History of Flight
On August 19, 2011, at 1555 eastern daylight time, a Piper PA-46-500TP, N133SR, was substantially damaged when it veered off the runway while landing at Manassas Regional Airport (HEF), Manassas, Virginia. The certificated private pilot and the passenger were not injured. Visual meteorological conditions prevailed. The airplane was operating on an instrument flight rules flight plan from Cobb County Airport – McCollum Field (RYY), Atlanta, Georgia, to HEF. The personal flight was conducted under 14 Code of Federal Regulations Part 91.
According to the pilot, the approach to runway 16L was unremarkable; he recalled glancing at the airspeed, which was 92 knots about 500 yards from the end of the runway. He then added the last notch of flaps, and the airplane landed on the main landing gear, on runway centerline. The pilot kept the nose wheel off the runway for 3 to 4 seconds; due to the runway length, he did not force the nose down.
About 3 to 4 seconds after the nose wheel touched down, the airplane began veering left. The pilot added right rudder, then more right rudder when the nose did not correct. He then applied brakes, and after that, put the propeller into Beta and reverse. The airplane veered off the left side of the runway into the median, where the nose landing gear separated.
The pilot stated that he did not land hard and had never experienced a hard landing in the airplane. The landing at his previous stop in Atlanta was similar with no issues. He was unaware of any logbook entries indicating a hard landing by the previous owner.
The passenger also noted nothing eventful until "right after" the nose wheel touched down, the airplane veered left off the runway.
Personnel Information
The pilot reported 2,612 hours total flight time, with 130 hours in make and model. His most recent flight review was August 3, 2011, in the same make and model. He stated familiarity with the PT-6 engine reversing characteristics and had flown a Beech C90A for the six years prior to purchasing the accident airplane in June 2010.
Aircraft Information
According to the airplane maintenance logbook, the latest annual inspection was performed on July 29, 2011, at 1,903.6 hours of operation. During that inspection, the tube was replaced in the nose tire, the steering arm clearance was adjusted per the maintenance manual, and the nosewheel bearings were replaced and the assembly was balanced.
Airport Information
Runway 16L was 5,700 feet long and 100 feet wide.
Meteorological Information
Winds recorded at the airport at the time of the accident were from 220 degrees magnetic at 4 knots.
Wreckage and Impact Information
On August 25, 2011, NTSB, FAA, and Piper personnel examined the airplane. By then, it had been recovered to a hangar and placed on jacks. All four propeller blades were bent opposite the direction of rotation, both wings and the fuselage exhibited impact damage, and multiple engine inlet vanes were fractured. The airplane's hour meter indicated 1,916.2 hours of operating time.
The nose landing gear wheel rotated freely, and the nose wheel bearings appeared pristine with new grease. The nose tire (8-ply Michelin Air 5.00-5) was inflated to 55 psi. The right main tire was at 46 psi, the left at 47 psi. According to the Piper investigator, a fully inflated nose tire should indicate 70 psi, and main tires 55 psi.
Examination of runway 16L revealed two skid marks about 200 feet long. One started just left of centerline, the other just right, consistent with nose and right main landing gear positions. Both arced left, exiting into grass. A third mark appeared in the grass near the left main gear location. Shortly after, the nose gear mark deepened, consistent with nose landing gear separation.
Research
A Piper Customer Information Letter (CIL) dated March 27, 2008, noted that early customers reported occasional right pull "at the instant of touchdown." Piper could not duplicate the events but implemented two improvements starting in 2002: replacing the 6-ply nose tire (50 psi) with an 8-ply tire (70 psi) to reduce contact patch size, and incorporating a stiffer bungee for greater steering control authority.
The CIL stated that historical data validated the changes: prior to changes, the yearly runway excursion rate per number of aircraft in fleet was 7.6 percent; after changes (2002-2007), the rate was consistent at 0.8 percent.
Airframes with serial numbers prior to and including 4697125 had the changes per Piper Service Bulletin 1106; later airframes had them at the factory. The accident airplane serial number was 4697161.
The CIL identified factors critical for optimal steering capability:
- Tire Pressure: Low pressure can increase steering forces. Both Michelin and Goodyear recommended daily cold inflation checks; for less frequent operations, check before each flight. Tires can lose up to 5% pressure in 24 hours normally. An example: a tire inflated to 70 psi could drop to 49 psi in a week and 15 psi in 30 days, appearing properly inflated but significantly underinflated. "Tire pressure should be checked by the pilot as part of the preflight inspection."
- Nose Gear Rake Angle: The relative angle between the belly skin and nose gear strut should be 90.0 to 90.5 degrees. Rake outside this range "may result in dynamic instability, creating steering forces that exceed the pilot's ability to control." The rake angle is set at the factory and should be inspected/adjusted by a licensed mechanic per the maintenance manual when poor steering occurs, or after service to related components.
- Steering Arm/Roller Gap: Two nylon rollers on the nose gear trunnion translate steering arm rotation into nose wheel movement. When gear is down and locked, the rollers are directly forward of the steering arm. Excessive clearance between rollers and arm results in loose steering, allowing nose wheel direction to differ from rudder pedal commands.
- Rudder Cable Tension: Low tension can create variations between rudder angle and nose wheel steering angle. Excessively low tension could result in nose wheel pointing differently from the aircraft's line of travel at touchdown, even with proper pilot technique.
Additional Information
The pilot noted that after the annual inspection, about every other flight, he would see a "Gear Warn" light at some point during the flight, but it did not occur on the accident flight. The Piper investigator noted that if a landing gear actuator were not rigged properly in the up position, a drooping or mis-rigged condition could allow airflow to pull the door away from the gear warning micro-switch, causing the light to illuminate in flight.