14 CFR § 27.610

The rotorcraft must be protected against catastrophic effects from lightning.

For metallic components, compliance with paragraph (a) of this section may be shown by—

Electrically bonding the components properly to the airframe; or

Designing the components so that a strike will not endanger the rotorcraft.

For nonmetallic components, compliance with paragraph (a) of this section may be shown by—

Designing the components to minimize the effect of a strike; or

Incorporating acceptable means of diverting the resulting electrical current so as not to endanger the rotorcraft.

The electrical bonding and protection against lightning and static electricity must—

Minimize the accumulation of electrostatic charge;

Minimize the risk of electric shock to crew, passengers, and service and maintenance personnel using normal precautions;

Provide an electrical return path, under both normal and fault conditions, on rotorcraft having grounded electrical systems; and

Reduce to an acceptable level the effects of static electricity on the functioning of essential electrical and electronic equipment.