Pratt & Whitney expects to complete aircraft certification of its newly developed PW4000 "anti-surge" high-pressure compressor (HPC) case on the Boeing 747 next March, clearing the way for first installations to begin that month.
The new HPC ring case design, developed to counter a string of surge issues that have nagged the 2.4m (109in)-fan diameter version for several years, is based on a set of one-piece rings that replaces the original segmented design.
The new ring, which took two years to develop and certificate, is based on principles used in the 2.8m (112in) fan diameter PW4084-derivative produced for the Boeing 777, says P&W commercial engines programmes and customer services vice-president Jean Colpin. The 2.4m fan PW4000 derivative used on the Airbus A300/A310 and Boeing 747, 767, MD-11 suffered "an asymmetric distortion of clearance due to case deformation, while the ring case for the 112in version of the engine remained perfectly round, offering much better control," says Colpin.
Better matching of the expansion co-efficient of the rotating stages and the casing has now been achieved for the critical high-power, low-altitude conditions that have often led to surges occurring at take-off, says the company.
Certification of the case for the 767 will be done "by extension", while flight testing of the case on the Airbus twins and MD-11 will be completed at the end of June, says Colpin. Between 70 and 75% of the 2,200 affected engines will be retrofitted during overhauls, while the balance will be "brought in on a managed basis" to meet a US Federal Aviation Administration deadline for fleet completion by the first quarter of 2007. Cost for the retrofit is to be negotiated with each operator.
Source: Flight International
