A Chicago-bound United Airlines 727 jetliner with 83 passengers on board returned to National Airport shortly after takeoff yesterday after one of the airplane's three engines failed.

Fire was detected in the engine after the landing and was doused with chemicals by airport firefighters, according to a Federal Aviation Administration spokesman. No injuries were reported.

Shortly after Flight 815 took off at 4:44 p.m., the pilot heard a loud noise and said he experienced vibration, according to Joe Hopkins, a United spokesman.

After shutting down the No. 3 engine, mounted near the rear of the plane on the right side of the fuselage, the pilot returned to the airport, Hopkins said. The plane landed at 4:53 p.m.

As the plane taxied to the gate, the engine emitted "smoke or sparks," and was sprayed with chemicals, the airline spokesman said.

An FAA spokesman said that the pilot "didn't know he had a fire," but that as the plane returned to the gate, the pilot of a passing aircraft "saw flame" coming from the engine.

The passengers exited by the plane's rear stairway. The airline spokesman said the flight was canceled and the passengers placed aboard other flights.

The cause of the incident was not immediately known. The FAA said it would be investigated.

Yesterday's incident came two days after an engine failure and fire caused the pilot of a United 727 bound for Tampa to abort a takeoff in Chicago. In that incident, six passengers received minor injuries while being evacuated down emergency chutes.

An FAA spokesman said last night that airline engine fires are not frequent, "but they happen."