Ambrosini SS 4
![]() The single-seat S.S.4 monoplane fighter designed by Ing Sergio Stefanutti was tail-first configuration with a retractable nosewheel undercarriage. Built by the Societa Aeronautica Italiana Ing A Ambrosini it was of all-metal construction and powered by a 960hp liquid-cooled 12-cylinder Isotta-Fraschini Asso XI R.C.40 engine driving a three-bladed variable-pitch pusher propeller.
The sole prototype was first flown on 7 March 1939, but was destroyed during its second flight on the following day when the starboard aileron separated, the wing developed a high amplitude oscillation and the aircraft entered a dive and crashed at Guidonia.
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