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

NOTES:

1. When grounding to a padeye, good metal to metal contact is recommended between clamp and padeye. Ensure connection contact point is free of paint or corrosion.

2. A Certified Power Ground will have a current certification (dated within a 24-month period) and be labeled with resistance values of less than 25 ohms referenced to the power system neutral. (Ref  NAVSEA OP5, Chapter 5)

3. When a MEPP is utilized, a grounding cable is recommended to be attached from the MEPP to the aircraft airframe (Refer to specific aircraft NATOPS Flight Manual or MIM)

4. Grounding triangulation is recommended during fueling/defueling operations. (Refer to specific aircraft NATOPS Flight Manual or MIM)

5. Refer to aircraft NATOPS and Helicopter Operating Procedures for Air-Capable Ships

(Ref. NAVAIR 00-80T-122)

6. Refer to aircraft NATOPS Flight Manual and Aircraft Refueling NATOPS Manual

(Ref. NAVAIR 00-80T-109, Chapter 16)

5.13.1 Aircraft tie-down chains. Aircraft tie-down chains do not provide an appropriate static ground.  For ordnance loading and downloading and aircraft fueling/de-fueling evolutions

a separate grounding cable should be used to connect the aircraft to an approved grounding point. If an approved grounding point is not available then the deck padeye is an acceptable static ground if metal-to-metal contact is ensured by grinding the teeth of the ground clamp into the padeye to ensure paint is not impeding the ground to padeye connection.

5.14 Grounding cable details. When using grounding cables, the specific type of connector used on the ends will be determined by the aircraft type.  Some Navy or Marine Corp aircraft may not have grounding receptacles available in other than the fueling area, and they are therefore not readily available for use as the static grounding point on the aircraft.  In these instances a cable having MIL-DTL-83413 clamps on each end, Figure 19, or a clamp and a plug, Figure 20, may be used, one end attached to an approved static ground point, the other to a clean metal area of the aircraft.  It is important to remember to attach the grounding cable to the approved ground point prior to attaching it to the aircraft.  The National Stock Numbers (NSNs) and part numbers (P/Ns) may be used to order cables and MIL-DTL-83413 connectors and

plugs.

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