NTSB Determines Cause of Ground Fire Aboard Cargo Airplane in San Francisco

Report blames design of oxygen system hoses and lack of positive separation between electrical wiring and electrically conductive oxygen system components.


As a result of the investigation, the Safety Board voted to recommend that the FAA: require operators to replace electrically conductive hoses with electrically nonconductive hoses and prohibit further use of conductive hoses unless the conductivity is an approved design element; formalize the airworthiness directive (AD) process so it addresses all possible uses of an appliance affected by an AD; require positive separation between electrical wiring and oxygen system tubing; ensure that oxygen system tubing in proximity to electrical wiring is made of, sleeved with, or coated with nonconductive material or is isolated from potential electrical sources; develop and implement electrical grounding requirements for oxygen system components for all transport-category aircraft; develop inspection criteria or service life limits for flexible oxygen hoses to ensure that they meet current certification and design standards and require that airplane operators replace hoses that do not meet these criteria or life limits; and require operators of transport-category cargo airplanes to install smoke detectors in the supernumerary or similar airplane compartments.

During its investigation, the Safety Board determined that reading lights located in passenger service units (PSU) could become a potential source of ignition to nearby combustible materials. Because of this, the Board recommended that the FAA require transport-category airplane operators to ensure that all reading lights in PSUs be installed with rubber boots or use other means to provide a greater level of electrical protection.

The Safety Board also voted to recommend that ABX Air modify its CASP so that all chronic discrepancies are effectively resolved. The Board reiterated a previous recommendation to the FAA about training on an emergency response firefighting device.

To view a synopsis of the accident investigation report, including the findings, probable cause, and safety recommendations, click here. The complete report will be available on the website in several weeks.

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