Incident Overview
On December 11, 2008, at approximately 1311 eastern standard time, a Cessna 402C, registration N522FA, experienced separation of its left main landing gear assembly during the landing roll at Fort Lauderdale/Hollywood International Airport (FLL) in Fort Lauderdale, Florida. The aircraft, registered to Friendship Airways Leasing, Inc. and operated by Friendship Airways, Inc., doing business as Yellow Air Taxi, was conducting an instructional flight under 14 CFR Part 91. No flight plan was filed. The flight had departed from Palm Beach County Glades Airport (PHK) in Pahokee, Florida.
The aircraft sustained minor damage. The airline transport-certificated check pilot, the commercial-certificated pilot receiving instruction, and two passengers were not injured.
Flight Crew and Sequence of Events
The pilot receiving instruction, seated in the left pilot seat and acting as pilot flying (PF), was undergoing training to become the company's chief pilot. The check pilot, also a certificated flight instructor, had provided training to the three pilots throughout the day. The two passengers were new-hire pilots observing.
After takeoff, the flight proceeded to Fort Lauderdale and was cleared to land on runway 27L. The winds at the time were from the south at 12 knots. Upon touchdown, the longitudinal axis of the airplane was aligned with the runway centerline. During the landing roll, the PF heard an abnormal sound from the left side of the airplane. One passenger shouted that the left wheel assembly had separated. The left propeller blades then contacted the runway. The PF secured both engines and the airplane's electrical system. The airplane turned to the left and contacted one runway light before coming to rest on the grass off the left side of the runway.
Weather Conditions
A surface observation weather report taken at FLL at 1253, approximately 18 minutes before the incident, indicated wind from 190 degrees at 14 knots with gusts to 20 knots, visibility 10 statute miles, broken clouds at 2,200 feet, temperature 26°C, dew point 22°C, and altimeter setting 29.86 inches of mercury.
Examination of the Landing Gear
Examination of the airplane revealed that the left upper barrel and trunnion assembly was fractured. The component was retained for further examination by the National Transportation Safety Board's Materials Laboratory.
Laboratory examination showed that the barrel assembly was fractured through the cylindrical barrel portion, starting about 0.20 inch below the side brace collar. The fracture followed the transition between the thinner wall section of the barrel below the side brace collar and the thicker wall region within the collar. A flat crescent-shaped fracture region existed around approximately 90 degrees of the barrel perimeter, oriented normal to the longitudinal axis. The topography indicated fatigue progression, which propagated through an estimated 70 percent of the barrel wall thickness. The remainder of the fracture was on a slant plane indicative of tensile shear overstress. Ratchet marks indicated fatigue initiated at multiple origins on the outer diameter surface. Crack arrest marks showed the fatigue crack propagated radially inward with little circumferential propagation.
Further examination revealed that the barrel material, heat treatment, and hardness were consistent with specifications, but the surface finish was less than the specified value. An area beneath the fracture surface exhibited smooth areas with corrosion pits. Moderate corrosion was also noted at the upper edge of the side brace collar after paint removal. Measurements of the inside diameter showed a maximum of 2.5138 inches, 0.0118 inch greater than the maximum specified. The minimum outside diameter was 2.6967 inches, 0.0133 inch less than the minimum specified. The transition area where the fracture occurred is specified to have a radius of 0.5 inch; the measured radius was uneven, with 0.135 inch on the thinner side wall and 0.339 inch near the thick wall region.
Maintenance History
The airplane was maintained under a Federal Aviation Administration Approved Aircraft Inspection Program (FAA AAIP) consisting of four inspections at 50-hour intervals. Visual inspection of the landing gear upper barrel and trunnion assembly is performed during the No. 4 inspection.
Review of maintenance records showed that the landing gear was last visually inspected on November 14, 2008. The inspection specified to check the barrel for corrosion, pitting, and cleanliness. No other inspection requirements are stipulated for the fracture area. At that time, the airplane total time was 9,957.4 hours. At the time of the incident, the total time was approximately 10,015 hours.
Prior Similar Events
The NTSB has investigated two other accidents involving fracture of the upper barrel and trunnion assembly: case numbers MIA04WA066 and MIA02LA089. Both cases involved fracture above the side brace collar.