Scaled Model Jettison Tests of External Stores During Helicopter Autorotation

There is great interest in the safety of the flight envelope of external stores jettisoned during autorotation. A helicopter can perform a safe landing in autorotation under a certain gross weight condition, making it necessary to jettison external stores that exceed that limit. To simulate these in-flight conditions, a 1:17th-scale model was produced using stereolithography, and outfitted with a radio-controlled jettison system. From one to four stores may be jettisoned separately in various sequences or jettisoned simultaneously. The stores were geometrically scaled to maintain their aerodynamic and dynamic characteristics. Various airspeeds and aircraft pitch and yaw angles were tested for each store configuration. For each airspeed, two airflow descent incident angles to simulate different autorotational speeds were tested. This was accomplished through a custom wind tunnel. The jettison tests were videotaped from multiple views, their motion analyzed and compared to a preliminary pass/fail criterion. The results will be used in the development of the full-scale flight tests.