Thanks to all for a wonderful thread. I flew as pax on Tridents many, many years ago when studying in the UK even though international flights in those days cost nearly a month's pay. One episode that stuck in my mind is a flight from Edinburgh when, shortly after starting the take-off roll, the plane braked hard and taxied rapidly to the other end of the runway.... whereupon it did a neat 180 and took off in the opposite direction. No explanation was forthcoming from the flight-deck although there was considerable buzz in the cabin!
Anyway back to autothrottles, just for fun I coded up a pid controller for David Maltby's sim that can couple independently to the three throttles - there's a screenshot at
http://img822.imageshack.us/img822/9435/t3ath.jpg . It is certainly odd seeing only two throttles moving, particularly in the descent when throttles 1 and 3 are near idle and the middle lever sticks up like a... sore thumb, I suppose.
One thing I've noted is that there isn't much reserve power with a Trident 3 on the glideslope at MLW with full flaps and gear down, and engine 2 set at 11200rpm. If it gets below the glideslope (thanks to FS's fickle wind system - DM's autoland does a superb job) it is hard put to climb back without adding power to No. 2. I suppose that's why the engine 2 setting on the T3 is higher than the T2, but even so it appears quite marginal.
Also, while engine 2 appears to be under-producing on the approach, it seems to produce too much thrust for the descent and the plane doesn't slow down easily at all, especially when clean.
Perhaps an ex-Trident pilot can comment on whether these are artefacts of the sim or whether the real planes were like this.