Despite the recent engine-related delays the Boeing 787 test team appears upbeat on achievements to-date as it closes on maximum brake energy rejected take-off certification tests scheduled for this weekend at Edwards AFB, Calif.
The dramatic brake tests can only be attempted at the weekends when the base’s long runways are closed to regular military traffic, and form the culmination of weeks of brake and runway performance test work that was interrupted by the Rolls-Royce Trent 1000 surge incident on ZA001 at Roswell, New Mexico on Sept 10.
“We’re just four conditions short of certificating brake conditions and we’re yet to blow a tire,” says 787 chief pilot Mike Carriker. Speaking at the Society of Experimental Test Pilots meeting in Anaheim, Calif, he adds the test will stress the electric brake system to the maximum. During recent rejected take-off tests some 16,000 W of power was used to actuate the carbon brakes which heated to around 1,400 deg F. “We expect the max brake energy (test) will almost triple the energy levels of those tests,” he adds.
The electric braking system, supplied by Goodrich and Messier-Bugatti, is made up of the aircraft wheels, electro-mechanically actuated carbon brakes and electro-mechanical actuator controllers. Certification tests of the Messier-Bugatti system are set for Sept 25, with the Goodrich brakes due for testing on Sunday.
Anatomy of a 787 carbon brake
1) Electric motor
2) Reduction gear
3) Ball screw and nut
4) Rotor carbon disc
5) Stator carbon disc
Goodrich's 787 carbon brake assembly. (Goodrich)
Upcoming program milestones also include low and high speed handling qualities certification tests, systems performance work, community noise, completion of cold weather tests, ETOPS and service-ready flights with All Nippon Airways (ANA). Also expected next month is the long-deferred first flight of ZA006 – the second General Electric GEnx-1B test airframe. Carriker says the most eagerly-awaited milestone is the start of ‘first of model’ tests for the first production unit to be delivered to All Nippon Airways early next year.
Major tests completed include clearing the flutter envelope out to 412 KIAS, Mach 0.97 and 43,300-ft, initial cold weather tests, icing with artificial shapes and in natural icing conditions as well as the flight loads survey. Also completed are ground minimum control speed (Vmcg), minimum control speed in the air (Vmca), minimum control speed in landing configuration (Vmcl) and the minimum demonstrated lift off speed (Vmu). Some cross wind testing up to 25 kt with autoland was recently accomplished in Iceland, and additional performance tests with manually flown approaches are also planned for certification. “We’ll try and shoot for 40 kt cross wind,” says 787 engineering test pilot Randy Neville.