A United Airlines DC10 on its way from Baltimore to Chicago with 175 passengers and crew aboard was forced to turn back and make an emergency landing at Baltimore-Washington International Airport yesterday morning after one of its three engines failed.

Airline officials and federal investigators said the plane was never in danger of crashing. They said the incident was totally unrelated to the engine support problems that led the Federal Aviation Administration to ground the controversial aircraft for 37 days over the past two months.

Still, the incident upset many passengers and crew who said they heard a loud bang or explosion about 10 minutes after takeoff, then sat helplessly for a short time as the plane lost speed and altitude.

"The plane started vibrating and made a weird grinding sound like it was working very hard," said Dr. Janet Moghbeli of Baltimore, interviewed yesterday afternoon at Dulles International Airport, where 30 passengers were bused to catch a later flight.

"Then the pilot came on and said: "Our right engine has just gone out and we are flying on two engines.""

Dennis McFadden, a minister from Chino, Calif., said he was "scared to death. I looked out the windows and saw the clouds above us instead of under us."

A stewardess said the plane lurched to the right after the bang and didn't level off for several minutes. "I walked up and down the aisle smiling," she recalled. "I felt like an actress."

Pilot J. G. Wise turned the plane around and landed without incident at BWI at about 11:45 a.m., some 20 minutes after takeoff. Airport spokesman Paul Moore said three fire trucks with nine crew members awaited the plane at the runway but were not needed.

As of last night, officials were not certain why the engine failed. Frank Taylor, director of the National Transportation Safety Board's bureau of accident investigation, said he saw evidence of broken fan blades and overheating in the engine's turbine section. Taylor said metal from the turbine blew out the engine's tailpipe and punched two small holes in the rear flaps of the plane's right wing.

"We won't know why it happened until they open up the engine," Taylor said.

Both Taylor and United Airlines spokesman Jim Linse said the engine failure did not endanger the plane. Linse estimated such failures occur as often as a dozen times a year in all jet aircraft and said they are not confined to DC10s.

"The airplane is perfectly capable of landing on two engines or even one," said Linse. "They're not going to make "Airport 1980" out of this incident."

Linse said the "bang" heard by passengers and crew was caused by blade failure, and was not an explosion. Both he and Taylor said there was no evidence that the engine caught fire.

Of the 164 passengers, 103 continued to Chicago on a special 3 p.m. flight from BWI, 30 were bused to Dulles for a later flight to Los Angeles, where the plane was scheduled to go after Chicago, and 20 others were rerouted to other destinations, according to Linse. He said 11 persons made other travel plans.

According to one passenger at Dulles, several frightened passengers canceled their flights after the incident.

"I wouldn't fly a DC10 again," said a physicist who refused to give his name. "It's a disconcerting plane to fly."

The aircraft, designed and built by McDonnell Douglas Aircraft Co. of St. Louis, was grounded by the FAA after a May 25 crash in Chicago killed 273 in what was the nation's worst aviation disaster. It was allowed back in service nine days ago by FAA Administrator Langhorne M. Bond, who ordered intensive inspections of the jumbo jet's engine support pylon, which investigators said caused the May tragedy.

Investigator Taylor said his agency now requires that every DC10 experiencing in-flight engine failure must undergo additional inspections of its pylons before being allowed back in service. Taylor said the plane involved in yesterday's incident would be subject to such an inspection.