A pilot is cleared for an ILS approach to Runway 36. The glideslope is captured, and the aircraft is established on the localizer. However, the pilot notices the localizer needle is fluctuating significantly, indicating poor signal quality. What is the most appropriate action?
- ASwitch to LNAV minimums and continue the approach as a non-precision approach.
- BIncrease airspeed to minimize the effect of signal fluctuations.
- CContinue the approach, as glideslope integrity is more critical for an ILS.
- DRequest a vector to another approach or execute a missed approach if unable to maintain localizer guidance.
Show answer & explanationAnswer & explanation
Correct answer: D. Request a vector to another approach or execute a missed approach if unable to maintain localizer guidance.
Both localizer and glideslope are critical for an ILS approach. Significant fluctuation of the localizer needle indicates unreliable lateral guidance. Continuing an approach with unreliable guidance is unsafe. The most appropriate action is to either request a different approach (e.g., a non-precision approach if available and suitable) or execute a missed approach if reliable guidance cannot be maintained.
Why the other options are wrong
- A. Switching to LNAV minimums is not possible for an ILS approach. LNAV is a GPS-based approach type. The pilot could request a different approach, such as a localizer (LOC) approach if published, but not 'LNAV minimums' for an ILS.
- B. Increasing airspeed would likely exacerbate the control issues due to unreliable guidance, not mitigate them.
- C. Both localizer and glideslope integrity are critical for an ILS. Poor localizer signal renders the ILS unusable.
ILS Localizer Unreliability
During an ILS approach, significant fluctuation or unreliability of the localizer signal indicates a loss of reliable lateral guidance. In such a situation, the pilot cannot continue the ILS approach and must either request an alternate approach or execute a missed approach.
- Localizer and glideslope are equally critical for ILS.
- Unreliable localizer means ILS approach cannot be continued.
- Pilot must request alternate approach or go missed.
Memory trick: Localizer Wiggles? Go Around or Change.