FAA Commercial Pilot Airplane (CAX)Navigation and Flight PlanningMedium
A pilot is flying a published 10 DME arc around a VORTAC. While maintaining the arc, the DME reading decreases to 9.5 NM without an intentional course change. Using the standard arc-correction technique, what should the pilot do to return to the 10 DME arc?
- AReduce airspeed until the DME reading corrects itself
- BTurn 20° away from the station until the DME reads 10.0 NM, then resume the arc heading
- CTurn 20° toward the station until the DME reads 10.0 NM, then resume the arc heading
- DIncrease airspeed until the DME reading corrects itself
Show answer & explanationAnswer & explanation
Correct answer: B. Turn 20° away from the station until the DME reads 10.0 NM, then resume the arc heading
On a DME arc, a decreasing distance means the aircraft has drifted inside the arc, closer to the station. The standard correction is to turn 20° away from the station until the correct distance is regained, then resume the tangential arc heading.
Why the other options are wrong
- A. Reducing airspeed does not address the geometric drift toward the station.
- C. Turning toward the station would decrease distance further, making the error worse.
- D. Airspeed changes do not correct lateral drift relative to the arc.
DME Arc Correction
A DME arc is flown by maintaining a constant distance from a VORTAC; drift is corrected using small heading changes toward or away from the station based on DME trend.
- Decreasing DME means aircraft is drifting inside the arc
- Standard correction is a 20° turn away from the station to regain distance
- Once corrected, resume the tangential heading for the arc
Memory trick: Too close? Turn away and toss the drift