Rare audio of Boeing/Vertol Rotor RPM Schedule Test of the A, C and Model 347 Chinooks.

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Model 347

    During January 1969, Vertol began a cooperative program with the Army to develop the Model 347 advanced-technology helicopter from CH-47A, #65-7992.
Major modifications included a fuselage stretch of 110", an aft pylon extended upward 30" to increase the distance between rotor planes (thus reducing noise levels), 4 blade duel rotor system, retractable landing gears, and hydraulically actuated wings, permitting incidence control throughout the aircraft's flight envelope.
On May 27, 1970, the Model 347 lifted off on it's first flight at the Vertol Division's Center 3 Flight Test Facility at Eddystone, Pennsylvania.

    Some of the Model 347's features were used to help design the "XCH-62 HLH" and CH-47D, including reliability improvements, flying qualities, flight control systems, external handling systems, and new hydraulic systems.    Regardless, the Army could not economically justify the four-bladed rotor system or fuselage modifications in future Chinook Models.

Following completion of it's test program, the Model 347 was retired from service and donated to the Army Aviation Museum, where she rest today.

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Sound file donated by Bob Patterson