An unknown feature of the 744 VNAV/VOR auto flight system which triggers GA thrust when the aircraft goes under the MDA, even on manual/FD approach. That Go Around is only identified by a "Thrust Ref" FMA annunciation.
That feature, at that time was unknown by the flightv deck population, including Boeing instructors.
This 'feature' has been known on 75's and 76's for some time now, it's a real gotcha if you're shooting a non-precision approach without a runway waypoint in the FMS database and the missed approach point is past the runway threshold. You get to minimums, see the runway, get an altitude capture and all hell breaks loose unless you immediately set the missed approach altitude in the window. Or, so they tell me.
