After the start of licence production of the SM-1, a team of Polish designers led by engineer J. Tyrcha began in 1957-59 to design its improved version, designated SM-2. Attention was drawn to the significant excess engine power, which could allow the helicopter to carry more people or cargo. An entirely new fuselage was designed with a large, comfortable cabin seating 5 people including the pilot. A stretcher with a patient could also be loaded into the cabin through the opening front.
Large sliding doors on both sides of the fuselage facilitated boarding and exiting, as well as conducting airborne rescue operations using a special hoist. The cabin’s extensive glazing provided the pilot with excellent visibility. In designing the SM-2, the Russian Mi-1’s powerplant together with the main rotor, a partially redesigned tail boom with tail rotor, and the landing gear were retained.
During operation, a decline in the helicopter’s performance became apparent. After additional testing, it turned out that the cause was a loss of engine power. This was caused by a design error in the new carburettor intake, which drew in hot air from the cooling system. A total of 85 SM-2 units were produced; several were exported, with Czechoslovakia as the buyer.
A total of 80 SM-2 helicopters were purchased for military aviation; several were later used in civilian air ambulance service. In Poland, the SM-2 was in service until 1979.
| Rotor diameter | 14.34 m |
| Fuselage length | 12.08 m |
| Takeoff weight | 2493 kg |
| Maximum speed | – |
| Ceiling | 3500 m |
| Range | 310 km |
| Armament | – |
| Engine | 7-cylinder radial Lit-3, 575 hp |
