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This question came to my mind when I saw the Emirates B773 (Dubai on Aug 3rd 2016) accident.

I saw a couple of 777 cockpit videos and I saw that autothrottle (A/T) is widely used during landing and they just turning the autothrottle knob left or right to set the speed. Question. Does anyone know what mode is the 777 in right after touch down? Especially the A/T? As far as I know the aircraft goes to roll out mode (whatever that means). Lets assume they initiated a go around right after touch down for whatever reason. The pilot assisting just turned the knob again (as usual) instead of pushing TO/GA but it was ineffective as A/T was disengaged automatically. So yes, it is guessing without any knowledge so lets focus on my question. What mode is the A/T in right after touch down?

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During the flare somewhere between 25' and 50', the A/T retards the thrust levers to idle. They remain in idle mode until reverse thrust is selected which automatically disconnects the A/T.

In the case of Emirates 521, eyewitnesses observed the aircraft do a bounced landing and then attempt a go-around reaching a max altitude of about 150'.

Because the aircraft had touched down, it can be assumed the A/T had automatically gone to idle, and it appears the thrust levers were not manually advanced. The aircraft then settled back on the runway as the gear was being retracted.

More speculation here: Emirates B777 crash was accident waiting to happen

a pilot colleague observed exactly what happened as he was there, waiting in his aircraft to cross runway 12L. The B777 bounced and began a go-around. The aircraft reached about 150 feet (45 metres) with its landing gear retracting, then began to sink to the runway.

This suggests that the pilots had initiated a go-around as they had been trained to do and had practised hundreds of times in simulators, but the engines failed to respond in time to the pilot-commanded thrust. Why?

Bounces are not uncommon. They happen to all pilots occasionally. What was different with the Emirates B777 bounce was that the pilot elected to go around. This should not have been a problem as pilots are trained to apply power, pitch up (raise the nose) and climb away. However pilots are not really trained for go-arounds after a bounce; we practise go-arounds from a low approach attitude.

Modern jets have autothrottles as part of the autoflight system. They have small TOGA (take off/go-around) switches on the throttle levers they click to command autothrottles to control the engines, to deliver the required thrust. Pilots do not physically push up the levers by themselves but trust the autothrottles to do that, although it is common to rest your hand on the top of the levers. So, on a go-around, all the pilot does is click the TOGA switches, pull back on the control column to raise the nose and — when the other pilot, after observing positive climb, announces it — calls “gear up” and away we go!

But in the Dubai case, because the wheels had touched the runway, the landing gear sensors told the autoflight system computers that the aircraft was landed. So when the pilot clicked TOGA, the computers — without him initially realising it — inhibited TOGA as part of their design protocols and refused to spool up the engines as the pilot commanded.

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  • $\begingroup$ thanks the answer it is really great to talk to a real 777 pilot. I don't have PPL yet so I am not a pilot but from my perspective I would rather like to have a full control during landing, including thrust. How do you feel about having A/T engaged all the time (if it is engaged all the time)? Do you like the idea? $\endgroup$ – Bela Vizer Aug 9 '16 at 11:50
  • $\begingroup$ I like having A/T on all the time. It is normal SOP to always have it on but it can be disconnected anytime by a small thumb switch on either Thrust Lever. At my airline we keep one hand on the thrust levers at all times when below 1000' above ground. When I do a go around, I always advance the trust levers manually and say "Go Around, Flaps 20", and then I press the TOGA switch after the Thrust Levers are well forward. $\endgroup$ – Mike Sowsun Aug 9 '16 at 13:49
  • $\begingroup$ Do you have to hold the levers forward for a certain amount of time? On the Amsterdam 737 crash the plane went into flare mode unexpectedly. They pushed the levers forward but since they didn't hold them there long enough the A/T put them back to idle $\endgroup$ – TomMcW Aug 9 '16 at 20:43
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    $\begingroup$ It should be mentioned that this describes Boeing logic. Airbus logic is very different (the A/T does not move the levers there, TO/GA does not have a switch, but is selected by moving the levers full forward and the pilots must move the levers to IDLE manually to disengage the A/T, otherwise it remains on even on the ground). $\endgroup$ – Jan Hudec Aug 10 '16 at 17:54
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    $\begingroup$ Yeah this has always seemed like a flaw in the Boeing system to me - touching down shouldn't disable the TOGA button, and I can't understand the logic of it. A pilot pressing TOGA expects the engines to spool up, and at an absolute minimum, pushing that button should not quietly do nothing: at least alert the pilot that nothing is going to happen. $\endgroup$ – Jon Story Aug 22 '16 at 15:20

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