FAA Instrument Flight Instructor (FII)IFR Procedures and ApproachesHard
During an ILS approach in IMC, the pilot's glideslope receiver fails just prior to the final approach fix. The approach chart publishes separate ILS and LOC (glideslope-inoperative) minimums. What should the pilot do?
- ADiscontinue the approach and request an ASR approach instead, since glideslope is required for any ILS
- BContinue to the published ILS DA, since the localizer signal remains valid for lateral guidance
- CUse the LOC-only minimums, which include a higher MDA and greater required visibility than the ILS DA
- DDescend to the ILS DA using the marker beacon or a DME fix as a substitute for glideslope guidance
Show answer & explanationAnswer & explanation
Correct answer: C. Use the LOC-only minimums, which include a higher MDA and greater required visibility than the ILS DA
When the glideslope is unusable, the approach reverts to a nonprecision localizer approach, which uses the LOC-only minimums published on the same chart. These minimums have a higher MDA and greater required visibility than the ILS DA because vertical guidance is no longer available.
Why the other options are wrong
- A. An ASR approach requires a separate request and radar service, not automatically substituted for a failed glideslope.
- B. The ILS DA assumes glideslope guidance is available; it cannot be used without it.
- D. Substituting a marker beacon or DME fix for glideslope does not restore the precision DA; the LOC minimums must be used instead.
LOC (Glideslope-Out) Minimums
When the glideslope becomes unusable during an ILS approach, the approach must be flown as a localizer-only nonprecision approach using the higher LOC MDA and increased visibility minimums published on the same chart.
- LOC minimums use MDA instead of DA
- LOC minimums require greater visibility than the full ILS
- Chart typically publishes both ILS and LOC minima in the same minimums block
Memory trick: 'Lose the Slope, Use the LOC line.'