Guy Norris/LOS ANGELES
JUBILATION OVER THE "flawless" first flight of a General Electric GE90-powered Boeing 777 on 2 February was overshadowed by an incident on another 777 test aircraft which was forced into an emergency landing at Boeing Field later the same day.
Boeing launched an immediate investigation into the causes of a sudden cabin-depressurisation which struck a Pratt & Whitney-P&W 4084-powered 777 as it descended rapidly from 43,000ft (13,000m) during a test flight.
"It was doing a test which involved operating using only battery power, when there was an air-conditioning duct clamp failure. The engines were running, but other systems were inoperative as part of a certification test," says Boeing.
The crew requested that emergency medical vehicles meet the aircraft and four flight-test engineers were taken to hospital for observation. "While we are still evaluating the impact of this event on the aircraft itself, there is no reason to believe that there will be any impact on the overall programme," says the company.
Earlier in the day at Everett, the long-awaited flight of the first GE90-powered 777 for British Airways took place within 2h of the US Federal Aviation Administration certificating the engine.
Described by Boeing as a "wonderful first flight", the aircraft was flown for 5h 20min. Although certificated at 380kN (85,000lb) thrust, each engine was producing up to 340kN for take-off at a planned gross weight of around 188,400kg. The flight plan took the 777 to 25,000ft, at a speed of up to 250kt (460km/h), or Mach 0.6 indicated air speed.
The crew says that the aircraft/engine combination handled excellently and the performance of the GE90 was described as "flawless." The GE-powered aircraft, is expected to be certificated in August after a test programme, which will include around 260 flights. It is scheduled to enter service with BA in September.
The tenth 777, another BA aircraft, will begin flying in the second quarter of this year and 1,000 simulated airline flights will be performed as part of the plan to gain approval for extended range twin-engine operations (ETOPS) at entry into service. The last 90 flights of the ETOPS programme will be undertaken from BA's London Heathrow base.
The Pratt & Whitney/777 ETOPS plan received a boost on 28 January, when a PW4084 underwent a 3,000-cycle endurance test at the company's site in West Palm Beach, Florida. The test, representing the equivalent of around six years' operations, was intended to be completed in November 1994, but was interrupted by a minor failure at around 700 cycles.
During the test, the engine was run at twice the vibration level expected in normal service and three ETOPS diversions were also simulated, running at maximum continuous power for 3h.
Another engine, which has already amassed 2,000 ground-based cycles, is now being flown on the P&W 777 ETOPS test aircraft. The engine will be replaced and inspected after undergoing 500 of the 1,000 cycles due to be flown. The P&W-powered 777 is scheduled for certification in late April.
Rolls-Royce was also able to celebrate a success for its contender to power the 777. The Trent 800, has been certificated by the FAA and the European Joint Aviation Authorities, at 400kN thrust.
Flight testing on the Boeing 747 testbed begins in March. First flight of the Trent-powered 777 is scheduled for May.
Source: Flight International
