Accident recreation.

[Mariano]

Talk about an accident being the summation of events...


http://www.tarpa.com/fdo-bcy/turkish2009.html

Mariano

[Avi]

Very interesting.
Still there is no answer to the question why 3 pilots didn't see the speed "falling" and the throttles remain in idle.
I guess there will never be an answer for that one.

Thanks,

[Hardy Heinlin]

General question: Aside from some switches, the autopilot can also be disengaged by moving the yoke against the autopilot intended direction (ca 15 kg force difference or so) -- unlike on the autothrottle: it remains engaged when the throttles are moved by the pilot. I see this has advantages when descending with FLCH or VNAV, but why is it so in SPD mode?


|-|

[MEade]

On approach, AT is in SPD mode (or SPDt for the plane I fly). If wind conditions are steady, the AT computer can maintain the selected speed very well with no intervention from the flight crew. If wind conditions are gusty, the AT computer is very slow on the thrust levers, and will have trouble maintaining the speed, so being able to manually intervene without disconnecting the levers is very useful in giving the AT a helping hand.

I hope that answers the question

[Lasse]

When in FLCH and VNAV the autotrottle is on ARM mode... So  if the pilot feels for adding thrust then it will just change the ROD and since its in ARM mode then the autothrottle computer is not following any FCC input and leave the throttle at the position.
During CAT II/III the FCC will follow GS and the MCP set Vref or ajusted Vref speed. The pilot may at all times advance the trust levers hence overwrite the system, since the pilot have "told" the FCC to follow the SPD then ofcause it will do so...
In this case the RA showed below 27' RA therefore the throttes are commanded in RETARD as if it was initiating the flare...

Basically it comes down right automatisation techniq to look at the FMA! Look there to see whats going on! Not at the small lights on the MCP panel...!

If gusty wind the 737 has a gust logic that will have the autothrottles move at different speeds. If the speed increases then they will retart slowly... If the speed drops they will add thrust fast giving it fine speed control in gusty Wx.

/L

[Hardy Heinlin]

Refering to this accident, if the manual intervention on the throttles would have disengaged the A/T (just like pushing the A/T disengage switches), then later on the following FLARE mode wouldn't have re-engaged the A/T, right?

I see, keeping the A/T engaged during manual intervention is useful during normal ops, but it may be deadly in those other cases.


Regards,

|-|ardy

[Jeroen Hoppenbrouwers]

In this specific case they did not need A/T -- they needed every pound they could get. I am a bit surprised that there was no near-instinctive TOGA TOGA TOGA button push included when the F/O went to full thrust at stick shaker. Possibly during those fatal five seconds everybody still had "continue approach" in mind, instead of "saving the day".


Jeroen

[Jeroen Hoppenbrouwers]

PS. Don't forget this final report:
http://www.onderzoeksraad.nl/docs/rapporten/Rapport_TA_ENG_web.pdf

[MEade]

With the company I work for, and I'm sure all companies would be somewhat the same, we must guard the controls below 2500ft AGL. This is to ensure you are always in the loop as to what the automation is commanding. That is, you can feel what the AT system is doing, you can feel the controls moving, and you are ready to push TOGA if you need to, or push the AP disconnect button. I can attest to this being very important in automated aircraft. We were flying a coupled approach (VMC) recently, had an aircraft cross the glideslope antenna which caused the GS signal to move full deflection up. Solution was to push the TCS button and handfly the aircraft until the GS area was clear. Had we not been guarding the controls, response would have been much slower, and would have possibly caused a very unwanted situation (very nose high attitude, slow AT response...)

I must add that in the last week, and as a result of the Turkish airlines incident, our company now says if the RadAlt's on the aircraft are unserviceable, then the recommendation is to now fly the approaches with the AT system disengaged.