Airframe noise, produced by unsteady flow around aircraft structures, is an important source of aircraft noise during approach and landing. Sound radiating from the undercarriage is a major contributor to airframe noise. This type of noise is broadband in nature, caused by the complex unsteady flow field associated with the multitude of bluff bodies of various sizes and shapes that collectively make up a landing gear. Previous noise reduction concepts rely on flow alteration and shielding of the more critical gear subcomponents such as the main post, torque links, etc. Such concepts include fairings made of flexible and rigid materials, porous fairings, and wire mesh screens.
This invention is a concept in which a wheel helmet (fairing) is used to shield the gear brake system and other finer-scale subcomponents adjacent to the wheels to reduce the amount of airframe noise radiated towards the ground during approach and landing operations. To cover the multitude of main landing gear designs on the current small and mid-sized civil transport fleet, several variations of the concept representing solid and partially porous were developed and tested. A telescopic version of the helmet was developed that accommodates main landing gear systems with an articulated main post.
To test its effectiveness as a noise reduction treatment, the wheel helmet concept was applied to an 18% scale replica of the main landing gear of an aircraft currently in production. As shown in the figure, the wheel covers the entire front portion of both wheels.
This work was done by Mehdi Khorrami of Langley Research Center. NASA is actively seeking licensees to commercialize this technology. Please contact LaRC-PatentLicensing@ mail.nasa.gov to initiate licensing discussions. Follow this link for more information: http://technology.nasa.gov/patent/LAR-TOPS-44 . LAR-18339-1