lomapaseo,
thank you. I've been reading my MD80 manuals. I was, and am, aware of ART (automatic reserve thrust) and ATR (automatic thrust restoration). Both features have previously been mentioned and put in context by xkoote in post 568 (
permalink). Thanks a lot for that.
Here's what the Manual says about various takeoff power settings:
Reduced thrust (FLEX T.O.): ART off
Normal thrust: ART on
Maximum thrust: ART off
Autothrottles can be used in all three cases.
So, ART can be only be used for "normal" takeoff thrust. The other mechanism, ATR, is always available.
I don't know which thrust setting was used here. A very long runway might indicate FLEX, but high weight, altitude and temperature might have dictated normal thrust.
When the ART system detects a 30% N1 difference, invalid N1 or some other conditions, it actuates, and directly opens a solenoid-operated fuel valve, giving maximum thrust, regardless of thrust lever position.
ATR has different actuation conditions, and if triggered, advanced autothrottles to the Go-Around EPR limit.
Bernd