Single-engine Part 135 Electrical Requirements Clarified

The FAA on January 27 published updated guidance - for agency inspectors and hence operators on emergency electrical requirements for Part 135-operated single-engine aircraft flying in instrument conditions. The agency’s Flight Standards Division (AFS-200) believes some operators are not aware of the differences between the emergency electrical equipment requirements of the original Part 23 certification standards and those of Part 135.163(f). Some single-engine aircraft operators, according to the FAA, erroneously believe Part 23 requirements offer them enough redundancy to meet their requirements under Part 135.

Part 23, however, requires only 30- minutes of battery power to sustain safe flight operations following after a primary power source failure, while Part 135 requires two independent electrical power-generating sources each capable of supplying all probable combinations of continuous in-flight electrical loads. Part 135 also could require a standby battery, or some other electric power source, capable of supplying 150 percent of the electrical loads of all required instruments and equipment necessary for safe emergency operation of the aircraft for at least 1one hour.