Kawanishi K-3

The Kawanishi K-3 was a Japanese, fast, multi-purpose civil transport aircraft from the early 1920s. Despite its good performance it was eclipsed by the release of Army surplus machines and only one was built.

The K-3, completed in October 1921, was designed as a fast civil transport able to carry two passengers or mail and other cargo. It was a development of the Kawanishi K-1 completed in December 1920 and was more powerful, aerodynamically cleaner and faster. Like most aircraft of its period it had a wooden structure and was fabric-covered.^[1]

It was a single bay biplane with rectangular plan wings braced by parallel pairs of interplane struts. The upper wing was joined to the upper fuselage by a cabane formed by pairs of transverse outward-leaning inverted V-struts to the forward wing spar and similar but longitudinal V's to the rear. The lower wing was joined as usual to the lower fuselage longerons.^[1]

At the end of World War I Japan received a large number of Maybach engines, designed to power airships, as part of its war reparations. The K-3 was the first Japanese aircraft to use one, a Maybach Mb.IVa six cylinder, water-cooled, upright straight engine producing 260–305 hp (194–227 kW). Its radiator was mounted horizontally in the upper wing centre section to reduce drag. It was nose-mounted and smoothly faired into the fuselage behind. An open, underwing cockpit seated two passengers side-by-side, with the pilot in a second open cockpit well behind the wing trailing edges.^[1]

The K-3 had a fixed, conventional undercarriage with mainwheels on a single axle with pairs of faired landing legs and rearward drag struts mounted on the lower fuselage longerons. There was a short tailskid.^[1]

The K-3 first flew in the early winter of 1921. It was the fastest civil aircraft in Japan, with the speed of a fighter and the load-carrying ability of a light bomber. Kawanishi had hopes of commercial success but instead the light civil transport market was filled by the lower-powered and slower Nakajima Type 5 Trainers released by the Army and no more K-3s were built.^[1]

In 1926 the sole K-3 was modified to take a straight six, 200–230 hp (150–170 kW) Benz Bz.IIIaV (Benz Bz.IV)^{[2][Notes 1]} engine as well as other changes to become the Kawanishi K-3B.

Kawanishi K-3

Prototype with 260–305 hp (194–227 kW) Maybach Mb.IVa.

Kawanishi K-3B

Prototype with 200–230 hp (150–170 kW) Benz Bz.IV and airframe modifications.

Data from Japanese Aircraft 1910-1941^[1]

General characteristics

• Crew: one
• Capacity: two passengers
• Length: 8.86 m (29 ft 1 in)
• Wingspan: 10.03 m (32 ft 11 in)
• Height: 2.60 m (8 ft 6 in)
• Wing area: 30.5 m² (328 sq ft)
• Airfoil: RAF 15
• Empty weight: 970 kg (2,138 lb)
• Gross weight: 1,400 kg (3,086 lb)
• Powerplant: 1 × Maybach Mb.IVa six cylinder water-cooled inline, 194–227 kW (260–305 hp)
• Propellers: wooden

Performance

• Maximum speed: 230 km/h (140 mph, 120 kn)
  
• Landing Speed: 97 km/h (60 mph; 52 kn)
• Endurance: 5 hr
• Service ceiling: 8,500 m (27,900 ft)
• Time to altitude: 10 min to 3,000 m (9,800 ft)