The minimum distance required for a Category I departing behind a Category III on the same runway is ___ feet.

• A. 4,000
• B. 6,000
• C. 2,000
• D. 8,000

Answer: (B)

Wake turbulence separation is the key idea here. A Category III aircraft is a heavier, more powerful plane, and it leaves stronger wake vortices than a Category I aircraft. When a lighter Category I follows on the same runway, it needs extra distance behind the preceding aircraft to ensure those vortices drift away from the path and lose strength before the trailing aircraft reaches takeoff or rollout. The minimum required separation for this pairing is 6,000 feet, which is enough time for the wake to decay and for the trailing aircraft to have a safe takeoff. Shorter distances wouldn’t provide adequate clearance, while larger distances aren’t necessary as the standard minimum.