NTSB Identification: ATL90FA099.
The docket is stored on NTSB microfiche number 45109.
Accident occurred Sunday, April 15, 1990 in CRESWELL, NC
Probable Cause Approval Date: 03/05/1993
Aircraft: AIRSHIP INDUSTRIES AIRSHIP 600, registration: N602SK
Injuries: 4 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

WHILE CRUISING AT 700 FT ON A CROSS-COUNTRY FLIGHT, THE AIRSHIP HAD A COMPLETE LOSS OF POWER IN BOTH ENGINES. SUBSEQUENTLY, THE AIRSHIP COLLIDED WITH TREES & THE TERRAIN DURING A FORCED LANDING IN 20 KT WINDS. AN INVESTIGATION REVEALED THAT THE AIRSHIP HAD TRAVERSED THE BEAM OF A HIGHLY DIRECTIONAL RADIO FREQUENCY BROADCAST FROM A VOICE OF AMERICA ANTENNA. THE SIGNAL RADIATING FROM THE ANTENNA HAD BEEN DEMONSTRATED TO DAMAGE ELECTRONIC IGNITION CONTROL UNITS OF THE SAME TYPE USED ON THE AIRSHIP ENGINES. SUBSEQUENT TESTS OF THE FAILED IGNITION UNITS SHOWED THAT THE FAILURE MODE IN THIS ACCIDENT REPLICATED THE FAILURES OF THE PREVIOUSLY TESTED IGNITION UNITS. AT THE TIME OF CERTIFICATION, AIRSHIP REQUIREMENTS FOR HIRF (HIGH INTNESITY RADIATED ELECTROMAGNETIC FIELDS) TESTING HAD NOT BEEN ISSUED.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

THE FAILURE OF THE ELECTRONIC IGNITION UNITS AS THE AIRSHIP TRAVERSED THE DIRECTIONAL ANTENNA BEAM OF A HIGH INTENSITY RADIATED ELECTROMAGNETIC FIELD (HIRF). FACTORS RELATED TO THE ACCIDENT WERE: THE UNFAVORABLE WIND AND THE LACK OF HIRF CERTIFICATION STANDARDS FOR AIRSHIPS AT THE TIME OF FAA CERTIFICATION.

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