Two Levels Of Protection For Systems Based On Known Failures

The FAA has amended the lightning protection airworthiness standards by establishing new lightning protection regulations for electrical and electronic systems installed on aircraft certificated under Parts 23, 27 and 29, and revises lightning protection regulations for electrical and electronic systems installed on airplanes certificated under Part 25.

This rule establishes two levels of lightning protection for aircraft systems based on consequences of system function failure: Catastrophic consequences which would prevent continued safe flight and landing; and hazardous or major consequences which would reduce the capability of the aircraft or the ability of the flightcrew to respond to an adverse operating condition. This rule also establishes lightning protection for aircraft systems according to the aircraft's potential for lightning exposure. The airworthiness standards establish consistent lightning protection requirements for aircraft electrical and electronic systems.
 
According to the FAA, the existing regulations for the lightning protection of electrical and electronic systems installed on aircraft certificated under Parts 23, 27 and 29 of Title 14, Code of Federal Regulations (14 CFR) require the type certification applicant only to "consider" the effects of lightning. Unlike system lightning protection regulations for Part 25 airplanes, these regulations have not been significantly amended since they were first adopted, and do not reflect current advances in technology.
 
Adopted in the 1960s, these regulations require that the aircraft be protected against catastrophic effects of lightning, but do not have specific requirements for electrical and electronic system lightning protection. At the time, most aircraft contained mechanical systems, or simple electrical and electronic systems. Airframe components were made from aluminum materials, with high electrical conductivity, and offered good protection against lightning. The early 1980s ushered in Part 25 transport airplane designs that routinely included more complex electrical and electronic systems. In addition, there has been a trend for increased use of composite aircraft materials with less inherent lightning protection than aluminum. As electrical and electronic systems became more common on Part 25 airplanes, the FAA issued Sec. 25.1316 on April 28, 1994 (59 FR 22112), specifically requiring protection for electrical and electronic systems on Part 25 transport category airplanes.

The NPRM, Notice No. 10-05, published in the Federal Register on April 2, 2010 (75 FR 16676), proposed the establishment of consistent performance standards for lightning protection of aircraft electrical and electronic systems against the catastrophic, hazardous or major failures of the functions these systems provide.
 
AEA is encouraging its members to review the final rule. This rule was developed specifically for protections for electrical and electronic systems. As a result, this change in standards will have a direct impact on avionics certifications and installations in legacy aircraft.

FMI: www.aea.net