Turkish Airliner Crash

[iskyfly]

Am I getting this right: The same airplane that crashed had had the exact same problem (wrong radar altitude - A/T going into retard/flare mode too early) twice within 25h before ithe accident and

a malfunctioning radalt to quote this 737 captain is "something that happens all the time."

I encourage people to read his replies on this subject as they are very informative and give us some insight on what happens on the flightdeck when your approaching the runway in IMC, vectored by ATC onto a tight / short final, above GS, have checklists to go through, looking out the window for the runway....

http://www.airdisaster.info/forums/viewtopic.php?f=6&t=2098&st=0&sk=t&sd=a&start=175#p27794

[iskyfly]

alright, just some more questions:

1. the airplane was on final approach when the accident happened. as far as I know, there is usually neither the A/P steering the aircraft nor the A/T engaged during final approach - unless, of course, there's low visibility and a automatic landing in progress (but this was not the case). so why was the airplane not flown manually?!

Because they were in IMC conditions.

[empiredude]

thanks for your replies iflysky

you're right, there are often a couple of systems malfunctioning or inop on a plane (without being a real danger to flight operations). but still, isn't it a bit terrifying that they were using a system to control their airspeed during final that had been broken for at least a couple of flights earlier - and didn't even seem to pay special attention to this system.

but again, flight crew definitely has a high workload during final and there was definitely only very little time to react to the problem after it had been noticed - apparently too little...

[joeyb747]

My question is: If they knew there was a problem with radio altimeter number one, why wasn't the crew operating in dual mode?

With so much redundancy in modern aircraft today, only the #1 radio altimeter handles the entire approach? What if #1 was inop? Can #2 be set up to handle the same functions as #1?

They were not using the redundancy they had available to them. They were not doing a dual channel full autoland. Had they been doing a dual channel autoland the AP would have disconnected which would give the crew another indication that something was wrong.

At least then as iflysky pointed out, the autopilot would have sensed a discrepancy between the two rad alt and disconnected the autopilot.

Aircraft keep a logbook for these such reasons. When something is wrong with the bird, you note it and pass it on to the next crew, or MX at the home base. Does anyone know for sure if this item was noted in the logbook?? I've seen logbook entries for some pretty trivial squawks. I find it hard to believe that was not noted in the logbook.

"Radio Altimeter Number One Intermittent" seems pretty important information!

[toogd]

It is simply strange that the plane was allowed in the air with a "temperamental" altimeter hooked up to its hands free landing system. Surely that calls for some intensive soul-searching at Turkish Airlines...

That the crew end up depending on this port side altimeter seems to be because it they'd done it properly, with dual altimeter input, the autopilot would have disconnected (as it damned well should do!), but I can't find anything here about the other alternative.
-Was it possible to use the right hand side altimeter for the approach?
-Why did the pilot opt to use the documented "temperamental" unit to control this fateful glide?

Is there some logic to this that I am missing? What would a pilot be trained to do in these circumstances?

I can appreciate that it might be easy to miss detecting that the plane was loosing air speed until it was too late, but how do you end up relying on a piece of equipment that you know is faulty and not notice that it is failing you? I'm not getting it.

[MathFox]

It is simply strange that the plane was allowed in the air with a "temperamental" altimeter hooked up to its hands free landing system. Surely that calls for some intensive soul-searching at Turkish Airlines...

[...]

Is there some logic to this that I am missing? What would a pilot be trained to do in these circumstances?

I can appreciate that it might be easy to miss detecting that the plane was loosing air speed until it was too late, but how do you end up relying on a piece of equipment that you know is faulty and not notice that it is failing you? I'm not getting it.

You assume that the defect was written down in the logbook... According to the AEI (international organisation of Airline mechanics) that does not always happen. (Commercial interests.) Published rumour (link in Dutch: http://www.luchtvaartnieuws.nl/news/?ID=29843 ) says that the two previous known failures were not written up in the plane's logbook.     

[joeyb747]

Wow. Thats amazing. Blows my mind actually. I've seen logbook entries like "Captains seat uncomfortable. Please change cushion." Trivial stuff. Why were these malfunctions not noted?? Thats what I don't understand. 

[MathFox]

joeyb747, you've got some good questions for the investigation. I am pretty sure that the OVV investigation will take a look into maintenance practices and procedures.

[joeyb747]

joeyb747, you've got some good questions for the investigation. I am pretty sure that the OVV investigation will take a look into maintenance practices and procedures.

Thanks!
We can only hope they will...

You know what they say about the FAA(or governing body in witch ever country the aircraft is operated):
Policies are written in the blood of their passengers...simply meaning, it takes a major disaster before they will change a policy.

I heard that somewhere...just can't remember where...

[toogd]

If the log books are blank regarding earlier malfunctions in this case, the implications are scarier than I care to even think about!

[joeyb747]

If the log books are blank regarding earlier malfunctions in this case, the implications are scarier than I care to even think about!

Indeed!!

[empiredude]

I just cannot believe they would have been using faulty radaralt if they had known it was malfunctioning - I would simply be ridiculous if it weren't so tragic...

on the other hand I also cannot believe they missed to note this in the A/C logbook - I mean you're supposed to note every stupid little thingy that wasn't working perfectly normal - and I'm no pilot, but a faulty radar altimeter causing the autothrottle to go idle for landing too early sounds like something pretty severe to me... and that apparently happened twice (!) within 25h...

just don't get it, should've never ever ever happened...

by the way, is there some official investigation report available on the internet somewehere?

[MathFox]

So far the best official report (in Dutch) is http://www.onderzoeksraad.nl/docs/rapporten/Persverklaring_4_maart_09.pdf and in English http://www.onderzoeksraad.nl/docs/rapporten/Press_statement_4_March_GB.pdf

If there are new reports they'll most likely be listed on:
http://www.onderzoeksraad.nl/en/index.php/onderzoeken/onderzoeksraad-start-onderzoek-crash-turkish-airlines-op-schiphol/

[iskyfly]

by the way, is there some official investigation report available on the internet somewehere?

No. The investigation is not complete. It will take 6 - 9 months.

Right now the only official releases are statements of facts leading up to the accident.

[empiredude]

thanks for the links to the report!

I know the whole redundancy issue has been discussed before - but just in general, shouldn't on a airplane every vital function be back-uped? I mean why is the A/T not in general configured to use both radio-alts no matter what?
just out of curiosity, how does airbus handle the subject? do their A/T also only use one radio alt to measure the distance to the ground? (I really don't wanna start some boing vs. airbus discussion!!! just wondering if this A/T configuration is standard (and if so, why?) or not...)