An acoustic panel comprises: a face sheet comprising a plurality of openings; a back sheet opposite to the face sheet; and an intermediate layer comprising a plurality of cells each comprising a cavity and a plurality of walls extending between the face sheet and the back sheet and surrounding the cavity, the plurality of walls comprising a plurality of drainage slots and a plurality of covers covering the plurality of drainage slots and openable for drainage. A method for making the acoustic panel is also described.

Acoustic structures for a gas turbine engine are disclosed. In various embodiments, the acoustic structures comprise a panel in the form of a cellular structure having a plurality of cells; and a housing configured to house the cellular structure, the housing including a first rail configured for attachment to a static structure within the gas turbine engine and a second rail configured for attachment to the static structure. In various embodiments, the acoustic structures comprise a liner in the form of a non-segmented or two-piece structure configured to extend about the inner barrel of a nacelle structure. The disclosed panels and liners are configured to maximize the operational area of the acoustic structures by eliminating obstructions from adjacent flow paths.

Systems and methods are provided for septa for acoustic cells. One embodiment is a method that includes fabricating a septum of a cell of an acoustic panel, by heating a material into a molten material, depositing the molten material to form a lower chamber of the septum that extends vertically upwards and includes an entry, iteratively depositing layers of the molten material, each layer comprising a filament at the entry that includes overhangs with respect to vertically adjacent layers, and forming openings at locations of the overhangs.

A sound-proofing covering comprising a cellular structure, each cell of which comprises a duct extending at least between the first face and the second face of the covering. The duct is formed between an outer wall and an inner wall of the cell and has a restriction of its cross section. The outer and inner walls have rounded forms, without sharp edges. The cell comprises a cavity in which the duct emerges. Thus, each cell forms a resonator comprising a neck formed by the duct and the cavity. Each cell is conformed such that the duct and the cavity are formed on either side of the inner wall. Such a covering is particularly suitable for reducing acoustic waves in aircraft engine plant nacelles, particularly in the low frequencies.

A flow path duct system for a propulsion system of an aircraft includes a base defining a flow surface. The base has an internal surface and an external surface. A plurality of perforations are formed through the base between the internal surface and the external surface. A plurality of supports define a plurality of cavities. The plurality of supports extend outwardly from the external surface of the of the base. One or more of the plurality of cavities are in fluid communication with the one or more of the plurality of perforations. A backing surface is secured to the plurality of supports. The plurality of supports are disposed between the base and the backing surface. The one or more of the plurality of cavities are in fluid communication with an internal volume defined by the internal surface of the base through the one or more of the plurality of perforations. The base, the plurality of supports, and the backing surface can be integrally formed together as a monolithic, load-bearing structure.

Noise attenuating devices and methods, precursors and abrasive blasting masks for manufacturing noise attenuating devices are disclosed. An exemplary method disclosed herein includes bonding a facing sheet of the noise attenuating device to a cellular core and then perforating the facing sheet. Perforating the facing sheet may be performed by abrasive blasting using a mask configured to prevent the abrasive blasting of an underlying structure.

A variable geometry inlet system of an aircraft engine includes an inlet duct. The inlet duct includes at least first and second sections moveable between extended and retracted positions such that the inlet duct defines a variable axial length of an inlet passage for selective flight conditions. The inclusion of acoustic treatment may assist in controlling noise.

An acoustic panel (200) for an aircraft nacelle (100) may comprise a perforated first skin (220), a second skin (230), and a core (210) sandwiched between them. A camera system (330) may scan a perforation pattern of a damaged portion (311) of the perforated first skin (220). The damaged portion (311) of the perforated first skin (220) may be removed. A replacement patch (660) may be formed. A CNC machine (450) may drill the replacement patch (660) according to the perforation pattern. The perforations (425) in the replacement patch (660) may be aligned with perforations (325) in the perforated first skin.

A compact inlet design including a single bulkhead and/or an acoustic panel extending into nacelle lip region for noise reduction. The compact inlet is used with a low power fluid ice protection system capable of preventing ice build-up on the acoustic panel in the nacelle lip region.

A drilling system includes a single robotic drilling unit having a drill end effector positioned inside a barrel section configured as a composite sandwich structure having an inner face sheet. The robotic drilling unit is operable to drill a plurality of perforations into the inner face sheet using the drill end effector. The robotic drilling unit is configured to index a hole pattern of the perforations to one or more cell walls of a honeycomb core of the composite sandwich structure. The robotic drilling unit is configured to form the hole pattern in the inner face sheet such that the perforations are located at a spaced distance from the cell walls of the honeycomb core.