History of the Flight
On July 3, 2020, at approximately 1157 eastern daylight time, a Piper PA-46-600TP, registration N89MA, was substantially damaged during a landing accident near Titusville, Florida. The pilot and two passengers were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
The pilot reported that the flight from Albert Whitted Airport (SPG), St. Petersburg, Florida, to Space Coast Regional Airport (TIX), Titusville, Florida, was uneventful except for turbulence. During the landing flare, the airplane veered left of the centerline. After the main landing gear (MLG) touched down, the airplane continued veering left, prompting the pilot to relax rudder pressure. When the nose landing gear (NLG) contacted the runway, the airplane began veering right. The pilot applied left aileron, rudder, and brakes, but the airplane did not respond. It exited the right side of the runway, skidded sideways through grass, and the left wing and propeller struck the ground, causing substantial damage. The airplane came to rest about 100 feet from the runway edge.
Data from the Garmin G3000 Integrated Avionics System showed that before takeoff at SPG, the airplane made several turns on the ramp and taxiways. During landing at TIX, after the MLG touched down at about 73 knots, the heading and track began to diverge, and lateral acceleration increased.
Aircraft Information
The NLG is steerable through a 50° arc (20° left, 30° right) using rudder pedals. The steering horn (part number 85154-012) is attached to the NLG strut with three bolts. Two steering pads and two rollers on the horn interface with the steering arm to transmit rudder pedal inputs to the strut. Piper identified alignment issues with certain steering horn assemblies where pad and roller positions were inconsistent due to tolerance stack-up; alignment could be corrected by machining the pad faces.
The accident airplane received its airworthiness certificate on December 7, 2019. On January 17, 2020, the airframe manufacturer reworked the steering horn to align the pads with the rollers and reinstalled it before delivery. The pilot purchased the airplane in June 2020 with about 23 total flight hours. After accruing 48.1 hours, a 50-hour maintenance interval was completed on July 1, 2020, during which the left MLG strut and tire were replaced, and the MLG alignment and NLG squat switch were adjusted. Four flights occurred after maintenance, with the accident on the fourth landing. Taxi data showed multiple turns before and after each flight. The pilot reported no evidence of tow exceedance during preflight inspection.
The airplane could be towed using a tow bar attached to the NLG axle. A placard on the trunnion limits towing turns to about 20° left and right, with red lines on the strut indicating the limits. The Pilot’s Operating Handbook cautions against turning beyond steering limits during towing. If the NLG is turned beyond the left limit, the steering arm left flange contacts the engine mount plate. Damage may occur to the steering arm and the three bolts attaching the steering horn. The pilot stated he was aware of towing limitations; the airplane was towed six times at his home airport, and he witnessed all except during maintenance. Whether the airplane was towed during maintenance could not be determined.
Wreckage and Impact Information
Examination revealed the left wing was deformed upward, with buckled skin and bent spars. The left aileron was buckled. Four of five propeller blades were fractured. The fuselage left side was buckled. The left MLG tire beads separated, and both MLG tires showed crosswise scuffing. The NLG tire was aligned with the longitudinal axis after the accident; the strut and lower fork were bent right, and the tire was offset about 25° from vertical. Steering horn was separated from the strut; all three attachment bolts were fractured. The left aft bolt fractured in tension with some shear; the aft right and forward bolts fractured in shear with bending. Directions of shear indicated the strut rotated left relative to the steering horn or vice versa.
NLG tire pressure measured 91 psi (recommended 92-97 psi with 5% loss acceptable). Mechanical damage was noted on the right turn stops on the trunnion and strut, and on the aft face of the left side of the steering arm (left turn mechanical stop). Wear marks were observed on the forward faces of the steering arm where it interfaced with the horn pads and rollers. The steering horn base and top plate were deformed; the left large roller bolt was bent forward about 7°. Paint was missing on the right machined stops, and a witness mark on the steering arm left flange matched the engine mount plate.
The left MLG torque links were separated at the apex; the apex bolt’s nut and cotter pin were not recovered. Thread deformation and a remnant of a stripped nut thread were observed.
Runway examination showed MLG touched down about 620 feet from the threshold, 4 feet left of centerline. NLG tire marks began about 770 feet from the threshold. Both MLG and NLG tire marks extended to where the airplane exited the runway right side at about 1,140 feet. Ground scars showed continuous right MLG marks, left MLG trenching, and heavy NLG trenching. A ground scar near the rest position was consistent with left wing strike.
Tests and Research
A simulated tow test was conducted to document interference points, witness marks, bolt failure sequence, and forces required to fracture the bolts. The NLG strut was rotated left until the steering arm left flange contacted the engine mount plate. Applying about 194 lbs of force (moment of 8,560 in-lbs) caused the aft left bolt to fracture. Subsequent forces of 144 lbs (6,354 in-lbs) and 35 lbs (1,544 in-lbs) fractured the aft right and forward bolts, respectively. After the forward bolt fractured, the steering horn completely separated. Examination of the steering arm after the test revealed a witness mark from contact with the engine mount.