Just Plain Broken

While in process of checking the individual oxygen masks during an annual inspection and five-year O2 bottle re-certification, a technician heard a very faint sound of a gas leak in the overhead interior paneling of the aircraft. After pulling the headliner for a closer inspection and plumbing in low-pressure nitrogen for troubleshooting, the technician narrowed down the "hiss" to a line just forward of the cabin door (p/n 5100107-46). To access this line, which passes through a structural beam in the overhead, it was necessary to drill out approximately 40 rivets securing a thin honeycomb panel to the overhead (structure). Above the panel is the ducting supplying the cabin Wemac vents. The line as pictured has been cleaned up and the corrosion removed for clarity. The corrosion occurred where the ducting passed under it. The ducting was removed to facilitate line removal, and was found to be totally deteriorated.

Key Takeaways:

• Maintenance checks revealed critical, often hidden, structural and system issues across various aircraft, including a severely corroded oxygen line and multiple instances of cracked flap handle support mounts.
• Two incidents involved failures of recently installed or new components: a new helicopter oil cooler cracked shortly after installation, and new engine through-bolts repeatedly snapped post-torquing.
• These reports underscore the importance of meticulous inspections, especially in difficult-to-access areas, and careful scrutiny of new or replacement parts to prevent unexpected failures.

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