Harrisonburg, VA, USA
N596JB
Bass RV-6A
The pilot of the RV-6A flew from his home airport to a private turf strip. The flight and initial portion of the landing were uneventful. During the latter part of the landing rollout the nose gear fork caught in a rut, the strut deformed, and the airplane nosed over onto its back. Two years prior to the accident, the kit manufacturer re-designed the nose gear for this airplane in an effort to reduce susceptibility to noseover events. The accident airplane was not equipped with the new-design nose gear leg and fork.
HISTORY OF FLIGHT On August 4, 2007, about 0900 eastern daylight time, an amateur-built Vans Aircraft RV-6A, N596JB, was substantially damaged when it nosed over during the landing rollout at a private airport near Harrisonburg, Virginia. The certificated private pilot, the sole occupant, was not injured. The personal flight was operated under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed. The airplane departed Eagle's Nest Airport (W13), Waynesboro, Virginia for a flight to the accident airport. The flight and the initial phase of the landing on runway 28 were uneventful. During the landing rollout, the nose gear fork caught in a rut, the strut deformed, and the airplane nosed over into the inverted position, facing in the direction it had come from. A fire broke out in the engine compartment. The pilot forcibly broke the canopy and exited through this opening, and extinguished the fire. The vertical stabilizer, rudder, canopy and forward fuselage sustained crush damage. The nose gear strut assembly was deformed up and aft with respect to the airplane's longitudinal axis. The pilot did not report any malfunctions of the airframe or engine. PERSONNEL INFORMATION The pilot held a private pilot certificate with an airplane single engine land rating. He also held a repairman certificate for experimental aircraft. The pilot had approximately 715 total hours of flight experience, with approximately 570 hours in the accident airplane make and model. His most recent third-class medical certificate was issued on February 12, 2007. AIRCRAFT INFORMATION The airplane was an all-metal, low-wing monoplane with a tricycle landing gear configuration. According to Federal Aviation Administration (FAA), the airplane was manufactured in 2000 by the pilot. It was equipped with a Mattituck TMX-O-360 engine. METEOROLOGICAL INFORMATION The 0920 surface weather observation at Shenandoah Valley Regional Airport (SHD), Harrisonburg, Virginia, located approximately 12 miles south of the accident airport, recorded calm winds, visibility 4 miles, clear skies, temperature 24 degrees Celsius (C), dew point 23 degrees C, and an altimeter setting of 30.08 inches of mercury. AIRPORT INFORMATION The airport was a private turf strip that belonged to an acquaintance of the pilot. This strip was not depicted on the aeronautical chart for the region. The airport owner stated that the strip dimensions were approximately 1,400 feet by 60 feet. The runway surface was dry and firm at the time of the accident, and the grass was 1 to 2 inches high. The rut that precipitated the event was shaped like a flattened "V", and was approximately 30 inches long, 12 inches wide and 2 inches deep. The bottom of the "V" was aligned with the long axis of the rut, which was aligned with both the runway and the airplane's direction of travel. The rut was devoid of grass. TEST AND RESEARCH In the spring of 2007, the National Transportation Safety Board examined data for 18 accidents and one incident in which Vans Aircraft series RV-6A, RV-7A, RV-8A, or RV-9A airplanes became inverted during landing. This study was conducted in conjunction with the investigation of an RV-6A accident (ANC05LA123), which occurred on August 12, 2005 near Palmer, Alaska. The study determined that ground roll dynamics, in combination with mechanical factors associated with the design of the nose landing gear, reduced the clearance between the nose gear fork and the ground, and increased the likelihood of a noseover event. ADDITIONAL INFORMATION In 2005, Vans Aircraft (the kit manufacturer) redesigned the nose gear leg and fork to provide an additional inch of fork-to-ground clearance, which equated to an approximately 25% increase in clearance. Manufacturer's kits shipped subsequent to this design change incorporated the new design. On November 9, 2007, three months after the accident, the kit manufacturer issued Mandatory Service Bulletin 07-11-09, applicable to all two-place tricycle gear RV airplanes. On the same date, the kit manufacturer also issued a Nose Gear Service Letter for pilots of RV-6A, -7A, -8A and -9A airplanes. The service bulletin required modification or replacement of the previous nose gear design with the new design prior to or during the next annual condition inspection. The service letter provided both servicing and operational guidelines intended to aid pilots in avoiding noseover events in the subject airplanes. The accident airplane was not equipped with the new-design nose gear leg and fork.
The limited fork-to-ground clearance provided by the nose gear design. Contributing to the accident was the uneven turf/dirt surface of the runway.
Source: NTSB Aviation Accident Database
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