A pilot is planning an IFR flight over mountainous terrain where no MEA or MOCA is prescribed for the intended route. According to 14 CFR Part 91.177, what is the minimum altitude the pilot must maintain?
- A1,500 feet above the highest obstacle within 2 nautical miles horizontally of the course.
- B2,000 feet above the highest obstacle within 5 nautical miles horizontally of the course.
- C2,000 feet above the highest obstacle within 4 nautical miles horizontally of the course.
- D1,000 feet above the highest obstacle within 4 nautical miles horizontally of the course.
Show answer & explanationAnswer & explanation
Correct answer: C. 2,000 feet above the highest obstacle within 4 nautical miles horizontally of the course.
According to 14 CFR Part 91.177(a)(2), for IFR operations over designated mountainous areas, if no MEA or MOCA is prescribed, the minimum altitude is 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown. For non-mountainous areas, it is 1,000 feet above the highest obstacle within 4 nautical miles.
Why the other options are wrong
- A. The altitude is 2,000 feet and the horizontal distance is 4 NM.
- B. The horizontal distance is 4 NM, not 5 NM.
- D. This applies to non-mountainous areas, not mountainous areas.
Minimum IFR Altitudes (Off-Route)
Under 14 CFR Part 91.177, when flying IFR off-route or where no MEA/MOCA is prescribed, pilots must maintain specific minimum altitudes: 1,000 feet above the highest obstacle within 4 NM in non-mountainous areas, and 2,000 feet above the highest obstacle within 4 NM in mountainous areas.
- Non-mountainous: 1,000 ft above highest obstacle within 4 NM.
- Mountainous: 2,000 ft above highest obstacle within 4 NM.
- Applies when no MEA/MOCA is specified.
- Ensures obstacle clearance during IFR flight.
Memory trick: Mountainous 2K, Non-Mountainous 1K, Always 4NM!