Gregory Karam, the air traffic controller who talked Air Canada's smoldering Flight 797 to the ground Thursday night, says that he thinks any controller could have done the job.

"It was simply a matter of chance," Karam said today, that he was on duty in the radar room at the Greater Cincinnati Airport tower when, suddenly, he found himself sharing with pilot Don Cameron responsibility for the lives of 46 people.

"There's no question in my mind all the others here would have done as well," said Karam, 36, who has been an air traffic controller for nine years and did not join the 1979 controllers' strike.

Eighteen passengers and all five crew members survived after the plane descended rapidly from 33,000 feet to the airport in suburban Kentucky. Investigators are concentrating on an electrical problem as the possible source of the fire that killed the other 23 passengers.

Karam's assignment was not a normal one. Most of the plane's navigational instruments failed or were obscured by thickening smoke. Thus, the pilot could not guide the plane to a specific compass heading. The controller became the compass.

Further, the plane's transponder, which makes a plane easier for radar to "see" and tells controllers a plane's altitude and speed, failed.

"The last altitude readout I saw was 33,000 feet," Karam said in a telephone interview today monitored by the Cincinnati tower chief. That is six miles higher than the airport.

Thus, Karam was left with what controllers call a primary target, a small blip on the radar screen unaccompanied by a computer-generated tag that identifies the airplane and tells what it is doing.

Flight 797 was switched to Karam's station immediately after the fire was reported to the regional air traffic control center in Indianapolis. The flight was en route from Dallas to Toronto and was 25 miles southwest of the Cincinnati airport at the time.

Karam alerted fire and rescue teams and told other controllers what to expect. A colleague took over the three other planes that had been Karam's responsibility.

When Karam started talking to Flight 797, a crew member told him that the only instruments he had were a gyro horizon (which tells whether a plane is going up or down) and an altimeter (which tells the altitude).

Karam said he had planned to bring the plane in due north on runway 36. But when the crew told him that the plane had descended to 8,000 feet, "he was too high and too close for 36." So Karam said that he switched the flight to runway 27 (due west), which eliminated time-consuming maneuvering.

Since Cameron did not have directional instruments, Karam told him to "turn right." Karem followed the blip on the screen until it was headed in the correct direction, then told him to "hold." Karam guided Cameron through four different turns to align flight 797 with the center of the runway.

It was the first time Karam had ever given that kind of approach in an actual emergency. "We practice them routinely," he said.

When the plane was eight miles east of the runway, a crew member asked Karam, "Is that the airport?" possibly referring to a nearby smaller airport. "I told him I'm not certain, but to stay on his heading, and he would see the runway," Karam said. The runway and approach lights were turned to maximum intensity. The plane landed.

Tower chief San Juan Romero was asked if one of his many trainee controllers could have handled the situation. "No way," he said.

Meanwhile, investigators from the National Transportation Safety Board began the laborious work of tracing wiring diagrams and examining charred pieces of electrical line to attempt to pinpoint the fire's source.

An electric motor that operated the pump that flushed the commode in the rear lavatory remains under great suspicion, because three circuit breakers that protect the motor tripped in the cockpit before the emergency became known to the crew. The motor's covering melted, "apparently from the outside," safety board member Donald Engen said today.

Engen also said:

* The pilot and co-pilot did not deploy the oxygen masks stowed above the passenger seats "because of concern" about feeding the fire. The crew members wore oxygen masks and smoke goggles.

* The pilot and co-pilot escaped through the cockpit windows because they were driven back by heat and smoke when they tried to enter the passenger cabin after landing.

* All the survivors had covered their faces with washcloths or tissues or, in one case, a vest. All the deaths have been attributed by the county coroner to smoke inhalation. Further tests are pending to determine the chemical composition of the smoke.

* Tests of the airplane's fuel system show that it did not leak and probably did not feed the fire.

* Studies of tape recordings show that the time of descent from 33,000 feet to the airport was 11 minutes.

Air Canada has declined to make the cockpit crew members available for interviews.