News 'Dozens dead' in Russian plane crash.

[C3PO]

A possible cause (or contributing factor) could be an engine failure during a go-around. If the aircraft for example was high and slow, loosing an engine with the throttles firewalled can spin you out very abruptly. A rudder hard-over can produce the same effect.

But as always we'll have to wait for the information to be gathered. I only hope we eventually can learn something from this tragedy.

 

[kerlix]

I don't see a single-engine failure causing that kind of extreme attitude. These planes are designed to (and have survived) single engine failures at VR, V2 and immediately after rotation and positive rate. While a significant amount of rudder would have been necessary, unless the engines were on the wingtips, I don't see the asymmetrical thrust causing such a violent roll and pitch down.

From the video, they were anywhere from 70-85* nose down. Even a stall wouldn't cause such extreme flight angles, unless they stalled REALLY hard in a very nose-high attitude near the ground. I guess that's a possibility. If there was a single-engine situation and they overcorrected for a nose-high "let's get the hell out of here" attitude and rendered the thrust they had mute, then hard-over'ed in an attempt to break the stall at the peak of the "climb trajectory", then they could have entered that flight angle. But that's difficult. A "perfect storm" of sorts.

Older 37's suffered from rudder reversal/hardover due to hydraulic fluid being ludicrously cold. I guess that could also be a possibility at low speeds and altitudes. I can't remember if Boeing corrected the rudder actuator, or simply advised for training to recognize and correct the problem if it ever presented itself.

I doubt suicide played into it. As others have stated, it's just too easy to accomplish either during takeoff or during cruise/descent.

I've heard this was on their 2nd landing attempt. What I'd be curious to know is it this happened on a 2nd pass, or immediately after initiating a go-around. If immediately after, then any of the scenarios, including spatial disorientation, could play into it.

If it was on a 2nd pass, then who knows? Rudder reversal/hardover? Engine failure during a 2nd abort combined with overly aggressive control input leading to a stall (perfect storm type incident).


In the end, it's best to wait and see what the investigation brings. It's easy to sit and point fingers after only have a few seconds of dark, grainy video footage as the only piece of evidence. The boots on the ground will have a much better idea, and probably already do.


I'll be keeping those killed and effected in my thoughts. Hopefully some good can come out of this tragedy to make future flights safer.

 

[C3PO]

I don't see a single-engine failure causing that kind of extreme attitude. These planes are designed to (and have survived) single engine failures at VR, V2 and immediately after rotation and positive rate. While a significant amount of rudder would have been necessary, unless the engines were on the wingtips, I don't see the asymmetrical thrust causing such a violent roll and pitch down.

An MD-80 was spun off the RWY AFTER touchdown by the thrust reverser after a single engine landing. Their engines weren't as far apart as on a 737.
If you have enough speed an engine failure isn't such a problem. But if you initiate a go-around from a slow state it can cause all kinds of trouble. You are spooling the engines up and raising the nose at the same time. If you add slip to that situation, you can quickly slow down enough to loose rudder authority to counter the thrust.

The plane hit the RWY threshold almost vertically, so they were no way near the glide slope just before the plane entered the final attitude. This makes me believe that the problems started further out on the approach. I'm guessing that they had problems with thrust and/or control, and were struggling to gain speed/altitude when they finally lost it.

The camera was vibrating more than the average CCTV, so wind shear could have been a factor too.

 

[Urwumpe]

Interesting detail cited on Wikipedia: The pilot aborted the second attempt to land because the aircraft was not properly configured for landing, shortly before the aircraft went into a dive.

This could indicate technical problems as well as a pilot error - even both at the same time.

 

[N_Molson]

The thing is that an aircraft that stalls doesn't necessarily pitch down : it just ceases to fly. Now I guess that fly-by-wire systems force the plane into a dive, the only way to regain speed and then lift.

 

[Urwumpe]

The thing is that an aircraft that stalls doesn't necessarily pitch down : it just ceases to fly. Now I guess that fly-by-wire systems force the plane into a dive, the only way to regain speed and then lift.

There is no fly-by-wire on a 737-500.

 

[C3PO]

Older 37's suffered from rudder reversal/hardover due to hydraulic fluid being ludicrously cold. I guess that could also be a possibility at low speeds and altitudes. I can't remember if Boeing corrected the rudder actuator, or simply advised for training to recognize and correct the problem if it ever presented itself.

It was the hydraulic actuators that were cold. The problem arose when hot hydraulic fluids were introduced after a long period without rudder inputs.
Boeing's solution was to mount a 3'rd actuator. 2 simultaneous actuator failures is highly unlikely. IIRC they cycled the actuator 70,000+ times before it failed.

 

[astrosammy]

The Avherald article has been updated with results of first Flight Data Recorder readouts.

http://www.pprune.org/8161768-post120.html
http://www.mak.ru/russian/info/news/main_frame.html

 

[Artlav]

Which version is the original - english or russian?
There are a few differences between the two, and them and the article.
One suggests the CVR was knocked out of it's case, while the other implies the case was intact, but empty.
One says the pilots were not following the approach procedure, in a deliberate decision tone, the other say they were unable to follow the approach procedure for some unknown reason.

One other thing not entirely clear - was the plane controlled into the ground?
They say the pitch started to decrease as the crew took control - does that mean that someone leaned on the stick and didn't let go until the impact?

 

[PeterRoss]

I'm not sure if it's worth posting at all because there's no way to prove if this information is right or wrong, but it's possible that this is a last piece of truth we will hear of this tragedy in Russian media. Equally, it may be just a yellow-press gossip and nothing more. You can't tell the difference when living under feudal democracy.

There was a bit of news appearing in media about the son of Tatarstan president was in the plane's cockpit at the moment the emergency situation arose. They said he may have affected the pilots' actions by his authority. If this is true it means that we have seen the wicked replay of the recent accident with Poland president's plane.

This news was quickly removed from direct access and now are mentioned on another news site as a wrong information dismissed by IAC.

 

[Artlav]

Now i wonder where the missing CVR went.
The black boxes are made to survive far worse.

 

[Urwumpe]

Now i wonder where the missing CVR went.
The black boxes are made to survive far worse.

The box would at least not be empty.

Now, we are talking about Russian airlines - the CVR box could even have been empty on take-off.

 

[MattBaker]

Now i wonder where the missing CVR went.
The black boxes are made to survive far worse.

If the news reports Peter described here have just a grain of truth...On some desk...in some storage...repeatedly fired on with an AK. Pick your favorite one.

 

[PeterRoss]

In fact, they did reported some time ago that they've found CVR tape and started to decypher it. The news I've reported were posed as a info leak from there.