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Enhancing Airworthiness: Addressing Oxygen Hose Safety and Conductivity Issues

In the mid-1990s, Boeing addressed critical safety concerns related to oxygen hoses following electrical leakage reports. The original conductive hoses were redesigned with plastic spacers to disrupt current pathways, which prevented hoses from melting due to excessive heat. Although the FAA reviewed proprietary service bulletins without issuing Airworthiness Directives (ADs), compliance is now mandated, emphasizing safe installation and proximity to electrical components. Regular inspections for aging hoses, potential leaks, and proper grounding are crucial to enhance oxygen system reliability and prevent future incidents.

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Enhancing Airworthiness: Addressing Oxygen Hose Safety and Conductivity Issues

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  1. ABX Air Ground Fire Bob Swaim Airworthiness

  2. Conductivity of Oxygen Hoses In mid-1990s, Boeing received leakage reports Electrical current heated internal spring • Hose redesign • Plastic spacer added to interrupt current path Original conductive hose hooked spring to hole New plastic spacer with hole to attach spring • PVC hose material melted • Production change and service bulletins issued in 1999

  3. Airworthiness Directive (AD) Process • FAA reviewed Boeing’s Service Bulletin (SB) but did not issue ADs • Issuance of AD mandates compliance with SB • FAA now mandating SB compliance • Expected to cite specific Boeing cockpit use of part numbers • Would not cite same parts used in non-cockpit installations or address hose manufacturer’s other customers

  4. Airworthiness Directive Process AD types: aircraft, engine, propeller, or appliances Appliances are not unique to one airplane design Appliance ADs address individual parts and assemblies FAA to coordinate with makers of vended parts Part makers to provide FAA with list of customers using similar parts FAA to check for additional applications using part

  5. Proximity of Oxygen Components to WiresProper Installation Clamps Ceiling panel Oxygen supply tube Wire

  6. Proximity of Oxygen Components to WiresImproper Installation Wires touch oxygen supply tube Ceiling panel

  7. Proximity of Oxygen Components to Wires • Conductive oxygen tubing needs protection • Physical isolation • Nonconductive sleeving • Nonconductive coating • Inadvertent wire contact found previously • Wires contacted critical oxygen tubing • Continuing problem

  8. Electrical Grounding of Oxygen System Stainless steel supply tube in rubber-lined clamps

  9. Aging Oxygen Hoses • Potential for cracks and oxygen leaks • Older hoses not as flexible as new hoses • PVC can harden with exposure to light and some chemicals • Inspection requirements • Periodic system leakage and general visual inspections • No tests or inspections for material properties • Operators could install older hoses into newly delivered airplanes

  10. Rubber boot, per design Potential arc Switch Boot missing from switch Rotation of light assembly Passenger Service Unit Reading Lights

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