The US NTSB is asking the FAA to require Boeing to make changes to 757 and 767 procedures and training materials based on a 22 September incident involving multiple systems failures during a flight.
Pilots of an American Airlines 757 enroute from Seattle to New York received a "standby power bus off" indication in the cockpit due to a failed electrical relay.
Using the aircraft's quick reference handbook, written by American but based on Boeing procedures, the crew reconfigured several key functions of the aircraft to use battery power as recommended, but failed to set a switch that would have kept the battery charged as the procedure did not specify to do so. The resulting series of failures ultimately caused the pilots to experience aircraft control problems, and to exit the side of the runway onto the grass at the Chicago O'Hare International Airport after diverting and declaring an emergency. None of the 185 passengers and seven crew members were injured. The aircraft (N197AN) received minor damage to its landing gear.
Though the FAA issued a safety alert for operators (SAFO) on 13 January alerting operators to the potential issues, NTSB says more must be done.
"The Board does not consider these improvements to be sufficient because SAFOs are not mandatory nor do they necessarily have a long-term impact," the NTSB states in the 24 April letter. "Improved procedures should be specified and required because of the potential severity of loss of battery power."
As such, the NSTB is asking that the FAA require Boeing to revise its 757 and 767 procedures and training for dealing with an illuminated standby power bus off light, "to include specific steps to take so that complete loss of battery power is avoided."
Once the changes are made, the NTSB is asking the FAA to require that all operators of the aircraft to adopt the new procedures.