News ATR-72 turboprop plane crash in Taipei

[Cosmic Penguin]

Well, many of you should have already seen the TransAsia Airlines ATR-72 crash in Taipei this morning. Right now at least 25 of 58 on board have been confirmed killed.

[ame="http://www.youtube.com/watch?v=hDshs7trY-I"]TransAsia Taipei Plane Crash (BEST QUALITY IMAGES) - Accidente Avión Taiwan (4-2-2015) [Must see!] - YouTube[/ame]

This one, given the flight speed and altitude data, really looks similar to an engine failure that people on the web are suspecting (especially with someone pointing out that the left engine propellers looks "feathered"). I can't remember of a turboprop engine failure and crash in recent years though (not with the ATR, or the Dash-8, or other older types).

Had this happened in somewhere colder, I would have guessed that icing conditions would be involved (remember the AA4184 crash 20 years ago? Or this ATR crash in Russia a few years earlier in which the plane was not de-iced)....but since this is in Taipei, the only other probable reasons I could think of are weight balance issues and maybe non-extended flaps (which I think is unlikely since it would probably crash immediately like several accidents in history, instead of being airborne for 3 minutes).

BTW, another ATR-72 from the same airline had a fatal crash last July, though the situation was completely different.


Any comments?

 

[Urwumpe]

Latest news here talking about the pilot reporting a flameout on one of the turboprop engines right after take-off.

Likely something technical, but it could also be a bird strike for example.

Still, such failures are extremely rare on turboprops, but not impossible. But the nearly stalled to stalled flight path of the plane supports this hypothesis, engine failures right after take-off, especially with obstacles to pass, are deadly.

 

[Izack]

Video was taken down.

 

[Cosmic Penguin]

Video was taken down.

And replaced with another source.

From what I read a single engine out, even with the propellers un-feathered, should not have caused it to stall (though in that case it would be close). I wonder what were the pilot inputs....

 

[Prowler901]

A left engine out is the worst of all possible scenarios on a twin engine propeller aircraft. The P-factor can induce such incredible rolls that are not recoverable at low speeds. The pilots must take quick and decisive actions to recover. However, there is very little to do when you are at low speed and altitude after take-off. Very tragic accident.

 

[Ripley]

If it's twin engine, propellers surely are contra-rotating.
So why should left engine be worse than right one?

 

[Prowler901]

Have a look at this page: http://www.multiengineairplane.com/flying-on-one-engine/. He explains it very well.

 

[kamaz]

But this assumes that both propellers are rotating in the same direction (to the right).

See also [ame="http://en.wikipedia.org/wiki/Critical_engine"]Critical engine - Wikipedia, the free encyclopedia[/ame]

...Ah yes, it appears that on ATR72 the left engine is critical.

 

[Prowler901]

Yes, I've been doing some research and both propellers turn clockwise as seen from behind.

 

[Ripley]

Well, I'm no aviation expert, but it surprises me to read about the existence of twin-engine non counter-rotating props.
I bet the reason has to be found in production costs, as usual.

 

[Prowler901]

Probably. Counter rotation would require two sets of gear boxes. Which would complicate repairs and supply costs.

 

[ex-orbinaut]

Blimey! There I was driving along with not a care in the world when...

Have not had a chance to look much more into this, but has it been confirmed as an engine failure?

I notice the flaps look retracted when it piled in? It was a very short acceleration segment, on the graph, perhaps a mismanaged flap retraction schedule, no check speed before flaps up? Bad news.

RIP.

 

[Urwumpe]

Well, you can still climb too fast at a single engine out and get too slow and at too high AOA to recover with just a single engine, since your drag is then much higher.

 

[ex-orbinaut]

Well, you can still climb too fast at a single engine out and get too slow and at too high AOA to recover with just a single engine, since your drag is then much higher.

Exactly, one of the parts I deleted in my previous post went into the consistent bleed off of speed during what was otherwise a good second segment, getting them behind the power drag curve you infer here.

 

[RisingFury]

The plane seems to be in a controlled descent right until the end there.

I wonder if the pilot let it roll deliberately to avoid the road.


I can't believe anyone survived that. 100 knot impact at what seems like 30° angle. Imagine crashing a car into a river at nearly 200 km/h...

 

[Hielor]

Looks to me like it actually clips the top of the building before the roll starts...

 

[kerlix]

Looks to me like it actually clips the top of the building before the roll starts...

I tried watching that portion of the video over and over again to see if it clipped. It looks like it actually misses (barely). At first I thought I saw debris coming off the roof, but I believe its actually just a smear from a rain drop on the windshield. At the same time the plane passes behind that (electrical?) structure making it a little hard to make out.


But the rolls begins immediately after passing that building. I wonder if the pilot thought he was going to hit it and tried banking to go over it on his right side. Could trying an aggressive avoidance maneuver at such a low speed cause a roll like that?

It seems like he knew he didn't have the ability to keep the plane in the air and was trying for a landing in the water but coming so close to that building made the pilot roll to avoid, but then control was lost. At such a low speed, turning into the critical engine would probably not, and didn't, end well.

 

[Hielor]

But the rolls begins immediately after passing that building. I wonder if the pilot thought he was going to hit it and tried banking to go over it on his right side. Could trying an aggressive avoidance maneuver at such a low speed cause a roll like that?

If you're already on the verge of stalling, using excessive aileron to try to roll one way can indeed result in a snap roll in the other direction as the wing you're trying to lift stalls and drops instead.

 

[Urwumpe]

If you're already on the verge of stalling, using excessive aileron to try to roll one way can indeed result in a snap roll in the other direction as the wing you're trying to lift stalls and drops instead.

It could even be rolling towards the damaged engine, because the prop wash is not producing additional lift on the wing at low speeds, while the opposite wing still gets this additional bit of lift force (which can be quite significant contributions for some aircraft during landing).

 

[C3PO]

If you're already on the verge of stalling, using excessive aileron to try to roll one way can indeed result in a snap roll in the other direction as the wing you're trying to lift stalls and drops instead.

To me it looks like a classic wing tip stall induced by the aileron. I've seen many RC-planes crash this way at our local RC-field. From those videos it looks to me like the right aileron is in full up position during the roll.

I suspect that the pilot was trying to avoid those power lines by turning perpendicular to them. (shortest path to pass over them) Instinctive manoeuvres can be very abrupt compared to planned ones, Seeing those lines during an emergency must have been a frightening sight.