On the night of Dec. 20, colleague Mike Sager covered a story about a power outage at Dulles International Airport.

Equipment failure at a Vepco substation had blacked out the huge airfield at dusk, and then "backup generators failed, snarling reservation and ticketing procedures, inconveniencing waiting passengers and causing at least one flight to be diverted."

When I saw Mike's story on the Metro news budget, I paid him a visit. "Your story doesn't explain why backup equipment failed," I complained. "Why does backup power fail when commercial power has failed and planes are trying to land? What the hell good is backup power if it doesn't back up Vepco's failures?"

"Good question," Mike said. "When I asked it, they told me it would take at least a week to track down the answer. But it's really not as bad as it sounds, because the control tower did have the use of battery-powered transmitters to keep in touch with planes that were trying to land."

That sounded reasonable, so I got off Mike's back and waited for Dulles to provide us with an explanation.

A week passed without a follow-up. Two weeks passed. Three weeks passed. Still no explanation.

So I called Dennis S. Feldman. Dennis is the newsman's friend at the Federal Aviation Administration. Whatever our problem is, Dennis knows where to find answers.

It took him all of two hours to ascertain what had happened.

"The backup generators didn't fail as they first thought," he told me. "The generators cut in as they should have, but a circuit breaker failed -- and was replaced as soon as they pinpointed the trouble.

"As The Post's story pointed out the next day, the control tower had immediate access to battery-powered transmitters that kept the tower in contact with planes waiting to land. So there was no danger, and no real emergency.

"After a while, the tower at Dulles turned things over to the Washington Air Route Traffic Control Center at Leesburg, and everything ran smoothly until Vepco restored commercial power to Dulles.

"That's one of the many safety features built into our system. Every control center can switch its communications to an adjacent center if the need arises, and there are multiple backup systems even beyond what I've described to you. Commercial aviation's record last year speaks for itself. In all of 1980, there was no fatal accident involving a trunk carrier. There was one that involved a local service in Wisconsin, but in the entire United States nobody died on a major airline. We had our safest year since 1933, and we're very pleased about that."

So are the millions of passengers who landed safely, in spite of circuit breakers that malfunctioned and power lines that suddenly decided to go dead. A tip of the hat to the American airline industry and to the FAA that rides herd on it. And to Dennis Feldman, who does more to bolster this airline passenger's morale than Dramamine. HOW'S THAT AGAIN?

Berny Krug has forwarded an interesting two-part clipping from our esteemed afternoon contemporary.

The headline on a story on page C-1 said, "Elderly Fear Helplessness, Not Death." The story was continued on C-4, where the headline on the continuation was, "The Elderly Fear Death More Than Helplessness."

This member of the elderly category fears the inattentiveness that marks so much of modern work in every field. It's not ineptness or lack of intelligence that causes our problems. Heavens, no! Today's young people are brighter than my generation ever was. They just don't think their assignments are worth the extra care that's needed to make sure things are done right.

They have not yet learned that if a thing is worth doing, it's worth doing right. What a pity. POSTSCRIPT

I'm reminded of the slogan of Hearst's International News Service, later merged into the "I" in UPI (United Press International): "Get it first, but first get it right." VAGRANT THOUGHT

What ever happened to the theory that we are burning so much fossil fuel that we are creating a greenhouse effect that is raising temperatures all over the world? Brrrrrrr!