Abstract: A duct section and system, including a laminated shroud, acting as a secondary duct, for aerospace and other applications, and a method for constructing same. The duct structure incorporates a metallic primary duct tube, with a laminated shroud surrounding the primary duct tube and separated therefrom by an annular gap. The laminated shroud includes a metallic inner layer and a polymeric outer layer. Preferably, the thin metallic layer is a corrosion resistant material such as corrosion resistant stainless steel or titanium. In one embodiment of the invention, the outer polymeric layer is a polyimide material, such as polyimide resin-impregnated fiberglass cloth.

Abstract: A leak detector for an insulated duct carrying pressurized hot air comprises a cuff secured over a circumferential cut in the insulation of the duct, thereby creating a reservoir of hot air which has leaked from the duct, a manifold defining a conduit therein in communication with the hot air reservoir and a cap for securing heat sensitive wires to manifold at the end of the conduit such that the hot air from the hot air reservoir impinges directly on the heat sensitive wires.