Engine manufacturer General Electric expects to receive US Federal Aviation Administration certification for the Boeing 777-300ER's GE90-115B powerplant by the end of June, later than originally scheduled because of an FAA request to re-run up to 63h of endurance "block test" runs at hot operating conditions. The delay is not expected to affect the 777 effort, which is scheduled for certification around March 2004.

The additional 63h tests will verify the endurance of the production configuration engine at "hot time" or "double redline" conditions. These include both maximum continuous redline and simulated take-off exhaust gas temperature redline conditions, and form the most rigorous part of the 150h block test.

The evaluation will complete testing of the modified cooling system on the second-stage high-pressure turbine, which failed towards the tail-end of the original block test in late 2002.

Boeing has, meanwhile, set a new maximum take-off weight (MTOW) record for a twin-engined aircraft with the first 777-300ER, WD501, which lifted off from Edwards AFB, California on 20 May at a weight of 351,300kg (773,800lb). Tests on the second aircraft, WD502, have also confirmed a 1% fuel consumption improvement over original predictions, leading Boeing to offer gains of up to 1,090kg in payload or an extra 140km (75nm) in range beyond nominal performance specifications.

Despite the additional weight capability demonstrated on 20 May, Boeing says it has no plans to certificate the 777-300ER at weights beyond 344,900kg. However, the tests support Boeing's recent decision to raise the target MTOW of the ultra long-range -200LR version to 347,800kg.

"The test data will allow our engineering to fine tune the projections for the 777-200LR, but the reasons for the heavier take-off weight is primarily down to facilitating repetitive take-offs for these tests," says 777-300ER programme manager Lars Andersen.

The recent tests of abused and aggressive take-offs have also proved the viability of the enhanced tail strike protection system which is integrated with the flight control system to monitor take-off angle. "This is intended to reduce tail skid contact, and during these take-off performance evaluations we generally expect to get contacts," says 777 chief pilot Frank Santoni.

As many as 13 tail strikes were recorded during the original 777-300 test effort in 1997 and "we got none on this", says Santoni.


Source: Flight International