BOEING IS AGAIN reviewing the design of the 777 cabin-pressurisation system, following the diversion of a United Airlines (UAL) aircraft to Gander, Newfoundland, while being flown on a transatlantic flight.

The 777 suffered "a loss of pressure" rather than a sudden depressurisation, says the airline, which adds that the diversion was made as a "precaution." The failure was traced to a clamp which cut into the "rubber-boot ducting" of one of the aircraft's two air-conditioning packs. The remaining pack could not maintain sufficient cabin pressure, so the crew took the aircraft down to 22,000ft (6,700m) and diverted. Oxygen masks were not required and were not deployed.

In February 1995, the US Federal Aviation Administration placed a 25,000ft-ceiling limit on the 777, following two cabin-decompression incidents, which occurred within hours of each, other in Hawaii and Seattle. These were related to the failure of a check clamp and led to the development of a modified duct clamp.

The General Electric GE90-powered 777 extended-range twinjet-operations (ETOPS) test effort and the Rolls-Royce Trent 800/777 ETOPS programme appear to be virtually neck and neck in the run-up to certification. Both have amassed more than 950 cycles and, barring further incident, looked set to complete testing by the end of the first week in August.

Source: Flight International