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NASA Reference Publication - Lightning Protection of Aircraft

This book is an attempt to pr&nt under one cover the current State Of 
knowledge concerning the potential lightning effects on aircraft and the means 
that are available to designers and operators to protect against effects. The 
impetus for Writing this book springs from two increased use of 
nonmetallic materials in the Structure of aircraft and the constant trend toward 
using electronic equipment to handle flight-critical control and navigation 
functions. NonfiEtallic Structures are inherently more likely to be damaged by a 
lightning strike than are metallic structures. Nonmetallic structures also provide 
less shielding against the electromagnetic fields of lightning than do 
metallic structures. These fields have demonstrated an ability to damage or Cause 
up*t of electronic equipment. 
Such concerns, When added to the continuing apprehension regarding 
the vulnerability of fuel systems to lightning, have led in the past dewde to 
increased research into lightning effects on aircraft. The results of this research 
are contained in the technical reports and literature published by ourselves and 
by researchers in other laboratories who are also working on these problems. 
Conferences and symposiurtb have been held so that researchers could exchange 
ideas and information; there is a high degree Of cooperation among all of those 
Working towards the goal of complete safety-of-flight in the lightning environ- 
menl. 
The persons who can best use information on aircraft protection from 
li$ltning are the aircraft designers and operators, but generally they are not 
among those Who produced this information. Moreover, they are often unaware 
of its existence, they seldom have the background to distill from it the 
important facts that can and should be applied 10 achieve safer designs. The 
purpose Of this book is to present the most important parts of this body Of 
knowledge in a manner most useful to the designer and the operator _ 
nis book is organized into seventeen chapters. In the first of these we 
review what lightning is and how it originates. The second chapter describes how 
the aircraft becomes involved with the lightning flash and why it is that aircraft 
do not produce their own lightning flashes, but may, we think, sometimes trigger 
natural ones. Chapter 3 considers how often and under what conditions aircraft 
have been struck, reviews avoidance procedures now in use by operators, and 
reviews their degree of success. We also take up the question of whether Or not 
strikes could be totally avoided. fourth chapter summarizes the various 
effects which have occurred when lightning has struck aircraft, giving the 
operator an idea Of the direct and indirect effects which he may expect when his 
ircraft is "zapped." 
Since our main purplR is 10 help the designer protect against those effects 
that may be hazardous, the remainder of the book is devoted to this purpose. 
Chapters 5, 6, and 7 deal with protection against the direct physical damage 
effects. Chapter 5 Forth three philosophical Steps which guide us in the 
design work that follows. Attention is also called to government standards or