5 - Lightning protection

The general approach used to protect the structure of the Cap 222 is as follows:

  · Exterior skin surfaces in critical lightning zones incorporate an expanded copper foil. The adequacy of the protection (or lack thereof) was established by conducting tests on samples (see pictures).

  · All skin components are electrically bonded to each other and to internal conduction paths with the use of integral copper connection tangs. The adequacy of the connection tang was tested.

  · An adequate lightning path was established, and bonding of this and other internal metallic components was designed to minimize pilot shock hazards.

  · Other aspects of the design were verified by similarity with tried and tested designs.

As different regions of the aircraft are in different lightning attachment zones, then different lightning threats apply, and greater or lesser lightning protection need be applied accordingly. The test levels varied from sample to sample in accordance with the appropriate lightning zoning requirement.

The tests show that the tangs were each capable of carrying the current. Pictured is damage from the arc attachment. The acceptability of the damage to the airframe was assessed by CAP Aviation.