The PZL SM-2 was a Polish light utility helicopter, enlarged version of license-built Mil Mi-1, developed and produced by WSK PZL-Świdnik. It was also known as the WSK SM-2.
Design and development
From 1956, the Soviet light three-seat or four-seat helicopter Mi-1 was produced under license in the Polish WSK PZL-Świdnik works in Świdnik, under a designation SM-1 – and as much, as 1594 were manufactured. In 1957, works started in WSK PZL-Świdnik to modernize the helicopter and fit it with an enlarged, five-seat cabin. One of the design goals was to make training easier, by placing the two pilots side by side. In air ambulance role, it was easier to treat a patient inside a fuselage, than in side capsules. The helicopter's main designer was Jerzy Tyrcha. The most obvious difference was a larger cabin, extended towards the front, but in fact most fuselage parts were reconstructed. The cabin had two wide side doors, sliding rearwards, being an improvement over the Mi-1, in which its automobile door could not be opened in flight and had to be removed for some purposes. Unchanged were: the engine, transmission and rotor, the fuselage boom and the landing gear. On contrary to the Mi-1, a headlight was movable. The prototype flew first on 18 November 1959. It appeared successful and a limited production started in 1960. Its take-off characteristics and performance were slightly worse, than of Mi-1/SM-1 – one of the reasons was an unsuitable carburetor intake, but it was improved only on some helicopters. Only 86 helicopters were produced, in four series, differing in details, plus three prototypes. They were produced almost exclusively for Poland, while the SM-1 remained main export product of Świdnik at that time. The helicopter was manufactured only in one variant, and could change its role to passenger, transport, air ambulance or flying crane. in Kraków . Visible is a hatch in a nose. Basic variant had seats for three passengers on a rear bench and one seat next to a pilot. There were no double controls. In the air ambulance configuration, single stretchers were carried in the fuselage – loaded through a special hatch in a fuselage front, on the right side. A physician could seat behind the pilot, other seats were removed. Additional two injured could be carried in detachable external closed capsules on either side of the fuselage, typical for Mi-1. All variants could carry additional external fuel tank 140 l on the left side, extending range to 500 km. The crane variant was used in limited numbers for search and rescue missions; it had a hydraulic winch that could lift 120 kg, in a place of a right front seat. After removal of all passenger seats, 320 kg of load could be carried. They had a durability of 600 flight hours, like contemporary SM-1 helicopters.
Operational history
SM-2s were used mainly by Polish military aviation – 80 were delivered, between March 1961 and 1964. They were operated in small numbers by several units of the Polish Air Force and Polish Navy, mostly for liaison, artillery spotting, air ambulance tasks and others. In Polish Navy they were used for search-and-rescue actions. This number included a flight assigned to Internal Security Corps, later Ministry of Internal Affairs. Only two ex-military SM-2 and the second prototype were used by civilian air ambulance service. One helicopter remained in PZL-Świdnik factory, and the other was acquired by the factory from the air force. Most SM-2s were withdrawn in late 1970s and replaced with Mil Mi-2. The last one was withdrawn from the air force in 1981, and flew until 1983. Only five SM-2 were exported. One was sold to Czechoslovakia, used in 1963–70 by the Ministry of Internal Affairs, then by Slov-Air until 1975 for internal transport. Four SM-2 were sold in 1963 to Romania, used by 1975 in the military aviation. Four SM-2s are preserved in museums in Poland: in Polish Aviation Museum in Kraków, in Museum of Polish Arms in Kołobrzeg, Drzonów and Dęblin. Apart from museums there exist SM-2 in a collection in Góraszka and in PZL Świdnik factory. One is preserved at the Helicopter Museum, Weston-super-Mare, in the United Kingdom. Two other SM-2 are preserved in the Czech Republic and Romania - both are stored.
