The Federal Aviation Administration has proposed that airlines be required to address a Boeing 777 rivet issue that raises concerns about potential pressure loss.
“The FAA has received a report indicating that an operator found solid rivets with missing heads at the left buttock line 25 on the sloping pressure deck web,” the FAA says in regulatory documents published on 9 April.
“The model 777–300 airplane had 23 solid rivet locations with missing manufactured heads,” the FAA adds.
That aircraft had logged 21,343 flight cycles and 53,979h of flight when the issue was identified.
Subsequent inspections revealed that four other 777-300s and one retired 777-200 had the same issue.
“Boeing analysis showed the root cause to be the 7050 aluminium solid rivets used on the sloping pressure deck web, which were inadequate for the complex tension loading environment, and led to premature fatigue cracking of the solid rivets,” says the FAA.
The agency warns that the issue, if not addressed, could “result in loss of sloping pressure deck panels, causing decompression and pressure loss, and loss of the hydraulic systems in the area for wheel brakes (both normal and alternate) and steering”.
The structural integrity of the jets could also be compromised, it adds.
Boeing did not respond to a request for comment.
In November 2020, Boeing issued an Alert Requirements Bulletin addressing the issue. That document specified procedures for inspecting an area of the 777’s “left and right side sloping pressure deck” for damaged rivets, missing rivet heads and gaps between the heads and the sloping pressure deck”.
The bulletin specified corrective actions that included repeat inspections, rivet replacements and other repairs.
The FAA’s proposed AD would require airlines to complete the steps detailed in Boeing’s bulletin. It would affect 224 777s registered in the USA.
The agency is accepting comments about the proposed order through 24 May.