Page 28 - October 2022

In the mid-1970s, the unique creation to emerge from Beech Aircraft Corporation’s engineering department was the unconventional Model PD 290. It was strictly an experimental systems testbed to evaluate the mating of turbofan engines to the airframe of a Model 200 Super King Air. Impetus for the PD 290 may have stemmed from competitor Cessna Aircraft Company that was achieving market success with its Citation business jet. Both the Citation and the PD 290 were powered by Pratt & Whitney JT15-series turbofan engines. The PD 290 program was terminated in 1977. (BEECHCRAFT CORPORATION; SPECIAL COLLECTIONS AND UNIVERSITY ARCHIVES, WICHITA STATE UNIVERSITY LIBRARIES)
“Conceived strictly as a tool to evaluate the feasibil- ity of mating small turbofan engines to a King Air cabin- class airframe, the PD 290 was exceedingly unique.”
to terminate further development. The last flight was made in January 1980 and the prototype eventually was scrapped.
Despite the end of the T36TC initiative, company officials were still enamored with the idea of a single- engine, pressurized Beechcraft. Their enthusiasm was warranted because it was clear that a market had emerged for just such a business aircraft.
26 • KING AIR MAGAZINE
The twin-engine, piston-powered Model 58P Baron offered a logical platform to test the single-engine concept and a 58P fuselage (designated serial number EJ-1) was selected as an engineering POC testbed. Chief changes included installation of different wings and a 630-shp (shaft horsepower) Garrett TPE-331-9 turboprop powerplant swinging a three-blade, fully-reversible propeller with a diameter of 92 inches. The POC, known within the company as PD (preliminary design) 336, existed solely to help Beech Aircraft engineers evaluate the compatibility of the turboprop engine and the 58P’s pressurized cabin.
Known unofficially around the Beechcraft factory as the Model 38P Lightning, the airplane took to the air in June 1982 with Lou Johansen at the controls. Although the company was mum about performance information, for the next 17 months Johansen and other test pilots flew the airplane on 133 flights. During that time the POC accumulated more than 100 hours of flight time that yielded useful information about the combination of turboprop power and pressurization.
The next step in the Lightning flight test program centered chiefly on replacement of the prototype airplane’s TPE-331-9 engine with a Pratt & Whitney Canada PT6A-40 turboprop powerplant that was flat rated to 630 shp. The purpose of the engine change
OCTOBER 2022