Reference
OpenAI's Answer
The Imperial Japanese Army used several designation systems for their aircraft. Here are the main types:
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Ki Number System: This was based on the abbreviation "Ki" for "Kitai" (meaning "airframe") followed by a number. For example, the Nakajima Ki-8 was an experimental two-seat fighter.
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Type Number System: Introduced in 1927, this system assigned numbers based on the last digits of the Japanese year when the aircraft type was accepted into service. For instance, a plane accepted in 1940 would have a type number including the digits '40'.
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Official Names and Popular Names: Some airplanes had official designations and popular names that were commonly used. The Allied forces also gave code names to Japanese aircraft during World War II.
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