One of Beechcraft's lesser known efforts has got to be the single King Air 400
(Model PD-290), a 1975 experimental turbojet conversion of a King Air 200
When Cessna unveiled its Citation in 1972, it was evident that at least some of Beech's future markets would have to be in jets, so in 1975, Beech built a testbed for jet aerodynamics and systems. Using the first King Air 200 prototype, engineers replaced the two turboprops in the wing nacelles with two Pratt & Whitney JT-15D-4 turbojets. The rather striking PD (Preliminary Design) 290 accumulated 93 hours on 103 flights between March 1975 and September 1977, apparently gathering enough information to convince the company to resume the search for a ready-built design. In late 1985, Beech announced it had purchased the design, tooling and rights to manufacture and market the Mitsubishi 300 jet.Source
The prototype was modified from the very first King Air 200
(c/n BB-1), which had been registered on Oct 27, 1972 as N38B. Its later disposition is not known very precisely, but presumably it was reverted to King Air 200
configuration with PT6A engines, and was written off in March 1980.
Any other pics or info would be much welcome!!