New engine may give older jets a reprieve from the scrap heap

Some noisy kerosine-guzzler jets are being fitted with new engines that not only muffle jet screams, but lower fuel bills.

Currently being used on McDonnell-Douglas DC-8s, the engines represent a step toward solving two crucial airline industry problems: hushing the din hitting noise-wracked neighborhoods close to metropolitan airports; and lowering fuel costs for airlines trying to adjust to the fierce competition born of the recent deregulation.

The new engine, called the ''high-bypass'' engine, was developed by General Electric and SNECMA, a French firm. GE long-range planner William Rodenbauch says the new engine cost $1 billion to develop, and works by moving the exhaust gases inside the engine through a fan instead of immediately jetting it out the back.

As the airlines struggle to survive, they have to obey federal government orders to either quiet down or put out to pasture the older, noiser jets such as the workhorse DC-8 and the Boeing 707. Delta, United, and several other airlines are now testing the modified DC-8s well ahead of the government deadline.

''The numbers (of DC-8s) are small, but they are the noisiest planes at Logan , and probably at most other airports,'' says Logan International Airport external affairs manager Claire Barrett here.

''Now instead of being the worst noise offender, the DC-8 is one of the quietest planes,'' she says.

The airline industry is taking a long, hard look at redesigning engines as a way to make it through the lean times, says David Venz, Trans World Airlines director of public affairs.

He said TWA is interested in modifying Boeing 727 engines to make them more fuel efficient. Even though TWA has some 40 707s out of a total fleet of about 70, the small size of the 707s simply made it too expensive to outfit them with new engines.

In other cases, though, redesigned engines seem to pay.

Charles Novak of United Airlines says his firm will spend $400 million to outfit its 29 DC-8s with new engines. He estimates the new powerplants will save up to 1.5 million gallons of fuel a year per aircraft. With jet fuel costing more than $1 a gallon, that amounts to savings of more than $30 million a year in fuel costs.

As of 1985, DC-8s that haven't been modified with quieter engines will be in violation of federal noise standards. Airlines will have a choice of either putting new engines on them, selling them to foreign countries that don't have strict noise abatement standards, or selling them for spare parts, as TWA recently did with 28 of its 707s.

So for people like Charlie Page of nearby Winthrop, the importance of the planes is in the quieter takeoff and landing.

Watching -- and listening to -- a DC-8 with the new engines take off over nearby East Boston, the clamor was noticeably less.

According to Massachusetts Port Authority statistics, the difference in the noise level discerned by the human ear is 17 decibels less in the modified DC-8, than the 112 to 95 decibels for older DC-8 engines.

For airline executives trying to steer their companies through harrowing economic times, the change in engines quiets complaints of neighborhood groups fighting for noise abatement. But it also is significant for its cost-cutting benefits.

The new DC-8s will be used by United and other lines such as Delta, Transamerica, Air Canada, and Capitol Airways, for freight, regular runs, and charter flights.