Metal fatigue led to engine blast

The engine that exploded aboard a Southwest Airlines flight Tuesday, killing a passenger, suffered from metal fatigue which caused it to lose a titanium fan blade, investigators have found.

National Transportation Safety Board chairman Robert Sumwalt said late Tuesday that the point where the blade broke free from the rest of the Boeing 737’s left engine had accumulated small cracks from repeated physical stress.

The CFM56-7B engine (right), manufactured by CFM International, is one of the most popular engines in passenger aviation, powering more than 6,700 aircraft worldwide, including many late-model 737s.

Southwest has announced a 30-day review of all planes in its fleet that use the engine model.

At another press briefing yesterday, Sumwalt provided greater insight into the chaos experienced by Flight 1380’s 144 passengers and five crew members after the engine explosion blew out a window and depressurized the cabin at 32,000 feet.

The 737 spiraled into an uncon- trolled, 41-degree roll to the left. An altitude-warning horn blared as the plane plunged below 14,000 feet, Sumwalt said.

Pilot Tammie Jo Shults struggled to level the craft, making an emergency landing at Philadelphia International Airport about 22 minutes after the explosion.

All the while, debris rained from the plane’s mangled engine in eastern Pennsylvania.

Part of the jet was found as far as 65 miles from the airport.