Individually Owned: 150,657
Corporate Owned: 137,281
Memphis International Airport
Aircraft Accident/Incident Report
Memphis, Tennessee
Tuesady, April 4, 2006 16:45 CST
NTSB Narrative Summary Released at Completion of Accident
As the airplane climbed through about FL260, the No. 3 engine low pressure turbine (LPT) stage 1 disk burst when a fatigue crack that initiated in the forward seal tooth serration arm ruptured. Fragments from the burst disk partially severed the LPT case and struck the fuselage in multiple locations. The airframe vibration increased to a severe level until the LPT rotor separated from the engine, about 14 minutes 30 seconds after the uncontained LPT stage 1 disk burst, when the high pressure turbine aft shaft and the fan mid shaft failed due to contact damage and torsional loading. Metallurgical examination of the portion of the LPT stage 1 disk that was imbedded in the right wing found that the disk burst due to a mixture of high cycle and low cycle fatigue. The fracture was located in the vicinity of the forward seal tooth serration, although the exact fracture origin could not be identified because the entire seal tooth and part of the seal tooth arm were missing at the fracture location. Examination of the forward seal tooth serration revealed the presence of two previous weld repairs that extended into the forward arm. Review of the manufacturing records revealed that the disk had been dabber weld repaired twice to correct anomalies and non-conformances found during the original manufacturing process. The dabber weld procedures did not authorize welding in the forward seal tooth serration, therefore, the weld repair performed on the failed LPT stage 1 disk did not conform to the approved repair instructions. Based on testing and analysis of sample, post-manufacture dabber weld repaired disks, the suspect population of CF6 disks was confined to those that had been repaired at original manufacture. Records indicated that, in addition to the accident disk, four other disks had been dabber weld repaired at original manufacture to correct forward seal tooth serration anomalies and non-conformances. None of these disks are any longer in service. Based on the estimated crack propagation rate, it is likely that either no crack existed at the last inspection of the disk or the crack size was below the reasonably detectable threshold. After the disk burst, the flight crew completed all required checklists; however, the crew could not manually shutdown the affected engine because the burst disk fragments had severed the fire shutoff valve cable, the power off cable, and the emergency shutoff cable. The engine eventually shutdown on its own due to airflow disruptions within the engine. The flight crew’s procedural coordination and use of available resources, consistent with cockpit resource management best practices, helped to ensure the safe landing of the airplane.
NTSB Probable Cause Narrative
The rupture of a fatigue crack in the forward air seal tooth serration of the No. 3 engine low pressure turbine stage 1 disk that initiated due to an improper weld repair performed during original manufacture. The improper weld repair changed the material properties of the disk near the weld feature, resulting in an accelerated crack propagation rate that allowed the crack to grow to rupture before the next inspection interval. Contributing to the severity of the accident was the inability of the flight crew to shutdown the engine as a result of the damage caused by a liberated piece of the low pressure turbine stage 1 disk when it punctured the right wing.
Event Information
| Type of Event | Accident |
| Event Date | 4/4/2006 |
| Event Day of the Week | Tuesday |
| Time of Event | 1645 |
| Event Time Zone | Central Standard Time |
| Event City | Memphis |
| Event State | TENNESSEE |
| Event Country | -- |
| Zipcode of the event site | -- |
| Event Date Year | 2006 |
| Event Date Month | 4 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | -- |
| Event Location Longitude | -- |
| Event Location Airport | Memphis International Airport |
| Event Location Nearest Airport ID | KMEM |
| Indicates whether the acc/inc occurred off or on an airport | Off Airport/Airstrip |
| Distance from airport in statute miles | -- |
| Degrees magnetic from airport | -- |
| Airport Elevation | -- |
| Weather Briefing Completeness | -- |
| Investigator's weather source | Unknown |
| Time of the weather observation | |
| Direction of event from weather observation facility (degrees) | -- |
| Weather Observation Facility ID | -- |
| Elevation of weather observation facility | -- |
| Distance of event from weather observation facility (units?) | -- |
| Time Zone of the weather observation | -- |
| Lighting Conditions | Day |
| Lowest Ceiling Height | -- |
| Lowest Non-Ceiling Height | -- |
| Sky/Lowest/Cloud Conditions | Clear |
| Sky Condition for Lowest Ceiling | -- |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | -- |
| Air Temperature at event time (in degrees celsius) | -- |
| Dew Point at event time (in degress fahrenheit) | -- |
| Wind Direction (degrees magnetic) | -- |
| Variable Wind Indicator | -- |
| Wind Speed (knots) | -- |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | -- |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | -- |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | -- |
| Event Highest Injury | None |
| On Ground, Fatal Injuries | -- |
| On Ground, Minor Injuries | -- |
| On Ground, Serious Injuries | -- |
| Injury Total Fatal | -- |
| Injury Total Minor | -- |
| Injury Total None | 3 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | -- |
| NTSB Notification Source | FAA |
| NTSB Notification Date | Apr 4 2006 12:00AM |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Apr 27 2011 4:08PM |
| User who most recently changed record | schd |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N386FE |
| NTSB Number | DCA06FA033 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 121: Air Carrier |
| Type of Flight Plan filed | IFR |
| Flight plan Was Activated? | Yes |
| Damage | Substantial |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | MCDONNELL DOUGLAS |
| Aircraft Model | DC10 |
| Aircraft Series Identifier | 10F |
| Aircraft Serial Number | 46620 |
| Certified Max Gross Weight | -- |
| Aircraft Category | Airplane |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | -- |
| Cabin Crew Seats | -- |
| Passenger Seats | -- |
| Total number of seats on the aircraft | -- |
| Number of Engines | 3 |
| Fixed gear or retractable gear | Retractable |
| Aircraft, Type of Last Inspection | Continuous Airworthiness |
| Date of Last Inspection | Mar 14 2006 12:00AM |
| Airframe hours since last inspection | -- |
| Airframe Hours | 59979 |
| ELT Installed | No |
| ELT Activated | No |
| ELT Aided Location of Event Site | No |
| ELT Type | -- |
| Aircraft Owner Name | FedEx Express |
| Aircraft Owner Street Address | -- |
| Aircraft Owner City | Memphis |
| Aircraft Owner State | TN |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 38125 |
| Operator is an individual? | No |
| Operator Name | FEDEX EXPRESS |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | No |
| Operator Street Address | -- |
| Operator City | Memphis |
| Operator State | TN |
| Operator Country | USA |
| Operator Zip code | 38125 |
| Operator Code | FDEA |
| Owner has at least one certificate | Yes - certificate holder |
| Other Operator of large aircraft? | No |
| Certified for Part 133 or 137 Operation | -- |
| Operator Certificate Number | FDEA140A |
| Indicates whether an air carrier operation was scheduled or not | Non-scheduled |
| Indicates Domestic or International Flight | Domestic |
| Operator carrying Pax/Cargo/Mail | Cargo |
| Type of Flying (Per_Bus / Primary) | -- |
| Second Pilot on Board | Yes |
| Departure Point Same as Event | No |
| Departure Airport Code | MEM |
| Departure City | MEMPHIS |
| Departure State | TN |
| Departure Country | USA |
| Departure Time | -- |
| Departure Time Zone | -- |
| Destination Same as Local Flt | -- |
| Destination Airport Code | SEA |
| Destination City | SEATTLE |
| Destination State | WA |
| Destination Country | USA |
| Specific Phase of Flight | Climb - to cruise |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Jan 13 2011 11:36AM |
| User who most recently changed record | sedj |
| Since inspection or accident | Time of Accident |
| Event Location Runway Number and Location | N/A |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |