For aircraft certified to FAA requirements, U.S. Federal Aviation Regulation (FAR) 25.581 states, "The aircraft must be protected against catastrophic effects of lightning." Requirements for commuter and light aircraft are detailed in FAR 23.867 and 23.954, for transport aircraft in FAR 25.581 and 25.954, and for rotorcraft in FAR 27.610 and 27.954. U.S. Federal Aviation Admin.-certified aircraft are classified into zones based on the likelihood and potential magnitude of direct lightning strikes and ensuing return and swept strokes (see zones at www.compositesworld.com/ hpc/issues/2006/July/1348). These zones help to specify materials and devices by quantifying how much current must be handled, the rate of charge rise and fall, and the potential for dwell and restrike.
For noncertified aircraft — such as the many composite kit-built planes and other experimental aircraft — there is no requirement to include lightning strike protection, and many in the general aviation consider it unaffordable and unnecessary. Pilot Paul McAllister no longer shares this point of view. On August 4, 2004, Paul and his wife were flying their Europa fiberglass composite two-seater from Oshkosh, Wis. to Calgary, Alberta, Canada. When they were struck by lightning, the sky off his starboard side, where the lightning entered, was clear blue, and the clouds to his port side were 15 to 20 miles away. The strike shocked McAllister through a valve touching his knee, but only three of the craft's 12 pieces of electronic equipment survived! (See "Static Charge Protection")