A dispatcher is preparing for a Part 121 domestic flight in a turbojet airplane. The takeoff alternate airport is required due to weather at the departure airport. Under 14 CFR 121.617, if the takeoff alternate is a two-engine turbojet, what is the maximum distance it can be from the departure airport?
- ANot more than 2 hours from the departure airport at normal cruising speed in still air with one engine inoperative.
- BNot more than 1 hour from the departure airport at normal cruising speed in still air with all engines operating.
- CNot more than 1 hour from the departure airport at normal cruising speed in still air with one engine inoperative.
- DNot more than 3 hours from the departure airport at normal cruising speed in still air with one engine inoperative.
Show answer & explanationAnswer & explanation
Correct answer: C. Not more than 1 hour from the departure airport at normal cruising speed in still air with one engine inoperative.
14 CFR 121.617(b)(1) specifies that a takeoff alternate airport for a two-engine airplane must not be more than 1 hour from the departure airport at normal cruising speed in still air with one engine inoperative. This ensures the aircraft can safely reach an alternate in case of an engine failure shortly after takeoff.
Why the other options are wrong
- A. Two hours is the limit for three-engine airplanes, not two-engine.
- B. The calculation must assume one engine inoperative, not all engines operating, for a two-engine aircraft when determining takeoff alternate distance.
- D. Three hours is the limit for four-engine airplanes, not two-engine.
Takeoff Alternate Requirement (121.617)
Mandates a takeoff alternate airport if weather at the departure airport is below specific minimums, and sets distance limits based on engine count and single-engine performance.
- Required if departure weather is below authorized landing minimums.
- Distance limit varies by number of engines.
- Calculation assumes one engine inoperative.
Memory trick: Takeoff Alternate: 'T' for Takeoff, 'A' for Alternate, 'D' for Distance. 'One' engine out, 'One' hour for a twin.