Guy Norris/MOJAVE
CFM INTERNATIONAL'S CFM56-7B turbofan, destined for the new Boeing 737 family now under development, has been flown for the first time on board General Electric's Boeing 747-100 test-bed at Mojave, California.
Five flights lasting around 25h had been accumulated by 25 January, nine days after the first sortie. Flight-testing is scheduled to continue until the end of March, when the focus of activity reverts to Peebles, Ohio, for a critical blade-out test and a re-run of the medium-bird-strike certification test.
This was originally performed in November, but, after the bird-strike, the engine thrust-level had to be reduced to 70% to clear the stall, missing the 75% required by US Federal Airworthiness Regulations. "We will be making some software control changes to the engine to help improve stall detection and recovery," says GE's CFM56-7B production test-centre programme leader, Peter Thompson, who adds that the fan passed its test. Testing of the fan on the -7B is critical because the engine is the first version of the CFM56 family to feature a wide-chord fan.
Flight-testing is going well, according to Mojave test director Al Krejmas. "We reached 41,000ft [12,500m) on our last flight," he says, adding that the team is "...very happy with the data quality. It's the best data we've had in the history of testing at GE." The flight test programme is aimed at several major objectives, including performance assessment, operability, bearing loads and lubrication-system tests. Others include validation of the control system and bleed system, dynamics testing and validation of the engine-mount structure.
Acoustic testing start this month and will be watched closely, to see if performance equates with ground-test results. "We have confidence in reaching Stage 3 [-4dB], which is our primary target," says CFM56 programme manager, Bruce Hughs. Nacelle-ventilation tests will be performed in February from the high-altitude airport at Casper, Wyoming.
Engine certification is expected in October, with first flight of the 737-700 due on 18 February 1997. The complete aircraft/engine certification is due in October 1997.
Source: Flight International
