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GENERAL ELECTRIC GE9X
As exclusive powerplant supplier for previous 777
variants (with the GE90-110 and -115), GE cannot
afford to be complacent about its proposed GE9X
lest any decision to maintain monopoly sourcing on
future models goes in favour of its P&W PW1000G
or R-R RB3025 competitors. More than four years'
discussion with Boeing about 777X requirements
has gone into the GE9X, for which tests on new
material have been under way for some time.
A high-pressure compressor (HPC) rig is
scheduled to run this year, with initial core tests
perhaps beginning in 2014. A planned first full core
run should follow in the following year -- when GE is
expected to decide on a design freeze -- ahead of a
full engine trial in 2016.
The HPC would feature a "very high" pressure
ratio of 27:1, about 17 percent greater than current-
generation engines. The overall pressure ratio (OPR)
is around 60:1, compared with the GE90's 42:1.
The GE9X fan, at 129.5 inches in diameter
similar in size to that of the GE90-115B, will sport
"fourth-generation" composite blades enclosed in
a composite case. The HPC will be driven by new
aerodynamics technology and "fourth-generation"
powder metal material. GE's twin-annular premixing
swirler combustor will be used, the HP turbine will
feature ceramic matrix composite (CMC) material,
and low-pressure turbine (LPT) airfoils will use
"enhanced titanium aluminide (TiAl)", GE says.
Last October, the US company announced a
"strategic partnership" with Japanese conglomerate
Mitsui to support technology development of future
large commercial engines, including covering part of
the GE9X development cost.
Rolls-Royce (R-R) has chosen a larger, 132.5-inch
diameter fan for its 99,500lb-thrust RB3025 entry
in the 777X-engine stakes, for which LP system
tests are scheduled to begin next year. The UK
manufacturer said in 2012 it would take a "year or
two" to optimise the engine around the conceptual
aircraft and would require about six years to fully
develop a new engine before entry into service (EIS).
"We're targeting an end-of-the-decade timescale,
but that will be entirely down to what Boeing tells us.
Then obviously we'll work backwards from that date,"
according to strategic marketing vice-president
The RB3025, which will be the company's first
commercial use of a composite fan, will sport a
12:1 bypass ratio and a 62:1 OPR, the highest
achieved on a commercial aircraft. Much of the
RB3025 derives from current Trent 1000 and
XWB powerplants, with technology coming from
R-R's Advance 3 "environmentally friendly" engine
programme and advanced low-pressure system
The RB3025 has TiAl low-pressure turbine (LPT)
blades and a "vortex amplifier" to simplify blade
cooling with extracted HPC air. Like all RB211-
derived engines, the RB3025's three-shaft design
provides a shorter, stiffer and "more robust" engine
that R-R claims offers better performance retention.
PRATT & WHITNEY GTF
P&W also highlights reduced engine length when
promoting its GTF technology, which requires fewer
moving parts. The company sees no restriction to
developing larger, more-powerful variants "right up
to 100,000lb thrust" and is "excited" by this potential
first widebody application of the technology, claiming
that "higher and higher" thrust levels provide stronger
A 777X application would require a new core "by
size, by [operating] temperatures and pressures",
with critical considerations seen as specific fuel
consumption (SFC), weight and drag. P&W says
that SFC accounts for perhaps 75-80 percent of
the equation and emphasises that a GTF fuel-burn
reduction of perhaps 18 percent is reduced by, say,
two percentage points because of higher weight or
The manufacturer is retaining a two-stage HPT, but
LPC and LPT stage counts will change with thrust.
"We can add a stage to the eight-stage HPC, or to
the LPC to provide the pressure rise." OPR is put
at the "50-55[:1] level", with a bypass ratio of up
The fan-drive system will have a gear ratio of
around 3.5:1 and the fan will be slightly larger than
the GE90-115's 128-inch diameter. Rather than
using CMCs to produce blades and disks, P&W
has opted for single-crystal and powder-metallurgy
As Boeing briefed potential 777X customers last
November, its salesmen were given permission to
talk to operators and lessors about the proposed
787-10X, for which Singapore Airlines, British
Airways, Germany's Lufthansa and lessor Air Lease
are potential launch customers. The move stopped
short of "authority to offer", that expected step
R-R is preoccupied with preparing engines for two other commercial aircraft
programmes -- the Trent XWB for the Airbus A350 XWB and Trent 1000-TEN for
the yet-to-be-launched 787-10X.
General Electric's GEnx, now in service on the Boeing 787 and 747-8 could be a candidate to power a potential re-engined Airbus A330.
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