THE FEDERAL Aviation Administration's decision to ground all DC10 aircraft was right. Once the evidence had reached Washington that more than one broken bolt was involved, FAA Administrator Langhorne Bond had no choice. Something is wrong with the engine mounts of the DC10s.

The ground of the planes will cause problems for many travelers. The share of the traffic these aircraft normally carry is big, and the airlines will be hard put to replace them. But how long the planes remain grounded is less important than the quality of the inspections they receive. Before the FAA permits the planes to fly again, it must be convinced not only that all damaged parts have been replaced, but also that future inspections will be adequate to spot such damage before it becomes serious. The FAA's actions so far in the aftermath of that terrible crash in Chicago last Friday have been reassuring. Mr. Bond - reasonably - refused to order the DC10s out of the air simply because one of them had crashed. But as soon as he knew a critical part had failed, he ordered the immediate inspections that produced the evidence on which the indefinite grounding is based. Although it can be argued, in retrospect, that he should have grounded the planes Friday night, it makes little sense to take such action before you know what the problem is you are trying to solve.

Correcting the engine mounts on these airplanes, however, will not be the end of the matter. There is the question to be answered of why previous inspections did not turn up the evidence of cracked bolts and other damage that led to this grounding. Perhaps the FAA's inspection requirements need a major overhaul. There is also the question of whether the pilot could have landed that plane safely in Chicago, even after the engine fell off, if all its controls had been undamaged. Most modern aircraft can continue to fly after losing an engine, and if the DC10 can, it means something else must have gone wrong.

Beyond these problems is a broader question about the DC10s. The first substantial changes in thses planes were made some time ago after one of them lost a cargo door and crashed near Paris. Now that the planes are on the ground, the FAA would be well-advised to run through all of its safety calculations about them again to see if it can spot any other potential problems. It is unnecessary to say, much less to argue, why this would be a good idea.