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Safety Recommendation Details

Safety Recommendation A-89-096
Details
Synopsis: THE NATIONAL TRANSPORTATION SAFETY BOARD'S INVESTIGATION OF THE UNITED AIRLINES DC-10 ACCIDENT AT SIOUX CITY, IOWA, ON JULY 19, 1989, IS CONTINUING. THE INVESTIGATION THUS FAR INDICATES THAT MOST OF THE FAN ROTOR ASSEMBLY SEPARATED FROM THE NO. 2 ENGINE IN FLIGHT. THE SEPARATION, FRAGMENTATION, AND FORCEFUL DISCHARGE OF FAN ROTOR PARTS SEVERED OR LOOSENED HYDRAULIC LINES ASSOCIATED WITH ALL THREE HYDRAULICS SYSTEMS, WHICH RESULTED IN THE LOSS OF ALL HYDAULIC SERVICES INCLUDING THOSE TO THE FLIGHT CONTROLS. FOLLOWING THE LOSS OF THE HYDRAULIC SERVICES, THE AIRPLANE COULD BE CONTROLLED ONLY BY THE FLIGHTCREW'S USE OF DIFFERENTIAL THRUST FROM THE NOS. 1 AND 3 ENGINES. THE AIRPLANE CRASHED DURING AN ATTEMPTED EMERGENCY LANDING AT SIOUX CITY. OF THE 296 PERSONS ON BOARD, 111 DIED FROM INJURIES RECEIVED IN THE CRASH, AND 185 PERSONS SURVIVED.
Recommendation: TO THE FEDERAL AVIATION ADMINISTRATION: Following completion of the directed safety investigation of the general electric cf6-6 turbine engine discussed in A-89-95, issue an airworthiness directive to require appropriate inspections of the fan disks and the fan forward shaft at appropriate cyclic intervals. (Superseded by A-90-089) (Urgent)
Original recommendation transmittal letter: PDF
Overall Status: Closed - Superseded
Mode: Aviation
Location: SIOUX CITY, IA, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA89MA063
Accident Reports: United Airlines Flight 232 McDonnell Douglas DC-10-10‚Äč
Report #: AAR-90-06
Accident Date: 7/19/1989
Issue Date: 8/17/1989
Date Closed: 6/18/1990
Addressee(s) and Addressee Status: FAA (Closed - Superseded)
Keyword(s):

Safety Recommendation History
From: NTSB
To: FAA
Date: 6/18/1990
Response: Per Green Sheet A-90-88 through -91: On August 17, 1989, the Safety Board issued Recommendations A-89-95, A-89-96, and A-89-97. These recommendations requested a directed safety study of the CF6-6 engine, issuance of an Airworthiness Directive to require inspections identified by the directed safety study, and an evaluation of the need for a directed safety study of all GEAE CF6 series engines. The Safety Board believes that Recommendations A-90-88, A-90-89, and A-90-90 (the first three recommendations in this letter) encompass these earlier recommendations, and the Safety Board is therefore classifying Recommendations A-89-95, A-89-96, and A-89-97 as "Closed--Superseded."

From: FAA
To: NTSB
Date: 4/6/1990
Response: The FAA agrees with this recommendation and has issued an AD to require an on-wing contact ultrasonic inspection to be followed within 500 cycles by a full immersion ultrasonic inspection of affected fan disk populations. To date, listed below are categories of fan disks which have completed inspection per the compliance section of the AD. Category 1 Category 2 Category 3 On-wing ultrasonic N/A 100% 100% inspection Immersion Ultrasonic 100% 40% 43% Inspection The FAA has determined that the cause of the Sioux City accident was the result of Type 1 hard alpha metallurgical imperfections. This condition causes a degradation in low- and high-cycle fatigue material properties, thereby adversely affecting the service life of the disk. A review of manufacturing process records has identified three populations of material heat lots having varying susceptibility of Type 1 imperfections. The fan forward shaft in no way contributed to the resultant fan disk failure at Sioux City. This problem is being addressed as a separate FAA airworthiness action.

From: NTSB
To: FAA
Date: 12/8/1989
Response: As you are aware, the Safety Board has just completed a 4-day hearing into the circumstances surrounding this accident, and the investigation is ongoing. For the present, therefore, we acknowledge the FAA's and GE's ongoing engineering evaluation and classify these safety recommendations as "Open--Acceptable Action."

From: FAA
To: NTSB
Date: 9/5/1989
Response: UPON COMPLETION OF THE ENGINEERING INVESTIGATION AND DEVELOPMENT OF A FIELD INSPECTION PROGRAM, AIRWORTHINESS ACTION WILL BE IMPLEMENTED TO ENSURE THE APPROPRIATE LEVEL OF SAFETY TO THE FAN DISK AND, AS NECESSARY, TO THE FAN FORWARD SHAFT.