The parasail carries the UAV to its 800-ft. launch altitude using a rigid harness. UAVs up to 400 lb. can be accommodated, with higher launch weights planned.
Runway in the Sky Evaluated For UAVs
" A simple and low-cost parasail-based launch system is being refined that could allow the reliable and efficient launch and recovery of unmanned aerial vehicles from moving platforms as small as 30-ft. boats.
The system, tentatively called Runway in the Sky or RITS, relies on an Exdrone delta-winged UAV and modified sport parasail, according to Randy McDonnell, president of St. Louis-based Advanced Aerospace Technologies Inc. (AATI). Tests from a slightly modified 30-ft. launch boat were observed in February by U.S. Coast Guard and Navy representatives in a government-paid demonstration.
Much like its usual sport use, the parasail gains altitude as it is towed behind a boat or other vehicle. Its normal human payload, however, is replaced with a lightweight, rigid launch harness from which the UAV is suspended. Using the current system, UAVs with gross weights up to 400 lb. can be accommodated, McDonnell said. AATI envisions launch and recovery of even larger UAVs, including the use of automated launch and recovery systems.
ONCE THE PARASAIL ATTAINS an attitude of about 800 ft., a radio command drops the UAV from the launch harness, similarly to a bomb. After a few seconds-dive, the UAV gains enough airspeed for control authority. The UAVs remote operator then pulls back on the control stick to achieve level flight and begins the mission, McDonnell said.
For recovery, the aircraft operator flies the UAV at low speed, on a right-angle course to the towing vehicle, directly into one or more recovery lines hanging from the tow line. The recovery lines are positioned midway between the ship and the parasail. After first contact, the aircraft's delta wing simply sweeps across the recovery line. The line quickly reaches a spring-loaded snap lock mechanism, which immediately envelops the line, closes and locks, capturing the UAV.
The recovery line used is slick and flexible, to avoid damaging puller prop aircraft configurations, McDonnell said. Load forces at capture are not excessive due to low aircraft speed and inherent "give" in the hanging recovery line and the resulting side-deflection of the tow-fine, he said. Loads also are much less than in standard net recovery systems, according to the company. If the recovery lines are arrayed in a closely space pattern, both of the UAVs wings can be captured nearly simultaneously. This would allow wings level delivery of the aircraft to waiting deck crew as the parasail is reeled in. AATI has successfully demonstrated both single- and multiline UAV recovery in ground-based tests. Planned recovery configurations for larger UAVs would capture the aircraft
near and above its center of gravity so the vehicle naturally hangs in an upright attitude. The latching system can be modified to accommodate UAVs with other wing planforms as well, McDonnell said.
Advantages of RITS include simplicity, low-cost and the ability to use smaller launch platforms, even those too small for helicopter UAVs. Air vehicle gross weight is not constrained by the launch system as with some catapult operations. Catapults are historically a major cause of UAV damage or loss.
RITS also requires little specialized operator and deck crew training. Launch and recovery take place at low airspeeds and a comfortable distance from the ship superstructure, related air turbulence and water. The UAV approach path does not have to be synchronized with the pitch and roll of the ship, McDonnell said. Once captured, the vehicle is winched down to recovery crews with its engine off.
OVERALL, UAVs LAUNCHED and recovered using the RITS system are less likely to be damaged in a collision with ship structure, a hard deck landing or inadvertent ditching, he said. RITS can be set up or broken down for storage quickly and the deflated parasail stuffed in a bag without special packing requirements.
During a mission, the parasail could be redeployed carrying a communications relay package that would allow UAV flights farther over the horizon, or long-distance operations at lower altitudes while maintaining line-of-sight control."