Definition
An instrument approach procedure that uses an LDA — a localizer-type signal that is not aligned with the runway centerline — and is monitored by Precision Runway Monitor (PRM) radar to permit simultaneous approaches to closely spaced parallel runways. The LDA PRM approach is flown when independent close parallel operations are in progress, with high-update-rate radar surveillance ensuring safe separation between aircraft on the adjacent approach.
Plain English
A special approach used at airports with two runways that sit very close together side by side. One runway uses an angled approach path (LDA) instead of a straight-in one, and a fast-updating radar watches both approaches at once so aircraft can land on both runways at the same time without bumping into each other.
Context Anchor
Seen on instrument approach charts and in air traffic control clearances at airports approved for PRM operations, especially where simultaneous arrivals use close parallel runways.
Derivation
Localizer comes from 'localize' — to pinpoint a position. The 'Type Directional Aid' wording signals that the signal works like a localizer but is not aligned with the runway, so it directs the aircraft toward the runway from an offset angle. 'Precision Runway Monitor' describes the high-update radar that precisely watches aircraft on the parallel approaches.
Why Pilots Care
Increases airport landing capacity during peak periods while maintaining safe separation between aircraft on parallel runways.
Grounding Statement
Picture two aircraft approaching parallel runways at the same time: the LDA guides one aircraft’s final course, and PRM lets controllers quickly spot and correct unsafe drift.
Intuition Check
Do not assume precision means the approach is automatically more exact for the pilot to fly. In this term, precision mainly refers to the close runway monitoring used by air traffic control.
Example Sentence 1
Before accepting the LDA PRM approach to runway 28R, the crew reviewed the breakout procedures and confirmed both pilots had completed the required PRM training.
Example Sentence 2
ATC cleared the flight for the LDA PRM approach and assigned a PRM monitor frequency for the parallel runway.