A pilot flying an ILS approach engages the autopilot in HDG mode to intercept the localizer course, then arms APR (approach) mode before reaching the course. What will the autopilot do as the aircraft nears the localizer centerline?
- ARemain in HDG mode until the localizer signal is captured, then automatically transition to APR mode and begin tracking the localizer and glideslope
- BImmediately turn the aircraft to intercept the localizer at a fixed 90° angle regardless of the armed heading
- CImmediately disconnect HDG mode and revert to wings-level flight until the pilot manually re-engages APR
- DContinue flying the selected heading indefinitely and ignore the localizer signal until APR is manually re-armed
Show answer & explanationAnswer & explanation
Correct answer: A. Remain in HDG mode until the localizer signal is captured, then automatically transition to APR mode and begin tracking the localizer and glideslope
When APR mode is armed, the autopilot continues flying the selected heading (or NAV track) until the localizer and glideslope signals reach capture criteria, at which point it automatically switches from armed to active APR mode and begins tracking both courses. This sequenced arm-then-capture logic is standard in most integrated autopilot/flight director systems.
Why the other options are wrong
- B. The intercept angle is set by the pilot's selected heading, not fixed at 90°.
- C. Arming APR does not disconnect HDG mode prematurely.
- D. Arming APR specifically enables automatic capture, not indefinite ignoring of the signal.
Autopilot Mode Arming and Capture
Arming a mode (e.g., APR, ALT) prepares the autopilot to automatically transition from an active mode (like HDG) to the armed mode once capture criteria are met, without pilot intervention.
- Armed mode shows on the flight mode annunciator (FMA) until capture
- Capture criteria are based on signal deviation and closure rate
- After capture, the mode annunciation changes from armed to active (e.g., LOC/GS)
Memory trick: Arm it, fly toward it, and it grabs the beam automatically.