Guy Norris/LOS ANGELES
Pratt & Whitney says it will make its final selection of a high pressure compressor (HPC) configuration for the PW6000 "within the first part of September" after beginning test flights of the engine with the original five-stage compressor on 21 August.
The company is evaluating its own five-stage, low-parts count HPC design, and an optional, six-stage compressor based on a design by partner MTU of Germany.
The alternative HPC is being evaluated by P&W after it failed to secure sufficiently high operating efficiency numbers with its own design (Flight International, 25-31 July). The engine is destined to power the Airbus A318 on its maiden flight in January 2002.
The US engine maker says that "both compressors look good, and both are giving the efficiencies we are looking for". It adds, however, that it has still not "made a formal decision on which way we will go with the compressor" and says the performance of the flight test engine will influence the final choice.
Results from the first flight on the company's Boeing 720B testbed, which lasted one hour and 20 minutes from P&W's test site at the former Plattsburgh AFB in New York, showed the five-stage compressor performed "as expected."
The engine, mounted in the 720's number three position on the right wing, was powered up to its full de-rated power setting of 17,500lb (77.8kN) for take-off. Bob Leduc says "...we met all our objectives and the engine ran as well in the air as it has been doing in our ground-based tests."
The initial flight test phase is expected to last 50 hours, and will concentrate mainly on validating performance levels seen during ground tests. A further two phases of flight tests are also planned, both with varying build standards of the engine.
Test phase two begins in January, and test phase three starts in May. The company still aims to achieve certification in October 2001, despite the continuing uncertainty of the HPC selection, and adds that it is still committed to meeting the A318 timescale which is aimed at entry into service in November 2002.
MTU says initial bench tests in Munich of its six-stage HPC, known as the HDV12, have been successfully completed. It describes the outcome as a "breakthrough in the development of highly-loaded compressors". The HDV12 is a six-stage transonic HPC with an overall compression ratio of close to 11:1.
Key milestones still to come, other than the HPC decision, include a 6lb (2.7kg) bird strike test in October and an imminent fan blade off test.
Additional reporting by Andrew Doyle in Munich.