Hidden Danger - United Airlines Flight 585

United Airlines Flight 585 was a scheduled passenger flight from the now-decommissioned Stapleton International Airport in Denver to Colorado Springs, Colorado.

On March 3, 1991, the Boeing 737-291 operating the flight, registered N999UA[1] (previously N7356F with Frontier Airlines), carrying 20 passengers plus a flight crew of 5, crashed while on final approach to runway 35 at Colorado Springs Municipal Airport. There were no survivors

USAir Flight 427 was a scheduled flight from Chicago's O'Hare International Airport to Pittsburgh International Airport, with a final destination of West Palm Beach, Florida. The flight crashed on Thursday, September 8, 1994, killing all 132 on board. The Boeing 737-3B7 flying the route, registered N513AU, and previously registered as N382AU, was approaching runway 28R of Pittsburgh International Airport, located in Findlay Township, Allegheny County, Pennsylvania, which was at the time the largest hub for the airline.

Eastwind Airlines Flight 517 was a scheduled domestic passenger flight from Trenton-Mercer Airport in Trenton, New Jersey to Richmond International Airport in Richmond, Virginia. On June 9, 1996 the crew of the Boeing 737-200 operating the flight lost rudder control but was able to land successfully. Only one flight attendant suffered minor injuries. No damage occurred to the aircraft as a result of the incident.

The flight crew of the Boeing 737-200, Captain Brian Bishop and First Officer Spencer Griffin, experienced loss of rudder control while on approach to Richmond. The airplane's airspeed was about 250 knots (460 km/h; 290 mph) and it was flying at an altitude of about 4,000 feet (1,200 m) MSL at the time of the incident. The crew experienced unexpected movement of the rudder, causing the airplane to roll to the right. They applied opposite aileron input to keep the plane from rolling over and thirty seconds later the plane righted itself back to leveled flight. As the crew performed the emergency checklist, the plane again rolled over to the right. After another thirty seconds, the plane snapped back to leveled flight. The crew declared an emergency and landed safely in Richmond. The resulting investigation of this incident would help to establish the cause of two earlier accidents involving 737's which had occurred several years prior, United Airlines Flight 585 (March 3, 1991) and USAir Flight 427 (September 8, 1994).

It was later reported that the airplane previously had problems with uncommanded rudder deflections. These reports consisted of "rudder bumps" during departure and a lack of proper trim.[1]