- 33.1 Scope
- Helicopter Duration comprises eleven events open to any single-stage model rocket that uses autorotation as the sole means of recovery. The purpose of this competition is to achieve the longest flight duration using an auto-rotating recovery system.
- 33.2 Autorotation
- Each entry must be decelerated during descent by its auto-rotating recovery device. The resulting autorotation must be around the vertical axis. An entry that descends nose first, or flips over during descent is permitted.
- 33.3 Recovery
- Recovery devices employing flexible (e.g., plastic film or cloth) surfaces are prohibited. Entries using a recovery system that is designed to act (or that actually acts) in a manner similar to a parachute, a rigid inverted bowl, or similar techniques are specifically excluded from this competition.
- 33.4 Qualification
- The entry must make a minimum of one complete rotation around its vertical axis during the recovery portion of the flight to be considered qualified.
- 33.5 Classes
- This event is divided into classes based on the permissible total impulse of the motor(s). The following classes of Helicopter Duration are established:
Motor Class Multi-Round Maximum (sec) NRC Maximum (sec) 1/8A 20 1/4A 30 90 1/2A 60 180 A 120 360 FAI A 180 B 180 C 240 D 300 E 300 F 300 G 300