Turkish Airlines B737-800 crash

[EHM-2155 Mariano]

I was stunned to see this on the news

Happened in the Netherlands when the airplaine was trying to land at Schiphol.

I thought the 800 was introduced pretty recently (10 years), as the upgraded version of a well known little ship, to have accidents like these already... 9 dead, 50sh wounded. Could have been pilot error?



RIP for those who lost their lives.

[EHM-2272 Callum]

RIP to all who died.

My thoughts and prayers are, too, with their families. May the injured have a speedy recovery!

[EHM-1392 Justin]

I live just under the approach of rwy 27 at EHAM, i see them fly over. If that runway was in use i could have had the 737 on my roof...  

I heard rumors of loss of all fuel in final approach... In any case it seemed like engine failure according to the media. On the other hand, eye accounts report that just before the crash the pilots gave full thrust to them, which is pretty difficult without fuel or broken engine so its causes are real shady for now.

Hope to learn why anyhow, because if the pilots did a fuel miscalculation it could be any airline or aircraft thats risky to fly.

[EHM-0948 Bruno]

I also think that windshear could cause that. But still, an engine failure can be fatal on this situation, that is on the final approach since the aircraft flies much more slowly and on a lower altitude.

Let's see what the report says ...

[EHM-2309 Joshua]

I read in the newspaper today that a Boeing 757 landed just before the turkish airline 737-800. It mentioned the 757 having a big turbulance wake (I do not know if this is true), but this could have bought the plane down if the wake was strong enough, and the pilot not experienced enough...

[EHM-2198 Didimo]

Apparently the pilot in command was the CoPilot who was in his last promotion flight. In other words, though he had been a pilot since 2004 he was getting his B737-800 type rating, if he managed to land this flight then he would have "graduated" but unfortunately that did not happen.

Factors are low altitude, on finals at low speed a very critical moment. To top that an a/c had landed just ahead so that may have given problems with the turbulence/wake if ATC did not instruct well or if the pilot did not manage to keep sufficient separation to avoid the wake.

So many things but we all have good ideas but they are just speculation at this moment. The B737 just fell off the skies according to eye witnesses and survivors, that seems to be supported by the fact that there was no dragging path on the ground.

All three pilots died :-( crushed by the instrument panel. Plus a few americans that were probably sitting on one of the parts where the a/c fractured. A sad affair...

And to add insult to injury some of the passengers that got out of the a/c actually returned to it, not to help other fellow passengers but to pick up their laptops and/or mobile phones!!!! outrageous!

[EHM-0005 Maarten]

The newspapers are full of speculations and it really tires me. There are so many possible causes that speculations are useless. The first results of the investigation are expected this week, so let's wait for those before putting our speculations in certain directions.

Didimo, what you say about those passengers is partly right. It feels very strange when you hear that people returned to the aircraft to get their personal belongings, but keep in mind that these people just had a major accident and may be psychologically hurt. It's a fact that people attach a lot of value to minor things when they just had an accident. This looks very strange to the outside world.

[EHM-0005 Maarten]

Today, a prelimenary report was released by the Dutch Transportation Safety Board with their first conclusions. You can find it here below. I made the most important parts extra bold.

Today 4 March 2009 the Safety investigation board issues a warning for the aircraft manufacturer Boeing and its first findings about the terrible accident with the Boeing 737/800 of Turkish Airlines.

In this accident nine people dies (5 passengers and 4 crew) and 80 passengers were injured, of which 28 injured are still in several hospitals.

The aircraft was en route from Istanbul to Schiphol (on Wednesday 25 February 2009) and was expected to land on Schiphol at 10.40 hours.
The Boeing had a normal flight, during which until before the approach no problems have occurred.

In the cockpit there were three persons, the captain, who was seated on the left. To the right a first officer was seated, for whom this was a training flight. (The first officer had all the permits) In addition there was an extra first officer seated in the centre of the cockpit.

The crew contacted the ATC (Amsterdam Radar) at 10.04 hours and is transferred at 10.14 hours – before the landing- to Schiphol tower. The tower clears the Boeing to land on the Polderbaan 18R.
De Polderbaan is approached according to the set procedure and without any delay, in which frame the Boeing is cleared to descend to 2000 feet (about 700 meters) and is cleared to set in for the landing towards the Polderbaan.

This descend is executed with the aid of the automatic pilot, which is a usual practice at Turkish Airlines (this method can be executed by everyone, likewise a manual landing can for that matter).

From the voice recorder and the black box, which are both in the possession of the investigation board, it appears that in the approach at 1950 feet an anomaly occurred.

At an altitude of 1950 feet the left radio-altimeter suddenly (indicated and) passed on a change in altitude to the automatic piloting system. Namely that the aircraft was not positioned at an altitude of 1950 feet but at an altitude of minus 8 feet. This change influenced directly the auto throttle system with which more or less power is given during the approach.

The radio altimeter normally measures very precisely in which altitude an aircraft is positioned in relation to the ground and can register this from 2500 feet downwards. As has been said, the left radio altimeter is of great importance for giving the right power in case of an automated landing. A Boeing is equipped with two radio altimeters, a left and a right one. From the black box it shows that this anomaly occurred only in the left radio altimeter.

From the voice recorder it shows that the malfunctioning of the left radio altimeter has been signalled to the crew (namely via the warning signal "landing gear should be put down"). From the preliminary data it shows that this signal was not perceived as a problem.

Because of this sudden change, in reality the aircraft has responded as if it were at a height of a few meters above the Polderbaan, by closing the engine power.

It appeared as if the automate – with retarded engines – was in the last stage of flight.

As a result the aircraft lost speed.

In first instance the crew did not respond to this development.

Because of the loss of speed the aircraft arrived at it its minimum flying speed (stall situation) causing warning signals (shaking of the control column at a height of 150 feet).

From the black box it shows that then power was given again immediately. However, for the reinstatement of flight this came too late, the aircraft was too low with the result that the Boeing crash 1 kilometer short of the runway.

From the black box – which can record 25 hours of flight- in this case for this aircraft this consisted of 8 different flights – this particular problem had occurred twice before in a same situation before landing.

The aircraft touched the ground on its tail in first instance and subsequently with its landing gear.
The forward velocity at this impact was around 175 km per hour.
And an airplane at this weight should normally have a landing speed of 260 km per hour.

Because of the agricultural land, which consisted of wet soaked clay, the aircraft was arrested quickly (after about 150 m).

Because of the fall and the braking effect of the ground, the aircraft broke into two parts, the tail section got detached and the aircraft split in the area of the business class section.

The landing gear was sheared off, as is intended by design. This also goes for the two engines.
Because of the full power and the abrupt breaking action both engines were projectiled forward for another 250 meter.

Most of the deadly victims were seated at the split in the business class section and the three crew members in the cockpit deceased as a result of the enormous forces of the breaking action, which also resulted from the stuck nose wheel and the forward pressure of the aircraft.
The parts around the wings have remained in tact mostly.

On board were 127 passengers and 7 crew, of which until now there are still 28 in hospitals.

The investigation of the OVV will from now onwards be fully concentrating on the functioning of the radio altimeters and the coupling towards the automatic throttle system (automatic piloting system).

The weather conditions, in particular the view because of the low cloud base and the fog, have probably contributed to the fact that at the height in which the lowering for approach was started, the Polderbaan was not yet very well visible.

In its investigation the OVV is assisted by the following organisations in order to learn:

The National Transport Safety Board,
Bureau d'Enquettes et d'Analyse (BEA)
Aviation Accident Investigation Branch (AAIB)
Directorate General of Civil Aviation (Turkish State Aviation Service DGCA)
Boieing
Turkish Airlines
The engine manufacturer, CFM
The Inspection for Transport (IVW)
Federal Aviation Agency (FAA, US)
Dutch Association of Airline Pilots
Dutch Association of Cabin Crew

Internationally, both by the ICAO and by the European Union, it is stipulated that parties concerned can be part of the investigation by the Board (Partysystem).

However, the Board is leading the investigation and has the responsibility for it.

For its investigation the Board has received many data from the Public Prosecutor.

In addition many police organisations have contributed in terms of content. The Corps of National Police Services (KLPD), in particular all staff of the National team of forensic detection, responsible for forensic investigation at the accident site, the Aviation police amongst others for making all aerial photographs and the National Transport Assistance Team which assisted the Board amongst others with measurings at the accident site.

Also the Public Prosecutor has confiscated/impounded the aircraft, as a result of which the guarding of the aircraft fully laid with the Public Prosecutor.
For that police personnel from all over the country were deployed.
We are very grateful for their outstanding and careful way of working and the guarding of the aircraft.

There has been a difference of opinion about the use of the data from the cockpit (voice recorder and flightdata recorder (black box).
However, according to Dutch law the Public Prosecutor can only have access to these data in case of hostage taking, terrorism, murder or manslaughter.

In such circumstances the Board is legally obliged to hand over these data to the Public Prosecutor.

In principle at the scene of the accident two investigations are ongoing:
The criminal investigation; the investigation into criminal fact and in relation to that into answering the question of guilt.
The independent investigation. This investigation is fully focussed on what has happened and to learn lessons from that.


Between the two investigations there is a field of tension. In the frame of the criminal investigation one is entitled to remain silent. No one has to contribute to his or her conviction. In the independent investigation one wants to stimulate that everything is said.

For this reason the reports of the Board are not allowed as evidence in legal disputes.

From today onwards the investigation of the Board is focussed on two subjects:

The technical investigation is directed to the functioning of the automatic pilot, the automatic throttle system and the coupling with/towards the radio-altimeter. <this is pursued with the same parties involved>.
Next to the technical investigation, the investigation is also focussing on crisis management. How was the disaster dealt with and what can be learnt from that.
In this investigation also attention will be paid to the passenger list.

The recovery of the wreckage will probably take place at the end of this week.
For – possible- further research the aircraft will be transported to another location.

It is the opinion of the Board that extra attention is necessary for the functioning of the radio altimeter when using the automatic pilot and the auto throttle. The Board has issued a warning to Boeing in which extra attention is requested for a part of a manual of the Boeing 737, in which it is said that in case the radio altimeter(s) is/are not functioning, the automatic pilot and auto throttles coupled to that can not be used for approach and landing. The Board has suggested Boeing to investigate whether this procedure should also be applied during the (red: other parts of) the flight.

[EHM-2097 Andrei]

For a preliminary report, it looks to me like it explains a lot of things. This seems consistent with the little bits of information that made their way to the media up to now (like the contradiction between "falling down from the sky" and "full throttled engines").

And it looks also like a reminder that the automatic pilot is called a pilot while in fact it is... you know, just a bunch of chips and wires.

Andrei

[EHM-2155 Mariano]

Does anyone agree that pilots are becoming too technologically dependent? What was the F/O gonna learn, if he was on training, by letting the autopilot do the landing?
If it was a fine day, why not fly it in manually? This wouldnt have happened.
Also wouldnt if someone had noticed this anomaly the two times it happened before...
What a sad avoidable accident... Unfortunately this is how we learn.

[EHM-2387 Eric-Jan]

As I understand, the F/O needed this autoland to complete his type rating. So that would be why they performed an autoland.

Another thing: the RADIO-atlimeter only presents a value to the automated systems (autothrottle, auto callout, if equiped). The (pressure) altimeter did not jump values, so the readout in the cockpit would remain 1950 ft minus about 750 foot per minute (acc. Google Earth path) on both screens. Just as the pilots would have expected to see. There are 2 radio-altimeters on board, of which only the left one provides values for the autothrottle system.

So if you (as a pilot) are observing what all happens or not during autoland, and you see all systems trying to correct an initially too high approach, which then results in a slightly too low approach, when do you start to intervene with the autoland procedure? Right, when you realise that the system is not going to recover the too low approach. By that time, the stall warnings just about kick in!
This is exactly what seems to have happened, if I read the evedence well.

Sadly, when the crew intervened, it was already too late to spool up the turbines and create enough thrust to regain speed and altitude. So all that remained was to pitch up, and hope to delay contact with the gound as long as possible. Thus bleeding off as much forward speed as possible before impact.

There are a couple of technical opportunities for improvement I can think of to help prevent this from happening in the future:
- a clearer warning that the radio-altimeter gives an abnormal value (calculated from value difference over last second, or percentage difference between the two readouts). Something about "landing gear needs to go down" does not directly associate with a wrong altitude readout of a gauge you don't see the readout of...
- average the readout of the two radio-altimeters to come to a value to present to the autothrottle logic
- have three radio-altimeters, and have some logic decide or calculate a value
Last two are common in redundant systems design, so I was a bit surprised to read that the AT system only got values form one of two sensors. I'm sure Boeing engineers will propose such an improvement in the near future.

With a clearer warning, chances are that a crew will pick up on it. It might (and now I start speculating here) be that on the previous occasions when this happened, the crews did not report it in the flight log (because they did not realise they were issued a warinig of such severity?), or that the airline did not pick up on those reports with corrective maintanance, or the jumping readout could be a structural design issue. Any three of these would unavoidably lead to a similar event happening at some time.


I don't think there should be anyone blaming anyone for this accident to have happened. It's just a sad culmination of factors that lead to an unfortunate event. That pretty much defines an accident.

My thoughts and sympathies are with those that lost their lives, their loved ones, and those that got injured (physically and/ or mentally).