Originally Posted by
J.L.Seagull
Yes, regular CFM engines on the A320. The FADEC does what it needs to on its own engine. There's no differential thrust protection function that compares thrust between engines, so from time to time you do see one engine taking 2 or 3 seconds longer to spool up. Can be unnerving if caught off guard, esp for the inexperienced guys
Seriously? You had CFM56-5 engines that took "2 or 3 seconds longer to spool up"
from a stabilized 50% N1 to takeoff N1? IF that really happened, one of those engines was seriously sick. Plus, it would never pass the 8 second go-around accel requirement. Heck, it shouldn't take the engine much longer than "2 or 3 seconds" to spool up from 50% to Takeoff N1 - forget having that much engine-to-engine variation.
From ground idle? Sure - as noted small engine variations can cause them to run on different idle schedules - with varying off-idle acceleration characteristics. That's why the procedures tell you to advance the levers and stabilize prior to advancing to takeoff - if you don't do that (or don't do it properly) there can be big acceleration differences. RTOs are not uncommon due to asymmetric thrust and the resultant yaw overwhelming the ability to counteract with rudder/steering if the stabilization procedure isn't followed properly.
Used to occasionally get FDR data from asymmetric thrust caused RTOs - pilots always said they'd followed procedure and stabilized (IIRC, Boeing procedures call for 40% N1), but a simple look at the data would reveal that wasn't the case. Typically, they'd advance the levers to a midpoint on the quadrant - then go to takeoff when the
first engine hit the target while the second engine lagged significantly.