Fuel leaks on two in-service Boeing 787s have been traced to improperly installed engine fuel line connectors, prompting the FAA to order inspections and Boeing to review its production process.

The FAA’s order, issued today, is based on a Boeing Multi Operator Message (MOM) from Nov. 25 that recommends operators inspect both rigid and full flexible fuel manifold couplings, and accomplish several other actions by Dec. 8, including inspecting lockwires for proper installation. The agency determined that inspecting lockwires by Dec. 8 and accomplishing the other tasks by Dec. 22 is sufficient to address the unsafe condition.

A Boeing spokeswoman says that about half of the 38 787s delivered have been inspected, but declined to provide details of any findings.

The inspections take about eight hours, she explains, while repairs, if necessary, take about an hour for each finding and require draining fuel lines.

Boeing’s MOM explains that an improperly installed O-ring on a rigid coupling caused one of the fuel leaks. Boeing launched a “production investigation,” which discovered “at least” five similar occurrences on the production line or with undelivered aircraft, the MOM reports.

The second leak was caused by a missing lockwire and improperly installed retainer halves on a flexible coupling. A production line check turned up four other occurrences of improperly installed lockwires, but no additional issues with retainer halves.

Boeing’s MOM also reports that the inspections require removal of some engine pylon fairing panels. During a check, an operator discovered a damaged engine pylon fairing blade. A Boeing investigation uncovered “at least” six occurrences on in-production or undelivered aircraft.

The Boeing spokeswoman declined to provide updates on the production investigation results reported in the AOM. She explains that the manufacturer “is taking appropriate steps to ensure proper installation on airplanes in production.”