The Federal Aviation Administration (FAA) has issued an Airworthiness Directive (AD) requiring airlines to inspect lightning protection features in the fuel tanks of all Boeing 747 variants. This measure was taken following reports from Boeing that lightning protection components in the engine fuel systems of this aircraft are degrading faster than expected.
The directive becomes effective in 16 days and sets deadlines for inspections. Airlines will have 90 days to inspect the passenger variants of the 747 and 120 days for the cargo variants. Inspections must be carried out annually.
The FAA’s order is considered a final rule, indicating the urgency of the situation. It applies to all 211 747 aircraft registered in the US, from the 747-100 variant to the 747-8.
According to the directive, «This is an urgent safety issue, as all lightning protection features of the fuel supply system now have evidence of compromise (…) the risk to the flying public justifies forgoing notice and comment prior to adoption of this rule because the lightning protection features for the engine fuel feed system could fail without being detected».
Boeing, the aircraft’s manufacturer, supports the measure and states that operators are already following the inspection recommendations provided by the company. Inspections should take two to three days.
The risk involves components designed to prevent sparks in the fuel tubes that penetrate the 747’s fuel tanks. The «bonding jumpers,» responsible for creating safe paths for electricity, are failing at an excessive rate, according to Boeing.
The failure of these components could result in a lack of lightning protection, which, combined with flammable fuel vapors, could lead to an explosion in the fuel tank.
In total, there are 495 747 aircraft in service or stored worldwide, with Atlas Air Worldwide Holdings and its affiliates operating the largest fleet, consisting of 56 aircraft. Other US carriers with considerable 747 fleets include UPS (41), Kalitta Air (24), and National Airlines (eight).
