Austin, TX, USA
N39RD
DARNEY GLASAIR III
The pilot reported that he landed the airplane with about 5 knots of extra airspeed in case he encountered a surface crosswind. The airplane touched down about 6 ft right of the runway centerline. Shortly after touchdown, the nosewheel began to shimmy violently. The pilot applied maximum braking to both pedals simultaneously to reduce the speed as he applied back stick pressure, but the nosewheel continued to shimmy. The nosewheel fork then failed, and the nose landing gear dug into the runway, which caused the airplane to veer off the right side of the runway. The nose landing gear collapsed in the soft ground, and the airplane subsequently nosed over. The postaccident examination of the nose landing gear, shimmy damper, and nosewheel revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The examination of the runway revealed a skid mark produced by the nosewheel tire, which indicated that the tire skidded back and forth while the airplane's direction continued straight down the runway. According to Federal Aviation Administration guidance, wheelbarrowing occurs when a pilot permits the airplane weight to become concentrated about the nosewheel during takeoff or landing, which can cause of a loss of directional control. One of the most common causes of wheelbarrowing during the landing roll is the simultaneous touchdown of the main wheels and nosewheel with excessive speed. The guidance states that "heavy braking should be avoided until the wings are devoid of lift and the airplane's full weight is resting on the landing gear," which is contrary to the pilot's actions. The circumstances of the accident were consistent with the airplane wheelbarrowing during the landing.
On September 12, 2014, about 1750 central daylight time, an experimental amateur-built Darney Glasair III, N39RD, sustained substantial damage while landing at the Austin Executive Airport (EDC), Austin, Texas, when it veered off the runway and nosed over. The pilot received minor injuries, and the passenger received serious injuries. The airplane was registered to and operated by the pilot under the provisions of the 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed at the time of the accident, and an instrument flight plan was filed. The airplane departed from the University-Oxford Airport (UOX), Oxford, Mississippi, about 1510. The pilot reported that the weather at EDC was good with no turbulence experienced during the approach, although there was rain and thunderstorms in the area. He configured the airplane for landing by lowering the landing gear and adding two notches of flaps, and he landed with about 5 knots of extra airspeed in case he encountered surface crosswinds. The airplane touched down within the touchdown zone and about 6 feet right of centerline. Shortly after touchdown, the nosewheel began to shimmy violently. The pilot applied hard braking to both pedals simultaneously to reduce speed as he applied back stick pressure on the yoke. He stated, "Since the shimmy started soon after touchdown, I still had significant airspeed and even with maximum braking, the shimmy continued unabated although the speed was dissipating normally under the circumstances." He reported that the nosewheel fork failed and the nose landing gear dug into the runway, causing the airplane to veer to the right. He applied full left brake, but the airplane continued to veer off the right side of the runway. The nose landing gear collapsed in the soft ground and the airplane subsequently nosed over. The examination of the runway revealed a skid mark produced by the nosewheel tire. The skid mark indicated that the tire appeared to be skidding back and forth while the airplane's direction continued straight down the runway. There were no skid marks that were associated with the main landing gear tires. There were 4 propeller strike marks about 40 inches apart found on the runway before the airplane departed the runway. A ground impact was observed in the infield that was consistent with the nose landing gear collapsing before the airplane nosed over. The examination of the nose landing gear revealed that the nosewheel tire sidewall was scuffed and rubbed on one side only. The nosewheel rim exhibited grinding of the edge of the rim from contact with the runway on the same side of the wheel that had the tire scuff marks. The torque and tension on the scissors connecting bolts was normal. The tire pressure measured 55 psi, which was within limits. One of the nosewheel travel stops was twisted. The damage to one of the drag links and scraping on the landing gear barrel was consistent with the drag link contacting the travel stop during the impact sequence. The shimmy damper, which consisted of a steel collar with a Teflon ring, was intact and exhibited no anomalies. However, the stop bolt was sheared off. The investigation was unable to determine if the bolt was sheared off during the accident sequence, or sometime before the flight. The pilot did not recall seeing it missing during his preflight inspection. The Federal Aviation Administration's "Airplane Flying Handbook" describes a takeoff and landing phenomenon termed "Wheelbarrowing." Wheelbarrowing occurs when a pilot permits the airplane weight to become concentrated about the nosewheel during takeoff or landing. The handbook stated the following: "Wheelbarrowing may cause the loss of directional control during landing roll because braking action becomes ineffective, and the airplane tends to swerve or pivot on the nosewheel, particularly in crosswind conditions. One of the most common causes of wheelbarrowing during landing roll is a simultaneous touchdown of the main and nosewheel, with excessive speed, followed by application of forward pressure on the elevator control." The handbook also stated: "The airplane should be allowed to decelerate normally, assisted by careful use of wheel brakes. Heavy braking should be avoided until the wings are devoid of lift and the airplane's full weight is resting on the landing gear."
The pilot’s use of an improper attitude and airspeed during landing followed by excessive braking, which resulted in the airplane wheelbarrowing on the runway and a subsequent loss of directional control.
Source: NTSB Aviation Accident Database
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