A Boeing 777 inspected by the agency contained nearly two dozen defective rivets. Boeing

The Federal Aviation Administration issued an airworthiness directive on April 9 to inspect all types of Boeing 777 jet airliners. The instruction is based on the agency's discovery that five 777 aircraft of different models lacked rivet heads for connecting aircraft skins. This directive is the second directive to affect 777 in less than two months. The last one was released after the Pratt & Whitney Canada PW 4000 engine exploded in February.

The FAA said it has received a report that an operator found a solid rivet without a head at the left hip line 25 on the web of the inclined pressure deck. The 777-300 aircraft has 23 solid rivet positions, but lacks a manufacturing head; the aircraft has accumulated 21,343 total flight cycles and 53,979 total flight hours at the time of discovery.

A fleet-wide multi-operator message (MOM) request discovered four other 777-300 aircraft and one decommissioned 777-200 aircraft, but lacked solid rivet heads. Boeing’s analysis shows that the root cause is that the 7050 aluminum solid rivets used on the inclined pressure deck webs are not sufficient to cope with the complex tensile load environment, leading to premature fatigue cracking of the solid rivets.

If this situation is not resolved, the rivet heads on the web of the inclined pressure deck may be undetected, damaged or lost, which may result in the loss of the inclined pressure deck panel, resulting in decompression and pressure loss, as well as the loss of the hydraulic system in the area. Braking (normal and standby) and steering-may cause runway deviation and adversely affect the structural integrity of the aircraft. The agency believes that the cost of repairing each affected 777 may be as high as $33,000 per aircraft. Airworthiness directives may affect nearly 225 aircraft. For more information, interested parties should contact Luis Cortez, Aerospace Engineer, Seattle ACO Branch, 2200 South 216th Avenue, Des Moines, Washington, 98198. The email contact is Luis.A.Cortez-Muniz@faa.gov.

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