BMW ROLLS-ROYCE is reconfiguring the high-pressure turbine of the BR710 to reduce fuel consumption and cut maintenance costs. The company plans to supply modified engines to power the third prototype of the Gulfstream V long-range business jet.
Despite the late change, which reflects performance-guarantee concerns discovered during early testing, the engine manufacturer is confident that the turbofan will remain on schedule for certification in August by the European Joint Aviation Authorities.
The change is being made to the second stage of the two-stage high-pressure turbine. The stage will be modified with shrouded blades similar to the existing configuration of the first stage. The company says that the change, which will be accompanied by a switch to single-crystal blade materials, will "...improve performance retention and retain our turbine-gas-temperature margin".
BMW R-R also plans to re-run a medium bird-ingestion test (four 0.68kg birds) which the engine has previously failed, saying: "We will perform the test in the next two months." In the flight-test, the engine was run at maximum thrust for 2min after the birdstrike.
Under new requirements, the engine must be run for 9min with 25% thrust.
"We fulfilled 8.5min with 25% thrust, but the tip of a blade came off and the full-authority digital engine-control shut down the engine," says the company.
The pre-production blades will be replaced for the purposes of the test with revised blades which have an additional 1degree twist.
Source: Flight International
