MIL-HDBK-274 Electrical Grounding For Aircraft SafetyThis handbook has been prepared to provide U.S. Navy and Marine Corps aircraft maintenance and operations personnel with the background and technical details of the different types of aircraft grounds and how they are applied. In addition, this handbook provides background information for aircraft grounding, static electricity theory and how it affects aircraft, and techniques used for measurement of grounding points. This handbook is intended for use by all U.S. Navy and Marine Corps aircraft maintenance and operations personnel for the purposes of ensuring that aircraft are properly and safely grounded. This handbook is for guidance only and cannot be cited as a requirement.

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MIL-HDBK-274A

4.4.1.3.1 Static charges on clothing. Static electrical charges are generated on clothing by friction, especially by the action of removing garments.  Since clothing is frequently of synthetic materials, which amplifies the effects of friction, personnel should exercise extreme caution in areas where hazardous conditions may be present.  The removal of clothing therefore, should be prohibited, especially in dry climates, during fueling and ordnance operations.  The buildup of static electrical charges can be minimized by use of cotton clothing and antistatic powders.

4.4.1.3.2 Charge generated by fuel movement. The friction generated in fueling an aircraft, with passage of fuel from the supply vehicle through the filter separator and fueling hose to the aircraft, generates high electrical charges.  Charge separation and consequent buildup of electrostatic charges occur between the moving fuel and fuel filters, hoses, and other surfaces. Since fuel is normally an excellent insulator, separated charges are easily removed by the

flowing fuel to a distant location.  If no electrically conductive return path is available, the charge accumulates on metallic surfaces and is a high potential energy source.  With the continued accumulation of charge, sufficient electrical potential is generated to cause an arc across insulating barriers.  These voltages build up within the aircraft fuel tank and are a serious danger.  If these voltages were to arc over to points of lower potential with the right fuel-air vapor mixture present, an explosion would occur.  Bonding the aircraft frame to the fuel supply vehicle provides a means of dissipating these high voltages.  Bonding does not prevent generation of high voltages within hoses or tanks, but provides a return path for the accumulated charges as contact is made with the inside fuel tank surface.

4.4.1.3.3 Garments. Static electricity is generated on clothing by friction, especially by the action of removing garments.  There is also a continuous generation of charges in the garments of a moving clothed person.  The total amounts of charge at any time will depend on the rate of charge production and the rate of charge decay.  If a person rubs against external objects, charges can be produced on the outside of the garments, otherwise, the charges will be produced within the clothing system as shown on Figure 3.

FIGURE 3.  Charge accumulation on clothing.

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