Narrative:USAir Flight 224 departed Philadelphia on a scheduled flight to Boston. While climbing through 4000 feet, the aircraft yawed and rolled to the right. Simultaneously, the crew noticed the nr. 2 throttle slam and lock to the idle position. A continuous airframe buffet began. Soon thereafter, the nr. 2 engine separated from the aircraft and the buffet stopped. The engine impacted in an open field, 6 miles from the airport. After separation, the 'B' hydraulic system lost pressure and the flaps would only extend to 10 deg. The aircraft was landed safely after an emergency gear extension and differential braking was used for steering. It appeared that the aft mount cone bolt for the nr. 2 engine had failed from fatigue through the thread relief undercut radius. Fatigue cracks had initiated on diametrically opposite sides of the radius. Subsequently, the forward mount cone bolts and secondary support cable failed from overload.
PROBABLE CAUSE: "Previous damage to the aft cone (engine mounting) bolt, which resulted in mismatched surfaces between the bolt and isolation mount, loss of torque during cyclic loading of the mounting bolt, and subsequent fatigue failure of the bolt."
» Aviation Week & Space Technology 30 Jan. 1989 (p.71)
Follow-up / safety actions
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not
display the exact flight path.
Distance from Philadelphia International Airport, PA to Boston-Logan International Airport, MA as the crow flies is 447 km (279 miles).