Bonding
Bonding is the electrical connecting of two or more conducting objects not otherwise adequately connected.
The following bonding requirements must be considered:
• Equipment bonding :
low-impedance paths to aircraft structure are normally required for
electronic equipment to provide radio frequency return circuits and for most
electrical equipment to facilitate a reduction in EMI. The cases of components
that produce electromagnetic energy should be grounded to the structure. To ensure
proper operation of electronic equipment, it is particularly important to
conform to the system’s installation specification when interconnections, bonding,
and grounding is being accomplished.
• Metallic surface bonding :
all conducting objects on the exterior of the airframe must be
electrically connected to the airframe through mechanical joints, conductive
hinges, or bond straps capable of conducting static charges and lightning
strikes. Exceptions may be necessary for some objects, such as antenna
elements, whose function requires them to be electrically isolated from the
airframe. Such items should be provided with an alternative means to conduct
static charges and/or lightning currents, as appropriate.
• Static bonds:
all isolated conducting
parts inside and outside the aircraft, having an area greater than 3 square
inches and a linear dimension over 3 inches, that are subjected to appreciable
electrostatic charging due to precipitation, fluid, or air in motion, should
have a mechanically secure electrical connection to the aircraft structure of
sufficient conductivity to dissipate possible static charges. A resistance of
less than 1 ohm when clean and dry generally ensures such dissipation on larger
objects.
Higher resistances are permissible in connecting smaller objects to
airframe structure.