On May 1, 2015, the FAA issued Airworthiness Directive 2015-09-07, which calls for near immediate and continuing efforts to fix a potentially catastrophic software issue with all models of the Boeing 787 aircraft. Boeing recently advised the FAA that a certain portion of the software related to the aircraft’s generator control units (GCUs) will malfunction after 248 days of continuous service. Each 787 has four GCUs and if all were powered up for the same continuous duration, all four would go into what is called “failsafe” mode, and that would result in a complete loss of AC electrical power to the plane, which could, in turn, result in a complete loss of aircraft controllability.
The FAA considered the problem serious enough that it waived the standard public commentary period prior to issuing the AD. The FAA estimates this unsafe condition affects 28 airplanes of U.S. registry.
Boeing is working on a solution to the problem, but in the meantime, the fix mandated by the FAA involves an electrical power deactivation of each of the GCUs, presumably to interrupt the continuous service counter in each to avoid the 248-day glitch. This procedure must be completed by May 8, 2015 and then be repeated continuously thereafter every 120 days. The estimated cost per aircraft for each electrical power deactivation is just under $2,400.
The 787 has a history of problems with its electrical systems. In January the entire global fleet was grounded for a period of time after serious issues were discovered with the airplanes’ batteries.