Audits by the Defense Department inspector general have found that the military regularly invests millions of dollars in weapon systems before the secretary of defense and his top aides have evaluated their need or potential cost.

The audits by Inspector General Joseph H. Sherick and his assistant for auditing, John W. Melchner, portray a central Pentagon bureaucracy unable or unwilling to control procurement decisions made by the Army, Navy and Air Force on weapons from mortars to fighter jets.

The Pentagon made the audits available to The Washington Post on request.

In some cases, the audits suggest that, despite sloppy or inadequate documentation, the services' actions made sense and the weapons being developed are needed. In others, the audits question whether any money should have been spent and whether estimates for future spending are realistic.

The Army, for example, embarked on a potential $87 billion helicopter purchase without any valid estimate of how much each helicopter will cost, one audit said. The Navy spent nine years and $65 million trying to develop a new communications system for its fleet without review from the defense secretary's office, without "clear program definition" or a "documented acquisition strategy," and without planning to make the system useful for the Air Force and Army as well as Navy, an audit found.

The inspector general examined eight weapon systems in various stages of development last summer and fall and found significant problems in each.

Pentagon officials would not discuss the audit results officially.

However, one official in the inspector general's office who asked not to be identified said that Defense Secretary Caspar W. Weinberger has supported the auditing process and efforts to correct weapons procurement problems. This official said he believes that the audits will lead to tighter control by Weinberger's staff.

Another official who asked not to be identified, a Navy officer, complained that the auditors want increased bureaucratic control that will delay new weapons and increase costs. The officer said the process will work better if the services are left alone with only broad oversight from the secretary.

The audits were designed to review the effectiveness of the Defense Systems Acquisition Review Council, or DSARC. That council, composed of Weinberger's top acquisition, budget and policy officials, is supposed to evaluate the affordability, need and effectiveness of every major weapon at several stages before key decisions are made to develop, test and produce them.

The system is intended to prevent cost overruns. In the past, the Pentagon frequently found itself committed to spending billions more than it projected for weapons that were not working as well as expected.

The audits found, however, that the services often make decisions without council approval and that the council often makes decisions without enough information from the services.

The best-known example of the problem, reported last year, involved the Army's Divad air defense gun, which won a DSARC green light while the Army withheld key test results, according to the inspector general. Weinberger since has suspended purchases of Divad, on which $1.7 billion had been spent, pending further tests.

In more recent examinations, auditors found:The Air Force made key decisions on a new air reconnaissance platform "without DSARC oversight" and without Weinberger's approval, a Nov. 7 audit found. Air Force officials unilaterally de-emphasized development of an unmanned drone, despite congressional pressure, and began developing a reconnaissance version of the F16 fighter jet, which could cost billions of dollars.

The audit noted that the Air Force drone program is "concurrent with Navy and Army reconnaissance programs using similar technology."The Air Force also embarked on a $6 billion research program to develop an advanced tactical fighter without adequate cost estimates, assessments of the threat the plane will meet or test plans, according to an Oct. 29 audit. The program proceeded without Navy cooperation, although the plane is supposed to serve Navy and Air Force needs beginning in the mid-1990s.The auditors concluded that the Army needs a new helicopter to replace the UH1 Huey and other older aircraft, but found serious problems in the Army's planning. For instance, estimates of each helicopter's cost range from $5 million to more than $8 million, which "clearly raises affordability as a major concern."

The Army also accelerated its procurement schedule, skipping certain testing phases, without Weinberger's approval, the Nov. 13 audit found.

Similar problems were found in the Army's guided anti-mortar mortar projectile; the Navy's high-frequency improvement program for fleet communications; the Air Force's advanced air-to-surface missile; the Army's terminal guidance warhead for the multiple launch rocket system, intended as another "smart" weapon for killing tanks; and the Joint Tactical Information Distribution System (JTIDS), intended as an eavesdrop-proof network for battlefield communications.

The audit on JTIDS was the only one for which the Pentagon provided responses from the services. The Air Force, which manages the joint program, accepted the inspector general's recommendations for improving oversight, but also said that documentation provided so far "was quite extensive."

"We think it is inappropriate, therefore, to imply that the . . . program is deficient in meeting the DSARC documentation requirements cited in your report," Martin F. Chen, acting assistant Air Force secretary, wrote.