GUY NORRIS / LOS ANGELES
Jet Engineering is set to begin trial programme for modified exhaust mixer to achieve Chapter 4 compliance
California-based aerospace company Jet Engineering expects this week to start flight testing a Boeing MD-80 fitted with a modified exhaust mixer designed to make the former McDonnell Douglas twinjet compliant with International Civil Aviation Organisation Chapter 4 noise limits.
The two-week flight test programme at Mojave, California, will be undertaken on an MD-81 and is due to begin around 4 October. It follows ground tests of the mixer at Pacific Gas Turbines in San Diego, which showed noise reductions and performance improvements. The company says reduced back-pressure from the modified mixer increases the cruise thrust of the Pratt & Whitney JT8D-200 engine by around 500lb (2.2kN), which translates to a specific fuel consumption saving of between 2% and 3% at reduced power settings. The new mixer, weighing around 20kg (44lb), adds around 0.15m (0.5ft) to the length of the exhaust.
Jet Engineering expects noise levels at take-off to be reduced by 2dB at each measurement point, contributing to an overall cumulative noise reduction totalling 10dB.
The modification is aimed at the European market, where around 300 of the 1,100 MD-80s in operation are flown. Jet Engineering is discussing the mixer modification with two European carriers, leasing companies and two US majors.
Although Chapter 4 is scheduled to take effect from 1 January, 2006, this applies to new aircraft and there is no phase-out date set for Chapter 3 aircraft. However, most MD-80 users in the region are expected to begin phasing out fleets in late 2003 to offset high costs associated with noise-related landing fee payments, overflight charges and other penalties. Diversified Aero Services, the Florida-based company supplying the testbed, says the modification is expected to save operators which fly about 1,000h a year around$1 million over the same period. Predicted savings include the elimination of noise-related charges, lower fuel costs, accessibility to more slots, extended economic life and enhanced market values. Certification of the kit is expected by year-end for all MD-80 variants, with kits available in early 2003.
Source: Flight International
