THE DECISION by District Judge Aubrey Robinson to order all of the nation's DC10s grounded is an astonishing vote of no confidence in the Federal Aviation Administration. It is rare for a federal judge to overrule a regulatory agency on a technical matter, especially one so clearly committed by Congress to an agency's care as air safety has been to the FAA. But Judge Robinson's action reflects a public sentiment that something is wrong with the plane despite the assurance by the FAA that it is airworthy when faulty engine mounts have been repaired.

Regardless of what happens to Judge Robinson's order on appeal or on a rehearing and regardless of how many flights it affects, the fact he has entered it will change the focus on the investigations now under way into the May 25 crash in Chicago. The first effort of the investigators will be to determine, precisely, why the engine fell off the wing; that's what the judge has demanded to know before he lets the planes go back into the air. But the investigators will then be forced to concentrate, as they should have all along, on questions concerning the performance of the FAA.

One question, in light of the judge's order, will be whether that agency has been negligent in the last 10 days in permitting the DC10s to continue to fly after their engine mounts passed new inspection requirements. That is whether the FAA's inspection requirements are broad enough and its enforcement procedures tough enough to make air travel, on the DC10s and other planes, as safe as it can possibly be.

The FAA, according to most aviation safety experts, has done a good job in recent years. Certainly, the statiscal evidence supports that claim; you are less likely to be killed flying in an airliner than riding in an automobile. And airliners are inspected and maintained in a way that puts to shame the mechanical condition of all other kinds of transportation equipment.

But doubts persist. That accident in Chicago probably would not have happened if someone had thought of the engine mounts as potential problems years or even months ago and persuaded the FAA to have them inspected regularly. How sure can we be that the thinking is any better now? Maybe the FAA needs to create a special task force to reconsider all of its inspection and maintenance requirements on all airliners. Even if that produced no new rules, it might quiet the growing sense of unease that somewhere in the sky is another plane with a problem no one has yet thought of.

Such unease reflected by Judge Robinson was encouraged recently when the chairman of the National Transportation Safety Board, James King, said the FAA is not enforcing its existing rules against commuter airlines stricly enough. There have been eight crashes involving small or commuter airplanes in the last 10 months and the safety board has found examples of what Mr. King called "bad or nonexistent maintenance."

If the rapid increase in commercial air traffic since last fall is more than the FAA can handle or if it needs more inspectors or more enforcement powers, now is the time for Federal Aviation Administrator Langhorne Bond to say so. His agency is on trial just as much as the design and maintenance of the DC10 are.