Guy Norris/LOS ANGELES
Kevin O'Toole/LONDON
THE SCHEDULE FOR delivery, of the first General Electric GE90-powered Boeing 777 to British Airways, continues to hang in the balance, with the engine undergoing a new series of icing tests in the USA and facing the possibility of further hurdles being established, by the UK Civil Aviation Authority in Europe.
The new icing tests are being undertaken to check whether recent engine modifications perform well enough to allow final US certification tests to begin.
The icing tests, scheduled for 1 October, come after Boeing finally conceded defeat in its race to deliver the first aircraft to British Airways before the end of September. The manufacturer says that the delay follows "...recent modifications on the GE90 engine, which became necessary based on earlier flight testing". It adds that the first BA aircraft will now be delivered "as early in October as possible".
The icing tests at Edwards AFB, California will verify a revised GE90 compressor-blade design introduced by GE after icing tests in August.
If the tests are successful, Boeing and GE still face the hurdle of full US Federal Aviation Administration icing tests, which will require the test team to scour North America in search of suitable weather conditions. The Edwards test will involve flying the second GE90-powered 777, WA077, in the wake of the US Air Force's specially modified NKC-135 tanker which was recently used for FAA testing of the Aerospatiale/Alenia ATR 72.
The WA077 was expected to have a functional check-flight on 29 September after receiving a new accessory gearbox following the failure of a horizontal drive-shaft in the original unit on 26 September. The WA077, the dedicated extended-range twin-operations test airframe, is being briefly joined in the final certification effort by the first production airframe, WA078.
Even if the engine clears the latest round of US tests, there is no guarantee that the GE-90-powered 777 will receive the necessary UK Civil Aviation Authority approval in time for an October delivery date.
A final recommendation from the European Joint Airworthiness Authorities (JAA) is expected by 11 October at the latest, says Koos van der Spek, who heads JAA certification. The findings of the multi-national certification team, are being reviewed by "senior engine specialists", as a final check before the recommendation is issued he says.
Van der Spek confirms that, at the same time, the JAA is attempting to secure a consensus on the recommendation among the national authorities, including the CAA. He points out, however, that, even if the JAA recommendation goes in favour of certification, the national authorities retain the right to impose their own special requirements.
"There is a degree of uncertainty because the JAA has yet to pronounce and also as to whether the CAA will support their position," admits GE.
The CAA does not rule out that it may impose its own special requirements regardless of the JAA position, and sources close to the programme now expect this to be the case. The CAA's concerns are understood to stem from the FAA's decision to allow a rule change on blade-off testing for the GE-90's composite fan-blades.
BA says that delivery of the first aircraft by the end of October would be broadly in line with its original timetable and allow it to receive the first five aircraft by March 1996 as scheduled.
Source: Flight International
