NTSB Identification: NYC00LA266.
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Accident occurred Sunday, September 24, 2000 in WARRENTON, VA
Probable Cause Approval Date: 07/17/2001
Aircraft: Morrison RANS-12, registration: N91337
Injuries: 1 Serious.
NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
As the airplane arrived in the airport area, the pilot observed a thunderstorm "moving in" from the west/northwest, at a distance of about 10 miles. As the pilot turned left base for final approach, about 150-200 feet above the ground, a gust of wind came over the trees and "flipped the airplane over." The airplane descended, impacted trees, and crashed onto the runway. The pilot additionally stated that he was at an indicated airspeed of 50-55mph when he encountered the wind gust and that the stalling speed of the airplane was 37 mph. Federal Aviation Administration (FAA) Airplane Flying Handbook, FAA-H-8083-3 stated, "After turning onto the base leg, the pilot should start the descent with reduced power and an airspeed of approximately 1.4 Vso." FAA Advisory Circular AC 61-67B stated, Stall and Spin Awareness Training, "Turbulence can cause an aircraft to stall at a significantly higher airspeed than in stable conditions. A vertical gust or windshear can cause a sudden change in the relative wind, and result in an abrupt increase in angle of attack. Although a gust may not be maintained long enough for a stall to develop, the aircraft may stall while the pilot is attempting to control the flightpath, particularly during an approach in gusty conditions. When flying in moderate to severe turbulence or strong crosswinds, a higher than normal approach speed should be maintained. In cruise flight in moderate or severe turbulence, an airspeed well above the indicated stall speed and below maneuvering speed should be used." The winds recorded at a nearby airport, about the time of the accident were from 350 degrees at 6 knots.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's inadequate airspeed which resulted in the inadvertent stall. A factor related to the accident was the gusting wind condition. Full narrative available
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