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Acoustic sources within the "jet pipe" also contribute to the noise, mainly at lower speeds, which include combustion noise, and sounds produced by interactions of a turbulent stream with fans, compressors, and turbine systems. [1] The jet mixing sound is created by the turbulent mixing of a jet with the ambient fluid, in most cases, air.
Noise-generating aircraft propeller. Aircraft noise is noise pollution produced by an aircraft or its components, whether on the ground while parked such as auxiliary power units, while taxiing, on run-up from propeller and jet exhaust, during takeoff, underneath and lateral to departure and arrival paths, over-flying while en route, or during landing.
Jet noise may be reduced by adding features to the exit of the nozzle which increase the surface area of the cylindrical jet. Commercial turbojets and early by-pass engines typically split the jet into multiple lobes. Modern high by-pass turbofans have triangular serrations, called chevrons, which protrude slightly into the propelling jet.
Other noise sources are the fan, compressor and turbine. [29] Modern commercial aircraft employ high-bypass-ratio (HBPR) engines with separate flow, non-mixing, short-duct exhaust systems. Their noise at takeoff is primarily from the fan and jet. [30] The primary source of jet noise is the turbulent mixing of shear layers in the engine's exhaust.
Below is a list of some notable aircraft previous operated by the Armed Forces of Indonesia. Indonesian Air Force MiG-21F-13 Fishbed C An OV-10F Bronco on display at an Air force Museum in Yogyakarta A B-25 Mitchell on display Republic of Indonesia Air Force Mil Mi-4 Hound Indonesian Air Force K5Y1 'Chureng'
For commercial jet aircraft the jet noise has reduced from the turbojet through bypass engines to turbofans as a result of a progressive reduction in propelling jet velocities. For example, the JT8D, a bypass engine, has a jet velocity of 400 m/s (1,450 ft/s) whereas the JT9D, a turbofan, has jet velocities of 300 m/s (885 ft/s) (cold) and 400 ...
During the early 1990s, German manufacturer Dornier had launched their turboprop-powered Dornier 328 onto the market. However, some prospective customers reported a negative perception of noise and reliability issues with turboprop engines, which motivated the company to study the manufacture of a turbofan-based variant, initially referred to as the 328-300. [3]
By November 2014, AC104 had completed 711 flights in 1,442 hours and 23 minutes. Certification tests included stall, high-speed, noise and simulated and natural icing. [19] AC105 returned to Yanliang airport on December 16, 2014, from Xi'an Xianyang International Airport after the last function and reliability flight. This completed the testing ...