the General Directorate of Rear Services along the Ho Chi Minh Trail linking to the 6908th security squadron. Six YQU-22A prototypes (modifications of the Beech 33 Debonair) were combat-tested in 1968, and two were lost during operations, with a civilian test pilot killed. Twenty-seven QU-22Bs were modified, 13 in 1969 and 14 in 1970, with six lost in combat. Two Air Force pilots were killed in action. All of the losses were due to engine failures or effects of turbulence. A large cowl bump above the spinner was faired-in for an AC current generator, and higher weight set of Baron wings and spars were used to handle the fuel load. Variants Model 33 Debonair/Bonanza 35-33 Debonair (1959) Based on Bonanza with conventional fin and tailplane, and basic trim and interior, powered by one Continental IO-470-J, 233 built. 35-A33 Debonair (1961) Fitted with improved interior trim, and powered by IO-470J or IO-470K. 154 built. B33 Debonair (1961-1965) Further refined version, with new instrument panel, contoured fin leading edge and fuel tank modifications (as per N35 Bonanza). IO-470K engine. 426 built. C33 Debonair (1965-1967) Higher gross weight and provision for enlarged rear windows. 304 built. C33A Debonair (1966-1967) Powered by Continental IO-520-B engine. 179 built. D33 One S35 modified as a military close-support prototype, with conventional tail assembly and six underwing hardpoints. E33 Bonanza (1968-1969) Powered by IO-470K. 116 built. E33A Bonanza (1968-1969) E33 with a 285 hp Continental IO-520-B engine, 85 built. E33B Bonanza E33 with strengthened airframe and certified for aerobatics. Unbuilt. E33C Bonanza (1968-1969) E33B with a 285 hp Continental IO-520-B engine, 25 built. F33 Bonanza (1970) E33 with modified rear side windows and minor improvements, 20 built F33A Bonanza (1970-1994) F33 with a 285 hp Continental IO-520-B engine, later aircraft have a longer S35/V35 cabin and extra seats, 1502 built. F33C Bonanza (1970 onwards) F33A certified for aerobatics, 154 built on special order up to 1987 G33 Bonanza (1972-1973) F33 with a Continental IO-470-N engine and V35B trim, 50 built. Model 35 Bonanza 35 (1947–1948), initial production version with Continental E-185 or E-185-1 engine, 1500 built. A35 (1949) Model 35 with higher takeoff weight, tubular wing spars and nosewheel steering, 701 built. B35 (1950) A35 with a Continental E-185-8 engine, 480 built. C35 (1950-1952) B35 with a 185hp Continental E-185-11 engine, metal propeller, larger tail surfaces, and higher takeoff weight, approved for the Lycoming GO-435-D1 engine, 719 built.