Su-12 (RK) reconnaissance artillery spotter by P.O.Sukhoj

The twin-boom configuration (despite not a novelty for Soviet designers) gained great official interest during War because of the successful operation of German Focke-Wulf 189 twin-boom reconnaissater. One of those machines was captured by the Soviets and flight tested in the NII VVS.

P.O.Sukhoj proposed his first twin-boom machine (RK 2xASh-62) near the end of 1943, but this design did not get approvals for manufacturing the prototype. Next project, despite closely resembling the RK 2xASh-62, was substantially larger and more capable.

The Su-12 RK was designed and built in a very short time. Preliminary studies started in the middle of 1946. One year later, in August 1947, new aircraft entered development (factory) flight tests. For several months N.Fikson, M.Gallay, S.Anokhin and G.Shiyanov conducted those flights.

Photographic equipment permitted photo reconnaissance missions both in day and night conditions. The Su-12 could be used not only as reconnaissance and artillery spotter, but also as a bomber. The bomber version could carry eight 100kg bombs, released one at a time or in a salvo.

Naturally, aircraft nickname was "Rama" (Frame), same as given by Soviet Army to the FW-189 of Luftwaffe. A crew of four occupied a short fuselage gondola and included pilot, navigator, front gunner, radio operator/rear gunner. Initially, the upper part of the nose section had spherical glazing, replaced later by set of flat panels. Front and rear cockpits had jetissonable door and hatch. Front cockpit had additional top emergency escape hatch.

Original variant of Su-12 had only partial 8mm steel armoring. This was soon found insufficient, and the crew nacelle was redesigned. The lower area of glazing now consisted of 12 bullet-proof 15mm glass plated, protecting pilot and navigator. Cockpit floor and side panels included steel armor plates. Rear turret had two 90mm armor glass and one steel armor plates for protection. All crew members seats had armored backrests, and wide 12mm plate fas situated in front of the radio operator/gunner. Total weight of armor was 450kg. All navigation, photographic and radio gear was located in the crew nacelle.

Single-spar stressed-skin wing consisted of the central section (integrated with engine nacells) and two outer wing panels. Flaps and ailerons with airdynamic and weight compensation were attached to the rear auxiliary spar. They had a metal framework with fabric cower. Controllable trim was installed on the port aileron, and balancing tab - on the starboard one.

Tailbooms were of monocoque structure with duralumin skin. Tailfins and empennage were structurally integrated with tailbooms. Rudder and elevator, same as ailerons, had airdynamic and weight compensation and were of metal/fabric design. Both rudders carried controllable trims, while elevator had controllable trim and balancing tab. Main undercarriage units were retracting backwards into the tailboom. The tailwheel at the center of the tailplane was also retractable.

Initially, Su-12 was equipped with two experimental ASh-82V engines. During factory trials, those were replaced by mass-built ASh-82FN of less power, driving 3.6m AV-9FV21K four-blade variable-pitch feathering propellers. Cooling system included the shutters in front and automatic cooling flaps behind the engine. Additional internal cowling also was used to regulate air flow around engine cylinders. Automatic shutter (dust filter) covered the engine air inlet if the main undercarriage is not completely retracted.

Armament included four 20mm B-20E guns (Jean Alexander insists of four NR-23). In a bomber role, Su-12 could accommodate eight 100kg bombs attached to four cluster bomb racks in the tailbooms behind the landing gear. Bombs could be released in pairs or individually by the means of hydraulic actuators.

The Su-12 entered the State Flight Tests in December 1947. NII VVS team included test pilots A.Kabanov, P.Stefanovsky, V.Zhdanov, M.Nukhtikov, A.Kubyshkin and G.Tinyakov. Conclusion was positive: "The aircraft is stable, it is easy to fly and control, climbing is performed easily, the field of view during climb is excellent, the aircraft can fly with one engine running at altitudes up to 6000m. Hands of control flight is permissible... the Su-12 aircraft powered by two ASH-82FN engines must be recommended for introduction into the inventory of the Air Force."

Su-12 program was abandoned in 1948. However, the one of two built Su-12 participated in 1948 the Soviet Aviation Day Display at Tushino - to take air-to-air film pf the show. The Su-12 was the last piston engine of the Sukhoj Design Bureau.

For several years they were used for various military and civil purposes, including aerial photography of the remote areas of the USSR. In reality, Su-12 proved to be a reliable aircraft in operation.