Date:	Saturday 5 December 1987
Time:	09:55
Type:	Boeing 737-2B7
Owner/operator:	USAir
Registration:	N319AU
MSN:	22887/976
Year of manufacture:	1983
Total airframe hrs:	12845 hours
Engine model:	Pratt & Whitney JT8D-15A
Fatalities:	Fatalities: 0 / Occupants: 67
Aircraft damage:	Substantial, repaired
Category:	Accident
Location:	Deptford, NJ -   United States of America
Phase:	En route
Nature:	Passenger - Scheduled
Departure airport:	Philadelphia International Airport, PA (PHL/KPHL)
Destination airport:	Boston-Logan International Airport, MA (BOS/KBOS)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

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 no. 2 throttle slam and lock to the idle position. A continuous airframe buffet began. Soon thereafter, the no. 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 no. 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)
NTSB

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