This was a CH-47A converted in 1969 to the BV-347 prototype as an entry for the Heavy Lift Helicopter (HLH) requirement, first flying at Vertol's test facility at Eddystone, PA in May 1970. Phase I changes included upgrades to CH-47C standards, four blade rotors, fuselage stretch, Phase II adding variable incidence wings for extra lift. Hydro-mechanical rotor controls were later replaced with a fly-by-wire system integrating wing and rotor controls automatically. Although successful the Army could not feasibly modify its entire Chinook fleet, but some improvements carried over to the CH-47D

Highly modified CH-47A. First flew as such in 1970 and used for various tests. To the museum around 1973 after testing was completed.

Highly modified CH-47A with first flight on 27 May 1970. Changes included lengthened cabin, retracting landing gear, four blade rotors, advanced cockpit instrumentation, and a variable incidence wing. It was capable of performing 2G turns. Although not put into production, many of the upgrades tested were later used in new generation helicopter designs.