Burbank Aeronautical (BAC) plans to begin flight tests in March 1998 of a Boeing 707-300 with winglets which are expected to reduce fuel consumption by as much as 7%.
California-based BAC says that plans for the winglet modification have attracted "a lot of interest" from commercial, corporate and military users of up to 140 in-service 707s, chiefly in Africa, Europe and Latin America. The 2.7m-tall composite winglets weigh around 114kg per shipset and will be attached directly to the end of the wingbox, replacing the current tip fairing. BAC says that the canted-out devices will also act as "wing sails" by creating additional lift, as well as dissipating vortex energy and reducing induced drag.
BAC had hoped to flight-test the winglets concurrently with a Stage 3 hushkit for the Pratt & Whitney JT3D engines, but "the FAA [US Federal Aviation Administration] required us to complete one before flight testing the other", says BAC. The hushkit flight-test effort, which began almost a year behind schedule because of greater-than-expected design complications, is reaching the final stages, with all flight testing due to be complete by mid-February 1998. "We have now finished noise-performance work on the JT3D-3B and -7 engines and have finished reference-profile tests [which match exhaust pressure-ratio settings with measured performance]," says BAC.
Further performance tests are under way at Mojave, California, including evaluation of the kit's new thrust-reverser assembly. This is hydraulically operated (instead of pneumatically, as on the original version), and has target-type blocker doors in place of the original cascade assembly.
Results achieved with the 80kN (18,000lb) JT3D-3B and 84.5kN thrust -7 have proved "better than expected", says BAC, which adds that the hushkit achieves all Stage 3 requirement at full take-off weights, with no payload restriction. It did discover, however, that heavyweight landings to Stage 3 could be achieved only with 25¹ landing flap, and not the 40/50¹ settings for which it had hoped. "We don't see that as a problem, however," adds the company, which expects to receive its supplemental type certificate in mid-March 1998.
BAC expects to perform Stage 3 hushkit and winglet flight tests on McDonnell Douglas DC-8-50s and -60s later in 1998.
Source: Flight International
