US safety regulators are ordering the replacement of oxygen hoses on the flightdeck of Boeing 777s to reduce the risk of a cockpit fire.
The directive has been issued in the wake of a serious ground fire that broke out on board an EgyptAir 777-200 on 29 July last year, while the aircraft (SU-GBP) was docked at gate F7 at Cairo airport's Terminal 3.
Although there were no injuries, Egyptian investigators state that the cockpit was "extensively damaged", with two holes burned through the fuselage skin below the windshield.
The fire started in the right side of the cockpit below the third window, where several oxygen system hoses are located. While the hoses were not required to be non-conductive when manufactured, test results indicate that sufficient electrical current in conductive hoses could cause ignition. The new US Federal Aviation Administration directive, effective from 16 August, orders low-pressure oxygen hoses to be replaced with non-conductive ones. The change aims to prevent electrical current passing through the hoses' internal anti-collapse spring - a situation that could result in the hose melting, and an oxygen-fed cockpit fire.
United Airlines sought to extend the 18-month compliance time to 24 months, while the US Air Line Pilots Association wanted the time shortened to 12 months. Both requests have since been rejected.
The FAA says it considered safety implications, parts availability and normal maintenance schedules and concluded that its proposal is "in keeping" with compliance times from manufacturers. Boeing also issued a service bulletin in June to correct a wiring anomaly - related to instrument panel illumination for identifying the location of oxygen masks - found in sister ships to the damaged EgyptAir 777. Evidence suggests the voltage in the affected wire was "too low" to have played a role in the Cairo fire, the airframer says.