MD-80s are legalized by hushkits
A new Pratt & Whitney noise-reduction kit will permit operators of McDonnell Douglas MD-80 twinjets to meet Chapter 4 International Civil Aviation Organization noise rules that are scheduled for introduction in six months’ time. The heavyweight version of the equipment comprises an improved fan-inlet liner, a 16-lobe exhaust mixer, a muffler and a tabbed nozzle. A lower-cost, lightweight variant excludes one or two of these features since lighter aircraft are less noisy.
With P&W assistance, Aviation Fleet Solutions (AFS) has been conducting air and ground noise, operability and performance tests on two complete sets of equipment and three partial kits using a leased McDonnell Douglas MD-83. Some 125 hours of concept-proving and airworthiness tests were performed in more than 40 flights over a 12-month period. Certification flights took place in April and May and are being followed by further ground work ahead of formal approval. Once a supplemental type certificate is issued, production of component parts by AFS and P&W will be established to match demand.
P&W already has made the JT8D less “dirty.” An emissions-reduction package (or E-Kit) introduced in 1999 reduced NOx by a claimed 25 percent, unburned hydrocarbons by 99 percent and smoke by 52 percent, while maintaining a “low” level of carbon monoxide.
This E-Kit can be combined with the new package, which is coupled with other enhancements such as improved fan-blade containment (achieved through fitting of a forged aluminum ring in the front fan liner).