S3 Viking History

BuNo: 159398
Location: NAF EL Centro, California
Date: Fri 08-Nov-1974
Cause: Undetermined
Findings: At approximately 1816Z at NAF EL Centro, California, performing FCLP's. RA-33 completed seven FCLP passes.

Subsequent to lift-off from the runway for the eighth pass, RA-33 obtained a nose high attitude and the left wing dropped, then the nose came down, the wings leveled, and the aircraft yawed to the right. The nose started to come up and the right wing dropped, the nose fell through and the aircraft's nose impacted the runway with the starboard wing hitting almost simultaneously. The aircraft exploded and burned.

Ejection sequence was initiated although the aircraft was out of the 'ejection envelope'.

Aircraft entered a flight regime from which recovery was only remotely possible.

Cause of mishap showed full nose up longitudinal trim as indicated by the position of the pitch trim actuator, whether pilot induced or due to a malfunction of the system, and subsequent disconnect of the pitch trim system.

Runaway Pitch Trim
The seats operated in accordance with established standards, However, since the whole accident from lift off to impact is considered to have occurred in less than 15 seconds, the published high pull force for the lower ejection handle may have delayed the ejection one or two seconds even though the actual pull force for the seats of RA-33 was in the range published.

Program for reducing lower ejection seat handle pull forces has been incorporated in production aircraft.

Crew of 2 killed.

Source: JAG Investigation Report

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