If an unairworthy mechanical, electrical, or structural condition occurs, FAR 91.7(b) requires the pilot in command to discontinue the flight. This means landing at the first available airport consistent with safe operations, even if it does not have services. For flights in controlled airspace under IFR, FAR 91.187 also requires the PIC to report as soon as practical to ATC any malfunctions of navigational, approach, or communication equipment. If an in-flight emergency requires immediate action, FAR 91.3(b) allows the PIC to deviate from the FARs to the extent required to meet that emergency.
Immediately following the flight, determine whether the malfunction triggers any of the reporting requirements under NTSB rules or the FARs. 49 CFR 830.5 specifies 12 “serious incidents” that require immediate notification to the NTSB, including but not limited to a flight control system malfunction or failure; in-flight fire; or a complete loss of information from more than 50 percent of certain displays. If the PIC deviated from any rules under FAR 91.3(b), a written report must be submitted, but only if requested by the FAA.
Often it’s after landing that some pilots get into legal trouble by deciding to fly the aircraft again without realizing the aircraft is in a potentially unairworthy condition. This might be because the malfunction seems insignificant, the pilot can’t replicate it on the ground, or a mechanic isn’t on site. FAR 91.7 prohibits operation of an aircraft unless it’s airworthy, meaning the aircraft complies with its type certificate, including any supplemental type certificates and airworthiness directives, and is also in a condition for safe operation. So even though an aircraft is flyable, it may not be airworthy.
If a pilot is alleged to have flown an unairworthy aircraft, the FAA need only show that the pilot knew or should have known that it didn’t comply with its type certificate or that it was in an unsafe condition. In one case, the PIC of a Cessna 150 didn’t know with certainty that a broken carburetor heat cable rendered his aircraft unairworthy, but it was found he should have known of the necessity of carburetor heat to the proper and safe operation of the aircraft. Even though he thought carb heat was not necessary on the 90-degree day and the flight was uneventful, the POH required full carburetor heat before landing.
Following an equipment malfunction, consider grounding the aircraft until it can be inspected by a mechanic, evaluating whether the inoperative equipment can be addressed under FAR 91.213, or obtaining a special flight permit to relocate the aircraft. If maintenance is necessary, comply with FARs 91.405 and 91.407, which require, among other things, that the aircraft be approved for return to service by an authorized person and the required maintenance record entry made. Even if a problem cannot be replicated, don’t fly off without a record of what was done in hand—it can be on a separate piece of paper—because it will almost certainly be requested if the FAA learns of the event.
But how are FAA investigations triggered, especially if the pilot wasn’t required to report it? Often, it’s by air traffic controllers, who are required to file “mandatory occurrence reports” (MORs). Any “abnormal event, other than an incident or accident,” can be considered an “occurrence” for which ATC must file an MOR (“Abnormal Findings,” March 2021 AOPA Pilot). In other cases, airport managers or FBOs have advised the FAA about such events.
Regardless, if the decision is made to investigate the matter an inspector will typically contact the PIC by phone or letter, or if the PIC has not been yet identified, the aircraft’s registered owner. The inspector will likely request a written statement detailing the event, along with a copy of any associated maintenance record entry. Assuming there are no other compliance issues with the flight, the matter will likely be closed once the statement and any required documentation are provided.
A safe approach following a flight that experiences an equipment malfunction is having it addressed by an appropriately certificated mechanic and obtaining a maintenance record entry prior to continuing operation. Out of an abundance of caution, it’s a good idea to file a NASA ASRS report within 10 days of the flight, and to call the AOPA Legal Services Plan before responding to any FAA inquiries.