Kawasaki Ki-64 "Rob" — Tandem-Engine Experimental Fighter

The Kawasaki Ki-64 (Allied codename "Rob") stands as one of the most technically audacious aircraft designs of the Second World War — an advanced experimental heavy interceptor conceived by chief designer Takeo Doi in 1939. Only a single prototype was ever completed. It flew just five times from December 1943 before a catastrophic engine fire on its fifth flight permanently ended the programme.

Due to the project's brief operational lifespan and the destruction of Japanese archives at war's end, original Kawasaki factory engineering bulletins are virtually non-existent. The primary surviving technical record is the post-war U.S. Army Air Force T-2 Technical Intelligence Report No. F-IR-100-RE, compiled at Wright Field, Dayton, Ohio — the cornerstone document of this Living Collection.

Collection Contents

No Variant — Common Documents

• Ki-64 Technical Publications — Kawasaki Ki-64 Tandem-Engine Fighter with Vapor-Phase Cooling · Technical Intelligence Report No. F-IR-100-RE · English Language · Released August 1946 · Headquarters Air Materiel Command, Wright Field, Dayton, Ohio
• Ki-64 Slides, Photos & Brochures — Ki-64 Photographic Collection · English Language

Aerodynamic & Design Overview

• Minimizing Drag: Designed explicitly to achieve extreme speeds by eliminating conventional drag-heavy scoop radiators entirely.
• Laminar Flow Wings: Ultra-smooth advanced laminar-profile wing panels for reduced boundary-layer drag.
• Surface Evaporative Cooling: A unique 258 sq. ft. steam-condensing network embedded directly into the wing skin replaced conventional radiators.
• Wind Tunnel Validation: A modified Ki-61 testbed confirmed the aerodynamic skin layout delivered approximately 35 mph speed advantage over conventional cooling arrangements.

Engine Technical Notes — Kawasaki Ha-201

The Ha-201 coupled two 12-cylinder inverted-Vee engines (derived from the licensed German Daimler-Benz DB 601Aa) into a single tandem powerplant of extraordinary complexity.

• Layout: Front engine in the nose; rear engine behind the cockpit, driving forward via a long extension shaft running between the pilot's legs.
• Power Output: 2,350 hp at takeoff · 2,200 hp at 12,795 ft operational altitude.
• Propeller System: Coaxial contra-rotating — rear engine drove the forward adjustable-pitch propeller; front engine drove the rear fixed-pitch propeller. An unfinished pitch synchronizer caused uneven rotation speeds.
• Cooling Cycle: Engine coolant pressurized to steam; 2% flashed to vapour and condensed through inner wing skins, recycling fluid continuously.

Handling, Stability & Operational Hazards

• Severe Overheating: Without conventional scoop radiators, the aircraft suffered extreme thermal spikes during ground idling, taxiing, and high-load climbs.
• Weight Distribution: Heavy fuselage-nose and spine mass concentration produced centre-of-gravity characteristics entirely unlike agile IJA fighters such as the A6M Zero.
• Fatal Defect: On the fifth test flight, rear cooling lines failed, triggering a massive engine fire that forced a structural crash landing and permanently ended the programme.

Performance Data

This is an archival, static-copy edition fixed at its original publication date. Intended for historical reference, flight simulation, museum restoration, and educational use only. Not approved for active airworthiness maintenance under FAA 14 CFR § 43.13, EASA Part-M, or equivalent international regulations. Operators of active aircraft must use current, revision-controlled publications from the Type Certificate holder or an authorized distributor.

Living Collections with Free Lifetime Updates — Please review our Disclaimer and Export Notice before purchasing.