A twin-shaft turboshaft helicopter engine. This engine has two turbines: one, mounted on a common shaft with the compressor, drives the compressor, while the other, mounted on a separate shaft — the so-called free (power) turbine — transmits drive through a reduction gearbox to the output shaft. This design is typical of low-power turboshaft helicopter engines intended to power light helicopters.
The GTD-350 engine was developed at the turn of the 1950s and 1960s at the Klimov Design Bureau in Leningrad under the direction of engineer Sergei Petrovich Izotov. The engine was structurally similar to the American Allison 250 helicopter engine. In 1961, the Mi-2 light helicopter, powered by two prototype GTD-350 engines, made its first flight in the USSR.
In January 1964, an agreement was signed between the governments of Poland and the USSR, under which production of the Mi-2 helicopter began at WSK-Swidnik in Poland and the GTD-350 engine at the Communications Equipment Factory in Rzeszow. Prototype documentation was delivered to Poland. Serial production of the GTD-350 engine began at WSK-Rzeszow in 1966. Over 11,000 units of the engine were produced, and it was improved numerous times.
| Engine weight | 135 kg |
| Time between overhauls | 1000 h |
| Maximum power | 400 hp |
| Rated power | 320 hp |
