If a preceding large aircraft has rotated, how many minutes must the following aircraft wait before starting its takeoff roll?

• A. 1 minute
• B. 3 minutes
• C. 2 minutes
• D. 4 minutes

Answer: (B)

Wake turbulence from a large aircraft is the key idea here. When a big airplane rotates and lifts off, it leaves strong wingtip vortices behind that sink and drift with the wind. If the following aircraft starts its takeoff roll too soon, it can encounter those vortices and experience unexpected rolling or loss of control. To reduce that risk, air traffic control requires a pause between departures. The standard practice is to wait three minutes after the preceding heavy has rotated before starting the next takeoff. This interval gives the vortices time to move clear of the takeoff path and dissipate to safer levels. Shorter waits (one or two minutes) wouldn’t provide enough separation, while waiting longer (four minutes) is more conservative than typically necessary under normal conditions.