Aviation week network | Boeing Halts 777-9 Certification Tests For Engine Mount Checks | GE Aerospace

 Boeing says it has halted certification flight testing of the 777-9 following the failure of a thrust link mounting component attached to one of the two GE Aerospace GE9X engines powering a test aircraft.

The discovery was made during post-flight inspections of the third test aircraft, WH003, following its return to Kailua-Kona, Hawaii, from a 5 hr. 31 min. certification test flight over the Pacific. Boeing says “during scheduled maintenance, we identified a component that did not perform as designed. Our team is replacing the part and capturing any learnings from the component and will resume flight testing when ready.”

The failure of the component, which was first reported by The Air Current, comes just as Boeing was accelerating into the first phase of 777-9 type inspection authorization (TIA), FAA-required testing for certification. Formal TIA tests began July 12 after a delay of almost three years and represent the last major milestone before anticipated FAA approval and initial deliveries—still currently scheduled for late 2025.

There are two fail-safe thrust links on each engine for redundancy and are designed to transfer vertical and lateral mechanical stresses between the engine and the aircraft. The Boeing-designed thrust links attach to the fan frame and carry mechanical loads—as well as engine torque about the engine axis and thrust—to the aft engine mount at the rear.

Company sources confirm the accuracy of reports that one of the links was severed, and that subsequent inspections on the other two active test aircraft, WH001 and WH002, have revealed cracks. Both of these aircraft are currently in lay-up undergoing scheduled maintenance at Boeing sites in Everett and Boeing Field, Seattle, respectively.

“We are inspecting the flight test fleet for this condition. No near-term flight tests were planned on the other flight test airplanes, which have scheduled maintenance and layup activities. We are keeping the FAA fully informed on the issue and have shared information with our customers,” says the company.

Although no further details of the issue have been made available pending completion of the investigation, a speed and altitude graph of WH003’s final flight before grounding shows several rapid accelerations and decelerations were conducted while flying at 38,000 ft. indicating testing that involved potentially rapid changes in thrust setting.