1. Field
The present invention relates to aircraft components. More particularly, the invention relates to an apparatus for improving acoustic attenuation within an inlet of a nacelle.
2. Related Art
An aircraft nacelle (A) surrounds an aircraft's engine (B) and typically comprises a fan cowl (C), a thrust reverser (D), and an inlet (E), as illustrated in FIG. 1. The inlet (E) typically comprises an outer barrel panel (F), a forward bulkhead (G), an aft bulkhead (H), a thermal anti-ice spray tube (I), a lip skin (J), and an acoustic barrel (K), also referred to as an acoustic panel, as illustrated in FIG. 2.
The acoustic barrel (K) is designed to provide acoustic attenuation, reducing engine and engine fan noise. For example, the acoustic barrel (K) can be made of a sandwich honeycomb panel, shaped to comprise a plurality of honeycomb cells. However, prior art acoustic panels are insufficient under certain conditions for reducing fan flutter cause by certain engine fan harmonics.
Accordingly, there is a need for an apparatus and method for reducing fan flutter caused by engine fan harmonics of an aircraft that overcomes the limitations of the prior art.