Boeing faces a delay to its 767-400ER certification and delivery schedule in the wake of its recently resolved engineering employees' strike.

Before the 40-day strike by Society for Professional Engineering Employees in Aerospace members, Boeing was on target to certificate the -400ER in April and deliver the first aircraft to Delta Air Lines the following month. Boeing plans to set up a "critical path" of final certification tests before delivery to Delta later this year.

The company plans to complete certification tests in mid-May, leading to speculation that first delivery could slip into June. The strike may have a knock-on effect on the hand-over of three refurbished test aircraft that were due for delivery in September, October and next March.

Despite the hold-ups, Boeing has completed 95% of development testing and up to 70% of the required flight testing, according to Ken Kirwan, chief engineer 767 validation. Certification tests, and the processing of performance data to support the application, have some way to go. He says that total flight test time has reached almost 679h and 264 cycles.

Kirwan says that flight tests of the first three aircraft produced no "big surprises", but some changes were made to improve post-stall roll-off characteristics. These include the addition of vortilons under the outboard slat sections. Three are mounted on each side to induce vortices at high angles of attack. "This allows the tips of the wing to stall, but prevents propagation [of the stall]," says Kirwan. Based on a similar change to the 767 airborne warning and control system aircraft, the inboard leading-edge flaps have been re-scheduled to improve stall characteristics.

The fourth and final -400ER test aircraft, VQ004, is in the paint hangar. It will be used for about 10h of "first of model" tests on internal systems such as in-flight entertainment and cabin services.

Source: Flight International