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

with the neutral wire connected to the aircraft structure. Equipment using AC power may use either single phase power consisting of neutral and phase A, B, or C, or 3-phase power which requires phases A, B, C, and N.

4.4.2.1.1 Mobile electric power plants. When the aircraft is on the ground, it is not practical to run the engines for electrical power, so the required AC and DC power is supplied by generators external to the aircraft. These sources may be mobile or fixed. The mobile sources

are called Mobile Electric Power Plants (MEPPs). Following are a few examples:

Use	Model	Type	Outputs
Ship	NC-2A	Engine-driven, self-propelled	115/200 VAC, 400 Hz, 30 kVA, 28 VDC, 500A
Ship	A/S37A-3	Mobile Electric Power Plant, self-propelled	115 VAC, 3-phase, 400 Hz, 28 VDC
Flight Line	NC-8A	Engine-driven, self-propelled	115/200 VAC, 400 Hz, 60 kVA, 28 VDC, 500A
Flight Line	NC-10A/B/C	Engine-driven, self-propelled	115/200 VAC, 400 Hz, 90 kVA, 28VDC, 750 A
Hangar	MMG-1A	Electric motor-driven	115/200 VAC, 400 Hz, trailer-mounted, 60 kVA, 28VDC, 500 A
Hangar	MMG-2	Electric motor-driven	115/200 VAC, 400 Hz, trailer-mounted, 30 kVA, 28VDC, 500 A
Land-based	PU-820/T	Diesel Generator Set	35 kW, 120/208 VAC, 60 Hz, 3-phase

A complete listing of MEPPs, together with a description of each model can be found at the

Naval Air Technical Data and Engineering Service Command (NATEC).

4.4.2.1.2 Alternative external electric power. The AC and DC generators are diesel engine-driven and are mounted on a self-propelled chassis on rubber tires. The AC neutral (N) and DC negative wires are both connected to the chassis. In this configuration, the supply cables provided with the MEPP are about 30 feet (ft) long. The AC and DC connector plugs are

non-government standard fittings which mate with most aircraft. Alternative equipment used to provide external electric power is: