Andrew Doyle/MUNICH Guy Norris/LOS ANGELES

Pratt & Whitney will decide by the end of next month whether to switch to a new high-pressure compressor (HPC) design for the PW6000 as it works to rectify performance problems which have hit the original unit.

The US manufacturer says the engine's target entry-into-service date of November 2002 on the Airbus A318 is not under threat despite the possible late change.

P&W executive vice-president Bob Leduc confirms an alternative, MTU-developed six-stage HPC is available. Bench tests on the MTU unit are to begin in Munich in the next few days.

"It is true that we had issues with the HPC early in the development programme. Those were discovered nine or 10 months ago. So we decided to work the [original] five-stage compressor and pull in a six-stage back-up design as an insurance policy," says Leduc.

Recent improvements to gas path sealings in the original HPC are about to be tested, which should recover the efficiency shortfall, says the P&W executive. "We are 95% confident the five-stage compressor will get us home," he says.

P&W's goal is to achieve the lowest possible maintenance costs and risk. Tests of both HPC versions will allow P&W to select a configuration by the end of August.

The back-up compressor has been designed by MTU based on technology derived from the German Government-funded "Engine 3E" research programme. The German company is a major PW6000 partner, with responsibility for the low-pressure turbine.

The six-stage compressor would be a "drop-in replacement", says Leduc. If it is picked, the reconfigured engine would make its first run around next May. Flight tests of the baseline, five-stage HPC-equipped engine set for next month will, however, go ahead as planned on a Boeing 720 testbed. The company aims to certificate the engine in October 2001.

Leduc dismisses any possibility of the rival CFM International CFM56 becoming the lead certification engine on the A318.

P&W says the improved performance of the new design also gives it more options to offer Airbus for alternative configurations. Leduc says the performance of the revised, five-stage design "may exceed the Airbus expectations".

Source: Flight International