Landing Gear Prepared for Flight

Aircraft landing gear is a complex system comprised of mechanical, electrical and hydraulic assemblies. The range of motion for these assemblies presents unique design challenges further complicated by the punishment that landing gear endures, which makes it one of the most maintenance intensive parts on an aircraft.

To minimize downtime and ensure gear reliability, Messier- Dowty (Vélizy Villacoublay Cedex, France), the world leader in landing gear systems, uses sophisticated tools for design, analysis and testing. In preparation for the test flight of the new Superjet 100 regional aircraft, which is manufactured by Sukhoi Civil Aircraft of Russia, Messier-Dowty Toronto validated the performance of the main landing gear with both digital and physical mock-ups. To make the 16-foot high physical mock-up, Messier-Dowty turned to RedEye RPM (Eden Prairie, MN) for rapid prototyping with its fused deposition modeling (FDM®) process.

Components for the production landing gears were coming from international locations, and many would be delivered just days before system testing commenced. Also, the landing gear would arrive at Sukhoi’s assembly facilities in Russia just a few weeks before the aircraft’s test flight. To better facilitate meeting these scheduling challenges, Messier-Dowty used mock-ups early in the development process to validate both function and durability.

Dressings—the hydraulic, brake and electrical systems in the landing gear—are critical components, which is why they are the primary focus of design validation and testing. As the gear folds and unfolds from the aircraft’s fuselage, the dressings are subject to chaffing, binding and pinching that can contribute to system failure. Although Messier-Dowty uses digital mock-ups for analysis of stresses, motion and kinematics, they are unsuitable for emulating the dynamic motion of the hoses and electrical harnesses. That is why Messier-Dowty employs physical mock-ups to evaluate the dressings.

Historically, Messier-Dowty’s mock-ups were machined from wood. However, the company discovered the advantages of rapid prototyping during a previous project. Therefore, they decided to use the FDM rapid prototyping process for the Superjet 100, which quickly delivered precise prototypes with more detail than the machining alternative.

Chris Brookfield, who was the principal designer of Messier-Dowty at the time, contracted the rapid prototyping services from RedEye RPM. In less than one month, Messier-Dowty received 29 landing gear components, with the largest measuring 18" x 24" x 75". “If we would have had these machined, it would have taken two to three times longer, even though design details would have been eliminated to expedite delivery and keep costs down,” stated Brookfield. “RedEye actually delivered all of the landing gear components, with every design detail, faster than we could use them.”

The part list included the landing gear’s piston, main fitting, linkages and trunnion. “With the exception of a few off-the-shelf hardware items, the entire mock-up was made with FDM,” Brookfield commented. He also included parts from the aircraft, such as the rear spar and bay doors in order to perform onsite retraction tests.

Delivered just four weeks after transmitting files, Messier-Dowty was able to successfully assemble the main gear and start its review. “With machining, we spent a lot of time creating drawings, discussing project and part details, reviewing suggested changes and fielding questions. That was all eliminated when we worked with RedEye RPM. Taking all of that labor out of the project saved us money and made us more productive,” Brookfield concluded. “Considering all of the other advantages of the FDM rapid prototypes, we will continue to use them wherever possible.”

For more information on RedEye RPM, a business unit of Stratasys, visit www.redeyerpm.com.