Landing gear door liners for airframe noise reduction

A landing gear door that covers retractable landing gear of an aircraft when the landing gear is retracted during flight, and shifts outwardly when the landing gear is deployed, the landing gear door comprising:

• a door structure defining first and second opposite sides having first and second opposite surfaces, respectively, and edge surfaces extending between the first and second sides, the door structure further defining an internal structure disposed between the first and second opposite sides, wherein the door structure defines a porous surface on at least one of the first and second opposite side surfaces, and wherein the internal structure defines a plurality of internal acoustic chambers each defining a first end that is acoustically connected to the porous surface such that at least a substantial portion of sound entering the acoustic chamber at the first end is absorbed by the internal structure of the landing gear door;
• wherein each of the plurality of internal acoustic chambers defines a second end disposed in spaced relationship to the porous surface, with a length extending between each of the first ends and second ends and wherein at least one of the plurality of internal acoustic chambers includes first and second portions that extend transverse relative to each other at an angle in the range of about 30° to 90°;
• and,
• wherein the lengths of at least two of the plurality of internal acoustic chambers are different from one another.