MIAMI — An industry bulletin issued by the Federal Aviation Administration announces the adopting of a new airworthiness directive for certain Boeing 747-8 aircraft after data analysis showed that in a limited flight envelope, with specific conditions, divergent flutter (a rapid and erratic vibration) could occur “during a “high g-load maneuver in combination with certain system failures,” hence compromising the safety of flight.
According to the bulletin, the incoming AD will require 747 operators to replace the lateral control electronic (LCE) modules and inboard elevator power control packages (PCPs), to install new external compensators for the PCPs, and the review of the maintenance or inspection programs in place. The bulletin also states that the AD seeks to “to prevent certain system failures from resulting in divergent flutter, and subsequent loss of continued safe flight and landing.”
Boeing fully supports the coming FAA’s AD, which would make mandatory the action that Boeing recommended to operators in February 2014. Karen Crabtree, a company spokesperson, assured that although Boeing’s recommendations are not binding on operators, the manufacturer “recommended operators of the 71 747-8s delivered prior to February 2014 ensure airplanes are configured with the latest certified software and system changes.”
The notification further indicates that operators are required to make wing repairs within the next five years to avoid potential safety issues. Repair costs are estimated around $400,000 per aircraft and may be covered by Boeing as some of these aircraft are still under warranty.
Back in October 2010, the 747-8 program delayed approximately six months the initial deliveries due to flutter issues on the wingtips, an issue solved by an award-winning software implemented by a team led by Dr. Pio Fitzgerald.
This type of issues are not uncommon. After the Qantas Flight 32 incident, an inspection determined that some some rib feet, an internal wing fitting, were found with cracks. Prompted by this finding, inspections were carried out on a number of other Airbus A380 aircraft, confirming the existence of these cracks, resulting in an Airworthiness Directive that affected a total of 20 aircraft.