does that mean that SAS and DLC ( & YD) remained active (or could remain if so commanded) after AP was disconnected as for instance during a manual approach?
DLC was also full time, either manual or autoflight, and was initiated when the flap handle passed the 30 degree position.
411A is right but there is one more requirement is needed: DLC is active anytime aircraft was in in the landing configuration: 2 of the 3 engines are less than full power and the flaps greater than 30 degrees.
The DLC system can be shut off by unlatching the DLC/AUTO SPOILER switch light on the pilots overhead panel. However, if the switch was unlatched the pilot would have to manualy deploy the spoilers, if required, after touchdown.
Seems I remember a problem with the "S-ducting" that routed air to the center engine. There were some fiberglass fittings that could break away and find themselves going into the engine? Caused some inflight shutdowns?
The S-Duct was made entirely of aluminum (2024-T3 and 7075-T6) no fiberglass. However there was acoustic material on the engine (just if front of the fan) this would disbond at times and be ingested by the engine. This acustic material was on all RB-211's not just the TriStars No. 2 engine.