Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Midlothian, Texas 76065
Wednesday, June 2, 2010 14:00 CDT
NTSB Narrative Summary Released at Completion of Accident
The helicopter was on a postmaintenance flight when it experienced an in-flight breakup about 8 minutes after departure, collided with the ground, and exploded into flames. Several witnesses reported seeing the tail boom, main rotor hub, main rotor blades, and other debris separate from the helicopter. One witness heard a "loud crack" sound. A postaccident examination revealed that the helicopter's swashplate A-side drive pin had failed in flight, which resulted in the helicopter's in-flight breakup and uncontrolled descent. The separated head of the drive pin remained in the interior of the swashplate. The fractured drive pin hole exhibited mechanical damage, with the markings of increased amplitude and spacing progressing outward, which suggests that the fractured drive pin oscillated and then ejected from its hole.
The fracture surface of the swashplate A-side drive pin displayed brittle cleavage-like fractures interspersed with intergranular separations and small regions of ductile dimples, consistent with hydrogen embrittlement. The B-side drive pin, on the opposite side, was found intact. Both drive pins met engineering drawing requirements for material, hardness, heat treatment and plating. However, there were no engineering standards for hydrogen content. During tests of two pins intentionally charged with hydrogen, one pin fractured under static load, and the fracture topography was consistent with the fracture topography on the failed A-side pin from the accident helicopter. Based on the fracture topography, it is likely that the swashplate A-side drive pin fractured as a result of hydrogen embrittlement. Investigators were unable to conclusively determine the source of the hydrogen. No other material discrepancies of the drive pin were found. Metallurgical examination revealed that fractures through the mast, B-side pitch link bolt and actuator attachments were consistent with overstress separations.
NTSB Probable Cause Narrative
The fracture of a swashplate drive pin as a result of hydrogen embrittlement due to an unknown source, which resulted in an in-flight breakup of the main rotor system during cruise flight.
Event Information
| Type of Event | Accident |
| Event Date | 6/2/2010 |
| Event Day of the Week | Wednesday |
| Time of Event | 1400 |
| Event Time Zone | Central Daylight Time |
| Event City | Midlothian |
| Event State | TEXAS |
| Event Country | -- |
| Zipcode of the event site | 76065 |
| Event Date Year | 2010 |
| Event Date Month | 6 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 322731N |
| Event Location Longitude | 0970220W |
| Event Location Airport | -- |
| Event Location Nearest Airport ID | -- |
| 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 | Weather Observation Facility |
| Time of the weather observation | 1353 Central Daylight Time |
| Direction of event from weather observation facility (degrees) | 338 |
| Weather Observation Facility ID | KGKY |
| Elevation of weather observation facility | 628 |
| Distance of event from weather observation facility (units?) | 11 |
| Time Zone of the weather observation | CDT |
| Lighting Conditions | Day |
| Lowest Ceiling Height | -- |
| Lowest Non-Ceiling Height | -- |
| Sky/Lowest/Cloud Conditions | Clear |
| Sky Condition for Lowest Ceiling | None |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | 33 |
| Dew Point at event time (in degress fahrenheit) | 19 |
| Wind Direction (degrees magnetic) | 200 |
| Variable Wind Indicator | Wind direction could be determined |
| Wind Speed (knots) | 8 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Gusting |
| Wind Gust (knots) | 14 |
| Altimeter Setting at event time (in. Hg) | 29.77 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | KJWY 021845Z AUTO 17012G19KT 7SM 33/20 A2977 RMK A |
| Event Highest Injury | Fatal |
| On Ground, Fatal Injuries | -- |
| On Ground, Minor Injuries | -- |
| On Ground, Serious Injuries | -- |
| Injury Total Fatal | 2 |
| Injury Total Minor | -- |
| Injury Total None | -- |
| Injury Total Serious | -- |
| Injury Total All | 2 |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 29535 |
| NTSB Notification Source | FAA Regional Operations Center |
| NTSB Notification Date | -- |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Apr 10 2012 8:36AM |
| User who most recently changed record | johb |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N515MK |
| NTSB Number | CEN10FA291 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 91: General Aviation |
| Type of Flight Plan filed | Company VFR |
| Flight plan Was Activated? | Yes |
| Damage | Substantial |
| Aircraft Fire | Ground and In-flight |
| Aircraft Explosion | Ground and In-flight |
| Aircraft Manufacturer's Full Name | BELL |
| Aircraft Model | 222 |
| Aircraft Series Identifier | U |
| Aircraft Serial Number | 47515 |
| Certified Max Gross Weight | 8250 |
| Aircraft Category | Helicopter |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | 2 |
| Cabin Crew Seats | -- |
| Passenger Seats | 3 |
| Total number of seats on the aircraft | 5 |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | AAIP |
| Date of Last Inspection | May 27 2010 12:00AM |
| Airframe hours since last inspection | 1 |
| Airframe Hours | 9925 |
| ELT Installed | Yes |
| ELT Activated | No |
| ELT Aided Location of Event Site | No |
| ELT Type | C91-A |
| Aircraft Owner Name | CareFlite |
| Aircraft Owner Street Address | 3110 S Great Southwest Pkwy |
| Aircraft Owner City | Grand Prairie |
| Aircraft Owner State | TX |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 75052-7238 |
| Operator is an individual? | No |
| Operator Name | CareFlite |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | Yes |
| Operator Street Address | 3110 S Great Southwest Pkwy |
| Operator City | Grand Prairie |
| Operator State | TX |
| Operator Country | USA |
| Operator Zip code | 75052-7238 |
| Operator Code | NXTA |
| 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 | NXTA457U |
| 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) | Other Work Use |
| Second Pilot on Board | No |
| Departure Point Same as Event | No |
| Departure Airport Code | GPM |
| Departure City | Grand Prairie |
| Departure State | TX |
| Departure Country | USA |
| Departure Time | 1352 |
| Departure Time Zone | CDT |
| Destination Same as Local Flt | dest & departure same, accident can occur anywhere |
| Destination Airport Code | GPM |
| Destination City | Grand Prairie |
| Destination State | TX |
| Destination Country | USA |
| Specific Phase of Flight | -- |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Mar 29 2012 1:15PM |
| User who most recently changed record | latt |
| 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 | -- |