The XC-142 aircraft was
the third aircraft evaluated in the Tri-Service Assault Transport
Program. It used four cross-linked 3,080 shp General Electric T64-GE-1
engines, each driving a 15.5 ft four-bladed propeller. Roll was controlled
by differential propeller pitch, and pitch by an 8 ft three-bladed
variable pitch tail rotor. Yaw was provided by ailerons powered
by propeller slipstream. The wing could tilt through 100° allowing
the XC-142 to hover in a tailwind. The tail rotor folded to the
port side to reduce the stowage length and to protect against accidental
damage during loading. This cargo aircraft was 58 ft long, had a wingspan
of 67 ft and was capable of transporting 32 troops and gear or 8,000
lb of cargo. It had a rear loading ramp and had a maximum gross
weight of 41,000 lb for a vertical take-off, or 45,000 lb for a
short take-off. It made its first conventional flight on 29 September
1964, first hover on 29 December 1964, and first transition on 11
January 1965. Air Force trials included cargo flights, cargo and
paratrooper drops, and desert, mountain, rescue, and carrier operations.
Five aircraft were built, but mechanical failures (primarily the
cross-shaft and gear boxes which could be damaged during wing flexing)
and operator error caused four of them to be damaged in hard landings.
One crash occurred as a result of a failure of the drive shaft to
the tail rotor, causing three fatalities. The XC-142 suffered from
excessive vibration and noise, resulting in a high pilot workload.
During the program, the XC-142 accrued 420 hours by 39 different
pilots as an operational evaluation aircraft.