How do I get permission to fly an airplane with a non-safety-related airworthiness issue, like being out of annual or having an inoperative radio in order to take it somewhere that it can be fixed?
You'll need to fill out Form 8130-6, Application for U.S. Airworthiness, appropriately calling out the reasons you need a SFP (ferry flight, etc). Once the form is submitted, you may be subject to an inspection by an FAA official or representative, verifying that your aircraft is in fact in a condition for safe operation.
Avemco, the insurance company, has a good article on ferry permits that might be worth an extended read and which I don't intend to copy here.
The FAA / Philidelphia FSDO already gave a perfect short and snappy official answer perfectly matching your question. Please note the restrictions mentioned in this handy sheet to stay absolutely legal :)
The short summary: contact your local FSDO to request a Special Flight Permit ("ferry permit"), which are commonly used for:
- Flying the aircraft to a base where repairs, alterations, or maintenance are to be performed
- Flying an aircraft whose annual inspection has expired to a base where an annual inspection can be accomplished.
- Production flight testing of new production aircraft.
- To authorize the operation of an aircraft at a weight in excess of its maximum certificated takeoff weight.
and many other reasons detailed in the link above.
To obtain a special flight permit you will need to provide the following info to the FAA:
- Purpose of the flight.
- Proposed flight itinerary.
- Essential crew required to operate the aircraft.
- The ways, if any, in which the aircraft does not comply with the applicable airworthiness requirements.
- Any other information they may request