Incident Details
On April 24, 2013, at approximately 1720 eastern daylight time, a Piaggio P180 airplane, registration N139SL, experienced a runway excursion during landing at St. Petersburg-Clearwater International Airport (KPIE), Clearwater, Florida. The aircraft was operated by Avantiar under 14 CFR Part 91 as a business flight, registered to Anoil Co. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated from KPIE at about 1550.
Landing and Runway Excursion
During the landing roll, after the nose wheel touched down, the pilot heard a tire squeal and felt the airplane gradually veer to the right. The pilot attempted to correct the deviation by applying left rudder, left braking, and left engine reverse thrust. The airplane came to a stop with the nose pointed more than 90 degrees to the right of the runway centerline. Only the nose landing gear exited the runway surface; the main landing gear remained on the pavement. The pilot and five passengers were not injured. The airplane sustained minor damage to the nose landing gear and wheel.
Post-Incident Examination
The operator examined the nose landing gear after the event. When the hydraulics were activated and the electric steering was turned off, the steering actuator deflected the wheels 50 degrees to the right. When electric steering was turned on, the actuator returned the wheels to the center position (0 degrees). The steering manifold (serial number M/DAG74/04; part number 114180003) was removed and retained for further analysis.
Maintenance and Overhaul Findings
The steering manifold had been overhauled by Advantage Aviation Technologies II, LLC (AAT) on March 15, 2013, in accordance with Component Maintenance Manual (CMM) 32-50-50, Revision 6. A post-incident examination aimed to identify mechanical malfunctions or failures and evaluate the overhaul procedures. Testing followed the manufacturer's CMMs, but feedback and control readings were taken using an analog scale provided by AAT, rather than a digital scale as specified. The required Test Box DRT66770 was not available during testing and had never been used by AAT, as they did not possess one. Instead, AAT used a 1985-era wiring diagram (Dowty-Rotol Ltd., 460006820, sheet 2 of 5) to construct a replacement test box. None of the other tooling and test boxes specified in the CMM were available at AAT.
Examination Results
The steering manifold was first connected to an exemplar Piaggio P180 landing gear. With the system electrically de-energized and hydraulic pressure available, the actuator moved the wheels to the left without any commands. A bias steering check repeated this leftward movement, measuring 6 degrees on the first application and approximately 14 degrees on the second. This did not replicate the uncommanded right turn experienced during the runway excursion.
Subsequently, the manifold was connected to a hydraulic test rig and tested per CMM 32-50-50, Revision 8. However, the group deemed the tests invalid because AAT lacked the specified test box. The manifold failed all other CMM functional tests because the solenoid valve inside would not close properly.
Disassembly of the manifold revealed multiple scratches and damage to the armature plate and retainer ring. Inside the sleeve assembly, one wave washer and two shims (each measuring 0.003 inches in thickness) were found. The wire connected to the electrical connector was damaged and had a white insulation sleeve installed by AAT during overhaul, a modification not specified in the CMM.
A review of the original overhaul paperwork disclosed multiple discrepancies. AAT omitted certain procedures, used alternative tooling not approved by the CMM, and did not reference the alternative tooling in the paperwork. Additionally, AAT lacked written procedures to validate that the work was completed correctly. The manifold could not be tested per CMM requirements because the overhaul facility did not possess the necessary equipment and tooling.