Kokusai Ki-105 Ohtori — Primary-Source Documentation Collection
The Kokusai Ki-105 Ohtori (大鵬, "Phoenix") was one of the most unconventional transport aircraft produced by Japan during the Pacific War — a twin-boom, motorized derivative of the Ku-7 glider, engineered out of desperate strategic necessity to address the acute fuel crisis gripping the home islands in 1944.
Aerodynamic & Structural Design
- Twin-Boom Layout: High-aspect-ratio main wing with a central pod nacelle housing the cockpit and cargo bay. The twin tail booms were slightly shortened from the Ku-7 glider variant to correct center of gravity with forward engine mounts.
- Composite Construction: Central nacelle in lightweight aluminum alloy; wings and tail booms primarily wood to conserve strategic metals.
- Landing Gear: Fixed heavy-duty tricycle undercarriage — four non-retractable main wheels on dual axles plus a single nose wheel — maintaining a level cabin floor for loading internal fuel bladders.
Engine Technical Notes
- Powerplant: Two Mitsubishi Ha-26-II (Ha-102) 14-cylinder twin-row air-cooled radials, 940–960 hp each.
- Rejected Option: Early designs considered the 450 hp Nakajima Ha-13; abandoned immediately due to severe power deficit.
- Propulsion: Three-blade constant-speed metal propellers mounted to the forward section of each tail boom.
Handling & Stability Studies
- Control Surfaces: Fabric-covered wooden ailerons, elevators, and twin rudders adapted directly from glider blueprints.
- Japanese Army Assessment (December 1944): Test pilots considered the platform remarkably stable for its size.
- Allied Evaluation: Retrospective flight safety journals noted the aircraft was sluggish, aerodynamically heavy to pilot, and highly vulnerable due to its slow cruise speeds.
Performance Data
| Parameter | Value |
|---|---|
| Wingspan | 35.00 m (114 ft 10 in) |
| Length | 19.92 m (65 ft 4 in) |
| Max Takeoff Weight | 12,500 kg (27,600 lbs) |
| Normal Freight Payload | 3,300 kg (7,300 lbs) |
| Cruising Speed | 220 km/h (140 mph / 120 kts) |
| Maximum Range | 2,500 km (1,600 miles) |
| Crew | 2 pilots |
Engineering Bulletins & Logistics
- The Sumatran Fuel Pipeline: Engineering bulletins designated the Ki-105 as a flying fuel tanker — flying unladen to Japanese-occupied oil fields in Sumatra, loading fuel reservoirs, and returning to Japan.
- Efficiency Deficit: Engineering estimates calculated that up to 80% of the loaded fuel cargo would be consumed by the engines on the return trip alone, rendering the concept operationally marginal.
Collection Manifest
Total Manuals: 2
- Ki-105 Aircraft Handbook: Kokusai Ki-105 Ohtori — Detailed Design Specifications, 設計明細書 キ一○五 (Japanese Language)
- Ki-105 Photo Archive: Ki-105 Photographic Collection (English Language)
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.
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