Accident Details
On October 8, 2013, about 1210 eastern daylight time, a Piper PA46-350P JetProp, registration N640BD, operated by Municipal Code Corporation, sustained minor damage when its nose landing gear collapsed while landing at Tallahassee Regional Airport (TLH), Tallahassee, Florida. The airline transport pilot was not injured. Visual meteorological conditions prevailed, and an instrument flight rules flight plan had been filed. The flight departed Sarasota-Bradenton International Airport (SRQ) and was destined for Gulfport, Mississippi. The business flight was conducted under Title 14 Code of Federal Regulations Part 91.
Pilot Actions
The pilot reported a normal takeoff from SRQ. After retracting the landing gear, the red landing gear warning annunciator light remained illuminated. He cycled the landing gear and observed three green lights when the gear handle was selected to the extended position, but the red warning light persisted after the gear was retracted. The pilot diverted to TLH, where the airplane was based. Prior to landing, cockpit indications showed all three landing gear down and locked. During touchdown, the nose of the airplane slowly dropped until the propeller contacted the runway.
Post-Accident Inspection
Subsequent inspection revealed that the aft nose landing gear actuator bolt was fractured. The bolt was installed through mounts on either side of the actuator fitting and through a spherical bearing in the upper fitting. The bolt head with about 1 inch of shank was not recovered. The remaining portion, including the locknut and a washer, was sent to the NTSB Materials Laboratory for examination.
Maintenance History
Review of maintenance records showed that the airplane had been operated for about 2,850 hours since modification under a Supplemental Type Certificate (STC) by Rocket Engineering Corporation on August 13, 2001. The STC replaced the original Lycoming TIO-540 series engine with a Pratt & Whitney Canada PT6A-34 series engine, including associated airframe alterations.
Metallurgical Examination
Examination by an NTSB metallurgist determined that the nose landing gear actuator attachment separated due to fracture of the bolt at the upper attachment fitting from reverse-bending fatigue. The missing bolt head prevented verification of the part number. The installed bolt contained a drilled shank, inconsistent with the specified part number NAS6607-38, but the diameter, hardness, and material composition met specifications. Fracture and wear patterns were consistent with some clamping force during installation, but the applied torque was unknown.
Tug Loads
An evaluation of the loading spectrum for the nose landing gear attachment and a conversation with the STC holder indicated that tug loads could significantly contribute to the overall load profile. A representative of the owner stated that the airplane took 180 to 270 trips per year, and a tug was used about 75 percent of the time. After repair, maintenance personnel noted that a washer was required to occupy a gap between the actuator and engine mounts; the washer was installed prior to the incident, and when properly torqued, no gaps were present.