(10 years on CFM-powered A320, thereafter mixed fleet)
It takes just under 2 sec from stabilized 50% (OEM procedure) to flex/TO/TOGA. J.L.S. most likely refers to the time needed from 18% ground idle to that 50% N1 stabilized, which once in a blue year varies just wildly.
The usual suspects: Dual or singular combustor (different engines), uneven use (asymmetrical thrust taxi), engine state (EGT margins), and a little crosswind seem to play a role. Waiting those 3 seconds for the slower engine to catch up (to 50%) feels like an eternity.
So 3+2 on one, 3+3+2 on the other.
Definitely saw that couple of times, and when the other person didn't, much screaming ensued.
Last edited by FlightDetent; 11th February 2023 at 18:55.