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NASA Technical Note - Lightning Damage to a General Aviation Aircraft; Description & Analysis

A Beechcraft King Air Model B90 aircraft was struck by Lightning at an altitude Of 
2743 meters (9000 it) during landing at the Jackson, Michigan, airport on February 19, 
1971. Witnesses on the ground and in the aircraft reported that there was only one 
lightning discharge at the time of the incident' and that it was ground and cloud. 
No other thunderstorms were reported in the area within 2 hours prior to or following 
the incident. 
The damage sustained by the aircraft was widespread, -rather severe, and unusual 
in several respects. The lightning attachment points on the aircraft were (1) the out- 
board traili1V edge Of the left wingtip, (2) the right engine propeller tip, (3) the ventral 
fin on the aft end of the fuselage, and (4) the navigation Light on the top of the vertical 
stabilizer. In addition to the usual melted metal and cracked nonm&llic materials at 
the attachment points, there was (1) severe implosion-type damage to the aircraft skin 
On the lower right wing from the fuselage to a short distance outboard of the engine 
nacelle, including the nacelle and both sections of flaps; (2) impact- and crushirv-type 
damage over an area of about 900 square centimeters (1 sq It) on the top and bottom sur- 
faces of the left wingtip at the lightning attachment point; (3) pitting by electrical 
Of all Support and control rod bearirv on both sections Of flaps on the left Side of the 
aircraft; and (4) interruption of electrical power due to trippirg Of the circuit breaker on 
the generator on the right 
Photographs the damage in detail are presented. Analyses are made that 
show (1) that the implosion-type damage was probably due to shock waves generated by 
the Mgh-current poräons of the lightning discharge, (2) that the impact-type damage 
was probably due to magnetic forces created by the lightning currents flowing along dif- 
ferent paths in the aircraft structure, and (3) that the lightning discharge was a multiple- 
stroke type with at least Il high-current strokes (spikes) with an average time between 
strokes Of about 4.5 milliseconds.