A Functional Check Flight is a description normally given to a non revenue flight which has the sole purpose of checking for the correct airborne function of certain aircraft systems. These flights can be conducted for a number of reasons, such as:
The term does not include formal test flights carried out by trained test pilots employed by an aircraft manufacturer or National Aviation Authority (NAA) for purposes such as customer acceptance of new aircraft or the renewal of a Certificate of Airworthiness, or any type of flight requiring trained test pilots.
A Functional Check Flight, has been associated with an above average risk of an Accident or Serious Incident. These flights are vital to insuring safe, reliable, and airworthy aircraft. How these flights are conducted, who conducts them, exactly what is to be accomplished on these flights, and how it is to be accomplished, are major issues that must be addressed by any organization that conducts functional check flights.
The operation of an aircraft with systems intentionally degraded in order to validate the operational status of an aircraft, or certain aircraft systems, may occur on functional check flights. A very thorough flight crew pre flight plan can help reduce the chances of unexpected events occurring in flight. Some of the potential issues and mitgations for this risk are examined in the more general article "Mitigating Risk for Non Standard Flights" and examples of Accidents and Serious Incidents can be found at "Accident and Serious Incident Reports: Non-Revenue Flights". A recognition that a specific process is needed for the selection and training of flight crew who are to perform this type of flight is essential, and this aspect is examined further in the article Crew Training for Functional Check Flights. Consideration should also be given to items such as minimum/maximum crew, weather requirements, and minimum and maximum speeds and altitudes for all portions of the functional check flight.