DEFENSE SECRETARY Frank Carlucci is doing the right thing with the defense budget. He is trying to bring it back within the confines of last November's truce between the president and Congress and, more than that, back toward a path that the country may be willing to sustain -- not by playing games but by cutting out and restructuring entire programs.

The latest example involves the Army's helicopter program. This has been a sleeper in the budget, a $60 billion program that has rarely made a headline. The Army has 5,000 Vietnam-era Cobra light attack and Huey transport helicopters that it says are no longer a match for Soviet aircraft and defenses and are increasingly difficult to maintain besides. In 1982 the service began planning to replace them, beginning in the early 1990s, with variations on a single, futuristic craft, the LHX or light helicopter experimental.

The LHX, the Army said, would be both quicker and cheaper than an intervening generation of helicopters now being built (Apache attack and Blackhawk transport) and would help meet a pilot shortage by requiring only one pilot per craft instead of two. But not everyone was sure the ambitious new design would work; nor was everyone willing to gamble and shut down the Apache and Blackhawk production lines as the Army proposed in an effort both to lock in the LHX decision and to help defray its cost.

What Mr. Carlucci has reportedly decided is to cut the LHX program in two, going forward with an attack helicopter but not with a transport craft. The transports will have to wait until another day. It is said there will be other such decisions. There will have to be to meet the budget targets without either temporizing -- leaving all the present programs in the budget but having them move forward at a crawl -- or draining off readiness funds, which has been done to protect the weapons buildup in the past but which no one thinks is a rational thing to do.

In earlier years the administration let defense drive fiscal policy instead of the other way around. Its theory was in part the tactical and political one that Congress would cut whatever it sent up, so why start low? The result of that aggressiveness has been two roller-coaster rides, one fiscal, the other for defense. Mr. Carlucci's job in the administration's last year is to smooth the process out as best he can, to try to rationalize, thin out and consolidate the buildup. Not everyone will agree with the choices he is making. But they can be debated; the important thing for now is that such choices are finally being made.