The RB162 in the Trident 3B was put in place to boost take off performance and in the type's early time in service it was regularly used making the type probably the loudest civil type in the world.
The engine was only used for the initial climb and was shut down after a maximum of five minutes. As time went by the engine was used infrequently, hot/high/heavy departures were the times the boost was used but as a number of the type in BA service were dedicated to internal shuttle flights, the engines were decommissioned (were they actually removed?) and the decommissioning was reportedly completed across the fleet when the 757 took over the longer European routes.