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Imanual

Automation and the Autothrottle

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So there I was ... 134 knots on runway 31R, autothrottle disconnect engaged, thrust levers idle (on my end), and spoilers ground flight engaged but I am not slowing fast enough. Autobrake was enabled minimum but I don't recall any braking occuring. Slowing down; 120, 115 but via friction with the runway only. My eyes glance up to see the end of the runway going by and now I am high speed on the taxiway heading quickly into a jet blast fence at the taxiway turn.

 

My mind flashes back to the approach: Autoflight disengaged and autothrottle giving me trouble. Prior to my predicament the aircraft was on the approach in dual land configuration. Some short time later the aircraft was in flare but the autothrottle had not disengaged and the aircraft simply flew down the runway just a few feet high. It was too late for an attempt to land and stop in time so I disconnected the autoflight and wanted to fly right traffic to perform a visual approach. The throttle was clamped in alpha protection and attempts to disconnect the autothrottle for climb power turned into a struggle between the aircraft and I and never was I confident the throttle is in my control only.

 

Once again, on final approach, hand flying the guidance when my wheels touch, ground spoilers activate, and, even though disconnected, the autothrottle again clamped for alpha protection and would not idle out for application of reverse thrust. I was a heavy aircraft with Vref 185 knots so, needless to say, when the throttle finally obeyed and relinquished, I had gone through the blast fence and was headed for a hangar which I unfortunately perforated at about 125 knots.

 

I can't explain this behavior. I hit, several times, autothrottle disconnect and while rumbling down the runway would glance at it to observe it deviating to near full power then back to idle and them to medium power. During my hand flown pattern around to perform a manual landing, gusty winds and no FSUIPC wind smoothing option set had the airspeed loose 25 knots and I reached alpha whereby the flight computer commanded movement of the throttles and would mot relinquish control even when commanded to. I feel at this point I will have to take control from the aircraft on final approach to avoid this ever happening again.

 

Imanual


Imanual Sims

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So there I was ... 134 knots on runway 31R, autothrottle disconnect engaged, thrust levers idle (on my end), and spoilers ground flight engaged but I am not slowing fast enough. Autobrake was enabled minimum but I don't recall any braking occuring

 

Did you try using reverse thrust ?

 

Autobrakes may disengage prematurely if you have toe brake pedals and you touch them, or have not calibrated with sufficient null zone.


 

 


The throttle was clamped in alpha protection and attempts to disconnect the autothrottle for climb power turned into a struggle

 

In this situation you press the G/A button for G/A thrust.


 

 


even though disconnected, the autothrottle again clamped for alpha protection

 

This would indicate your approach was flown too slow so that alpha protection kicked in. Alpha protection will operate even if A/T is disengaged.


 

 


I hit, several times, autothrottle disconnect and while rumbling down the runway would glance at it to observe it deviating to near full power then back to idle and them to medium power.

 

This would seem to indicate the aircraft did not recognise it was on the ground ?  Try at another airport.


Peter Schluter

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