Quiet Technology Aerospace (QTA) has received US certification for its Stage 3 hushkit on all models of Rolls-Royce Spey-powered Gulf-stream II, IIB and III business jets. The Miami-based company has hushkitted the first GIII after completing flight tests on a GII.

The hushkit includes a 12-lobe exhaust mixer, acoustically treated carbonfibre-composite bullets in the inlet and exhaust, and a translating ejector nozzle designed to allow retention of the original Gulfstream target-type thrust reverser.

A mechanical link ensures the ejector translates aft, out of the way, when the thrust reverser is deployed. The ejector is attached to the thrust-reverser mountings, and installing the hushkit does not require any change to the engine pylon, says director of engineering Martin Gardner.

Take-off noise is reduced to 6.5dB below Stage 3 for lighter GIIs and 3.1dB below for heavier GIIIs, says Gardner. There is no change in take-off and climb performance, and testing has shown a cruise range penalty of less than 2%, he says.

The GIII may see a performance benefit from installation of the hushkit, which increases empty weight by 106kg (234lb), because it moves the centre of gravity aft and reduces trim drag, Gardner says. Range testing is planned on the first hushkitted GIII.

QTA has orders for 10 hushkits, which sell for $1.65 million following certification. The company estimates there are 420 eligible aircraft still flying, divided roughly equally between the GII and GIIB/GIII. Also competing for the market is Really Quiet, which had received US certification for its $1.95 million translating-ejector hushkit a year earlier.

Source: Flight International