General Electric completed testing a
35%-additive manufactured demonstrator engine designed to validate
additive parts in its clean-sheet-design Advanced Turboprop (ATP), which
will power the all-new Cessna Denali single-engine turboprop aircraft.
Additive components reduce the ATP’s weight by 5% while contributing a
1% improvement in specific fuel consumption (SFC).
An additive CT7-2E1 technology demonstrator engine, dubbed the “a-CT7,”
was designed, built and tested in 18 months, reducing more than 900
subtractive manufactured parts to 16 additive manufactured parts. The
ATP engine architecture is derived from the CT7, allowing for part
commonality between the two additive test programs.
The ATP will utilize more additive parts than any production engine in
aviation history; 855 subtractive manufactured parts will be reduced to
12 additive parts. Additive components constitute 35% of the ATP’s total
part count. The 12 additive ATP parts include: sumps, bearing housings,
frames, exhaust case, combustor liner, heat exchangers and stationary
flowpath components. By comparison, the CFM LEAP engine includes one
additive part category, the fuel nozzle tip.
The same team of eight engineers responsible for designing the CFM LEAP
additive fuel nozzle tip led the design effort for the 16 additive parts
tested in the a-CT7. GE is building more additive hardware for
additional a-CT7 tests (which will include an even greater number of
additive parts than the first a-CT7) in Lynn, Massachusetts. The
additive components for a-CT7 and ATP tests are built at GE Aviation’s
Additive Development Center (ADC) in Cincinnati, Ohio. GE expects to run
its first full ATP engine test by the end of 2017.
Additive manufacturing allows GE to build parts at lower weight with
better performance and durability.
“With subtractive manufactured
parts and assemblies, you traditionally use bolts, welds or other
interfaces to attach the parts together, which adds weight to the
engine,” said Gordon Follin, ATP Engineering GM at GE Aviation. “On the
ATP, additive reduces weight by eliminating those attaching features
while also optimizing design of the parts.”
An additional benefit to the ATP is an expedited engine certification
schedule. GE recently completed ATP combustor rig tests six months ahead
of schedule due to the faster part production speeds allowed by additive
manufacturing. For example, the combustor liners were printed in merely
“A huge benefit of additive is expedited test schedules,” said Follin.
“For a program like ATP, one of our big philosophical points of emphasis
is getting hardware to test faster instead of spending too much time
with models on a computer. By putting real hardware on test as quickly
as we can, we can use the resultant data to help us design the next
iteration for a better product, and we get that product much faster than
if we were to use conventional manufacturing methods.”
new 1,240SHP-rated ATP is the first entry in GE’s new family of
turboprop engines aimed at Business and General Aviation aircraft in the
1,000-1,600 SHP range. The ATP features an industry-best 16:1 overall
pressure ratio (OPR), enabling the engine to achieve as much as 20%
lower fuel burn and 10% higher cruise power compared to competitor
offerings in the same size class with 4000-6000-hour maintenance time
between overhauls (MTBO) and class-leading performance retention.
The Cessna Denali will have a range of 1,600 nautical miles and speeds
higher than 285 knots. Key features of GE’s new ATP engine include: -
Ruggedized, modular architecture based on the CT7 turboshaft for better
performance at lower operating costs. - All-titanium, 3D aerodynamic
compressor for light-weight and efficient power generation. - Cooled
turbine blades enabling higher thrust and fuel efficiency… leveraging
the CT7 family’s 100 million flight hours and more than 5 million flight
hours in hot/harsh environments. - Integrated electronic propulsion
control for optimized single-lever engine and propeller control.