B787 Dreamliner - Serious problem - Another one which bypassed the certification authorities

FAA Warns 787s Can Lose All Electrical Power in Certain Circumstances

Issue can occur after Boeing Dreamliners remain connected to power source for extended periods

By ANDY PASZTOR and JON OSTROWER

Nearly four years after Boeing Co.'s 787 Dreamliner entered commercial service, federal regulators are moving to combat a potentially dangerous software glitch they said can cause a total loss of electrical power that would endanger the aircraft.

A Federal Aviation Administration safety directive that became public on Thursday reveals that Boeing's laboratory tests discovered that under certain circumstances, all of the 787's power systems can suddenly shut down entirely during a flight.

Such a problem, which the FAA said risks loss of control of the airplane, can occur after a jetliner remains connected to on-board or ground-based electric power without a break for a stretch of 248 consecutive days, the agency said. The FAA is ordering airlines to shut down power systems periodically to alleviate the hazard.
Boeing said such shutdowns are part of regular maintenance, and it would be rare for a jet to have power uninterrupted for so long. The plane maker roughly a week ago recommended that airlines voluntarily turn off power systems at least every four months.

During the early stages of the plane's introduction, Boeing drafted an internal report concluding that Dreamliners experienced most of their reliability problems just after being powered up. The company recommended adding additional time before flights to deal with erroneous "nuisance" messages.
As a result, many airlines made efforts to keep aircraft powered over unusually long stretches to avoid some nagging technical headaches and keep their Dreamliners flying on schedule.

According to the FAA document, a 787 "that has been powered continuously" for about eight months can trip software causing all four of its main generator control units "to go into fail-safe mode at the same time." The result, according to the FAA, can be "a loss of all AC electrical power regardless" of the phase of flight. Such a scenario can develop if the control units were powered up at the same time.

In the event of such a failure, the aircraft would revert to battery power momentarily before deploying its ram air turbine, a wind-driven propeller that generates a small amount of emergency power.
The FAA's move is a minor headache for Boeing and its global 787 operators, but underscores the turbulent journey to maturing the jet's advanced electrical systems.

The FAA's move is the latest complication for Boeing and its global 787 operators involving the jet's electrical systems. In January 2013, after two Japanese carriers experienced fire or smoke emergencies with advanced lithium batteries, the FAA pressured Boeing and all 787 operators to ground the planes for several months until design changes were made to the batteries and their containers.

In its latest directive, which isn't related to those battery problems, the FAA is requiring mechanics to temporarily turn off electrical systems on aircraft to briefly "deactivate" them. For some 787s, that could be required by the end of next week.

Released on the Federal Register's website Thursday, the directive applies to more than two dozen Dreamliner aircraft currently flown by U.S. carriers. But foreign regulators are expected follow the FAA's lead and apply it to about 230 other 787s flying world-wide. Longer-term fixes to revise the problematic software are expected later this year.


The Dreamliner's need for power is extraordinary: its advanced electrical system generates nearly twice as much juice as Airbus's double-deck A380 superjumbo jet despite being half its size.

United Continental Holdings Inc., the largest 787 operator in the U.S. and an early customer for the jet, last year replaced many ground power units where the aircraft was operating, including its Houston hub. The earlier units, which sit at the gates and connect to the power-hungry aircraft, were unexpectedly switching off, causing a loss of power on the aircraft. When the aircraft was repowered, nuisance messages would have to be cleared before a flight could be operated.

Boeing and United said that software and hardware changes to the aircraft have now significantly reduced those messages.

But previously, United said its ground crews would leave a small onboard generator, known as the auxiliary power unit, running as an "alternate power source for [the 787] to ensure stable electrical power while on the ground."

On other aircraft, such units typically are only operated in an emergency or immediately after landing and just before pushing back from the gate.

A Boeing spokesman said the laboratory testing that revealed the potential shutdown problem was unrelated to the earlier nuisance messages or any reliability or other in-service issues with the Dreamliner fleet. In a statement, Boeing said all airplanes have performed a power cycle as part of maintenance activities, eliminating the risk of losing power from all the generators at the same time.

Boeing said a software update to solve the issue would be provided to airlines starting in the fourth quarter of this year.

US aviation authority: Boeing 787 bug could cause 'loss of control'

More trouble for Dreamliner as Federal Aviation Administration warns glitch in control unit causes generators to shut down if left powered on for 248 days


The Boeing 787 has four generator-control units that, if powered on at the same, could fail simultaneously and cause a complete electrical shutdown.

The US air safety authority has issued a warning and maintenance order over a software bug that causes a complete electric shutdown of Boeing's 787 and potentially "loss of control" of the aircraft.

In the latest of a long line of problems plaguing Boeing's 787 Dreamliner, which saw the company's fleet grounded over battery issues and concerns raised over possible hacking vulnerabilities, the new software bug was found in plane's generator-control units.

The plane's electrical generators fall into a failsafe mode if kept continuously powered on for 248 days. The 787 has four such main generator-control units that, if powered on at the same time, could fail simultaneously and cause a complete electrical shutdown.

"We are issuing this AD [airworthiness directive] to prevent loss of all AC electrical power, which could result in loss of control of the aeroplane," said the Federal Aviation Administration directive. "If the four main generator control units (associated with the engine-mounted generators) were powered up at the same time, after 248 days of continuous power, all four GCUs will go into failsafe mode at the same time, resulting in a loss of all AC electrical power regardless of flight phase."

Should the electrical shutdown happen at a critical phase in flight such as take-off or landing, or while manoeuvring in the air, the loss of control could be catastrophic.

The FAA considered the situation critical and issued the new rule without allowing time for comment. Boeing is working on a software upgrade for the control units that should rectify the bug.

"The airworthiness directive action addresses a condition that only occurred in the lab. Simulated testing determined that this condition is possible in cases where an aeroplane's power is left on for more than eight continuous months. No airplane in the fleet experienced that condition," a Boeing spokesman told the Guardian.

According to Boeing's records, all of the 787s currently in service have been turned off and turned on again as part of maintenance. The FAA's directive mandates action recommended by Boeing on 19 April.

"If there is a definitive record of a powercycle within the last 120 days, no operator action is immediately required. Operators will perform periodic power cycling at scheduled intervals until incorporating a software update. Boeing will issue in the fourth quarter of 2015," said the Boeing spokesman.