FAA Airline Transport Pilot (ATM)Navigation, Air Traffic Control and ProceduresMedium
An aircraft is flying a published DME arc transition to an instrument approach using VOR/DME. To remain on the arc, which technique should the pilot use?
- AUse a bracketing technique, making small heading changes toward or away from the station as DME distance deviates from the arc, producing a stair-step ground track
- BRely solely on GPS OBS mode and disregard the DME readout entirely
- CFly one continuous standard-rate turn that precisely follows the arc radius from start to finish
- DMaintain a single constant heading throughout the arc and adjust only altitude as needed
Show answer & explanationAnswer & explanation
Correct answer: A. Use a bracketing technique, making small heading changes toward or away from the station as DME distance deviates from the arc, producing a stair-step ground track
Flying a DME arc manually is accomplished by bracketing: making small (about 10-degree) heading corrections toward the station if the DME shows the aircraft outside the arc, and away from the station if inside, producing a stair-step path that approximates the arc.
Why the other options are wrong
- B. Ignoring DME defeats the purpose of the arc procedure, which is defined by distance from the station.
- C. A single continuous turn is impractical without RNAV/autopilot arc capability; manual flying uses small stepped corrections.
- D. A constant heading would cause the aircraft to drift off the arc as the geometry changes.
DME Arc Flying Technique
A method of flying a curved course at a constant distance from a VOR/DME station using small bracketing heading changes.
- Distance deviation of about 0.5 NM triggers a 10-degree correction
- Cross-check bearing pointer/RMI and DME distance together
- Lead the turn onto the inbound course before reaching it
Memory trick: 10 out, 10 in — stair-step your way around the arc.