The Next, More Ambitious Step: The Piper PA-30

Encouraged by the results of the Hyper III experiment, Reed and his team decided to convert a full-scale production airplane into a RPRV. They selected the Flight Research Center’s modified Piper PA-30 Twin Comanche, a light, twin-engine propeller plane that was equipped with both conventional and fly-by-wire control systems. Technicians installed uplink/downlink telemetry equipment to transmit radio commands and data. A television camera, mounted above the cockpit windscreen, transmitted images to the ground pilot to provide a visual reference—a significant improvement over the Hyper III cockpit. To provide the pilot with physical cues, as well, the team developed a harness with small elec­tronic motors connected to straps surrounding the pilot’s torso. During maneuvers such as sideslips and stalls, the straps exerted forces to sim­ulate lateral accelerations in accordance with data telemetered from the RPRV, thus providing the pilot with a more natural "feel.”[895] The origi­nal control system of pulleys and cables was left intact, but a few minor modifications were incorporated. The right-hand, or safety pilot’s, con­trols were connected directly to the flight control surfaces via conven­tional control cables and to the nose gear steering system via pushrods. The left-hand control wheel and rudder pedals were completely inde­pendent of the control cables, instead operating the control surfaces via hydraulic actuators through an electronic stability-augmentation system.

Bungees were installed to give the left-hand controls an artificial "feel.” A friction control was added to provide free movement of the throttles while still providing friction control on the propellers when the remote throttle was in operation.

When flown in RPRV configuration, the left-hand cockpit controls were disabled, and signals from a remote control receiver fed directly into the control system electronics. Control of the airplane from the ground cockpit was functionally identical to control from the pilot’s seat. A safety trip channel was added to disengage the control system whenever the airborne remote control system failed to receive intelli­gible commands. In such a situation, the safety pilot would immedi­ately take control.[896] Flight trials began in October 1971, with research pilot Einar Enevoldson flying the PA-30 from the ground while Thomas C. McMurtry rode on board as safety pilot, ready to take con­trol if problems developed. Following a series of incremental buildup flights, Enevoldson eventually flew the airplane unassisted from takeoff to landing, demonstrating precise instrument landing system approaches, stall recovery, and other maneuvers.[897] By February 1973, the project was nearly complete. The research team had successfully developed and demonstrated basic RPRV hardware and operating techniques quickly and at relatively low cost. These achievements were critical to follow-on programs that would rely on the use of remotely piloted vehicles to reduce the cost of flight research while maintaining or expanding data return.[898]