Normal category aircraft, including normal category airplanes and normal category rotorcraft, are the main models in the general aviation industry. The engine inlet system is an important part of such aircraft. The quality of its design is related to the normal operation of the engine, which needs to be focused on airworthiness certification. In order to comprehensively study the airworthiness compliance of air inlet clauses for normal category aircraft, the airworthiness standards and recommended compliance verification methods for normal category airplane and normal category rotorcraft were analyzed, and a comparative study was carried out in combination with the airworthiness certification cases of a certain agricultural and forestry airplane and a certain helicopter. The research results show that both normal category airplane and normal category rotorcraft air inlet clauses use explanatory documents and flight tests to indicate compliance. Illustrative documents need to introduce the design principle and composition of the air inlet system. In specific models, this part can be given separately or included in the power system design description document. The flight test verification does not need to be carried out separately, but can be carried out in combination with the inspection of the working characteristics of the power unit. By comparing the validation cases of different models, the compliance verification methods and ideas of air inlet terms for normal category aircraft are given, which can provide reference for the subsequent development and airworthiness certification of similar models in the future.