In 1971, preliminary studies were conducted in the USSR to establish a new concept for an agricultural aircraft. Poland was also involved in this task. The preliminary design by constructor Izmailov, which envisaged the use of the AI-25 bypass turbojet engine to power the new agricultural aircraft, was considered the most promising. This powerplant was popular in both civil and military aviation. The AI-25 was used to power the Soviet Yak-40 passenger aircraft and the Aero L-39 “Albatros” military trainer, designed and manufactured in Czechoslovakia.
The widespread familiarity with this engine’s maintenance was expected to facilitate its future operation. The choice of a turbojet powerplant was also supported by lower maintenance costs compared to piston engines. Although the adopted concept was quite heavily criticised by Soviet specialists in agricultural aviation, their opinions were dismissed by the USSR Ministry of Aviation Industry.
In December 1971, an agreement was signed with the government of the Polish People’s Republic for the joint development of a new agricultural aircraft, named the M-15. The design work was to be carried out in Poland by a joint Soviet-Polish design team working at the Mielec plant, led by Soviet chief design consultant R.A. Izmailov, while the Polish side was represented by chief designer K. Gocyla.
The aircraft was designed as a biplane, with the engine mounted above its short fuselage under the upper wing. This was intended to protect the engine, operating close to the ground, from ingesting stones and other objects that would cause premature wear. Two chemical tanks were placed on either side of the fuselage between the wings. The airframe had two tail booms ending in vertical stabilizers, which were connected at their top by a horizontal stabilizer. This structural layout allowed unobstructed, free exhaust gas flow and did not interfere with chemical spraying.
At the front of the fuselage there was a hermetically sealed cockpit, providing excellent visibility and protecting the pilot from chemicals. Behind the cockpit there was a compartment that could accommodate two people, e.g. ground crew. At the rear of the fuselage, a starter unit was installed. The aircraft had fixed tricycle landing gear with a nose wheel. Wing mechanisation (slats and flaps) was used to improve handling characteristics. The lower wing served as an aerodynamic fairing for the spraying equipment.
At the end of May 1973, the experimental LLM-15 (Flying Laboratory M-15) began test flights. The M-15 prototype was first flown in January 1974. On subsequent prototypes, the air intake was shortened, and the shape of the chemical tanks, holding a total of 2200 kg of payload, was changed several times. Changes were also made to the pre-production series built in 1975. In the meantime, a pilot training version (with cockpits for student and instructor) was test-flown, and work was also underway on other applications for the aircraft.
After the completion of operational trials in 1976, serial production and deliveries began. In 1977, the M-15 was displayed at the Paris Air Show.
The M-15 proved extremely expensive to produce and operate. Its use in the USSR brought enormous disappointment. The M-15 was heavily criticised by users, often for non-technical reasons.
In 1979, the Soviet Union cancelled further orders for the M-15, which led to the termination of its production. By that time, 175 M-15 aircraft had been built.
| Wingspan | 22.4 m |
| Length | 12.7 m |
| Takeoff weight | 5650 kg |
| Maximum speed | 200 km/h |
| Ceiling | 4500 m |
| Range | 400 km |
| Armament | – |
| Engine | turbojet, AI-25 with 1500 kG thrust |
