Originally Posted by
BugBear
Pardon my perhaps ignorant post, but based on what is known, as I read it....
TCMA CONSTANTLY monitors WoW and the thrust
At a possible RTO, with gear still on runway, the thrust would be closed?
Brakes on, a change of solution? Gotta avoid the overrun ?
Brakes off levers slammed full open ....
Does TCMA act too quickly.?
1) If the crew rejects the takeoff, and pulls the thrust lever to idle,
and then IF one of the engines does not spool down (fast enough),
TCMA will shut it off,
because an engine that's thrusting will not help with stopping,
and it might blow the aircraft sideways off the runway as the aircraft slows and rudder authority is lost.
So that is good!
2) But that did not happen, and the crew now wants to take off anyway (why....?).
PF pushes TO/GA or slams the throttle.
Now the engine is accelerating as commanded.
TCMA does not care about acceleration.
And should you be asking that in this thread? The incident here is a landing, not a take-off.
What may have happened here was
1) engines idle on glide,
2) touchdown, PF starts reversing
3) engines run up, PF undoes reverser and moves throttle to idle
4) maybe, maybe TCMA expects engine to decelerate faster from that than it does
So it's the exact opposite of a RTO, and because the throttle ends up on idle, TCMA can trigger. But on the RRTO, it ends up at full thrust, where TCMA won't trigger.