Boeing's first stretched 787-9 is undergoing initial ground tests at Everett, Wash., in readiness for first flight, which is expected to take place this month.

Trials began in late August with evaluations of the fuel system and the aircraft's gross weight processor, following a low-key rollout in front of employees and customers on Aug. 24. The auxiliary power unit in the aircraft, a 20-ft.-longer derivative of the baseline 787-8, was started for the first time on Aug. 28. Assuming no issues are discovered during system activation and initial “gauntlet” testing, taxi tests and first flight are likely to take place around the middle of the month. The first 787-9 is scheduled to be delivered to launch customer Air New Zealand in mid-2014.

Boeing is allocating three dedicated test aircraft to the approximately six-month-long certification and test effort, and will introduce a fourth fully configured aircraft late in the program for function and reliability work.

The first aircraft, ZB001, is the 126th 787 to roll off the combined Everett and Charleston, S.C., production lines. Boeing says the second and third 787-9s, ZB002 and ZB021, are already in final assembly.

After the extreme challenges and delays encountered with the 787-8, the pressure is on the manufacturer to ensure the 787-9 flight-test effort goes far more smoothly. However, despite the ambitious requirements of the design, which is configured to carry 40 more passengers an additional 300 nm than the 787-8, Boeing appears quietly confident of meeting performance guarantees as well as program schedule.

Compared with the 787-8, the -9 is extended with two five-frame stretch sections on either side of the wing. Maximum takeoff weight is 553,000 lb., or just over 50,000 lb. more than the baseline -8, while empty weight is reportedly as much as 2% better than specification.

Boeing currently holds 376 orders for the 787-9, or 40% of the total 787 firm orderbook of 936.