FAA Instrument Rating Airplane (IRA)IFR Procedures and ChartsHard
A pilot is planning an IFR flight over mountainous terrain where no MEA or MOCA is prescribed for a segment of the route. What is the minimum altitude the pilot must maintain, assuming the aircraft is not on a published route segment?
- A1,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course.
- B1,000 feet above the highest obstacle within a horizontal distance of 5 nautical miles from the course.
- C2,000 feet above the highest obstacle within a horizontal distance of 5 nautical miles from the course.
- D2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course.
Show answer & explanationAnswer & explanation
Correct answer: D. 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course.
According to 14 CFR Part 91.177(a)(2), over mountainous areas, the minimum IFR altitude is 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course.
Why the other options are wrong
- A. This is incorrect; 1,000 feet is for non-mountainous terrain.
- B. Both the altitude and distance are incorrect for mountainous terrain.
- C. This is incorrect; 5 nautical miles is not the specified distance.
Minimum IFR Altitudes (Off-Route)
When not on a published route or when no MEA/MOCA is prescribed, specific minimum IFR altitudes are required based on terrain type.
- Part 91.177 governs minimum IFR altitudes.
- Non-mountainous: 1,000 ft above obstacles within 4 NM.
- Mountainous: 2,000 ft above obstacles within 4 NM.
- These are absolute minimums for obstacle clearance.
Memory trick: Off-route, always clear the peaks and trees, 4 miles wide, 1 or 2 thousand high.