History of Flight
On February 4, 2009, about 1230 mountain standard time, a Piper PA-46-500TP airplane, registration N535JR, departed the runway during landing at Aspen-Pitkin County Airport (ASE) in Aspen, Colorado. Visual meteorological conditions prevailed. The aircraft received minor damage; the private pilot and passenger were not injured. The cross-country flight was operated as a personal flight under 14 CFR Part 91, and an instrument flight rules flight plan was filed. The flight originated at Richard Lloyd Jones Airport (RVS) in Tulsa, Oklahoma, and was terminating at the time.
The pilot stated that after a smooth landing on the main wheels, as soon as the nose wheel touched down, the airplane began veering left and right uncontrollably. The airplane exited the right side of Runway 15 about 2,000 feet down the runway and came to rest in a snow bank. The pilot also reported that this airplane had seven previous events of pulling to the left during landing, all occurring upon nose wheel touchdown; the pilot regained control each time. No reports were made to the NTSB or FAA for those prior events.
Aircraft and Personnel Information
The pilot, age 50, held a private pilot certificate with airplane single-engine land and instrument ratings. His last flight review was November 3, 2008, and last third-class medical examination was June 1, 2007. He reported 1,600 total flight hours, with 500 hours in the accident make and model.
The six-seat, low-wing, retractable-gear airplane, serial number 4697253, was manufactured in 2006. It was powered by a Pratt and Whitney Canada PT6A-42A 500-horsepower engine and a Hartzell HC-E4N-3Q propeller. An annual inspection was completed September 9, 2008, at 527.8 hours airframe total time; at the incident, the airplane had accumulated 680 hours total time.
The landing gear is a retractable tricycle air-oil strut type, hydraulically operated by an electric hydraulic pump. The nose gear is steerable through a 60-degree arc via rudder pedals, with a steering bungee incorporated.
Meteorological and Aerodrome Information
Weather at ASE at 1153 was reported as clear skies, temperature 33°F, altimeter 30.43, and winds calm. The pilot and airport personnel reported variable winds at 5 knots at the time of the accident. Runway 15 at ASE is 7,006 feet by 100 feet, elevation 7,679.8 feet MSL, with a grooved asphalt surface and a 2.0 percent up-sloping gradient.
Examination and Testing
The landing gear and nose wheel steering systems were examined for anomalies and proper operation. With weight on wheels, nose gear strut extension measured 2.212 inches, right main landing gear strut extension 2.75 inches, and left main 2.8125 inches. Nose wheel tire pressure was 70 psi. The steering rake angle measured between -0.5 and -0.7 degrees. The Piper Maintenance Manual specified the proper rake angle as 0.0 to +0.5 degrees. Nose wheel steering roller clearance was measured: with weight-off-wheels, left and right clearances both greater than 0.035 inches; with weight-on-wheels, both measured 0.020 inches (recommended: 0.010–0.030 inches). Rudder cable tension was appropriately set.
Piper Aircraft engineers computed a shimmy analysis using the pilot's reported landing conditions (285 lbs passengers, 560 lbs fuel, 75 lbs cargo, 78-knot touchdown speed). The analysis showed a positive margin of safety against dynamic shimmy even with a -0.70 degree rake angle.
The engine mount was examined and showed no evidence of flexing, cracking, impact damage, or misalignment. The nose gear actuator attachment bolt and nut were intact and turned freely.
Additional Information
Piper Aircraft provided historical data on takeoff and landing excursions of PA-46-500TP airplanes, indicating twenty events prior to this incident. Of those, six were investigated by the NTSB; four were attributed to deficiencies or failures of the engine mount, one to pilot error, and one to undetermined reasons. This event was the second recorded runway departure in an airplane equipped with the newest third-generation engine mount (part number 102460-036); the first occurred February 27, 2008, with minor damage and undetermined cause.
The Piper Maintenance Manual included guidance on nose gear adjustment, but no procedure for measuring nose gear rake angle. On March 27, 2008, Piper issued a Customer Information Letter (CIL) providing specific procedures for setting rake angle and steering arm/roller clearances. The CIL stated the proper nose gear rake angle is zero to one-half degree forward from vertical, measured using the airframe lower skin as a horizontal datum. It also specified that the steering arm/roller clearance should be 0.010–0.030 inches with weight on wheels.
A review of the airplane maintenance log revealed the nose gear system had been worked on eight times since the airplane was purchased. Seven of those were performed by Sun Aviation, Inc.; five work orders involved adjustment of the nose gear steering roller gap, and one involved adjustment of both the roller gap and rake angle. The NTSB interviewed the Sun Aviation technician who performed the last work; he was unaware of the CIL. When setting the steering roller clearance, he set a 0.020-inch gap between one roller and the steering arm while the second roller touched the arm. For rake angle, he used a measurement of 38.75 inches from the back edge of the nose wheel steering support plate to the lower aft edge of the nose gear trunnion. Piper personnel replicated this measurement technique on a production aircraft and found the resulting rake angle was -0.4 degrees.