Following an inspection last October, Boeing had to suspend flight testing of its newest twin-engined jet after a technical issue occurred during the GE9X post-certification engineering test. The problem was resolved, and the aircraft manufacturer resumed flight testing last month, but how active have its Boeing 777X test aircraft been lately as Boeing races to deliver by 2025?
An update on the Boeing 777X’s latest test flights
Boeing currently has four test aircraft for its Boeing 777X program – N779XW, N779XX, N779XY, and N779XZ. However, only half have been actively flying, while the other two have not operated a test flight for over six months.
The first of the four Boeing 777X test aircraft, N779XW, is primarily used to test electronics, taxi tests, avionics brakes, flutter, icing, stability, control, and low-speed aerodynamics. The aircraft has been reasonably active recently, with test flights conducted nearly daily for this month. The most recent test flight at the time of writing was on January 22nd, when it flew for four hours over Seattle Boeing Field.
Before that, N779XW was flying twice on January 21st, with a relatively short flight of over one hour in the morning from Seattle Boeing Field to Moses Lake. Then in the afternoon, the aircraft took off from Moses Lake and flew for over three hours before landing back at Seattle Boeing Field.
Also actively flying is N779XX, which is in charge of testing auto-landing, ground effects, stability, and controls. In comparison to the first Boeing 777X prototype, N779XX hasn’t been flying as much this month. Although the aircraft last flew on January 22nd, it was for a mere nine minutes over Yuma International Airport and an earlier morning flight that lasted less than 50 minutes.
The aircraft also flew twice on January 21st, with the morning flight lasting approximately 48 minutes and the afternoon flight lasting a minute longer. Both test flights also took place over Yuma International Airport. Since N779XX is not purposed to test as many variations as N779XW, the aircraft generally has lower flight times, typically flying for under an hour or up to two hours at most.
The activity for the test aircraft gets further reduced when talking about N779XY, which tests for the Boeing 777X’s auxiliary power unit, avionics, flight loads, and propulsion performance. It’s also the only test aircraft already booked in to go to a future airline operator, German flag carrier Lufthansa.
N779XY last took off last year on July 12th, when it flew for nearly two hours from Moses Lake to Everett Paine Field.
The fourth and final Boeing 777X prototype, N779XZ, is primarily used to test environmental control systems, extended twin-engine operations, noise, general functionality, and reliability.
N779XZ hasn’t flown in more than a year, with its last test flight occurring on November 18th, 2021. The aircraft flew for only 18 minutes from Seattle Boeing Field to Everett Paine Field but was actively flying almost daily before that. However, the aircraft is expected to start back in the test program in July this year.
Hopeful for the start of the final certification
In May 2021, the Federal Aviation Administration (FAA) emphasized it would not certify the Boeing 777X program until mid-to-late 2023. This means that all four Boeing 777X testbeds should be up and test-flying in the coming months to prepare for the Type Inspection Authorization before the FAA can start the final certification process.
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