PROJECT AIMS TO LOWER THE BOOM.

Byline: Daily News

Northrop Grumman will modify a Vietnam War-era F-5 fighter jet for a government research project on making sonic booms quieter.

The modification work will probably be done at Northrop Grumman's plant in El Segundo and flight testing will start in 2002, likely at Mojave Airport or Edwards Air Force Base, officials said.

``There could be commercial and military applications,'' Northrop Grumman spokesman Jim Hart said.

Northrop Grumman's work is part of a much larger effort by the Defense Advanced Research Projects Agency, which is spending $35 million to try to come up with ways to substantially reduce the sonic booms created by supersonic airport, as well as their takeoff and landing noise.

The federal government prohibits supersonic flight over land - except with waivers like those granted for military airplanes in test or training areas - because the pressure wave that creates sonic booms can rattle buildings and break glass windows.

``There's a lot of benefits. It's a pretty difficult technical challenge,'' DARPA spokeswoman Jan Walker said of reducing sonic booms.

Northrop Grumman's F-5E will be fitted with a specially shaped forward fuselage, then tested by flying behind an unmodified F-5E.

This ``back-to-back'' test approach is intended to highlight the effect that aircraft shaping can have on the mitigation of sonic booms, the company said.

Northrop Grumman will perform the F-5E demonstration under a cooperative agreement with DARPA valued at approximately $3 million. Northrop Grumman last year got a $2.5 million DARPA contract for system integration studies and technology development.

Boeing's Long Beach operation and Lockheed Martin in Palmdale also received contracts in the program.

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Photo:

(ran in AV edition only -- color) This illustration shows an artist's concept of the plume of a ``shaped'' sonic boom, left, compared with the plume of a conventional boom. The shaped sonic boom may be quieter.