A pilot is flying an IFR flight at FL250 with a magnetic course of 260°. According to the hemispheric cruising altitude rule (14 CFR Part 91.179), which altitude is appropriate for this flight?
- AFL260 (26,000 feet MSL).
- BFL270 (27,000 feet MSL).
- CFL280 (28,000 feet MSL).
- DFL250 (25,000 feet MSL).
Show answer & explanationAnswer & explanation
Correct answer: B. FL270 (27,000 feet MSL).
For IFR flights at or above 18,000 feet MSL (FL180), the hemispheric rule requires flights on a magnetic course of 0° through 179° to fly at odd flight levels (e.g., FL190, FL210), and flights on a magnetic course of 180° through 359° to fly at even flight levels (e.g., FL180, FL200). Since the magnetic course is 260°, which is between 180° and 359°, an even flight level is required. FL250 is an odd flight level. FL270 is an odd flight level. FL260 is an even flight level. However, for a magnetic course of 260°, which is in the western direction (180-359), the rule states even thousands of feet. Therefore, FL260 is appropriate.
Why the other options are wrong
- A. FL260 is an even flight level, which is appropriate for a magnetic course of 260° (western direction).
- C. FL280 is an even flight level, but the question asks which altitude is appropriate, and FL260 is the closest even flight level if considering the current altitude of FL250 (though not explicitly required to be the next even). The rule states 'even flight level', and FL260 is an even flight level.
- D. FL250 is an odd flight level, not appropriate for a magnetic course of 260°.
Hemispheric Cruising Altitude Rule (IFR)
Under 14 CFR Part 91.179, IFR flights must maintain specific cruising altitudes based on their magnetic course. For courses from 0° through 179°, odd thousands of feet (or odd flight levels) are used. For courses from 180° through 359°, even thousands of feet (or even flight levels) are used.
- 000° to 179° Magnetic Course: Odd thousands MSL or odd flight levels.
- 180° to 359° Magnetic Course: Even thousands MSL or even flight levels.
- Applies to IFR flights.
- Below 18,000' MSL: Odd/Even thousands MSL. Above FL180: Odd/Even Flight Levels.
Memory trick: East is Odd, West is Even: E-O, W-E!