General Electric's GE90-115B for the Boeing 777-200LR/300ER is
the first of a new generation of engines being designed and tested
to tougher standards that could allow as much as 330 minutes extended
twin-engine operations overwater (ETOPS), nearly double the current
180 minutes. This would let twin-engine commercial transports fly
any route now serviced by three- or four-engine aircraft.
Current rules for 180-min. ETOPS demand an inflight shutdown rate
below 0.020 events per 1,000 flight hours. According to Dick Ostrom,
General Electric's manager of GE90 advanced program integration,
the GE90 family is now operating at 0.006, and the rate has hovered
between zero and 0.010 for the past five years. GE's objective is
total elimination of inflight shutdowns.
Now, in a multi-million dollar program, GE will run a series of
comprehensive reliability and maturation tests totaling 30,000 cycles
to uncover and correct any of the weak points in the GE90-115B.
"We plan to go beyond the typical visual inspections, to
proactively identify potential problem areas or durability issues
that will help us, once in service, avoid operational events and
unscheduled removals," Ostrom said.
Three developmental engines and five flight test engines, including
one flight test spare, have been assigned to the GE90-115B maturation
effort, which is expected to conclude in late 2006. Additionally,
two of the five flight test engines will be "diagnostically"
disassembled after their trials, with each piece of hardware assessed
for wear. This is expected to occur in the first quarter of 2004.
General Electric recently beat the
world engine-thrust record with its GE90-115B turbofan for
the Boeing 777-300ER, reaching 127,900 pounds thrust during
final certification runs. The previous record, published in
the Guinness Book Of World Records, was 122,965 pounds thrust.
The first ground test engine will be run for more than 13,000 cycles-the
equivalent of 15-20 years of typical airline service. It will be
maintained using standard shop practices and equipment, reflecting
actual airline environments. To increase the aggressiveness of testing,
this engine-as well as the two others dedicated to the ground test
maturation effort-will be run with "high levels" of imbalance
in their high- and low-pressure sections to subject them to elevated
vibratory loads.
"The cycles reflect how an airline would actually operate
an engine and schedule maintenance," Ostrom said. The modules
to be examined during each maintenance period are those that airlines
typically inspect during scheduled maintenance.
The second GE90 dedicated to the maturation program will begin
trials this summer, running in a 3,000-hour ETOPS demonstration
that should conclude sometime late in the third quarter. GE will
go so far as to strip components of their coatings in its attempt
to find "weak links" in the engine. A second 3,000-cycle
run will evaluate the powerplant's external components under increased
heat loads.
"We will maintain the built-in imbalance for this test, and
also intentionally elevate under-cowl temperatures," Ostrom
said. "Problems with under-cowl components are key contributors
to flight delays and cancellations," he observed.
The GE90-115B will be rated at 115,000 pounds thrust for the Boeing
777-300ER, and at 110,000 pounds thrust for the 777-200LR transport.
