Ambrosini SAI.207
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| SAI.207 | |
|---|---|
| Type | Light fighter |
| Manufacturer | Ambrosini |
| Maiden flight | 1940 |
| Number built | 14 |
| Variants | Ambrosini SAI.403 |
The Ambrosini SAI.207 was a lightweight fighter aircraft developed in Italy during World War II.
Sergio Stefanutti, chief-designer of several aircraft models, tried to make competitive aircraft with several very fast models made when he was working for the Societa Aeronautica Italiana (SAI) of Ing. A. Ambrosini in Passignano sul Trasimeno, Umbria.
The first success was the SAI-Ambrosini S.7 (s for Stefanutti), designed around 1937, flown in 1939 and produced in 12 examples. It arrived second to Messerschmitt Bf 108 Taifun in 1939 Rimini Aviomeeting, but after conquering one of the last records set by Italian aircraft, with 392 km/h over 100 km distance (27 August 1939)[1], a Military version was ordered as training aircraft, using a Isotta-Fraschini Beta six cylinder air cooled engine. This was to be the base for several SAI-Ambrosini fighters.
SAI-Ambrosini, with Stefanutti as chief-designer, started to make fighter aircraft in 1939, trying to compete with Fiat, and also because this, tried with several unconventional machines (Fiat designs were by comparison instead quite conservative).
The first was SAI SS.4, characterized by canard wings (It looked a bit like the Curtiss XP-55 Ascender or the Kyushu J7W1 Shinden), extrapolated by other Stefanutti projects. But this machine soon crashed, killing the pilot.
Stefanutti returned to more convenctional designs with the light SAI.107, derived from the successful S.7 trainer. The light fighter concept, followed also in the post war period, was quite popular in early '40s, with some realizations (the most prominent was arguably the Caudron C.760). With a great care for low drag design, it was possible build fighters with engines quite weak (around the half or litte more than usual) and still have fast machines. The too light construction and the unfavourable power-to weight ratio (evident in climb times) however allowed only little success to them. Among them one of the faster was the SAI.207, derived from the SAI.107.
The first of the three prototypes (designated MM 441 till MM 443) flew in Autumn 1940. MM 441 seems to have been the sole SAI.107, while MM 442 and MM443 were the true SAI.207 prototypes, but MM 442 already crashed on 5 December, killing test pilot Mario Faccioli[2]. The MM 441 was lost together with test pilot Arturo Ferrarin on 18 July 1941[3].
The second SAI.207 prototype, MM 443, did not take to the air until Spring 1942, witnessing the troubles that this project gave for ing. Stefanutti team were never quite solved.
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[edit] Design and development
It was a single-seat, low-wing aircraft of conventional tailwheel configuration developed from the SAI.107 prototype. It had very light construction, in spite of being made with wood (spruce). It was powered with an inline Isotta-Fraschini, that had low power and so, it was tried to use only air cooling, to make the design slimmer as possible with a reduced frontal section and without radiator cooling air intake (airflow passed trought the nose air intake to cool the engine). The weaponry was the usual light set for an Italian fighter, two relatively powerful 12,7 mm Breda machine guns.
The horizontal performance of this aircraft was spectacular, achieving a level speed of 580 km/h (360 mph) with only 560 kW (750 hp) of engine power[4], and so was for diving speed (over 800 km/h). The Ministero dell' Aeronautica soon placed a production order for 2,000 machines, plus a batch of 12 for operational testing, which was undertaken from March to July 1943.
The real problem was about the whole light fighter conception, with too much compromises that affected the reliability. Despite the SAI.207's wooden structure, it was very light and this was possible only with some 'unconvenctional' solutions. The undercarriage bays, as example, were without internal carenatures. The bigger problem was the engine: especially when recovering from dives, the aft cylinders tended to overheat because the insufficient airflow. This was a real danger for a fighter machine. Stefanutti proposed many modifications, but Ambrosini rejected them systematically. Once he even said that SAI.207 must flight away from airfield, so if one accident happened, people did not see it.
[edit] Tests and service
This machine had very small wings and so an excessive high wingloading. Overall, it was more a racer than a real combat aircraft. Guido Tassinari, a former pilot who tested this machine, was clear about SAI.207's real validity. Despite it had responsive commands, a very clean airframe to use at the scarce power available, it had also many shortcomings. The wingoad was too high (also because the weight, empty, was 1750 kg compared to 1000 of S.107), and while horizontal speed was good and dive speed was amazing, the climbing performance and agility were poor. With this reputation, flying the SAI.207 was a difficult task. Tassinari flew the machine (MM 443) several times and the last occasion, was dramatic. He recovered from a dive, but that for once the problem was not overheating, but the undercarriage gear opening. Due to the lack of undercarriage internal wing carenatures, the wing was pressed with a powerful airflow internally, and so, the aft structure literally exploded. The aircraft got out of control and Tassinari escaped from the wreck, jumping out of the aircraft and using his parachute, to splash in Lake Trasimeno waters from low altitude. The danger for him was not ended, however, because the parachute trapped Tassinari, almost drowning him and was saved only thanks to some fisherman's boats quickly arriving on the scene.
As for production, MM.442 and 443 were the protypes, both lost in accidents. The pre-production batch was for another 12 machines, MM.8425-36. One of them (MM 8433) had two 20 mm guns in the wings, but their recoil, as is easily understandable, was too strong for the light aircraft and they were removed.
The SAI.207s had not really success in operational squadrons either. They served briefly with three squadrons, the first one (after testing at Guidonia airbase) was 83th Squadriglia, 19 Gruppo, 3 Stormo, led by Guglielmo Specker (one of the RA best known 'aces') at Cerveteri airfield, near Rome. They went in service in July and made some combat flights, without results, against the heavy allied raids over the that city. After one month, they were sent to Castiglione del Lago G.Eleuteri airfield (at that time one of the main Regia Aereonautica training airbase), where also 161 and 162th Squadriglia were planned to have these fighters.
Despite the speed, Italian pilots were not impressed by the type, seen that in 1943 they usually flew with all-metall fighters like the Bf-109, MC.202 Folgore and MC.205 Veltro. The bad weather hampered the aircraft structure, that started to be spoiled by rain and humidity. So the service, in summer 1943, quickly ended. The aircraft of 83th Squadriglia were sent to SAI-Ambrosini to be refurbished, but the Armistice made it impossible for them the return to their squadron.
The next Stefanutti fighter was to be the SAI.403, in favour of which the Ministero dell' Aeronautica cancelled the SAI.207 order already in January 1943.
Stefanutti, who had started his experience with this aircraft family (S.7/107/207/403/404) with SAI.7 training aircraft, returned on this project after the war, and the result was the Super 7, the only one that was to achieve mass production of all his models.
[edit] Specifications
General characteristics
- Crew: one pilot
- Length: 8.02 m (26 ft 4 in)
- Wingspan: 9.00 m (29 ft 6 in)
- Height: 2.4 m (7 ft 10 in)
- Wing area: 13.9 m² (150 ft²)
- Empty weight: 1,750 kg (3,860 lb)
- Gross weight: 2,420 kg (5,340 lb)
- Powerplant: 1 × Isotta-Fraschini Delta inverted V, 560 kW (750 hp)
Performance
- Maximum speed: 575-625 (dep on sources) km/h (400 mph)
- Range: 850 km (530 miles)
- Service ceiling: 12,000 m (39,400 ft)
- Rate of climb: 13.2 m/s (2,600 ft/min)
Armament
- 2 × 12.7 mm Breda-SAFAT machine guns
[edit] References
[edit] Notes
[edit] Bibliography
- Cattaneo, Gianni. SAI-Ambrosini 207 e derivati (bilingual Italian/English). Roma, Italy: La Bancarella Aeronautica, 2005.
- Emiliani, Angelo. "Il Volo e la Scaramanzia" (in Italian). Storia Militare magazine No.77, February 2000.
- Green, William. Warplanes of the Second World War, Volume Two: Fighters. London: Macdonald & Co. (Publishers) Ltd., 1961.
- Lembo, Daniele I caccia SAI-Ambrosini (in Italian). Aerei nella Storia magazine No.39, December 2003.
- Taylor, Michael J. H. Jane's Encyclopedia of Aviation. London: Studio Editions, 1989.
[edit] External links
[edit] See also
Comparable aircraft
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