Engine Failure and Emergency Descent
The McDonnell Douglas MD-83, operating as a scheduled passenger flight, experienced a catastrophic failure of the left engine while at 31,000 feet. The flightcrew heard a thud and observed the left engine surging. White smoke filled the cabin and cockpit, prompting the crew to don oxygen masks, declare an emergency, and initiate an emergency descent to Kansas City International Airport (MCI), Kansas City, Missouri.
Diversion to Whiteman Air Force Base
During the descent toward MCI, the crew changed their landing destination to Whiteman Air Force Base (SZL), Knob Noster, Missouri, when approximately 18 miles north of SZL. The airline did not provide approach charts for SZL to its flight crews. The flight crew requested the ILS frequency for runway 19 from air traffic control (ATC) and received an incorrect frequency. They also requested and were given the inbound course for ILS 19 but never obtained the correct ILS frequency for the remainder of the flight, relying instead on a radar approach to SZL.
Descent Below Minimum Vectoring Altitude
During the radar approach, ATC instructed the flightcrew to maintain a minimum vectoring altitude of 2,500 feet mean sea level. The crew descended below this altitude to 1,800 feet msl in order to descend below a cloud layer that was at 1,400 feet above ground level.
Examination of the Engine
Metallurgical examination revealed a fatigue fracture of one fan blade. Examination of the left engine showed that the fan exit case had a 360-degree fracture. Several service bulletins (SBs) applicable to the fan exit case introduced a newer steel engine case to replace the older aluminum case and recommended installation of stops to restrict axial separation of the case in the event of fracturing. The SBs noted that there had been five instances of full 360-degree fan exit case fracture, all due to fan blade fracture, and that when the case fractures, the front of the engine with the cowl shifts forward. The incident engine had an aluminum fan exit case and did not have stops installed.