What is the maximum distance to a takeoff alternate in terms of flight time on a single engine?

• A. Thirty minutes
• B. Two hours
• C. Three hours
• D. One hour flying time on a single engine

Answer: (D)

In flight planning for an alternate, you must consider how far you can get if you lose an engine. The rule uses the aircraft’s performance with one engine inoperative to set a practical limit. Because engine-out performance is reduced, the takeoff alternate has to be within a distance that you can reach safely within a certain amount of time if you’re flying OEI. That time-based limit is one hour of flying time on a single engine, which translates to a reasonable safety margin for routing, winds, and fuel.

So the maximum distance, expressed as flight time on a single engine, is one hour.