Weather radar that holds the key to warning pilots about dangerous wind shear cannot be obtained "off the shelf," and further tinkering with specifications is not likely to lower its cost, the chairman of an advisory committee told Congress yesterday.

Raymond G. Kammer, deputy director of the National Bureau of Standards and chairman of a committee of experts convened at the insistence of the Office of Management and Budget, said:

"In the opinion of the committee, the only way to make a substantial difference in price would be to reduce performance. The committee advises strongly against such a decision." He also said, "There does not seem to be any justification for slipping the schedule." Kammer's report was made in testimony before two subcommittees of the House Science and Technology Committee and was seized upon by subcommittee members and other members of Congress who demanded that the OMB expedite development.

The program is called NEXRAD, for "next generation radar," and is a $1 billion joint project of the Air Force, the Federal Aviation Administration and the National Oceanic and Atmospheric Administration. NEXRAD is a Doppler radar system that will warn of tornadoes and other major atmospheric hazards at relatively high altitudes.

The FAA plans a "terminal Doppler radar" as a follow-on to NEXRAD. It would be installed at 110 airports to detect low-level microburst wind shear of the type suspected of causing the Delta Airlines crash at Dallas-Fort Worth International Airport recently that killed 136 people. Terminal Doppler, which would cost about $500 million, cannot move forward until NEXRAD is approved.

Rep. James H. Scheuer (D-N.Y.), a subcommittee chairman, said, "It is time for OMB to stop scouring the shelves and starting installing life-saving terminal radars around the country."

An OMB spokesman said, "We have envisaged all along having to fish or cut bait on the development and procurement of the NEXRAD system in the forthcoming budget and have always said we would weigh carefully the report of the Kammer committee."

The FAA's 20 percent share of NEXRAD and 100 percent share of terminal Doppler would be paid from the aviation trust fund.