FAA Orders Urgent Inspections for Boeing 747 Lightning Protection System
The FAA has issued an airworthiness directive requiring inspections of the lightning protection system on all U.S.-registered Boeing 747 aircraft. The move follows Boeing’s recommendation for inspections due to the degradation of key components in the system. These components play a critical role in preventing ignition sources during lightning strikes near fuel tanks.
Boeing’s recent discovery of undetected degradation in key components of the lightning protection system has prompted the company to recommend urgent inspections for all Boeing 747 aircraft. The Federal Aviation Administration (FAA) is now mandating these inspections for U.S.-registered planes, and the implications may extend globally.
Boeing employs multiple layers of protection to prevent feed tubes leading to fuel tanks from becoming ignition sources during lightning strikes near the engine nacelles. These layers include bonding jumpers and sealant, serving as secondary protection beyond the primary electrical path provided by wing spar fittings. However, these fittings can degrade over time, compromising the effectiveness of lightning protection, underscoring the critical role of secondary safeguards.
The FAA is set to publish an airworthiness directive (AD) on November 30, highlighting the alarming rate at which 747 jumpers have been failing. Boeing also identified another concerning issue—a complete crack around the fuel feed fitting encapsulation inside a 747-8 fuel tank. This encapsulation is designed to isolate sparks/arcing generated during a lightning strike from flammable fuel vapors in the tank.
The FAA deems this a pressing safety concern, as evidence suggests a compromise in all fuel feed lightning protection features across 747 variants.
The FAA directive, driven by the severity of the issue, mandates inspections for 747 operators within 90 days of its effective date, expected to be December 15. For other 747 variants, inspections must be conducted within 120 days of that date, with subsequent annual checks.
While initially applicable to 211 U.S.-registered aircraft, this directive is likely to have worldwide implications. Globally, there are 402 747s in service, with an additional 56 in storage, though fewer than 100 of these in-service models carry passengers.
Boeing issued messages to operators in mid-November 2023, outlining the problem and recommending inspections. The FAA directive aligns with Boeing’s instructions.
Operators’ specific actions include inspecting jumpers for damage and measuring their electrical bonding resistance. All results must be reported to Boeing.
“The inspection reports will provide the manufacturer with crucial insights into the nature, cause, and extent of bonding degradation and failures, enabling the development of final actions to address this unsafe condition,” stated the FAA.
This development underscores the importance of ongoing safety measures in the aviation industry, as well as the potential global impact of these inspections.
Sources: AirGuide Business airguide.info, bing.com, aviationweek.com