Airworthiness Directive · Amendment 39-18153 · Electrical power
The Boeing Company Airplanes
Superseded. A later AD replaced this one: AD 2018-20-15. Comply with the one in force.
This AD applies to all The Boeing Company Model 787 airplanes, certificated in any category.
We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 787 airplanes. This AD requires a repetitive maintenance task for electrical power deactivation on Model 787 airplanes. This AD was prompted by the determination that a Model 787 airplane that has been powered continuously for 248 days can lose all alternating current (AC) electrical power due to the generator control units (GCUs) simultaneously going into failsafe mode. This condition is caused by a software counter internal to the GCUs that will overflow after 248 days of continuous power. We are issuing this AD to prevent loss of all AC electrical power, which could result in loss of control of the airplane.
At the latest of the times specified in paragraphs (g)(1), (g)(2), and (g)(3) of this AD, accomplish electrical power deactivation on the airplane, in accordance with step 2) in “DESIRED ACTION” of Boeing Multi Operator Message MOM-MOM-15-0248-01B, dated April 19, 2015; or Boeing Multi Operator Message MOM-MOM-15-0248-01B(R1), dated April 20, 2015. The main and auxiliary power unit (APU) batteries do not need to be disconnected when performing the electrical power deactivation. Repeat the electrical power deactivation thereafter at intervals not to exceed 120 days.
(1) Within 120 days after the last electrical power deactivation in accordance with step 2) in “DESIRED ACTION” of Boeing Multi Operator Message MOM-MOM-15-0248-01B, dated April 19, 2015; or Boeing Multi Operator Message MOM-MOM-15-0248-01B(R1), dated April 20, 2015.
(2) Within 120 days after the date of issuance of the original certificate of airworthiness or the date of issuance of the original export certificate of airworthiness.
(3) Within 7 days after the effective date of this AD.
