Accident Overview
On September 12, 2014, at about 1750 central daylight time, an experimental amateur-built Darney Glasair III, registration N39RD, sustained substantial damage while landing at Austin Executive Airport (EDC) in Austin, Texas. The airplane veered off the runway and nosed over. The pilot received minor injuries, and the passenger received serious injuries. The aircraft was registered to and operated by the pilot under 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed, and an instrument flight plan was filed. The flight departed from University-Oxford Airport (UOX) in Oxford, Mississippi, around 1510.
Pilot Report
The pilot reported that the weather at EDC was good with no turbulence during the approach, although rain and thunderstorms were present in the area. He configured the airplane for landing by lowering the landing gear and adding two notches of flaps, and landed with about 5 knots of extra airspeed in case of surface crosswinds. The airplane touched down within the touchdown zone, approximately 6 feet right of centerline. Shortly after touchdown, the nosewheel began to shimmy violently. The pilot applied hard braking to both pedals simultaneously while applying back stick pressure on the yoke. He stated that the shimmy continued unabated despite maximum braking, though speed dissipated normally. The nosewheel fork failed, and the nose landing gear dug into the runway, causing the airplane to veer right. He applied full left brake, but the airplane continued to the right off the runway. The nose landing gear collapsed in the soft ground, and the airplane subsequently nosed over.
Runway and Aircraft Examination
Examination of the runway revealed a skid mark produced by the nosewheel tire, indicating back-and-forth skidding while the airplane's direction remained straight. No skid marks were associated with the main landing gear tires. Four propeller strike marks, spaced about 40 inches apart, were found on the runway before the airplane departed the runway. A ground impact in the infield was consistent with the nose landing gear collapsing before the nose-over.
Inspection of the nose landing gear showed that the nosewheel tire sidewall was scuffed and rubbed on one side only. The nosewheel rim exhibited grinding on the edge of the rim from runway contact on the same side. The torque and tension on the scissors connecting bolts were normal. Tire pressure measured 55 psi, within limits. One nosewheel travel stop was twisted. Damage to one drag link and scraping on the landing gear barrel were consistent with the drag link contacting the travel stop during the impact sequence. The shimmy damper, consisting of a steel collar with a Teflon ring, was intact with no anomalies. However, the stop bolt was sheared off. The investigation was unable to determine if the bolt was sheared during the accident sequence or before the flight. The pilot did not recall seeing it missing during his preflight inspection.
Wheelbarrowing Phenomenon
The Federal Aviation Administration's "Airplane Flying Handbook" describes a takeoff and landing phenomenon termed "Wheelbarrowing." This occurs when a pilot permits the airplane weight to become concentrated about the nosewheel during takeoff or landing. The handbook states that wheelbarrowing may cause loss of directional control during the landing roll because braking action becomes ineffective, and the airplane tends to swerve or pivot on the nosewheel, particularly in crosswind conditions. One common cause is simultaneous touchdown of the main and nosewheel with excessive speed, followed by forward elevator pressure. The handbook also advises that the airplane should be allowed to decelerate normally with careful use of wheel brakes, and heavy braking should be avoided until the wings are devoid of lift and the airplane's full weight rests on the landing gear.