Certification of the Pratt & Whitney PW4098-powered Boeing 777-300 is expected to be delayed following the last-minute discovery of problems with the engine during testbed runs at the powerplant maker's East Hartford site in Connecticut.

The engine "-was performing very well on the flying testbed", says Boeing, which was operating one of the five 777-300 test aircraft fitted with one PW4090 and one PW4098. The powerplant - at 436kN (98,000lb) thrust the largest engine ever developed by the US engine maker - was removed in late April when the problems, thought to be related to unspecified issues with the stators and possibly the fan, cropped up on the ground test engine.

The engine was certificated on schedule in March and was originally due to be cleared for operation on the 777-300 around late June or early July, with entry into service with Korean Air Lines planned for September 1998.

Boeing believes airframe/engine certification will still be achieved "in the summer", but admits that the programme is "moving a little to the right". In delivery terms, neither Boeing nor P&W is clear what the impact will be as there is some margin within the programme.

P&W says the issues with the stator blades emerged during endurance tests.

Source: Flight International