February 2012 FAA Maintenance Alerts

Cessna: 335; Corroded Wing Attach Fittings; ATA 5741

A technician for an air charter service says, "During a 100-hour inspection, the forward upper L/H wing attach point (was found to have) corrosion on the wing attach fitting (P/N 08113507). After removing the upper wing-fuselage fairing, inspection revealed intergranular corrosion on the fitting, and severe rust on the mounting bolt heads. The fitting was replaced due to the severity of the corrosion. Probable cause (for this corrosion) is the fuselage-wing fairing not being sealed properly in the area above the fitting. This allowed moisture to pool in the recessed area of the fitting, causing the rust and corrosion. The fuselage-wing fairing is riveted to the fuselage, making (detailed) inspection of the upper forward mounts difficult."

Part Total Time: 5,559.0 hours

Hawker: 800XP; Corroded Fuselage Attachment Links; ATA 5741

A repair station technician says, "Severe corrosion was found in the L/H lower, wing-to-fuselage casting lug during a 12/8 year links/brackets/bolts inspection. Probable cause: exposure to constant moisture from improper fuselage-to-wing fairing sealing practices (produced the corrosion), and/or constant exposure to TKS anti-icing fluid from improper plumbing practices that may have lead to system leaks (and then subsequent corrosion). Recommendation: proper sealing methods (should be employed) when attaching wing-to-fuselage fairings. And proper plumbing practices (should be used) when performing maintenance on wing anti-ice systems. Note: Use of a corrosion preventative compound ... at this location may prevent this condition ...with scheduled applications." (Wing-to-fuselage link/bearing P/N: 25-8WS3103-1.)

Part Total Time: 4,420.0 hours

Bell, Robinson, Agusta Westland: (All) Hardware Failures; ATA (n/a)

Helicopter manufacturers have reported failed MS 21042 and NAS 1291 series self-locking nuts, and have issued Safety Letters and Bulletins. These failures are typical of hydrogen-induced delayed cracking, a condition found during improper heat-treating during manufacture. The bolt may fall out and/or higher loads may be transferred to remaining fasteners which may result in overloading and subsequent failure of the bolts or studs some time after the bolts have been replaced. It is recommended that pilots and maintenance personnel closely monitor the occurrence of hydrogen-induced delayed cracking in high-strength steel standard aircraft hardware following installation and during daily and periodic inspections. Before simply replacing cracked/failed nuts consider contacting the manufacturer for advice regarding replacement of associated fasteners which may have suffered overloading as a result of a failure of one or more nuts.