Hush kit
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A hush kit is a device for reducing noise from an engine; most commonly the term refers to devices which reduce noise emissions from turbojets.
Jet aircraft generate a considerable amount of noise, contributing to noise pollution near airports. In modern turbofan engines, a fan is mounted before the actual jet engine, accelerating and cooling the airflow around the core engine, reducing its noise emissions. A hush kit produces a similar effect, mixing the exhaust gases of the old engine with the surrounding air and reducing its noise output.
Modern aircraft, equipped with high-bypass turbofan engines, are able to comply with contemporary aviation noise abatement laws and ICAO regulations. Hush kits are used on the many older freight and passenger aircraft stil in service, such as the B-727, DC-9 and DC-8. They are also deployed on smaller business and personal jets which are too small for turbofans.
While hush kits effectively reduce noise emissions from older aircraft, noise cannot always be reduced to the level of modern planes at a reasonable cost. In 1999 this has led to a dispute between the United States and the European Union. The EU's proposed noise ordinances effectively prevented the use of hush kitted aircraft in Europe, reducing the value of the mostly American used airplanes so equipped and hurting the profits of American hush kit manufacturers. EU Regulation 925/99 passed over US threats to ban the Concorde, but was superseded and effectively repealed bu EU Directive No. 2002/30/EC issued March 26, 2002.
External link
- BBC News, "Hell-bent on a trade war (http://news.bbc.co.uk/1/hi/business/the_economy/291304.stm)," March 5, 1999