Boeing completes 787 “high-blow” test, strike stalls wing test

The airframe was subjected to internal pressures 150 percent of maximum levels expected in service.

The Boeing Co. (Everett, Wash.) successfully completed a high-pressure test, known as “high blow,” on the 787 Dreamliner static test airframe at its Everett factory on Sept. 27, but further work was postponed in the wake of a machinists strike, still unresolved as HPC went to press.

The airframe pressure test was one of three static tests that must be cleared prior to first flight. During the test, the carbon/epoxy airframe reached an internal pressure of 150 percent of the maximum levels it is expected to see in service — 14.9 lb/in² (1.05 kg/cm²). It took nearly two hours to complete the test because pressure was increased slowly to ensure airframe integrity.

“We had every confidence going into this test because of the extensive work we’ve done on larger and larger pieces of composite, from small coupons to fuselage sections,” said Pat Shanahan, VP and general manager of the 787 program. “Still, it’s very rewarding to see a whole airplane being tested and having the results we expected.”

Mark Jenks, Boeing’s VP of development for the 787, noted at the recent Society of Manufacturing Engineers (SME) Tooling for Composites technical conference (see Learn More, at right) that the test confirms one of the design goals for the aircraft: The carbon composite fuselage is capable of handling higher cabin pressure than an aluminum construction, allowing airlines to maintain a “lower” cabin altitude for greater passenger comfort. “We can also raise the humidity in the cabin,” notes Jenks. “With aluminum aircraft, humidity must remain low to minimize potential corrosion, but that’s not an issue with composites.”

The ultimate stress test on the 787 wing was in progress when Boeing machinists went on strike Sept. 6. The strike remained unsettled despite several rounds of negotiation. That test, says Jenks, will be completed when a collective bargaining agreement is struck and work resumes on the aircraft.

Meanwhile, American Airlines surprised financial analysts with a major order for the 787. Boeing confirmed that the airline will purchase 42 Dreamliner aircraft, while a published Oct. 15 story in the Chicago Tribune says the order could go as high as 100 planes, despite the current gloomy economic forecast.