Nakajima Hikari

Nakajima Hikari
Name	Nakajima Hikari
Type	Radial aircraft engine
National origin	Empire of Japan
Manufacturer	Nakajima Aircraft Company
First run	1933
Major applications	Aichi D1A, Kawanishi E7K, Nakajima E8N

Nakajima Hikari. The Nakajima Hikari was a nine-cylinder, air-cooled, radial aircraft engine developed in Japan during the 1930s. It was a significant powerplant for the Imperial Japanese Navy, powering several key reconnaissance and dive-bomber aircraft in the years leading up to the Second World War. The engine represented an important step in Japan's move towards domestically designed and manufactured military aviation technology.

Design and development

The Hikari was developed by the Nakajima Aircraft Company in the early 1930s as a more powerful successor to the Nakajima Kotobuki engine. It was a single-row, nine-cylinder design that utilized advanced features for its time, including a supercharger to maintain performance at higher altitudes. The engine's development was part of a broader push by the Imperial Japanese Navy Air Service to equip its frontline aircraft with reliable, high-output domestic engines. Design work was led by a team of engineers at Nakajima's Musashi Plant, drawing on experience gained from earlier license-production of foreign designs like the Bristol Jupiter. The Hikari 1 model entered production in 1933, with subsequent versions featuring increased displacement and improved supercharging.

Operational history

The Hikari engine entered service with the Imperial Japanese Navy in the mid-1930s and saw extensive use on several prominent aircraft. It was the primary powerplant for the Aichi D1A carrier-based dive bomber, which saw combat during the Second Sino-Japanese War. The engine also equipped the Kawanishi E7K and Nakajima E8N reconnaissance floatplanes, which served as the eyes of the fleet aboard battleships and cruisers. These aircraft participated in numerous naval engagements and patrols in the lead-up to the Pacific War. While largely superseded by more powerful engines like the Nakajima Sakae by the time of the attack on Pearl Harbor, Hikari-powered aircraft remained in secondary roles throughout the early years of the conflict, including during the Battle of the Coral Sea and the Guadalcanal campaign.

Variants

* Hikari 1: Initial production model. * Hikari 2: Increased bore, yielding greater displacement and power output; the most common variant. * Hikari 3: Further development with a modified supercharger for improved high-altitude performance. Some sources also reference a Hikari Kai (modified) version with minor refinements.

Operators

The primary and sole military operator was the Imperial Japanese Navy Air Service. The engine was installed on aircraft operated from aircraft carriers such as the Kaga and Ryūjō, as well as on seaplanes deployed by the Imperial Japanese Navy's surface fleet and shore-based units. No evidence exists of export or use by other national air forces, such as the Royal Air Force or the United States Army Air Forces.

Specifications (Hikari 2)

General characteristics * **Type:** 9-cylinder air-cooled radial piston engine * **Bore:** 146 mm * **Stroke:** 160 mm * **Displacement:** 24.1 L * **Length:** 1,325 mm * **Diameter:** 1,280 mm * **Dry weight:** 470 kg

Components * **Valvetrain:** Overhead valve, two valves per cylinder * **Supercharger:** Gear-driven centrifugal type * **Fuel system:** Carburetor * **Cooling system:** Air-cooled

Performance * **Power output:** 730–800 hp at take-off * **Compression ratio:** 6.0:1

Category:Aircraft engines Category:Imperial Japanese Navy aircraft engines Category:Nakajima aircraft engines Category:Radial aircraft engines