A variant aircraft is one that embodies certain design features which differ from one for which a Certificate of Airworthiness (C of A) has previously been issued; that is a Prototype.
Where the design changes are such that they materially affect the type design, they must of course be investigated by the C.A.A. before another C of A can be issued to cover the modified status of the aircraft.
An application is made to the C.A.A. for the issue of a C of A in a similar manner to that for the prototype C of A issue. This time however, the design data to be submitted by the design and manufacturing organisation concerned will not be quite as extensive as for the prototype.
The Certificate of Design is also required but, unlike that for the prototype, it will contain an additional certified statement concerning the design changes introduced. A list of the changes also has to be prepared which shows how they affect the information contained in the original Type Record document.