为了降低飞机的维修成本,航空公司希望尽量使用国产航材作为飞机某些原装零部件的代用品。于是,国内许多厂家力所能及地研制并生产飞机零部件成品,供航空公司在维修飞机时选用。但是,在进口的飞机上使用国产代用品的前提是:国产代用品的使用不能降低飞机的安全性。也就是说, In order to reduce the cost of aircraft maintenance, airlines hope to make full use of domestic aviation materials as a substitute for certain original aircraft parts. As a result, many domestic manufacturers try their best to develop and produce aircraft parts finished products for airlines in the maintenance of aircraft selection. However, the premise for using domestically produced substitutes on imported aircraft is that the use of domestically produced substitutes can not reduce the safety of the aircraft. In other words,