Preparing for Takeoff
Two conduit sections installed for ground testing.
Bell Helicopter manufactures the heavy-lift “tilt-rotor” Osprey, the hybrid aircraft that combines features of both airplane and helicopter to accomplish what none of its forbears can do. It can lift off, hover, and land vertically yet it can cruise at high
altitudes at jet speeds.
When the aircraft recently underwent an experimental tail-wiring upgrade, technicians at the rapid prototyping lab at Bell Xworx used a Fortus FDM system to build tough polycarbonate wiring conduits. Technicians
installed the branching conduits in six mating sections inside the Osprey’s twin vertical stabilizers for on-the-ground testing of its wiring.
“We built the conduit for one stabilizer, and the development team installed it on the mock-up. It was successful so they immediately requested a second set for the other stabilizer,” says RP lab technician Mike Storp. After some minor variations
the team requested five more complete sets for a total of 42 conduit models. “It took only two and a half days to make them all. The Fortus system ran around the clock.” The development group was pleased because Bell could keep control of the project
in-house, but also because they would have had to wait six weeks if the prototypes were made traditionally, of cast aluminum. “We obviously saved money as well,” Storp says.
The lab chose the process because it can model with PC (polycarbonate) and PPSF (polyphenylsulfone). These thermoplastics work well for functional testing, which is important for demanding applications, like aerospace. “The traditional
epoxy-based RP processes can’t match FDM in this area,” says Storp.
PC characteristics include dimensional stability, high heat-distortion temperature, high tensile and flex strength, and a hardness exceeding that of ABS plastic. PPSF characteristics include a VØ Flammability rating, the highest impact strength of
any rapid prototyping plastic, very high tensile and flex strength, dimensional stability, and resistance to petroleum products, acids, bases, and chemicals. “You’ll never see an epoxy part on an aircraft for a functional test,” says Storp. “Fuels and
hydraulic fluids would actually dissolve it.”
“FDM has strong points besides durability, but ease of post-processing is at the top of the
list for me,” Storp says. “With some other processes, it’s frustrating what you have to go
through. They might require three times longer in post-processing than it took to build the
part. FDM is a faster, cleaner process. After removing the support material, there are no
post-processing steps. You’re done.
“All processes are easy when it comes to building the part. But with some of them, you
really have to stay on top of it after the part is built. They can be very messy and time
consuming. That’s a big issue. We don’t have that hassle with FDM.”
“It takes a long time to design an aircraft. Starting from scratch it can take five years, and
it’s a rigorous development process to go through,” says Storp. “When using FDM over
the course of development for a new aircraft, there is great potential to reduce costs and
Those qualities make fused deposition modeling essential to the lab’s purpose, which is to
contribute to aircraft prototype development and support Bell Helicopter’s long-range plan
to become the heavy-lift tilt-rotor aircraft leader. “The efficient process allows us to do
more iterations than we could with other processes,” Storp says. “That results in betterdesigned
Better-designed components help to build a better end product. And when your product is
as sophisticated as the Osprey, that’s an important aim.