Grounding and Bonding in Aircraft

GROUNDING AND BONDING IN AIRCRAFT

electrostatic discharge (ESD), electrical arcing, and ultimately electromagnetic interference. US Federal Aviation Regulations (FARs) and equivalent European EASA standards govern bonding and grounding in civil aviation. Here are two key paragraphs from the Part 25 FAR on bonding: § 25.899 Electrical bonding and protection against static electricity. (a) Electrical bonding and protection against static electricity must be designed to minimize accumu- lation of electrostatic charge that would cause— (1) Human injury from electrical shock, (2) Ignition of flammable vapors, or (3) Interference with installed electrical/electronic equip- ment. (b) Compliance with paragraph (a) of this section may be shown by— (1) Bonding the components properly to the airframe; or (2) Incorporating other accept- able means to dissipate the static charge so as not to

endanger the airplane, personnel, or operation of the installed electrical/electronic systems.

This special edition of QwikConnect explores the important topics of grounding and bonding in aircraft. Bonding refers to the prac- tice of electrically connecting various metallic components within an aircraft to minimize differences in electrical poten- tial and prevent the buildup of static electricity. Bonding ensures electrical continu- ity and equalizes the electrical potential among and between different metallic compo- nents. It eliminates potential differences that could cause

The goal of bonding is to ensure all electrical pathways and circuits within the frame of the aircraft share the same electrical potential. During assembly and maintenance, special loop and resistance testers are used to measure the impedance between metallic elements within the structure of the aircraft—and their flexible bond joints—to hunt down any high-resistance areas within the system. The term electrical engineers use for this shared electrical-potential state is “continuity.” Ultimately, using exacting assembly techniques and testing, a Metallic Bonding Network (MBN) is established throughout the aircraft. Grounding is the process of connecting structural and mechanical elements within the pressurized fuselage of the aircraft to a current return path capable of carrying a

QwikConnect • July 2023