FAA Instrument Rating Airplane (IRA)IFR Procedures and ChartsMedium
A pilot is flying a published DME arc as part of an instrument approach. The arc has a radius of 12 DME, and the chart specifies a lead radial to begin the turn from the arc onto the final approach course. Why is the lead radial necessary?
- ATo indicate the missed approach point along the arc
- BTo ensure the pilot stays exactly on the 12 DME arc throughout the turn
- CTo compensate for the aircraft's turning radius so it rolls out precisely on the final approach course
- DTo provide a mandatory position report to ATC before intercepting final
Show answer & explanationAnswer & explanation
Correct answer: C. To compensate for the aircraft's turning radius so it rolls out precisely on the final approach course
The lead radial marks the point at which a turn should be started, prior to reaching the intersection of the arc and the final approach course, to allow for the aircraft's turn radius so it rolls out on course rather than overshooting.
Why the other options are wrong
- A. Missed approach points are defined separately from lead radials on arcs
- B. The lead radial signals departure from the arc, not continuation on it
- D. Lead radials are navigational references, not communication requirements
DME Arc Lead Radial
A charted radial on a DME arc approach indicating where a pilot should begin turning from the arc onto the final approach course to compensate for turn radius.
- Typically begin turn 2-5° before reaching the course radial depending on speed/bank
- Prevents overshooting the final approach course
- Found on approach charts using DME arc transitions
Memory trick: Lead early, roll out neatly onto final.