lauantai 30. heinäkuuta 2016

Sai-Ambrosini 207

The Ambrosini SAI.207 was a light fighter interceptor built entirely from wood and developed in Italy during World War II. Powered by a single 750 hp Isotta-Fraschini Delta, the SAI.207 enjoyed limited success during evaluation of the 12 pre-production aircraft.

The SAI.207 was developed from the Ambrosini SAI.7 racing and sporting monoplane after the light fighter concept had been proven with the Ambrosini SAI.107 prototype. Steffanuti designed the aircraft to have a lightweight structure and light armament to allow lower-powered engines to be used, without unduly reducing performance.

The first of three prototypes was completed and flown in the Autumn of 1940 as the sole SAI.107, which was a minimum change fighter development of the SAI.7, with identical dimensions, apart from length, at 8.02 m and the 402.7 kW / 540 hp Isotta-Fraschini Gamma engine. Weighing only 1,000 kg the Sai.107 reached a speed of 563 km/h in trials held at the Guidonia research establishment and manoeuvrability proved to be excellent. The SAI.107 was lost, along with pilot Arturo Ferrarin, in a crash on 18 July 1941.

Two more fighter prototypes were built as SAI.207s, flying for the first time in the spring of 1941 and 1942.
The SAI.207 was a single-seat, low-wing monoplane with a conventional tail-wheel undercarriage, developed from the Ambrosini SAI.7. Of wooden construction, giving a light structure, power was supplied by 559.3 kW / 750 hp Isotta-Fraschini Delta R.C.40 engine, cooling air entering the engine through a central intake. Armament consisted of two 12.7 mm Breda-SAFAT machine guns.

In level flight the performance of this aircraft was impressive, achieving a speed of 580 km/h  and over 800 km/h in a dive. The Ministero dell' Aeronautica soon placed a production order for 2,000 machines, plus a pre-production batch of 12 aircraft for operational testing. After the mixed results of operational evaluation and the signing of the Armistice, no production aircraft were built.

Flight testing revealed some major shortcomings, most of which were not rectified before the Armistice in 1943; the low power and high wing loading resulted in poor climb performance; the light structure prevented more powerful cannon from being used as the recoil forces overstressed the mounting structure; the rear cylinders of the engine overheated during recovery from a dive; the light structure also led to problems, with the second prototype wing exploding during a dive recovery due to internal pressure built up, caused by the lack of internal fairings in the undercarriage bays. The wooden structure was also badly affected by rain or humidity.
The pre-production batch of 12 aircraft served briefly with three squadrons. The first was 83rd Squadriglia, 18 Gruppo, 3 Stormo, led by Guglielmo Specker, one of the Regia Aeronauticas best known "aces", at Cerveteri airfield, near Rome. The aircraft entered service in July 1943, flying a number of combat missions against heavy Allied raids over the Italian capital, but without success. After one month, they were sent to Castiglione del Lago G.Eleuteri airfield (at that time one of the main RA training airbases), where it was planned that 161 and 162nd Squadriglia would take the aircraft into service.

Despite its speed, Italian pilots were not impressed by the type and its service in the summer of 1943 quickly ended. The aircraft of 83rd Squadriglia were returned to SAI-Ambrosini to be refurbished, but the Armistice made it impossible for them to return to their squadron.

Italian Kingdom
Regia Aeronautica

Specifications SAI.207
Crew: 1
Length: 8.0201 m 
Wingspan: 9.004 m 
Height: 2.87 m 
Wing area: 13.90 m2 
Empty weight: 1,750 kg 
Gross weight: 2,415 kg 
Powerplant: 1 × Isotta-Fraschini Delta inverted V-12 air-cooled piston engine
Maximum speed: 641 km/h 
Cruise speed: 489 km/h
Range: 850 km; 459 nmi 
Service ceiling: 12,000 m
Rate of climb: 13.25 m/s 
Time to altitude: 6,000 m in 7 minutes 33 seconds
Armament: 2 × 12.7 mm  Breda-SAFAT mg, + (MM8433 only) 2 × 20 mm cannon

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