the 600, only available once the YD is engaged.

Yes that definitely looks feathered to me.

if you engage yd. AFTER engine flame out...autotrim is not operative

Big time speculation here...
 

With the retrieval of the black boxes we should know soon enough what happened. It will be interesting to see if the stall warning was activated but for the time being I'll just ask questions to the pilots that fly the 600 and to those who know the airport of departure.

First… To those who know this airport. Do we know if one of the SIDs at this airport requires a right turn after departure?

Flight tracking shows a right turn followed by a left turn and then back to the right where the aircraft is almost on runway ending but off its centre axis. To me this seems they were struggling to control the aircraft.

Second… To ATR 600 pilots. What is the Vmca of this aircraft? What is the Stalling speed of this aircraft assuming a normal fuel load and pax load (58 + crew) to make this flight to destination? Assuming we can come close to its GTOW figures, we can probably figure out the takeoff speeds, a clean stall speed and one with flaps at takeoff position.

Weather was basically VFR with some rain and IIRC the winds on the ground were 10-15kts.

Now for the speculation part…

We know from the flight tracker that the aircraft reached about 1300 feet. The highest speed attained was 116kts, the lowest was 81kts and in its final stage prior to impact was increasing slightly to show a recorded speed of 85kts.

Now these speed are most likely ground speeds so if we take a 10kts headwind component we can assume the IAS would have been 126kts, 91kts and 95kts. Now assuming those IAS speeds are correct are we close to a stalling speed for flap 0 or flap in takeoff position for an ATR 600 for a given weight at takeoff?

We know one of the pilots called the “mayday and engine flame out” so we can almost ascertain there was an engine failure and most likely the left one. Why the left one? Because of the pictures showing us it was feathered or almost feathered, but definitely had a different pitch angle on its blades versus the right engine’s blades and finally it was turning slower than the right engine.

I think there is the possibility that the left hard over was a Vmca departure, a stall or a combination of both. From the video we see the aircraft seems to be level and descending then the left roll occurs.

Was this just a stall or a Vmca departure?

Perhaps has they were “gliding” towards the open area beyond the elevated highway, the pilots knew they were not going to clear it and added power to the one engine producing power, the right engine (on the pictures we see this because the prop is rotating faster).

At that moment perhaps they were close to Vmca and as the power came up there was not enough authority on the controls to keep it level and the aircraft rolled left.

This is just an exercise and is all speculative on my part… I’m not blaming anyone or pointing the figure at anyone, it is merely here for discussion purposes…

Now for your thoughts and view point and please keep it civilized!

http://i17.photobucket.com/albums/b7...pskxwc2wew.png


In regards to the left hand engine and its propeller, if indeed this pictures shows that left engine it seems to me to be in a feathered position.

http://i17.photobucket.com/albums/b7...ps9vd62zhw.jpg

Adding power doesn't increase Np.

What's the difference between a VMCA departure and a spin entry?

For a spin, we increase AoA to the stall, and induce a yaw input using rudder (deliberate, or unintended through mishandling of the rudder), the inner wing lets go and drops, followed by the nose, and you're spinning. I know this having done it deliberately literally hundreds of times.

I'm not a multi-engine pilot so VMCA is theory to me. However, as I understand it the mechanism is similar to that of spin entry, except the yaw is induced by assymetric power overcoming the ability of the rudder to compensate, due low airspeed. Also, a VMCA departure can presumably happen when both wings are (before the event) below stall AoA. But the outcome is the same - inner wing stalled, un-commanded wing drop, and you're spinning.

the inner wing doesn't stall.

You run out of rudder the aircraft continues to yaw. The wing starts lifting you hit full cross controls and it continues to yaw into the failed engine and the wing keeps going up. All happens in a matter of seconds.

Only way you can get out of it is by chopping the power on the good engine.

Thanks Mad Jock. Didn't realise the inner wing didn't stall in the latter stages of a VMCA incident.

It is always worth trying to remember that the occupants of an aircraft, have a 90% chance of survival if you contact the ground UNDER CONTROL. Fly the thing on!!

If the aircraft is flown in under control, the wings, elevators etc will absorb a lot of energy. It's the lack of control and vertical speed that mostly kills.

The glide stretch mindset must not be a reflex action, ever. If indeed this was the course of events in this accident, we don't know yet.

What we do know from photographic evidence the aircraft was not under control.

More info on "speeds"
 

Hope this helps to better understand the various speeds: http://www.skybrary.aero/bookshelf/books/493.pdf

It may stall depending the reason why you are hitting Vmca

But it certainly doesn't have to stall. Its the yaw which causes the roll not loosing lift.

And the rapid roll is a typical 'auto-rotation' entry to a spin.

Given the evidence from the flight tracking (which has to be taken with a pinch of salt but is the best we have until the FDR is decoded), it looks like they had engine and/or propeller problems somewhere around AA.

Whatever happened and how it was handled left them with significantly less airspeed than before, probably well behind the drag curve for SE flight. The RoD appears to be c. 1,000fpm at that stage.

In the final moments, the airframe got so slow that it departed, looking like a mix of Vmca effects and a stall/spin. The still frames from the video, as others have pointed out, show what looks like substantial/full up elevator deflection (the “gap” in the stabiliser), which ties in with a stall/spin.

As to what actually happened to start this chain of events, there are many failure modes for a turboprop power plant, some much nastier than others... :ouch:

I don't normally comment on these threads as I don't fly TP's however aerodynamics are aerodynamics regardless of the type and something strikes me looking at the speed / time / alt plot.

From the point just after rotation at about 100' the speed starts to decay, however the ROC remains surprisingly steady until they pass approx. 1100' when the ROC is reduced slightly. By this point speed is now passing below 100kts and then drops suddenly with associated loss in altitude of around 500' which looks like a stall and attempted recovery. The speed however never gets back above 100kts from this point and altitude continues to reduce steadily until the point of impact.

It looks to me that the speed was allowed to decline with constant ROC until the point of stall following which insufficient speed was attained during the recovery and the aircraft remained on the back of the drag curve unable to accelerate or climb on one engine.

Looking at the final video clip the aircraft is descending with significant positive AoA and I suspect the poor crew, out of options, attempted one last pull to avoid hitting the building resulting in a wing drop.
As it happens this might have been the one thing that saved lives Vs actually hitting the building.

"On Feb 5th 2015 the airline reported that the two pilots at the controls had 4,914 hours and 6,922 hours total flying experience, an instructor with 16,121 hours total occupied the observer's seat. The crew had signed the flight papers, that showed no unusual circumstances"

The instructor wouldn't pull an engine on a Line Check would he?

@ offa...
 

I certainly hope not. That would go I'm sure against any decent airline's policies.

If he did that would be seen as criminal I'm sure with dire consequences for all involved.

The line check is supposed to be an observation of a normal operation to ensure that all SOPs are adhered to.
Nothing more.

Perhaps he was there to help observe what the pilots had reported with a problem on the left engine.

With 3 pilots in the cockpit it will be interesting to see how or if any crew coordination occurred.

Looking at the footage of the luggage being retrieved from the tail section in the river, it appears there are a large number of extremely heavy suitcases being removed. I know they will be full of water but still ...

If the “speed” in question is groundspeed (which I think is what is reported), then that would be normal for a takeoff into-wind as you climb at constant IAS into an increasing headwind. The ROC reduction is normal at flap retraction height.
Yes, it’s all going wrong now. Only one thing is certain and that is that drag is more than thrust so the flight path is now angled downwards. Why there is that imbalance remains to be seen. Could be a) high induced and trim drag from slow (IAS) flight, b) drag from an unsecured power unit, c) lack of power from the good(?) engine, etc. Or a combination of all of them...

Without (as yet) knowing the full circumstances of the accident, it's noteworthy that a 'mayday' was sent apparently before aircraft control was established, which perhaps is not the best prioritisation of actions. As an examiner I noted that some crews did this during sim checks, which prompted me to write:

in my article 'How To Do Well In The Sim'. Of course, if the situation is beyond recovery then a 'mayday' is vital to alert SAR services who might be able to rescue potential survivors.

Perhaps the "Mayday and engine flameout" message to ATC was sent after the initial memory items were completed and aircraft under control.

Quote:

---

Looking at the footage of the luggage being retrieved from the tail section in the river, it appears there are a large number of extremely heavy suitcases being removed. I know they will be full of water but still ...

---

A standard size cabin bag flooded with water would tip the scales at around 50kg, let alone an item of hold luggage.

If things were going TU at a very early stage, he may well have over-dramatized the turn away from high-ish ground. His local knowledge might also have influenced him to turn well away from huge gas/fuel bottles and go for low terrain. That would certainly indicate he feared a normal single engine profile was not going to be achieved.

CAA Taïwan
All ATR grounded ?
http://www.reuters.com/article/2015/...0VF1TX20150205
Well .............
http://edition.cnn.com/2015/02/05/as...safety-record/

Mmm . . . what do they know that we don't?

@ jcjeant...
 

All the ATRs or just the 600 model?

Sorry but I do not necessaryly agree with the idea that a Mayday is not necessary asap.

It is vital that WHEN TIME ALLOWS, to warn ATC that you are in trouble.

Why?

1) they will not interfere when seing you swerve rom flightpath

2) they can reroute, hold all other traffic asap freeing your way to whatever course you must go

3) in case of you being behind the aircraft and headingmtowards terrain, they can warn and offer escape vector. ( in a radar environment)

This is of course when in a terminal area below msa etc...

Obviously,maircraft under control comes first, then memory items, but you are with two on the flightdeck.

Deep Stall
 

Anyone get the impression that with that nose high atitude and steep angle of descent as it crosses the buildings, it may have been in an unrecoverable stall at that point?

Despeque

Aviate, navigate, communicate. When the sh1t hits the fan even more so.

This very same aircraft B-22816 on the morning of 19th April last year declared a mayday and then cnl in favour of a full standby prevention at Macau due to the Hidraulic System lost at Engine 1, minutes before landing.

Looking at the Mode S transponder graph, I get a different impression of what happened.

First, as far as I know, the "speed" being sent from the transponder is IAS, not ground speed. What it appears then is that the aircraft accelerated to near 116 knots and took off. At this point the climb profile is immediately abnormal. The plane is climbing steeply, but the IAS is immediately decreasing, instead of pilots making sure the speed stays constant or accelerating. Whatever their throttle settings or whether they have 2 or 1 good engines.......clearly the pilots are not monitoring their speed (seen that so many times now) through the departure climb, and they never regained that lost situational awareness.

For a full minute after take-off, the pilots keep the same rate of climb, but the speed decays every so slowly and gradually. Finally, at ~105 knots the plane gently stalls (From reading ATR-72 specs this is about the normal stall speed when clean and heavy), and we see a immediate reduction in the rate of climb. But it is still climbing....slower, but still climbing and still recoverable. Wings lost a lot of lift, but the AoA and high engine thrust still pulling them up, but unable to maintain speed and going to be in deep trouble if don't immediately start proper stall recovery procedure.

Then in those crucial seconds the pilots do what so many other pilots have done before them. Instead of gently easing the stick pressure and letting the engines pull them back onto the curve, they pull the nose up further and now the speed REALLY drops off. Now they got no speed, and losing altitude. And that's where they hold the nose all the way down, staying below stall speed until they crash. Look at the crash video, nose was kept above the horizon......all the way down until hit the bridge.

I don't buy the "engine failure" reports. It does happen, but statistically it is so very rare on these aircraft, and besides this aircraft is capable of a single engine departure (albeit tricky). We know that instead from crashes that depressingly the single most probable cause is pilot error, particularly in this neck of the woods.

"Engine failure" is probably what they thought or yelled in the few seconds they had during a high workload environment as the only thing that made "sense". Throttles set high/full, my nose is above the horizon, but the plane dropping out of the sky......hmmm, must be engine failure! Particularly as we know a lot of these pilots have probably never experienced a real-world stall/near-stall situation before. We've seen this before on several crashes, same thing on Colgan Air, AF447 etc. In the confusion the pilots brain just can't detect the reason they are descending with throttle levers pushed up and nose up is because they are stalled. "Engine failure" is the only rationale explanation that comes in those confused moments.

http://s21.postimg.org/cfhuno2mf/640...5b3d6e7f35.jpg
free image uploading


Unconfirmed seating chart. Not final.

Red = Survivors
White = Empty seats
Blue = Deceased or Missing

The flight crew are confirmed deceased sadly.

You'll never get a final seating chart because (some) people make changes inside the plane to sit alone or together.

Nevertheless, still amazing some got out alive!

Passenger’s statement about engine:
 

Huang Chin-shun, a 72-year-old man, said he helped save four lives by unclipping safety belts.

"Shortly after taking off, I felt something was not right," he told CNN affiliate ETTV. "I thought: 'something's wrong with the engine,' because I always take this flight."

I read that figure before but according to airfleets , Transasia just has ( had) 11 ATRs , all 72s, in operation, where do the other 11 come from ?

The passengers`s statement may be meaningful. Possible indication of engine loss after V2 and crew forced to take problem into the air. The real mystery is unless they also lost thrust on the remaining engine, then why were they unable to maintain altitude or climb.
As and when the power plants and props are recovered we might get a better idea whether or not the props were under power or not. Has anyone seen any photos of the recovered props or blades.

Contaminated fuel?
 

Is there any risk the a/c was fueled wtht water contaminated or incorrect fuel, that dergraded the trust om the left and later took out the engines one by one, when the "dirty" fuel reached the engines?:confused:
does Someone have experiance about that?

TV footage of the wreckage being recovered appeared to show an engine with feathered prop. All supposition at this time.

http://www.bbc.com/news/31143640

Look around the 38 second point.

synchrophaser
 

The engine and chewed up prop looks feathered.

In the event the synchrophaser malfunctioned or was not selected off, would this lead to autofeathering, especially with ATPCS disarmed. Has there been any previous issues realting to this on type.