FAA Airline Transport Pilot (ATM)Regulations (14 CFR 117/121/61)Hard
A dispatcher is planning a Part 121 flight in a twin-engine jet where forecast weather at the departure airport is below the landing minimums that would apply if a return were required. Under 14 CFR 121.617, what is the maximum distance from the departure airport, expressed in flight time, at which a takeoff alternate may be listed for this twin-engine airplane?
- A2 hours at normal cruise speed, one engine inoperative, in still air
- BAny distance, provided sufficient fuel reserves are carried
- C1 hour at normal cruise speed, one engine inoperative, in still air
- D30 minutes at normal cruise speed, all engines operating
Show answer & explanationAnswer & explanation
Correct answer: C. 1 hour at normal cruise speed, one engine inoperative, in still air
Under 14 CFR 121.617, when weather conditions at the departure airport are below the applicable landing minimums, a takeoff alternate must be designated. For a two-engine airplane, the alternate must be within 1 hour of flight time at normal cruise speed in still air with one engine inoperative; three- or four-engine airplanes get a 2-hour allowance.
Why the other options are wrong
- A. 2 hours one-engine-inoperative applies to airplanes with three or more engines, not two-engine airplanes.
- B. An unlimited distance is not permitted; 121.617 sets a specific time-distance limit.
- D. 30 minutes all-engine cruise is not the standard used; the rule specifies one-engine-inoperative time.
Takeoff Alternate (121.617)
When departure weather is below landing minimums, Part 121 requires designation of a takeoff alternate within specified one-engine-inoperative flight time limits.
- Two-engine airplanes: within 1 hour, one engine inoperative, still air
- Three/four-engine airplanes: within 2 hours, one engine inoperative
- Applies only when departure weather is below applicable landing minimums
Memory trick: 'Two engines, one hour; three-plus engines, two hours' — count engines to set the clock.