Certiffication of Boeing's Next Generation 737 has been delayed until later this month by late structural and control-system modifications, spare-parts shortages and continued evaluations by the European Joint Aviation Authorities.

The company had hoped that the first member of the new family, the 737-700, would have been certificated in September, but says that this "-may not be until the middle or end of October". Boeing, however, still intends to hand over the first aircraft to launch customer Southwest in "late October".

The most serious delays appear to be related to structural modifications of the horizontal stabiliser, which exhibited unacceptably high levels of in-spar rib vibration during recent testing at the high-speed corner of the flight envelope. The change involves adding a composite panel to the trailing-edge spar to stiffen up the stabiliser. The modification has been flight tested and validated, says Boeing, which is adding the revised stabiliser to the first 737-800, aircraft YC001.

Two of the four flying-testbed 737-700s are in the middle of a hectic schedule during which Boeing aims to clear the revised stabiliser and make late changes to the lateral-control system, which is also being modified on the 737-800. Aircraft YA002 was due to have a trailing-edge-vibration clearance flight and YA003 a lateral-control-system test on 3 October.

Aircraft YA002 was also expected to have a 3h JAA certification demonstration flight later that same day. Boeing, meanwhile, adds that it has "-yet to receive an answer from the JAA" on the revised emergency-exit design, redesigned by Boeing to comply with JAA regulations.

Boeing also says that the parts shortage plaguing the production line is also having an effect.

Source: Flight International