What is the process for registering a Cessna that has been modified to use an automobile engine?
ANSWER: Registering a modified aircraft is the same as registering any other aircraft. You simply provide the required information to the FAA Aircraft Registration Branch in Oklahoma City. Refer to the aircraft registration section of this website.
Before the aircraft could be flown, it would have to have been modified using FAA approved data, for example a Supplemental Type Certificate (STC). A record of that modification would have to be made, and any supplements would have to be inserted in the flight manual.
If the modification was not done using FAA approved data, then an experimental certificate would be needed and the aircraft would have to be entered into a flight test program to show compliance with the FAR’s. Refer to the aircraft certification/special airworthiness certification section of this web site and FAR 21.191 (b)