"Weight means fuel dollars in the aircraft industry, and manufacturers have an ongoing need to reduce the cost of fuel consumed, without sacrificing performance," observed Flexfab Director of Sales Engineering Rod Ward. "Because this new design is typically 1/2 - 1/3 the weight of conventional ECS ducting, it can eliminate a significant amount of weight, yet it shows better results in performance testing than the heavier urethane/nylon and silicone/fiberglass ductwork currently in use." Ward went on to describe the construction as multiple layers of an elastomeric laminate with an extruded polyester helix, supported by non-metallic filaments. The tough, thermoplastic elastomer resists solvents, petroleum products and hydraulic fluids, and the finished product has demonstrated a service temperature range of at least -65° F to 190° F without delamination.

Cuffs (both straight and quick-attach) are constructed of silicone over woven fiberglass. Semi-rigid adapters are designed with multiple layers of the polyester film with non-metallic threaded ends that mate with the flexible hose. When the lamination and welding processes are complete, the result is essentially a single piece construction.

"This new design is currently being used in the production of commuter and business jets," Ward continued. "It contributes to lighter weight and fuel economy in those applications, but the savings will be particularly apparent in larger aircraft, where the total ECS duct weight can be 100-150 pounds," he said.

ECS ductwork is typically hidden in the sidewalls and overhead spaces in the cabin, and during flight, it is subjected to the pressures and temperatures required to maintain passenger comfort. Parked at an airport gate, however, ground support heating and air conditioning systems can introduce source temperatures as low as -40° F or in excess of 175° F. Layovers can also bring arctic cold or desert sun conditions, with ductwork being deep frozen or baked within the sidewall. Depending on the plane’s routes, its itinerary could bring alternating periods of both extremes.

Although the patented design has been proven in commercial production, its thin-walled construction raised questions about the ability of the materials to withstand the rigors of installation, when the duct is dragged through multiple penetrations in the aluminum framework during assembly of the plane. To prove its resistance to abrasion and puncture, the duct undergoes a special test regimen under which it is subjected to an elevated number of pulls through penetrations in an aluminum frame. Results show that the NGD construction has the physical toughness required for installation in the application, despite its extremely light weight.

Flexfab manufactures the Next Generation Duct in straight sections, Ts, Y-shapes and ID transition couplings. It is available with a straight cuff for clamping or taping to non-beaded stems, and can be ordered with a stretch/latch cuff for conventional SAE J 1231 beaded stems (no clamp required) or with a "Quick Attach" threaded cuff for assembling to bulk lengths of NGD duct and to SAE J 1231 beaded stems. The construction can be used to create insulated or uninsulated configurations.