NTSB Identification: NYC05IA052.
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Incident occurred Friday, February 11, 2005 in Hyannis, MA
Probable Cause Approval Date: 08/29/2006
Aircraft: Cessna 402C, registration: N403BK
Injuries: 1 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

During a positioning flight, the pilot noticed the airplane required aileron trim to maintain level flight. The airplane landed without incident. Subsequent examination of the airplane revealed two rivets missing on the underside of the left wing, between the heat shield and a factory-installed doubler. The lower forward spar cap was cracked at wing station (WS) 114, at a rivet hole located just outboard of the outboard engine beam. The web doublers, both forward and aft, were split near the end of the inboard wing spar web at WS 112.5. The skin was cracked from the front spar lower cap up to the first stringer location behind the front spar. The airplane had been operated for about 20,510 total hours, and was required to have its forward, aft, and auxiliary wing spars inspected for cracks per FAA AD 2000-23-01, at intervals not to exceed 110 hours time-in-service. The cracked portion of the forward spar, skin and the aft web doubler were removed for further examination. The examinations revealed fatigue damage, that originated at the forward portion of the rivet hole on the spar cap at WS 114. Blackening and corrosion were observed on the fracture surface, consistent with the fracture being present at the time of the airplane's last inspection, which was conducted about a week earlier, and 12 operational hours prior to the incident.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

The mechanic's inadequate inspection, which failed to discover cracks in the left wing spar around wing station 114.

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