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Lightning Protection of Low Density Aircraft Structures

Ab str act 
Low density aircraft structures are charact— 
erized by wing and empennage surfaces employing 
thin rnetal semi—monocoque construction and ex— 
tensive metal to metal adhesive bonding. The 
lightning strike damage potential of these features 
necessitates a high Of protection. 
This paper reviews the lightning protection 
techniques which may be incorporated to protect 
low density aircraft structures from the hazards 
of a Lightning strike. These techniques have aris- 
en from testing carried out on the de Havilland 
Lightning Surge Simulator in association with 
government funded programs as well as an analy— 
sis and simulation of actual in-flight lightning 
strikes to low density aircraft. 
Introduction 
There is an increasing amount of time and 
effort being spent on aircraft safety from a light— 
ning standpoint. This is reflected in the large 
body Of literature which has appeared on the sub— 
ject over the past few years. A recent document 
has been published by the SAE Committee AE4, 
and is entitled "Aerospace Recommended Pract— 
ice: Lightning Effects Tests on Aerospace 
Vehicles and Hardware" ( l), which summarizes 
the test waveforms and techniques recommended 
for lightning simulation testing in the United 
The inherent design of low density aircraft 
structure warrants a careful examination of the 
lightning strike susceptibility of such an aircraft. 
The low characteristics of a S. T. O. 
aircraft are enhanced by Wing and 
surface areas constructed Of thin gauge aluminum 
with extensive metal to metal adhesive bonding. 
One also finds an increase in the number of air- 
craft parts fabricated from high strength metallic 
and non-metallic composites. When such a design 
is applied to fuel tank structure which 
is exB)Sed to a lightning strike, lightning pro— 
tective schemes must be instituted to prevent 
possible fuel ignition due to Sparking across 
joints or penetration Of the skin structure. 
In the interests Of weight reduction the nose 
structure of some aircraft may be fabricated of 
a non-metallic composite and may contain avion—