Currently, the CH-47 Chinook helicopter legacy tunnel covers are composed of an aluminum inner and outer skin, which is bonded to an aluminum honeycomb core. The six covers are located on the top of the aircraft between the fore and aft pylons and prevent environmental and physical damage to underlying components. The legacy covers are attached with rivets and metal bonding, which requires significant surface preparation. They can suffer from poor fit, corrosion, seals that are difficult to maintain and limitations on step zones for mechanics to perform maintenance.
ManTech’s proposed redesign uses an improved composite structure that not only lowers weight but increases durability and sustainability and lowers maintenance costs. A single, modular tool is able to manufacture all six of the individual tunnel covers.
During the project redesign, ManTech compared the viability of three potential composite solutions. The legacy aluminum design was evaluated against an autoclave cured sandwich configuration using Nomex® OX-core, an out-of-autoclave (OoA) cured sandwich configuration using Nomex® OX-core and an OoA cured sandwich configuration with 2.5-pound X-CorTM. Skin materials, configurations and resin systems utilized in these trials included those previously approved for use in Army aviation systems. Trades, testing and analysis conducted under the program indicated the Nomex® OX-core material would yield the best overall configuration to meet the requirement while optimizing component weight and durability.
“We have verified a 17-pound weight savings per aircraft with these new covers,” says White. Manufacturability and performance also were improved: The modular tooling concept improved production efficiency, part count was reduced by 54 percent and recurring costs were reduced by 44 percent, according to White.
The Chinook composite tunnel cover assemblies are currently undergoing flight testing at the U.S. Army’s Redstone Arsenal flight test facility in Huntsville, Ala.
The UH-60 Black Hawk and AH-64 Apache
ManTech is working with General Electric in the final year of a program, started in 2010, to improve the fuel efficiency and reduce the weight of propulsion engines for UH-60 Black Hawk and AH-64 Apache helicopters through the use of lighter weight, higher temperature capable ceramic matrix composite (CMC) engine components.