DIVAD gun gets the axe. Pentagon decision to cut Army's Sergeant York gun may mean closer scrutiny of other weapons

Chalk one up for Caspar Weinberger. The Defense Secretary's decision to cancel a costly and ineffective new weapon -- the Army's Sergeant York antiaircraft gun -- wins him plaudits in this town. Those who keep an eye on the defense purse say his image as a go-for-broke arms builder may have to be modified.

``He took a tough decision and deserves credit for it,'' says one defense expert on Capitol Hill.

But cancellation of the Sergeant York (also called the DIVAD), after $1.8 billion had been spent producing 65 of the guns, is expected to renew debate over other controversial items in the defense budget. It may also heighten pressures on the Pentagon to revise its long-range planning in the light of a new climate of fiscal responsibility.

The military authorization for fiscal 1986, to be approved in conference committee when lawmakers return in September, stands at $302.5 billion. This is a freeze at last year's level plus a 3 percent increase for inflation.

Because of soaring budget deficits, legislators expect a low-growth trend in military spending. This will require a rethinking of many weapons systems which have been put in the works under a Pentagon plan that projects higher increases in defense spending.

Sen. Sam Nunn (D) of Georgia, ranking minority member of the Senate Armed Services Committee, is at the forefront of efforts to bring more rationality and efficiency to the defense buildup. He stresses that the United States has committed itself to a large number of new systems that entail large future costs. Yet it is producing existing systems at inefficient rates -- i.e., buying in small quantities and thereby driving up unit costs.

An amendment to the defense authorization bill sponsored by Senator Nunn would require the Pentagon to update its five-year plan, taking account of slower growth.

``We have to know the impact of zero-growth budgets on the production of existing systems and on new starts,'' says an aide with the Senate Armed Services Committee. ``Should you cancel new starts? Or improve the production of existing systems? The Pentagon should be taking a hard look at long-term defense planning and bring realism to it.''

Congress still has an opportunity to look at individual defense items for next year. The defense authorization process is followed by the passing of appropriations bills, which provide the actual money for specific programs.

Some defense specialists, highly critical of the acceleration in military spending since 1980, believe many other weapons systems could be canceled without impairing the national defense. For example, the Center for Defense Information includes these items on its list of unnecessary programs:

The medium-range air-to-air missile. More than $1 billion has been spent on this weapon, and is behind schedule. Its elimination would save $540 million.

The C-17 cargo aircraft. It is only entering the development phase. Cancellation would save $453 million.

The JVX vertical-lift aircraft. It too is in the research and development stage. Ending this $24 billion program now would save $608 million in fiscal 1986.

Critics of these programs say that the Pentagon is carried away with developing highly advanced, ``perfect'' systems. They argue that many of these weapons are tested under optimum conditions but later prove inadequate for combat.

``They want performance and function, but they ignore the realities of battle which are unlike those in laboratory conditions,'' says Eugene Carroll, a rear admiral (ret.) and deputy director of the Center for Defense Information.

The ill-fated DIVAD is a case in point says Admiral Carroll, ``You build a camel which is simply not adequate for combat.''

In announcing cancellation of the DIVAD, Secretary Weinberger said that tests this summer demonstrated the gun offered only ``marginal improvements'' over current air-defense weapons and therefore was ``not worth the additional cost.'' He said elimination of the program would save $3 billion.