Systems and methods for forming perforations in a barrel structure

A method of fabricating an engine inlet, comprising the steps of:

• providing an engine inlet inner barrel section configured as a composite sandwich structure having an inner face sheet;
• drilling, using a drill end effector of a single robotic drilling unit in which the drill end effector is positioned inside the barrel section, a plurality of perforations in the inner face sheet after final cure of the composite sandwich structure, wherein the drilling comprises indexing a hole pattern of the perforations to one or more cell walls of a honeycomb core of the composite sandwich structure, and positioning the hole pattern such that each perforation is located at a spaced distance from the cell walls;
• and
• forming the plurality of perforations in a quantity providing a predetermined percent-open-area of the inner face sheet.

A drilling system, comprising:

• a single robotic drilling unit having a drill end effector positionable inside a barrel structure supported on a system base;
• the single robotic drilling unit being operable to drill a hole pattern of perforations into an inner surface of the barrel structure using the drill end effector;
• and
• the single robotic drilling unit is configured to index the perforations relative to internal structure of the barrel structure such that all of the perforations are at a spaced distance relative to the internal structure, the internal structure being oriented perpendicular to the inner surface and located on a side of the inner surface opposite the single robotic drilling unit.

A method of drilling perforations in a barrel structure, comprising the steps of:

• supporting a barrel structure on a system base;
• drilling, using a robotic drilling unit having a drill end effector positionable inside the barrel structure, a hole pattern of perforations into an inner surface of the barrel structure using the drill end effector;
• and
• indexing, using the robotic drilling unit, the perforations relative to internal structure of the barrel structure such that all of the perforations are at a spaced distance relative to the internal structure, the internal structure being oriented perpendicular to the inner surface and located on a side of the inner surface opposite the robotic drilling unit.