Boeing’s 777X testing back on track after thrust link issues resolved
January 16, 2025
Boeing has resolved a critical issue with the 777X’s engine thrust links, enabling the airframe manufacturer to resume certification flights for the long-delayed aircraft.
The thrust link issue had grounded all four test aircraft in the 777X functional testing programme, halting progress toward certification.
Boeing is now targeting certification of the 777X in 2026, six years behind its initial planned service entry in 2020. Despite the setbacks, including mechanical failures which have been exacerbated by labour strikes in late 2024, Boeing is regaining momentum with its testing programme now back on track, as reported by Aviation Week.
Technical challenges
Since its introduction in 2013, the 777X has faced various technical challenges during testing. A significant setback occurred in 2020, when “an uncommanded pitch event” caused the aircraft’s nose to pitch up without pilot input, delaying the programme by years. More recently, thrust link failures were detected in mid-August 2024 during flight testing, which stalled the 777X’s certification programme further. These delays compounded by a seven-week labour strike in late 2024.
The four 777-9 test aircraft have remained grounded since September 2024The last flight involved the lead test aircraft, N779XY (known as WH003), from Kona Airport in Hawaii to King County Airport in Seattle. According to the report in Aviation Week, WH003 has been pivotal in propulsion testing, using a production-standard GE Aerospace GE9X engine with an updated combustor liner and the latest engine control software. The aircraft has been used primarily to evaluate flight loads and performance of the auxiliary power unit, as well as avionics and engines.
Meanwhile, the three other test aircraft have been inactive for extended periods. The last outings for N779XX(WH002) and N779XW’s (WH001) were last year on 9 August and 12 August respectively. N779X (WH004), which incorporates a production-representative cabin configuration, has not flown since November 2021.
Despite these challenges, Boeing’s progress in resolving the thrust link issue marks a major step toward the 777X’s eventual certification and service entry. It also aligns with the OEM’s plans to reset itself in 2025 following a year marred by safety incidents, labour strikes and general turmoil.
