From time to time, components of every aircraft are likely to fail. Is this
aircraft now unairworthy? Not necessarily. The FAA has prescribed a specific
process whereby an aircraft can be operated with certain instruments or
equipment not working. This process must be followed exactly in order to have a
legal operation. If the aircraft cannot be considered airworthy due to the
specific failure and a repair cannot be made at the current location, a
Special Flight Permit may be required to get
the aircraft to a location where a fix can be made.
It must be stated, however, that although this process may make an aircraft
with inoperative equipment legal to fly, if the Pilot-In-Command (PIC)
determines that such an operation incurs an unacceptably high level of risk,
they have a duty to not operate that aircraft. Before commencing such an
operation, the PIC should review all risk factors of the flight with either the
5-P or PAVE checklists.