Tuesday, February 17, 2015

AMBROSINI S.A.I. 7 series

The excellent aerodynamics of the S.A.I. 7 are well illustrated here. Finish was red overall.

The more orthodox two-seat fighter trainer version of the S.A.I. 7 was produced in 1941.

The S.A.I. 107 employed a 540 h.p. Isotta-Fraschini Gamma engine driving a two-bladed airscrew

Certainly the most successful Ambrosini designs were the series of lightweight fighters developed from the S.A.I. 7 sport monoplane. This two-seat model was the first Ambrosini product with retractable landing gear; possessing exceptional lines, it achieved 251 m.p.h. with a Hirth H.M.508D eight-cylinder inverted air-cooled engine of only 280 h.p. Piloted by Giorgio Parodi, an S.A.I. 7 won the 1939 Raduno del Littorio (Littorio Air Rally), subsequently capturing the 100-km. (62.1-mile) closed circuit record for F.A.I. Category I at 244 m.p.h. The most striking feature of the design was the beautifully faired windscreen originating forward of the engine cowling and extending in a continuous arc to the fin. Empty, the S.A.1. 7 weighed 1650 lb.; the normal loaded weight was 2640 lb., although a maximum of 3025 lb. was possible. Span was 29 ft. 5 in., length 23 ft. 9 in., height 7 ft., and wing area 141.4 sq. ft. The S.A.I. 7 could climb to 19,680 ft. in 14 minutes. Cruising range was 2020 miles.

Ing. Stefanutti was aware of the military potential of the basic design, and in 1941 produced a two-seat fighter trainer. In most· respects the trainer was similar to the sport model, except for the substitution of an Isotta Fraschini Beta R.C.I0 of 280 h.p. for the German Hirth engine. This lengthened the fuselage to 26 ft. 11 in. Span was also slightly increased to 29 ft. 61/3 in. In addition, the fully streamlined windscreen was replaced by a normal cockpit canopy for pilot and pupil. Loaded weight was 3003 lb. The maximum speed was only slightly less than that of the original at 248 m.p.h. The war situation halted further development of the trainer, as combat aircraft received higher priority, but the design has been built in improved form since the war as the S.7 and Supersette.

S.A.I. 107 In view of the great need for combat aircraft by the Regia Aeronautica, the design was developed into the S.A.I. 107 experimental fighter in 1942. Intended only as a preliminary prototype, the S.A.I. 107 fitted a 540 h.p. Isotta Fraschini Gamma engine driving a two-bladed airscrew. Fully loaded, this single-seat machine weighed only 2200 lb., and reached nearly 350 m.p.h. in trials held at the Guidonia research establishment. Maneuvrabilily proved to be excellent. Except for the length of 26 ft. 3 3/4 in., dimensions of the S.A.I. 107 were the same as those of the S.A.I. 7 trainer.

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