Date:	Wednesday 3 February 1993
Time:	13:27
Type:	Lockheed L-100-20 Hercules
Owner/operator:	Lockheed
Registration:	N130X
MSN:	4412
Year of manufacture:	1971
Total airframe hrs:	6708 hours
Engine model:	Allison 501-M71K
Fatalities:	Fatalities: 7 / Occupants: 7
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	Marietta-Dobbins AFB, GA (MGE) -   United States of America
Phase:	Taxi
Nature:	Test
Departure airport:	Marietta-Dobbins AFB, GA (MGE/KMGE)
Destination airport:	Marietta-Dobbins AFB, GA (MGE/KMGE)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
The Lockheed engineering testbed was used to evaluate the fly-by-wire rudder actuator and the ground minimum control speed (VMCG). During the final high-speed ground test-run, the aircraft accidentally veered left and became airborne. The Hercules climbed to 250 feet and crashed.

PROBABLE CAUSE: "Disengagement of the rudder fly-by-wire flight control system resulting in a total loss of rudder control capability while conducting ground minimum control speed tests. The disengagement was a result of the inadequate design of the rudder's integrated actuator package by its manufacturer; the operator's insufficient system safety review failed to consider the consequences of the inadequate design to all operating regimes. A factor which contributed to the accident was the flight crew's lack of engineering flight test training."

Flight International 6-12 April 1994 (12)
Air Safety Week 8 February 1993 (p. 4, 5)
Flight International 10-16 February 1993 (6)
ICAO Adrep Summary 1/95
NTSB Safety Recommendation A-94-101
Scramble 165

photo (c) via Werner Fischdick; Cambridge Airport (CBG); March 1976

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