Boeing will deliver the first 737-900, the last major derivative of the twinjet family, to launch carrier Alaska Airlines in mid-May. US Federal Aviation Administration certification was awarded on 17 April, and European clearance was due as Flight International closed for press.
Certification comes around six weeks later than originally planned and flight tests are continuing on minor flight control refinements including adjustments to the lateral trim, and an "improved" main flap seal configuration. Tests are being undertaken by YD501,while the second test -900 YD502 completed its certification effort on 16 March. The two aircraft have logged 649 flight hours in 296 flights and 156h of ground tests.
The effort was delayed, however, by the unexpected discovery late last year of a vibration mode in the elevator which required the redesign of the elevator hinge and strengthening of the tab. Extra tests were scheduled to validate the design and assess the impact on tab flutter susceptibility, as well as to test trim system modifications.
Boeing will focus on the proposed 737-900X increased passenger load version and on boosting stretch sales which stand at 45 aircraft to Alaska, Continental Airlines, KLM and Korean Airlines.
Source: Flight International
