Inspection of Aircraft Electrical Bonding & Grounds

Correct Aircraft bonding is of critical importance Inadequate bonding or grounding may lead to poor performance or in the very worst case contribute to the loss of the aircraft.

Poor bonding performance may cause Electromagnetic Interference (EMI), Electrostatic Discharge Damage (ESD) and lead to intermittent defects. Normal operations impose many stresses and environmental conditions on the many kilometers of Electrical Wiring. It is important that periodic inspections are performed to detect any deterioration.

Inspections should look for Abrasions, Integrity of Insulation, and Condition of all terminations and the possibility of terminal corrosion.

All Electrical Grounds must be given special attention to ensure that the bonding resistance has not increased by corrosion or the loosening of the connections.

Care should be taken to ensure that grounds are separated for example AC & DC earths should not be connected to the same ground point, as this may cause an interaction and possible Radio Frequency Noise “RF”.

Typically grounds should be identified as “AC”, “DC” and others.

Attention should be paid to the capacity of the ground return circuit to ensure an adequate current rating together with an acceptable volt drop to ensure acceptable operation of the equipment.

Sometimes it is possible to reduce the EMI by locating the associated ground near the origin of the power supply. In general equipment items should have an external ground, including when for example it is internally grounded.

Heavy current grounds require to be attached to aircraft structure with an appropriately designed metal to metal bonding structure attachment, able to provide an adequate current path through all normal and expected overload conditions.

A typical bracket will be seen to consist of a minimum of three fasteners typically in a triangular pattern to afford protection against vibration. 

For new composite structures, for example carbon fiber composite “CFC” It is necessary to install alternative ground paths for power return, great care must be taken with Composite Aircraft.

Typical defects which require special attention during inspection of Ground points include evidence of corrosion and signs of arcing or burning, ensure it is secure.

Typical Defects which should be considered during inspection of Bonding Wire include evidence that the Braid is frayed or broken, pay careful attention to the possibility either of broken strands or corroded strands.

Sofema Aviation Service provides EWIS Regulatory Training for all target groups, either as classroom based training please see www.sassofia.com or online through www.sofemaonline.com

Please see more details about the content of the courses and prices in the following links:

EWIS for Target Groups 1 and 2 (Initial) with VO
EWIS for Target Groups 1 and 2 (Recurrent) with VO
EWIS for Target Groups 3 and 4 with VO
EWIS for Target Groups 3 to 6
EWIS for Target Groups 5 and 6 with VO
EWIS for Target Groups 7 and 8 with VO

If you have any questions regarding SofemaOnline please email us at online@sassofia.com