FCMs Could Reset During Flight If Left On More Than 22 Consecutive Days

An Airworthiness Directive published in the Federal Register Friday requires repetitive cycling of either the airplane electrical power or the power to the three flight control modules (FCMs). This AD was prompted by a report indicating that all three FCMs might simultaneously reset if continuously powered on for 22 days on all Boeing 787-8 and 787-9 airplanes.

According to the FAA, reports have been received indicating that an FCM will reset if continuously powered on for 22 days. This condition, if not corrected, could result in simultaneous resets of all three FCMs, which could result in flight control surfaces not moving in response to flight crew inputs for a short time and consequent temporary loss of controllability.

The FAA is requiring compliance with the AD by all 99 Dreamliners registered to U.S. operators within a week.

The FAA considers this AD interim action. Boeing and its suppliers are developing a terminating solution to address the identified unsafe condition. Once this terminating solution is developed, approved, and available, the agency might consider additional rulemaking, according to the published AD.

The Seattle Times reports that in a statement, Boeing said that the AD addresses an issue that it has already been brought to the attention of Dreamliner operators. The company says a permanent software fix "is anticipated in the second quarter of 2017."

An aviation analyst who requested anonymity told the paper that airlines almost never leave a jet powered on for longer than a week.

The FAA estimates that the cost of cycling the power on the airplanes will cost about $85 per airplane per cycle.

(Image from file)

FMI: AD