In a joined programme by the US Army and Boeing Vertol a CH-47A was used to
demonstrate advanced helicopter technology. Modifications included a
stretched fuselage, taller aft pylon, retractable gear, small experimental
wings, and four-blade rotors. A fly-by-wire control system was used to
integrate rotor and wing functions automatically. In this configuration it
was first flown at Eddystone, Pennsylvania, on May 27, 1970.
Later the hydro-mechanical rotor control was also altered to fly-by-wire
concept, the 347 becoming the world's first helicopter to be flown with an
electrical connection between pilot and rotor system.
Later, in the program for the Model 301 HLH, the wings were removed and it
was fitted with a retractable capsule behind the cockpit to evaluate the
load-controlling crewman's station and functioins for the rearward-facing