Kubulius Ku-3

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Kubulius Ku-3
Ku-3.jpg
Role Fighter
National origin Silua
Manufacturer Kubulius Design Bureau
Designer Vaida and Iruna Cibaite
First flight 1933
Introduction 1935
Retired 1947
Status Retired
Primary user Siluan Air Force
Produced 1940-1948
Number built 10,955
Developed into Kubulius Ku-13

The Kubulius Ku-3 was a family of Siluan light fighter aircraft of the 1940s. The Ku-3 was produced in large numbers and was exported throughout Tyran

Development

The original specification that led to the Ku-3 series was offered in 1936 in order to quickly raise the number of modern aircraft in Siluan service, by supplying a "light fighter" of simple construction that could be built rapidly in large numbers. The contract originally resulted in three designs, the N.O.G. 52, the Talin Ta-17 and the Ku-00. Prototypes of all three were ordered.

Because Military Order 13478-93X which diverted all metal to the army and navy, the Ku-00 was all wooden in construction, using plywood over stringers in a semi-monocoque construction. The layout was conventional, a low-wing monoplane. Armament consisted of a 20mm Tanin MG 32 cannon firing through the propeller hub, and four 7.5mm Mogh MG 30 drum-fed machine guns, two in each wing. The design was supposed to be powered by the Kavu Dc 31 flat-12 air-cooled inline engine, but this ran into development problems. The prototype was then fitted with a Ravumo Varikliai12Xcrs instead, and flew in this form in October 1938.

In order to find some solution to the engine problem, the Ku-1 was to use the 632 kW (860 hp) Ravumo Varikliai12Y-31and the Ku-2 the Gilbert V-1710C-15. The Ku-1 flew in 1939 and proved to have excellent performance. The prototype Ku-2 was completed in 1940.

The Ku-3 was a modified version of the Ku-1 using the same 12Y-31, and first flew on April 25, 1939. It had a surprisingly good performance of 560 km/h (348mph), and was ordered into production with a contract for 220 aircraft in September, later raised to 1,000. Production did not take long to start and progressed quickly

Further developments continued while the Ku-3 production started. The Ku-4 mounted the newer 688 kW (935 hp) 12Y-45, the Ku-6 used the 735 kW (1,000 hp) 12Y-51 originally intended for the Ku-5, and introduced a new streamlined radiator. Single prototypes of all three were built and flown in early 1940. The Ku-7 was an extended-range version of the Ku-6, while the Ku-8 was to have used the 12Y-77, but neither was built.

The last in the series was the Ku-9, originally powered by the new 882 kW(1,200 hp) 12Y-89 using an extension shaft on the propeller to streamline the nose profile, giving the plane an excellent speed of 625 km/h (388 mph) even when loaded down with two more machine guns. The Ku-9 used the streamlined radiator intake design from the Ku-6. With the development of the Ku-9, 500 of the original Ku-3 order were changed to the Ku-9 with additional 1,000 Ku-9s ordered and production began in June of 1940.

Operational History

Variants

  • Ku-00 – The original powerplant was the Kavu Dc 31 flat-12 air-cooled inline engine, but the prototype was fitted with a Ravumo Varikliai 12Xcrs, and flew in this form in October 1938.
  • Ku-1 – Ravumo Varikliai 12Y-31 powered prototype.
  • Ku-2 – Gilbert V-1710C-15 powered prototype.
  • Ku-3 – First production model with Ravumo Varikliai 12Y-31 engine
  • Ku-4 – 697 kW (935 hp) Ravumo Varikliai 12Y-45 engine. 360 mph (600 km/h). Prototype only.
  • Ku-5 – Ku-3 variant with newer engine. One built.
  • Ku-6 – 746 kW (1,000 hp) Ravumo Varikliai 12Y-51 engine. Prototype only.
  • Ku-7 – Extended-range version of the Ku-6. Not built.
  • Ku-8 – projected for Ravumo Varikliai 12Y-77 engine. Not built.
  • Ku-9 – Final prototype version powered by the 954 kW (1,280 hp) Ravumo Varikliai 12Z engine. 393 mph (655 km/h).
  • Ku-9sal - Production variant powered by the 1177 kW (1,600 hp) Ravumo Varikliai 12Z-17 engine. 4x 13 mm Mogh MG 41 replaced 4x Mogh MG 30 7.5 mm machine guns.

Operators

Silua

Specifications (Ku-9)

Orthographically projected diagram of the Ku-9 N3M

General characteristics

  • Crew: 1
  • Length: 8.75 m (28 ft 8 in)
  • Wingspan: 10.5 m (34 ft 5 in)
  • Height: 3.70 m (12 ft 2 in)
  • Wing area: 14 m2 (150 sq ft)
  • Empty weight: 2,110 kg (4,652 lb)
  • Gross weight: 3,000 kg (6,614 lb)
  • Powerplant: 1 × Ravumo Varikliai 12Z V-12 inverted liquid-cooled piston engine 1,177 kW (1,578 hp)
  • Propellers: 3-bladed light-alloy constant-speed propellers, 3 m (9 ft 10 in) diameter

Performance

  • Maximum speed: 633 km/h (393 mph; 342 kn) at 7,000 m (22,966 ft)
  • Cruise speed: 466 km/h (290 mph; 252 kn)
  • Stall speed: 100 km/h (62 mph; 54 kn)
  • Range: 1,350 km (839 mi; 729 nmi)
  • Combat range: 675 km (419 mi; 364 nmi)
  • Ferry range: 2,700 km (1,678 mi; 1,458 nmi)
  • Service ceiling: 12,000 m (39,000 ft)
  • Rate of climb: 24.8 m/s (4,880 ft/min)
  • Time to altitude: 6,000 m (19,685 ft) in 4 minutes

Armament

  • Guns:
  • 6 × 13 mm (0.512 in) Mogh MG 41 machine guns in the wings with 400 rpg
  • 1 × 20 mm (0.787 in) Tanin MG 32 cannon in propeller hub with 150 rpg