Individually Owned: 150,657
Corporate Owned: 137,281
Minneapolis - St. Paul Interna Airport
Aircraft Accident/Incident Report
Minneapolis, Minnesota 55450
Monday, June 14, 2010 19:45 CST
NTSB Narrative Summary Released at Completion of Accident
On June 4, 2010, a Delta Air Lines Boeing DC9-51, N671MC, had a case-uncontained, nacelle-contained 1st stage fan blade separation in the No. 1 (left) engine, A Pratt & Whitney (P&W) JT8D-17 turbofan, during a ground run for maintenance at the Minneapolis-St. Paul International Airport. Delta Air Lines maintenance personnel were conducting a trim run on the No. 2 (right) engine. After they had checked the No. 2 engine's power, they advanced the No. 1 engine's throttle to check its power when at about 1.7 EPR [engine pressure ratio], they heard a boom and felt a vibration. They shut down the engines and upon exiting the airplane, noticed the No. 1 engine's fan blades were damaged. One 1st stage fan blade was completely missing from the front compressor front hub's blade slot. Several pieces of the missing 1st stage fan blade were recovered from the engine's fan duct. The metallurgical examination of the fan blade pieces revealed a fatigue fracture on the blade's suction-side blade root bedding flank. In addition, there were fatigue fractures on the fractured fan blade's suction-side midspan shroud from the upper and lower surfaces of the shroud. A dimensional inspection of the fractured fan blade's leading edge revealed the radius was 0.035 inch in comparison to the required 0.009 inch. According to P&W, the leading edges of the 1st stage fan blades erode during normal operation. However, P&W also advised that the amount of wear observed on the separated blade would be associated with approximately 11,000 flight cycles rather than the engine's 2,685 flight cycles since the last overhaul, during which the 1st stage fan blades were overhauled. According to P&W, a worn and blunt leading edge can cause a flutter mode that can lead to increased stresses in the fan blade and cause fatigue fractures in the root and airfoil. The erosion of the fan blade leading edge was likely the result of faulty restoration of the leading edge profile or failure to restore the leading edge in a timely manner.
NTSB Probable Cause Narrative
The failure of the facility that overhauled the 1st stage fan blade to properly restore the leading edge, which caused a flutter mode resulting in a fatigue crack and fracture of the fan blade.
Event Information
| Type of Event | Incident |
| Event Date | 6/14/2010 |
| Event Day of the Week | Monday |
| Time of Event | 1945 |
| Event Time Zone | Central Standard Time |
| Event City | Minneapolis |
| Event State | MINNESOTA |
| Event Country | -- |
| Zipcode of the event site | 55450 |
| Event Date Year | 2010 |
| Event Date Month | 6 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 440514N |
| Event Location Longitude | 0931354W |
| Event Location Airport | Minneapolis - St. Paul Interna |
| Event Location Nearest Airport ID | KMSP |
| Indicates whether the acc/inc occurred off or on an airport | On Airport |
| Distance from airport in statute miles | 0 |
| Degrees magnetic from airport | -- |
| Airport Elevation | 842 |
| 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 | -- |
| 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 | -- |
| On Ground, Fatal Injuries | -- |
| On Ground, Minor Injuries | -- |
| On Ground, Serious Injuries | -- |
| Injury Total Fatal | -- |
| Injury Total Minor | -- |
| Injury Total None | -- |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 31837 |
| NTSB Notification Source | Delta Flight Safety Office |
| NTSB Notification Date | -- |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Sep 17 2013 1:48PM |
| User who most recently changed record | hooj |
| Basic weather conditions | Unknown |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N671MC |
| NTSB Number | ENG10IA037 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Unknown |
| Type of Flight Plan filed | None |
| Flight plan Was Activated? | -- |
| Damage | Minor |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | DOUGLAS |
| Aircraft Model | DC9 |
| Aircraft Series Identifier | 51 |
| Aircraft Serial Number | 47660 |
| Certified Max Gross Weight | 122000 |
| Aircraft Category | Airplane |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | 2 |
| Cabin Crew Seats | 4 |
| Passenger Seats | 125 |
| Total number of seats on the aircraft | 131 |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | -- |
| Date of Last Inspection | -- |
| Airframe hours since last inspection | -- |
| Airframe Hours | 69397 |
| ELT Installed | Yes |
| ELT Activated | No |
| ELT Aided Location of Event Site | No |
| ELT Type | Unknown |
| Aircraft Owner Name | Delta Air Lines |
| Aircraft Owner Street Address | -- |
| Aircraft Owner City | Atlanta |
| Aircraft Owner State | GA |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | -- |
| Operator is an individual? | No |
| Operator Name | Delta Air Lines |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | Yes |
| Operator Street Address | -- |
| Operator City | Atlanta |
| Operator State | GA |
| Operator Country | USA |
| Operator Zip code | -- |
| Operator Code | D02M |
| Owner has at least one certificate | Yes - certificate holder |
| Other Operator of large aircraft? | -- |
| Certified for Part 133 or 137 Operation | -- |
| Operator Certificate Number | -- |
| Indicates whether an air carrier operation was scheduled or not | -- |
| Indicates Domestic or International Flight | -- |
| Operator carrying Pax/Cargo/Mail | -- |
| Type of Flying (Per_Bus / Primary) | -- |
| Second Pilot on Board | -- |
| Departure Point Same as Event | Yes |
| Departure Airport Code | KMSP |
| Departure City | Minneapolis |
| Departure State | MN |
| Departure Country | USA |
| Departure Time | -- |
| Departure Time Zone | CST |
| Destination Same as Local Flt | crash at destination city |
| Destination Airport Code | KMSP |
| Destination City | Minneapolis |
| Destination State | MN |
| Destination Country | USA |
| Specific Phase of Flight | -- |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Sep 17 2013 1:40PM |
| User who most recently changed record | hooj |
| Since inspection or accident | -- |
| Event Location Runway Number and Location | N/A |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |