The National Transportation Safety Board is stretched to the breaking point and is becoming too dependent on experts from manufacturers and airlines that have a heavy financial stake in air crash investigations, an outside report said yesterday.

The independent board, with five presidentially appointed members and a staff of about 400, is one of the smallest agencies in government but has a worldwide reputation. NTSB has the statutory authority to take charge of the investigation of any transportation disaster or incident.

The RAND report, in effect, painted the safety board staff as dedicated workaholics who generally perform their detective work well, but who are in danger of losing their edge through overwork, outdated facilities and a lack of training on increasingly complex new aircraft.

But while the report praised the agency's work, it said that NTSB's management practices are so disorganized that managers do not know how much investigations cost. Better management and information tools are necessary, it said.

"The NTSB is an agency coping with serious overload and is in urgent need of additional resources and management reform," the report said.

Cynthia C. Lebow, one of the report's authors, said that so far, the NTSB's investigative work remains high quality for the most part, but "that is only through the heroic efforts of the staff."

The report from the think tank RAND was requested by board Chairman Jim Hall, who in unusually blunt language laid much of the problem at the door of the White House Office of Management and Budget, which he said has "zeroed out" his request for more personnel every year.

"The OMB is zeroing out the welfare of the American people," said Hall, who hopes to persuade Congress to increase his staff by 40 to 50 people.

The report was also significant for what it did not recommend.

The report rejected any major changes in the "party" process under which those involved in a crash--the airline, manufacturers, the Federal Aviation Administration, pilot unions and others--have official status to provide technical help under the supervision of the board. The theory of the party process is that it is in everyone's best interest to discover safety flaws and correct them.

The report, however, expressed strong concerns that the party system could be compromised by increasingly large legal settlements and competitive pressures.

"Today the rising financial stakes surrounding a major crash can put the integrity of information supplied to the NTSB's investigation at risk," the report said.

The report recommended that the board reach out to nonparty experts for information drawing on NASA, the Defense Department, government laboratories and private sector experts.

RAND rejected the request of trial lawyers and family groups to participate as official parties to an investigation, acknowledging an "emotional appeal" to the idea but saying it would amplify fears about conflicts of interest already inherent in the party process.

According to the report, NTSB must be trained to better manage increasingly complex investigations so that it will not be overly dependent on the airlines, equipment manufacturers and others.

The board's investigative and operational practices are "archaic" in a world where airplanes and systems are more complex, the report said, and "tin kicking"--investigations of physical wreckage--are not enough in a day when planes run as much on software as on aluminum.