An Eastern Airlines jetliner carrying 140 persons here from Miami skidded to a grinding halt at Dulles International Airport last night after making an emergency landing with its wheels up.

Passengers and crew members were quickly evacuated from the Boeing 727 after the 6:51 p.m. incident, and there were no immediate reports of injury.

The plane, Flight 974, had been scheduled to land at National Airport but was diverted after a cockpit warning light indicated a landing gear problem. The exact cause of the incident is under investigation.

Praising the calm and competent assistance of the crew, passengers described the touchdown as smooth, but they recalled a grinding roar as the three-engine plane slid to a halt on its metal underside.

To John Schelble, aide to a Florida congressman, who was one of the 132 passengers, it seemed as if "the plane was wearing away under the soles of my feet."

When all aboard were finally safe and assembled shivering on the ground outside the plane in the chill darkness, he said, "Everybody just started applauding. It was a spontaneous thing."

Based on the accounts of airline and Federal Aviation Administration officials as well as passengers, rescue workers and other witnesses, the crisis that ended in applause on runway 19-Right at Dulles Airport began unexpectedly a short time earlier as the jetliner was heading south over the Potomac River on its final approach to National.

In the cockpit, as the flight crew attempted to extend the landing gear, they got a "gear unsafe" indication, according to an Eastern spokesman.

Such an indication, an FAA official said, may mean that the wheels are partly extended or not extended at all. Basically, he said, "It says they are not in a safe condition to land on."

From his seat on the left side of the plane in row 25, Schelble, press spokesman for Rep. William Lehman (D-Fla.), could hear the flight crew repeatedly opening and closing the wheel housings, apparently in an attempt to extend the wheels.

Through the window on Schelble's left, the Jefferson Memorial came into view. Then suddenly, with National only seconds away, the approach was aborted. The airplane accelerated and headed south past the airport.

From the cockpit came an announcement. The indicator light showed a problem.

The plane banked to the right, toward Virginia. The plane's captain, Robert Welch, "elected to go to Dulles" and to make a wheels-up landing there, said airline spokesman Jim Cosley.

Authorities said the longer runways at Dulles provide a greater margin of safety for such landings, which they described as rare in commercial airline operations.

Over the intercom came the voice of pilot Welch, describing the problem and calling on passengers to follow crew members' instructions.

Passengers said that at one point the plane's second officer opened a hatch in the cabin in an apparent attempt to operate the landing gear manually. They said the plane made at least one sharp turn designed to try to free the gear.

None of it seemed to work. Welch told his passengers that he would land the jetliner on "its belly," Schelble said.

Meanwhile, according to Robin Weir, a Washington hair stylist who was a passenger, the "stewards and stewardesses briefed us" on safety measures. "They were so good," said Weir, whose clients include Nancy Reagan.

As the plane approached Dulles, passengers were advised to bend forward and keep their heads down. They were briefed on the operation of the emergency exits.

At Dulles, ambulances and fire trucks were gathering around Runway 19-Right. No fire-suppressant foam was spread, however. Airline spokesman Cosley said it is believed that treating the runway in that manner would impair the pilot's ability to control the plane in a wheels-up landing.

The calmness of the crew did not dispel all uncertainty. After the landing gear problem was discovered, one passenger said, he wrote a brief note to his wife and family, who were waiting for him on the ground.

"We didn't know," he said.

As the plane prepared to land, passengers were told to fasten seat belts "tighter than you ever made it" before, Schelble said.

Interviewed afterward, several passengers remembered one thing in particular: the cabin crew urging them to "Keep your heads down! Keep your heads down! . . . Down, down, down."

Approaching Dulles from the north, the jetliner was heading for the runway at 145 miles per hour, an FAA official estimated.

The cabin was quiet. Scott Daskey prayed silently. Across from Schelble a married couple sat. Their hands were intertwined and their knuckles were white, Schelble recalled. A baby cried.

Many passengers recalled the touchdown as particularly smooth.

"I'm a frequent flyer," said passenger Lee Bowman. "I've had worse landings."

The plane skidded. One witness said sparks flew from the plane's hull. Passenger Keith Weil said that "it was like when you were sledding as a kid and hit a patch of dirt." After 10 to 20 seconds and about 1,000 feet, the skid ended.

"The chief stewardess said 'evacuate!' and everybody did," said passenger Jerry Dittberner.

Some passengers slid down emergency chutes deployed at front and rear doors. Others climbed out of the cabin and onto a wing, then slid down the wing flaps to the ground.

As did all passengers interviewed, Paul Spector of Bethesda praised the crew. "The passengers were good, too," he said.

Damage to the blue and silver airplane appeared to be minor. FAA regulations require hull strength sufficient to withstand a belly landing.

Flight 974, which originated in the Caribbean, was scheduled to leave Miami at 3:05 p.m. and arrive at National at 5:16 p.m. Passengers said it was about an hour late in leaving Miami yesterday.

On Jan. 9, FAA officials, concerned about reports that Eastern was deferring maintenance on many airplanes, said they were making an intensive safety investigation of the carrier.

"There's nothing wrong with deferred maintenance" in itself, Eastern spokesman Cosley said last night. He said any possible relevance of deferred maintenance to last night's incident could be determined only after the specific cause is found.

Authorities said they would be unable to retrieve baggage, assess damage and inspect the landing gear until the plane is raised. They said it might take until early today to lift the plane.