FAA Aircraft Dispatcher (ADX)Flight Planning and PerformanceEasy
A Part 121 dispatcher is releasing a two-engine turbojet under 14 CFR 121.617. The weather at the departure airport is below the landing minimums authorized for that airport. What is the maximum distance the takeoff alternate may be located from the departure airport, based on one-engine-inoperative cruising speed in still air?
- A30 minutes
- B3 hours
- C1 hour
- D2 hours
Show answer & explanationAnswer & explanation
Correct answer: C. 1 hour
Under 14 CFR 121.617, when weather at the departure airport is below landing minimums, a takeoff alternate must be designated. For two-engine airplanes, the alternate must be within 1 hour of flying time at one-engine-inoperative cruising speed in still air; three- and four-engine airplanes are allowed 2 hours.
Why the other options are wrong
- A. 30 minutes is not a regulatory limit under 121.617.
- B. 3 hours exceeds any 121.617 limit.
- D. 2 hours applies to three- and four-engine airplanes, not two-engine.
Takeoff Alternate (121.617)
A takeoff alternate is required when departure weather is below landing minimums, and must be within a specified diversion time based on engine number.
- 2-engine airplanes: 1 hour OEI cruise speed
- 3/4-engine airplanes: 2 hours OEI cruise speed
- Alternate must meet forecast landing weather minimums
Memory trick: 'One for two, two for more' — one hour for two engines, two hours for three or more.