Category I departing behind a Category E aircraft on the same runway requires a time separation of 2 minutes or radar separation of 4 miles.

• A. 1 minute; 2 miles
• B. 2 minutes; 6 miles
• C. 2.5 minutes; 3 miles
• D. 2 minutes; 4 miles

Answer: (D)

Wake turbulence separation minima for departures on the same runway require careful spacing when a lighter following aircraft trails a heavier lead. In this scenario, when a Category I aircraft departs behind a Category E lead, you must maintain either a 2-minute time separation or a radar separation of 4 miles. The 2-minute interval accounts for how long it typically takes the wake from the heavier aircraft to move far enough away and dissipate for the following plane to climb out safely. If radar separation is being used, keeping at least 4 miles between the two targets ensures the trailing aircraft is sufficiently behind the wake, even with wind and speed differences. The other numbers don’t meet the published minima for this specific lead-following pairing, since they would either be too short in time or too short in radar distance to provide the required protection from wake turbulence.