British Airways and NATS intend to implement the third phase of MLS operations at LHR. This reduces the spacing between aircraft flying an MLS approach in LVPs by one mile. As part of the rollout, ATC needs to be confident that MLS-equipped aeroplanes will, in practice, fly MLS approaches.
In particular, the Heathrow Directors (who set the arrival spacing) have no indication of MLS capability on their flight progress strips. Hence, without asking, they do not know if an aeroplane is MLS-capable unless or until the crew asks for an MLS approach, and even if so equipped they cannot be confident that the planned spacing will be possible between the aircraft.
All flight crew and ATC need to have shared confidence that all MLS-equipped aircraft can and will fly an MLS in all weathers so that it becomes a fully ‘normal’ procedure. If ATC cannot be confident that that all MLS-equipped aircraft will fly the MLS without individual requests, they will not be able to apply the reduced spacing on final approach that only MLS can safely support.