Boeing 777X Flight-Test Campaign Takes Off

Envelope expansion
The initial 777-9 WH001 has continued envelope expansion since its first flight on Jan. 25.
Credit: Paul Weatherman/Boeing

The 777X is already pivotal to Boeing’s future, but the newly begun flight-test and certification campaign for the long-range flagship has assumed even greater significance as the company strives to rebuild trust amid the crisis over the 737 MAX.

The success of the first flight on Jan. 25, after two days of frustrating bad-weather delays, therefore marked a significant boost for the beleaguered manufacturer as it prioritizes the return to service for the MAX and scours the market for new business to offset the recent slump in twin-aisle orders.

  • 777-9 test effort will involve four dedicated aircraft
  • Initial tests showed trouble-free operation of folding wingtips

Coming more than 25 years after the first flight of the original 777 and almost 17 years after the first flight of the GE90-115B-powered 777-300ER, the test debut of the 777-9—the first member of the 777X family-—also marks a critical positive step for the company’s long-term widebody strategy. The big twin is designed to succeed earlier generations of 747s, 777s, Airbus A340s and A380s, and is expected to satisfy a demand that Boeing forecasts could be between 60-100 aircraft per year through 2030 for replacements alone.

First deliveries of the 777-9 are expected to launch customer Emirates in 2021, a year later than planned, after initial development issues and a six-month delay to the start of flight tests caused by durability issues with the General Electric GE9X engines. After recent adjustments, the 777X family orderbook stands at 309, including an unspecified number of the 777-9’s shorter 777-8 sibling, the introduction of which is being deferred to 2024.

Although some of the initial orders from key Middle Eastern and Asian carriers, including Emirates and Cathay Pacific, are thought to be vulnerable to deferral, substitution or even cancellation, Boeing says the 13% lower operating costs of the 777-9 compared to the 777-300ER will underpin the long-term demand. “There are about 800 aircraft out there that need to be replaced over the next decade, and that’s not including additional demand for growth” says Boeing 777X Marketing Director Wendy Sowers.

However, the program’s success ultimately hinges on the performance of the aircraft and the progress of its passage through what will be an intense and closely scrutinized test campaign. This finally got underway when the 777-9—flown by chief test pilot Van Chaney and Craig Bomben, vice president of flight operations and 777-9 chief test pilot—took off from the company’s Everett, Washington, facility at Paine Field at 10:09 a.m. and landed at Boeing Field, Seattle, after a 3-hr. 51-min. flight.

The flight began with a standard first-of-model departure to the north from Paine Field’s Runway 34 Left. The 777-9, with the Boeing code WH001, disappeared almost immediately after takeoff into the low clouds before heading to eastern Washington, where system checks as well as basic flying qualities and handling assessments were conducted at an altitude of 15,000 ft. and speeds of 160-270 kt.

A series of low-speed checks were made while the crew flew a racetrack pattern over the northern part of the state. The 777-9 was then flown southwest, reaching an altitude of over 16,500 ft. before joining up with a chase aircraft for a photoshoot session around Mount Rainier. The 777-9 then returned to Seattle for its first landing on Boeing Field’s Runway 14R.

Observers noted the relatively shallow pitch attitude used for rotation on takeoff as well as for the landing flare, most likely associated with the aircraft’s 252-ft. overall length. The 777-9 is the largest twinjet ever built and is 43 ft. longer than the initial 777-200 variant. The very low noise signature of the GE9X engines was also noted on both departure and arrival. The crew reported the aircraft performed well and flew like the -300ER, despite the increased fuselage length and wingspan.

Following a brief post-flight ground-test period, WH001 flew for a second time on Jan. 29 to continue envelope expansion. The 4-hr. 43-min. flight, conducted over eastern Washington, will be followed over the following weeks with additional flights for further envelope expansion and flutter clearance testing. The second of four dedicated test aircraft, WH002, is expected to join the program in the coming weeks.

Initial tests using WH001 will clear the way for FAA Type Inspection Authority, which will enable Boeing and the regulatory authority to begin the certification campaign along with ongoing engineering tests. The 777X’s new 235.4-ft. span wing, and the folding tip sections that make up almost 24-ft. of span, will be a focus for the tests. The fourth-generation composite design incorporates a modified trailing edge variable camber system derived from the 787 as well as a maneuver load alleviation system to limit stresses on the wing and reduce structural weight.

The folding tips, which resemble 777-9 winglets while stowed on the ground, appear to have performed as expected during the initial flights. The tips were seen to deploy rapidly as the aircraft took to the runway before takeoff and retracted promptly into stowed position after landing. The folding wingtip is extended by a command from the flight crew before takeoff, but on landing, it is designed to automatically fold after touchdown, as soon as ground speed slows below 50 kt. The characteristic feature, the first of its type ever to fly on a commercial airliner, was developed to maximize aerodynamic performance while simultaneously enabling the 777-8/9 to operate at International Civil Aviation Organization Code E standard taxiways, as well as gate and ramp areas in common with the current 747-400 and 777-300ER.

Ground testing will evaluate standard and nonstandard operations of the device, which in normal operational mode will take 20 sec. to fully extend and fold. For nonstandard operations, such as in the event of a rejected takeoff (RTO), the autofold feature is enabled along with autobrakes and speed brakes if the takeoff is abandoned at a ground speed of 85 kt. or more. However, if the RTO occurs at less than 85 kt., the autofold function will not trigger, and the crew will need to manually activate the wingtip folding system.

Designed to meet a set of special certification conditions developed by the FAA, the wingtip ground tests will cover checks of additional safeguards to ensure against accidental retraction in flight or unlocking during takeoff, as well as checking robust performance in gusting winds. Test standards for the wingtips are designed to conform with the same certification requirements as other moving surfaces such as ailerons and flaps.

Guy Norris

Guy is a Senior Editor for Aviation Week, covering technology and propulsion. He is based in Colorado Springs.