All Boeing 747s will be required to have their fuel tank lightning protection features inspected following reports of cracking on certain components.
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SUMMARY
The FAA has issued an urgent airworthiness directive (AD) for Boeing 747s to address concerns about cracking and compromised safety features on the lightning protection systems.
The AD covers 362 active aircraft globally, with inspections expected to take between two and three days to prevent potential risks to the flying public.
As reported by FlightGlobal, all 747s in active service will be required to have the lightning protection features on their fuel tanks inspected after the FAA received reports that some components had failed or begun to crack, limiting the effectiveness of the safety features that prevent sparks in the fuel tubes entering fuel tanks.
Ordered on Wednesday, the FAA’s AD has been issued as a final rule, with the agency urging airlines to inspect all 747 variants as soon as possible. Inspections are expected to take between two and three days.
“The FAA has found that the risk to the flying public justifies forgoing notice and comment prior to adoption of this rule. This is an urgent safety issue, as all fuel feed lightning protection features now have evidence of compromise.”
In a statement shared with Simple Flying, a Boeing spokesperson noted that it was in communication with the FAA regarding the issue,
“Boeing supports the U.S. Federal Aviation Administration’s Immediately Adopted Rule, which makes mandatory the guidance we have provided to operators. We remain in communication with the FAA and our customers on this matter.”
Preventing problems
The AD covers 362 active aircraft worldwide, ranging from the -100 in service with the Islamic Republic of Iran’s Air Force to the last -8F delivered to Atlas Air in January. Despite the relatively young age of the -8 airframe, the FAA noted it had found a complete crack around components that isolated sparks on a 747-8.
When lightning does strike an aircraft, it is often not a cause for concern.
A failure of the fuel tank’s safety systems could leave an aircraft without adequate protection from lightning strikes, potentially leading to a fuel tank explosion under certain conditions. The FAA added,
“The lightning protection features for the engine fuel feed system could fail without being detected. This could result in no lightning protection features remaining.”
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The -100 variant 747 has notably been involved in two high-profile fuel tank explosions. In 1976, an Iranian Air Force 747-100 (5-283) crashed on approach to Madrid-Barajas Airport (MAD) after a lightning strike passing through the fuselage ignited the fuel vapor in the outer left-hand engine. The explosion caused the left wing to disintegrate, bringing down the aircraft and its 17 occupants.
Similar ADs have been issued by the FAA previously, with 747-400s and 747-8s operators cautioned about wear within the horizontal stabilizer fuel tanks causing unsafe conditions in 2022. The AD came into effect in January 2023, covering almost 150 aircraft registered in the US.
