Two departing aircraft are planned to diverge by 90 degrees after takeoff; what is the earliest permissible release time?

Two departing aircraft are planned to diverge by 90 degrees after takeoff; what is the earliest permissible release time?

• A. 0 Minutes
• B. 3 Minutes
• C. 1 Minute
• D. 2 Minutes

Answer: (C)

The situation tests wake turbulence safety and how quickly the second aircraft can be released when departures diverge, here by 90 degrees. When two planes take off on paths that separate quickly laterally, there is still wake from the first aircraft that the second could encounter if released too soon. The rule is to use the smallest safe interval between releases—the minimum nonzero time that reliably clears the first aircraft’s wake from the second aircraft’s path. Why this is the best answer: releasing at the minimum safe interval satisfies safety by ensuring the wake has moved clear, while not unnecessarily delaying the second departure and reducing overall throughput. Releasing at zero time would place the second aircraft into the first aircraft’s wake, which is unsafe. Waiting longer than the minimum is acceptable from a safety standpoint but is inefficient for traffic flow. In this scenario, the 90-degree divergence means the lateral separation grows quickly, allowing only the smallest safe interval to be required.

The situation tests wake turbulence safety and how quickly the second aircraft can be released when departures diverge, here by 90 degrees. When two planes take off on paths that separate quickly laterally, there is still wake from the first aircraft that the second could encounter if released too soon. The rule is to use the smallest safe interval between releases—the minimum nonzero time that reliably clears the first aircraft’s wake from the second aircraft’s path.

Why this is the best answer: releasing at the minimum safe interval satisfies safety by ensuring the wake has moved clear, while not unnecessarily delaying the second departure and reducing overall throughput. Releasing at zero time would place the second aircraft into the first aircraft’s wake, which is unsafe. Waiting longer than the minimum is acceptable from a safety standpoint but is inefficient for traffic flow.

In this scenario, the 90-degree divergence means the lateral separation grows quickly, allowing only the smallest safe interval to be required.