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Moskalev SAM-7 (Sigma)


Twin-Seat, Single-Engine Fighter Prototype


The Moskalev SAM-7 never fulfilled its potential in testing - owning largely to an unproven and wholly unique design arrangement.
Authored By: Staff Writer | Edited: 1/17/2019
National Flag Graphic

Specifications


Year: 1936
Status: Cancelled
Manufacturer(s): Moskalev UN31 / Plant 18 - Soviet Union
Production: 1
Capabilities: Fighter; X-Plane;
Crew: 3
Length: 22.97 ft (7 m)
Width: 31.50 ft (9.6 m)
Weight (Empty): 2,205 lb (1,000 kg)
Weight (MTOW): 3,307 lb (1,500 kg)
Power: 1 x Mikulin M-34 V-12 liquid-cooled inline piston engine developing 750 horsepower and driving a four-bladed propeller unit at the nose.
Speed: 311 mph (500 kph; 270 kts)
Ceiling: 30,184 feet (9,200 m; 5.72 miles)
Range: 497 miles (800 km; 432 nm)
Operators: Soviet Union (cancelled)
By mid-1930s aircraft standards, the Moskalev SAM-7 "Sigma" was a wholly unique, two-seat, single-engine "tailless" fighter proposal of the World War 2-era (1939-1945) to emerge from the Soviet Union Appearing in 1936, the aircraft never saw service as a production aircraft. Such experiments proved common for all major participants of the Second World War with many such designs never seeing the light of day, let along functional prototypes. Design of this aircraft is attributed to Alexsandr A. Moskalev.

The aircraft incorporated a mid-set monoplane arrangement with full-length slotted flaps were to act as elevators and ailerons to handle pitch, roll, and elevation controls. The wing mainplanes were fitted to the sides of the fuselage in typical fashion and given a tapered shape from fuselage to the wingtips. Furthermore, the wingtips were capped by oversized, rounded fins. The pilot sat in his usual place near midships with the engine mounted direct forward, this used to drive a four-bladed wooden propeller unit. Construction was of all-metal including metal skinning of aluminum alloy. The undercarriage was of a "tail dragger" arrangement incorporating two main (wheeled) legs under the wings and a simple tail skid aft. The main legs retracted (by means of a manual mechanism) into the wings towards the fuselage centerline while the tail skid was fixed.

Power was from a single Mikulin M-34 series V12 liquid-cooled piston engine of 750 horsepower which drove the propeller unit at the nose. This same mass-production engine (over 10,500 individual units produced from 1934 to 1943) powered such types as the Tupolev TB-3 and TB-4, the Petlyakov Pe-8, and the Kalinin K-7.

The aircraft's wingspan reached 9.6 meters with an overall fuselage length of 7 meters. Empty weight was 1,000kg against an MTOW of 1,500kg.

Proposed armament was 2 x 7.62mm ShKAS machine guns synchronized to fire through the spinning propeller blades while the rear cockpit was managed by the dedicated rear gunner who had access to 2 x 7.62mm ShKAS machine guns. In this way, the aircraft could attack both aerial and land-based targets while being actively defensed from the rear.

The SAM-7 saw only limited testing and quickly found to be an inherently unstable design - no surprise considering the departure from the aircraft design norms of the time. Instead, the Soviet aeronautic focus remained on more conventional, traditional fighter designs for the foreseeable future.

Captured performance specs included a maximum speed of 500 kmh, range of 800 kilometers, and a service ceiling of 9,200 meters.






Armament



PROPOSED:
2 x 7.76mm ShKAS machine guns in fixed, forward-firing mounts over the nose synchronized to fire through the spinning propeller blades.
2 x 7.62mm ShKAS machine guns paired in a trainable, rear-facing gun position at the aft-section of the fuselage.

Graphical image of an aircraft medium machine gun

Variants / Models



• SAM-7 - Base Project Designation; single prototype completed and lightly tested.
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