Nakajima G5N Shinzan


The Nakajima G5N Shinzan was a four-engined, long-range heavy bomber designed and built for the Imperial Japanese Navy prior to World War II. The Navy designation was "Experimental Type 13 Attack Bomber"; the Allied code name was "Liz".

Design and development

The Nakajima G5N Shinzan originated due to the Imperial Japanese Navy's interest in developing a long-range attack bomber capable of carrying heavy loads of bombs or torpedoes a minimum distance of. To meet this requirement, it became apparent a four-engine lay-out would be necessary. As Japanese aircraft manufacturers lacked experience in building such large, complex aircraft, the Navy was forced to search for a suitable, existing, foreign-made model upon which to base the new design. It settled on the American Douglas DC-4E airliner. In 1939, the sole prototype of this airliner was purchased by Nippon Koku K.K and clandestinely handed over to the Nakajima Aircraft Company for dismantling and inspection.
The design that emerged from this study was for an all-metal, mid-wing monoplane with fabric-covered control surfaces, powered by four 1,530 hp Mitsubishi MK4B Kasei 12 air-cooled radial engines driving four-bladed propellers. A long ventral bomb-bay, glazed nose, and twin tailfins, replacing the DC-4E's distinctive triple rudder, were included. The DC-4E's retractable tricycle undercarriage was retained, as well as the original wing form and powerplant arrangement. Defensive armament comprised two 20 mm Type 99 Model 1 autocannon, plus single-mount, hand-operated 7.7 mm Type 92 machine guns in the nose, ventral, and waist positions.
The first prototype G5N1 made its maiden flight on 8 April 1941. However, overall performance proved disappointingly poor due to a combination of excessive weight, the low power of the Kasei engines, and the complexity of the design. Only one additional prototype was completed. In an attempt to salvage the project, four additional airframes were built and fitted with 1,870 hp Nakajima NK7A Mamori 11 engines and redesignated G5N2. Although the Nakajima engines were more powerful than the original Kasei 12s, their unreliability and the aircraft’s increased weight led to the termination of further development.

Operational history

Of the six completed Shinzans, four were relegated for use as long-range Navy transports under the designation G5N2-L Shinzan-Kai Transport. The Allies allocated the code-name "Liz" to the aircraft, in the expectation it would be used as a bomber.

Variants

;G5N1 Experimental Type 13 Land-based Attack Bomber Shinzan
;G5N2 Test production Shinzan Kai
;G5N2-L Shinzan Kai Freighter
;Ki-68
;Ki-85

Operators