It was the standard hand-held machine gun in multi-place IJN aircraft during the most part of the Pacific War. It proved to be seriously inadequate. Aircraft produced in the later part of the conflict often were equipped with weapons such as Type 1 and Type 2 machine guns or Type 99 cannon.
Essentially a copy of the shroudless post-World War I aircraft-mounted version of the British Lewis gun, the Type 92 was fed with a 97-round drum magazine and used on a flexible mount. It was chambered in a Japanese copy of the .303 British cartridge. The main external difference between the two models was the trigger guard, and cooling fins around the barrel and gas piston tube. Neither the post-World War I British aircraft Lewis nor the Japanese copy featured the distinctive thick barrel shroud of the original gun (although ground-based versions generally retained it). It was removed as it was found that the airflow past the aircraft was sufficient for cooling the barrel and eliminating the shroud reduced the mass.
Type 92 Japanese Navy machine gun
This was a copy of the British Lewis gun, the difference being a trigger guard whilst the barrel shroud was removed in naval aircraft but maintained for ground operations as shown here. 
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Description
Type 92 (Lewis) aircraft machine gun. The air cooled barrel does not have the tubular steel jacket and aluminium cooling fins. The receiver has a wooden pistol grip trigger assembly and there is a leather covered spade grip at the rear. A crude bipod has been attached to the barrel for ground use. The sights are missing from this weapon.
History / Summary
This type of gun would have originally been fitted to Japanese Navy aircraft on a flexible mount but it has been modified for ground use with a bipod.