THE ROLLS-ROYCE Trent 800-powered Boeing 777 extended-range twinjet-operations (ETOPS) test effort has been "-put on hold" until the engine maker completes investigations into the cause of a surge which caused a take-off of the test aircraft to be aborted on 16 June.

The aircraft, WA102, was accelerating at "-between 30 and 60kt [55-110km/h], when the crew heard a bang and performed a rejected take-off", says Boeing. Investigations are focusing on the high-pressure compressor (HPC) which is identical to that used in the Trent 700. R-R swapped the damaged engine for another "aged" Trent, which will be used for the remainder of the ETOPS test.

The engine was returned to the manufacturer's Derby headquarters in the UK, where it was stripped down. "Component parts have been sent to the laboratory for investigation," says R-R, which is mystified by the surge. "It was not the highest-time Trent 800 engine, so there's nothing indicative of the cause there. The HPC is also the same as that of the Trent 700, which has had 50,000 trouble-free cycles."

At the time of the incident, which occurred at Williams Gateway airport in Mesa, Arizona, the R-R Trent ETOPS efforts had been "doing well", says Boeing. Some 886 cycles had been completed, representing almost 90% of the estimated 1,008 cycles required for ETOPS clearance. Despite the incident, Boeing and R-R maintain that the programme has a "good chance" of being completed by the end of July.

Under Boeing's original development timescale for the Trent-powered 777, ETOPS testing was due to be completed by mid-March 1996. The planned seven-month effort was delayed by modifications to the aft pylon and nacelle, following the discovery of an unexpected vibration mode in the structure.

Emirates, Thai International and Cathay Pacific are the only operators of Trent-powered 777s.

The programme for the General Electric GE90-powered 777 ETOPS, based at Hawaii, has meanwhile amassed around 690 cycles. The GE90 is expected to receive ETOPS clearance in late August or early September, about a year later than originally scheduled.

The 400kN (90,000lb)-thrust Pratt & Whitney PW4090 for the 777-200 Increased Gross Weight (IGW) and stretched -300 versions has received US Federal Aviation Administration certification. The more powerful engine will be flight-tested on the first -200IGW (with a maximum take-off weight of 287,000kg) in September.

Source: Flight International