Plane crash in Nigeria

[Gabriel]

Originally Posted by Highkeas

Add poor maintenance - remember the L1011 where all three engines shut down because o-rings were not replaced in the engine. This and other examples here:
http://www.boeing.com/commercial/aer...ly/m02txt.html

Point taken.

Not very likely though. I'd expect problems to develop earlier during the flight and the failures not happening at the same time or very close together.

Yet, whatever killed this plane it had to be an unlikely thing.

Extreme hail or water ingestion would be another possible (not probable) cause.

And as we are with the unlikely thing, let's not discard two fully independent engine failures. It would be an all-times first.

[Evan]

A man known as David Chukwunonso Allison has filed a 56-page lawsuit against Boeing, McDonnell Douglas, Pratt & Whitney and United Technologies. Apparently the MD-80 was unsafe all along. And this after decades of reliable service. It was only a matter of time before both engines would fail due to it being poorly designed. Who knew.

Also targeted in the suit is the estate of the deceased pilot. David Chukwunonso Allison sounds like a classy guy.

http://edition.cnn.com/2012/06/07/wo...html?hpt=hp_t3

[Gabriel]

Originally Posted by Evan

Really? Contagious engine failure on an MD-80?

Why not? Believe me the fuselage will not do much to stop it.

[Gabriel]

Originally Posted by Evan

A man known as David Chukwunonso Allison has filed a 56-page lawsuit against Boeing, McDonnell Douglas, Pratt & Whitney and United Technologies. Apparently the MD-80 was unsafe all along. And this after decades of reliable service. It was only a matter of time before both engines would fail due to it being poorly designed. Who knew.

Also targeted in the suit is the estate of the deceased pilot. David Chukwunonso Allison sounds like a classy guy.

http://edition.cnn.com/2012/06/07/wo...html?hpt=hp_t3

Let me guess.
- The suit is just for liability, not crimininal.
- He didn't target the Airline or the Nigerian regulator. What could him get from them anyway?

[ErwinS]

Originally Posted by Evan

Really? Contagious engine failure on an MD-80?

Off course not. Really no way that one engine could take out the other on a Mad Dog.

Latest rumours are about bird remains found in one engine.

[Gabriel]

Originally Posted by ErwinS

Off course not. Really no way that one engine could take out the other on a Mad Dog.

Ok guys. You and Evan know something that I don't. Please share.

[ErwinS]

Originally Posted by Gabriel

Ok guys. You and Evan know something that I don't. Please share.

Well look only at the general layout of the engines on a MD-80 srs. If you have an uncontained engine failure how would that reach the other engine with the fuselage in between? Surely the fan or compressor blades wouldn't go through the fuselage and enter the other engine.

http://www.airdisaster.com/photos/dl1288/photo.shtml
Uncontained engien failure on a MD. True shrapnhel entered the cabin but not the other engine.

[Evan]

Originally Posted by Gabriel

Ok guys. You and Evan know something that I don't. Please share.

I suppose it's possible... you were pointing out a list of possibilities. It would be a very freak thing. I'm betting on birds though. Shitting down the wrong engine wouldn't exactly surprise me either.

[Gabriel]

Originally Posted by Evan

I suppose it's possible... you were pointing out a list of possibilities. It would be a very freak thing.

I don't see why it would be freak at all, really.
I'm seriusly asking, why would it be so unexpected?
Do you seriusly think that a few sheets of thin aluminium would stop a titanium compressor disk projected at about the speed of sound?

An uncontained engine failure is not a frequent thing but, given an uncontained engine failure, a "contagious" (I liked the word) second engine falilure wouldn't surprise me either.

[Evan]

With foreign object ingestion (birds, hail, what-have-you) one important factor is in how the compressor stalls are handled. If the engines are not throttled down sufficiently, the engines can suffer destructive effects beyond the deformation of fan blades. This had led to two DC-9/MD-80 dual engine failure crashes that I can think of...

http://en.wikipedia.org/wiki/Scandin...nes_Flight_751

http://en.wikipedia.org/wiki/Souther...ays_Flight_242

I wonder if we have a third case on our hands?

[Highkeas]

Originally Posted by Gabriel

I don't see why it would be freak at all, really.
I'm seriusly asking, why would it be so unexpected?
Do you seriusly think that a few sheets of thin aluminium would stop a titanium compressor disk projected at about the speed of sound?

An uncontained engine failure is not a frequent thing but, given an uncontained engine failure, a "contagious" (I liked the word) second engine falilure wouldn't surprise me either.

An uncontained fragment could possibly enter the fuselage and cut control or fuel lines to the opposite engine.

[ErwinS]

Originally Posted by Evan

With foreign object ingestion (birds, hail, what-have-you) one important factor is in how the compressor stalls are handled. If the engines are not throttled down sufficiently, the engines can suffer destructive effects beyond the deformation of fan blades. This had led to two DC-9/MD-80 dual engine failure crashes that I can think of...

http://en.wikipedia.org/wiki/Scandin...nes_Flight_751

http://en.wikipedia.org/wiki/Souther...ays_Flight_242

I wonder if we have a third case on our hands?

SAS was Clear Ice and the Southern was also weather related. Not one engine taking the other one out.

[Evan]

Originally Posted by ErwinS

SAS was Clear Ice and the Southern was also weather related. Not one engine taking the other one out.

Yes, as I said, both were foreign object ingestion. Both were mishandled by applying too much thrust to a compressor-stalled pair of engines.

[ErwinS]

On Jun 10th 2012 Dana Air's Director of Flight reported on Lagos' TV, that the remains of one or more birds have been found in one of the engines recovered from the crash site. However, the cause of the crash is still to be determined.

[Gabriel]

Originally Posted by ErwinS

On Jun 10th 2012 Dana Air's Director of Flight reported on Lagos' TV, that the remains of one or more birds have been found in one of the engines recovered from the crash site. However, the cause of the crash is still to be determined.

Copy-pasted from AvHerald. Give credit.

If correct, the "reallistic" choices for a double engine failure have pretty much narrowed to:
- Double bird ingestion
- Wrong-engine shut-down

[ErwinS]

Originally Posted by Gabriel

Copy-pasted from AvHerald. Give credit.

If correct, the "reallistic" choices for a double engine failure have pretty much narrowed to:
- Double bird ingestion
- Wrong-engine shut-down

Not only Avherald had that quote

[Spectator]

The probe into the June 3 Dana Air crash traced the cause "to the loss of two engines and non-functionality of the throttles on final descent from Abuja to Lagos", the Accident Investigation Bureau (AIB) report said.

Preliminary report, that is. Source: http://www.news24.com/Africa/News/En...crash-20120713

[Gabriel]

From the link above:

At 15:43:27 hours, the captain informed the FO (flight officer), 'we just lost everything, we lost an engine. I lost both engines'.

During the next 25 seconds until the end of the CVR (cockpit voice recorder) recording, the flight crew was attempting to restart the engines

In this airplane that lacks a RAT, if the APU was off (which most likely was), then the double engine failure means that the plane lost every powered system (hydraulic and AC electric). This basically means:

no flaps/slats (which would stay at their last position)
no spoilers (which, more important than for airbrake and lift killer, they are an integral part of the roll control)
no antiskid, no autobrakes, no reversers (as if they were of any use with the engines off)
no nosewheel steering
no rudder
no trim
no elevator boost (that kicks in when you command large nose-down inputs to help recover a stall)
no pressurization, no air conditioning
no pneumatic pressure to feed the engine start motors

30 minutes of essential DC (feed from the battery)
Reserve hydro pressure in the accumulators for the brakes
"Gravity powered" alternate landing gear extension
And, most important of all, the famous "aerodynamically powered" ailerons and elevator.

So you have degraded but enough flight control for the glide:
In pitch, normal elevator (except boost) but no trim.
In roll, normal ailerons but no spoilers.
In yaw, nothing but that's not so severe (the main functions of the rudder is to arrest asymmetric thrust, to give directional control on the ground at high speeds, and to allow sideslips which is mostly used to make smooth landings in crosswind).

At altitude cruise altitude, the usual procedure would be to make a descent to the altitude and speed needed for the windmilling restart and attempt a restart, or to descend below the max APU altitude, start the APU (the APU start motor is DC which you have from the batteries, and the APU will give you AC, hidro from the electric pump, and pneumatic pressure for the engine start motors), and attempt an engine restart. Even if the engines fail to restart, the APU will give you most of the systems back.

During all that you should be considering that the engines might not relight so from the start you act like you are going to make a power-off landing, that means finding a suitable (or the least unsuitable) place to put the plane down, navigating to there, brief the cabin, advice ATC, etc.

Now, if you are really low, somehow slow (windmill start not possible), and are flying over a densely populated area, like in this case, you better concentrate all of your efforts in the best way to crash the plane. It takes maybe 1.5 minute to start the APU and get the systems on-line and then maybe another half a minute to start an engine and have it spooled up. So if you don't have 2 minutes of glide, don't even bother: the engines don't work very well underground, and the chances of a restart are not very good anyway (the engine quit for something after all).

I know it's easy from this chair and very difficult in the real life, but at some point one has to accept that you are going to crash and change from "complete the flight" mode to "survive the crash" mode. The captain should take the controls, keep the plane within its envelope, concentrate on finding a highway, a patch of green, an avenue, even a river, where to crash-land it, advise the ATC and the cabin, (that is: aviate, navigate, communicate) and forget about any troubleshooting. That he can leave to the FO, or maybe (if it is clear that there is not time to even start the APU and put the systems on-line) even the FO should forget that too and help the captain find a place, lowering the gear, briefing the cabin, etc...

I don't know how much time passed since the captain called the double engine failure until the crash. Probably it was more than the 25 seconds mentioned because the CVR and FDR stop working when the generators are lost (the 25 seconds was probably the spool down if the last engine) and because it makes no sense a time so short, even with very little altitude they would have more than that while trading altitude to keep speed and then bleeding off excess speed. But it sounds that, at least for those 25 seconds, both of them were concentrated with the restart of the engines. The article is not clear, but they mention only that and not any comment about where to put it down.

[Gabriel]

The core of the report
http://www.aib.gov.ng/reports/Interi...2%20prelim.pdf

The cockpit voice recorder (CVR) retained about 31 minutes of the flight and starts about 1515 [Gabriel's note: the plane was already at cruise] at which time

the captain and first officer were in a discussion of a nonnormal condition regarding the correlation between the engine throttle setting and an engine power indication

3.
However, they did not voice concerns then that the condition would affect the continuation of the flight. The flight crew continued to monitor the condition and became increasingly concerned as the flight transition through the initial descent from cruise altitude at 1522 and the subsequent approach phase. DAN 992 reported passing through 18,100 and 7,700 ft, respectively, at 1530 and 1540 hours. After receiving a series of heading and altitude assignments from the controller, DAN 992 was issued the final heading to intercept the final approach course for runway 18R.
During the period of 1537 and 15:41 the flight crew engaged in pre-landing tasks including deployment of the slats, and extension of the flaps and landing gear. At
15:41:16 the first officer (FO) inquired, "both engines coming up?" and the captain (Capt) replied “negative.” The flight crew subsequently discussed and agreed to declare an emergency. At 1542:10, DANA 992 radioed an emergency distress call indicating "dual engine failure . . . negative response from throttle."
At 1542:35, the flight crew lowered the flaps further and continued with the approach and discussed landing alternatively on runway 18L. At 1542:45, the Capt reported the runway in sight and instructed the FO to raise the flaps up and 4 seconds later to raise the landing gear.
At 1543:27 hours, the Capt informed the FO "we just lost everything, we lost an engine. I lost both engines". During the next 25 seconds until the end of the CVR recording, the flight crew was attempting to restart the engines.

Underlining is mine. It called my attention that they lowered the flaps farther after declaring a dual engine failure (which apparently was not total yet) and, 10 seconds later, retracted the flaps and the gear.

It's another tough call: flaps, slats and gear add drag and worsen the glide ratio and hence the distance that you can glide from a given altitude. On the other hand, the slats and flaps reduce the stall speed (and hence the crash speed) a lot, and the gear can absorb a good bunch of energy during a crash landing.

If I knew that my engines would quit in a minute and that I can reach the runway (or some very flat, smooth and long place) gliding only if I clean up the plane, then I would happily trade the benefit of a slower speed and gear cushion for the benefit of the runway. On the other hand, if I knew that my engines would quit in a minute and that I will not reach a runway or equivalent place, I want the slats out and some flaps (a take-off-ish config) right now, while I have power to move them. Slats and a bit of flaps give you most of the reduction in stall speed with no so much drag (further flaps add more drag than they increase lift). If the crash is not imminent and I want to preserve glide ratio, the landing gear can come down later with the alternate gravity extension.

The problem is that when you see the runway out there, it is very hard to avoid the temptation to try to reach it because a runway is so much more a safe for a crash landing than the middle of the city, but on the other hand the middle of the city and with twice the energy and no landing gear is even more dangerous and a runway beyond reach is useless. That's why I praised Sully not for the water landing itself, but for his decision making, like he himself said "The Hudson river was the only place long enough, wide enough and smooth enough that I KNEW that I could reach". Later, simulation showed that if he did everything perfect he could have reached La Guardia, but he didn't know that at that time. Of course he didn't know that he could not reach it either, and that's why I applauded him for resisting the temptation of trying. That is really hard for a pilot: to accept that you are not only not reaching your destination, but that you are going to crash this plane and that loss of lives might be involved. But that acceptance is crucial to change to survival mode and start to concentrate not on reaching a runway but on how to crash to maximize the chances of saving some lives (including yours).

[Gabriel]

Not that it is related to the accident, but someone please explain this:

He [the FO] had 1,143 hours of total time, including about 200 hours as pilot-in-command. The first officer had 808 hours in the accident model airplane all of which was second-in-command [...] had accrued about 3, 42, and 154 flight hours, respectively, during the preceding 24 hours, 30 and 90 days.

He's been in the right seat of an MD-80 since 300 hours total time???

Again, not that it is related to the accident. If it is for the experience only, given a 1100 hours FO I choose one with 800 hours in the type (and who's been flying some 50 hours a month on the type) over one with 20 hours in the type.