Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Columbus, Ohio 43224
Saturday, August 19, 2006 16:39 EDT
NTSB Narrative Summary Released at Completion of Accident
The public-use helicopter was conducting a routine patrol flight when it experienced an uncontained engine failure. The pilot immediately performed an autorotation and run-on landing to an open parking lot area without further incident. The helicopter was damaged with several punctures with outward deformation consistent with projectile damage originating from an uncontained engine failure. Inspection of the engine revealed that portions of the 1st-stage gas producer wheel had departed the engine. The gas producer turbine tie bolt (part number 23068265, serial number NM81907) was identified as the primary failed component. The tie bolt fractured immediately adjacent to the torque nut. Further examination revealed fracture features consistent with fatigue, initiating at the thread root radius. The microstructure, chemistry, and hardness of the turbine tie bolt met engineering drawing specifications. No material anomalies were detected at the fracture surface. Damage to the fracture surface precluded the determination if the failure was associated with low or high cycle fatigue. The tie bolt had completed 3,427 cycles, about 38 percent, of its published life limit of 9,000 cycles.
The failure was the first documented since the tie bolt was redesigned during the late 1990s. The redesigned tie bolt incorporated a thicker and stiffer cross-section that had a higher resonant frequency. The manufacturer reviewed the testing and analysis that was preformed when the tie bolt was redesigned. Their review confirmed that the current life limit of 9,000 cycles was within design guidelines. Additionally, the stress modeling and analysis performed during the component redesign was reviewed and no discrepancies were noted. The manufacturer also reviewed the reengineered tie bolt service history and several tie bolts with between 5,000 and 9,000 cycles were taken out of service for examination. Component examinations and database reviews failed to show any similar failures within the fleet.
The tie bolt installation required that the bolt length be measured in order to determine the exact stretch of the bolt after the nut was torqued to specification. The original stretch requirement was used with the redesigned tie bolt to eliminate confusion during assembly. A subsequent service bulletin and FAA airworthiness directive mandated that the older design be removed from service, but the installation stretch requirement was not modified. To mitigate future tie bolt fractures, Rolls-Royce reduced the stretch requirement on the tie bolt during the assembly process. As a result, the mean stress on the tie bolt was reduced. The reduced stretch is also expected to increase both high and low cycle fatigue margins in the part. The assembly instructions were updated with the new stretch callout during the first quarter of 2008.
NTSB Probable Cause Narrative
The uncontained engine failure due to the fatigue failure of the gas producer turbine tie bolt.
Event Information
| Type of Event | Accident |
| Event Date | 8/19/2006 |
| Event Day of the Week | Saturday |
| Time of Event | 1639 |
| Event Time Zone | Eastern Daylight Time |
| Event City | Columbus |
| Event State | OHIO |
| Event Country | -- |
| Zipcode of the event site | 43224 |
| Event Date Year | 2006 |
| Event Date Month | 8 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 400408N |
| Event Location Longitude | 0825806W |
| 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 | 1653 Eastern Daylight Time |
| Direction of event from weather observation facility (degrees) | 292 |
| Weather Observation Facility ID | OSU |
| Elevation of weather observation facility | 905 |
| Distance of event from weather observation facility (units?) | 5 |
| Time Zone of the weather observation | EDT |
| Lighting Conditions | Day |
| Lowest Ceiling Height | 4700 |
| Lowest Non-Ceiling Height | 3600 |
| Sky/Lowest/Cloud Conditions | Scattered |
| Sky Condition for Lowest Ceiling | Broken |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | 28 |
| Dew Point at event time (in degress fahrenheit) | 21 |
| Wind Direction (degrees magnetic) | 310 |
| Variable Wind Indicator | Wind direction could be determined |
| Wind Speed (knots) | 11 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | 29.91 |
| 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 | 2 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 24574 |
| NTSB Notification Source | FAA |
| NTSB Notification Date | Aug 19 2006 12:00AM |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Nov 12 2008 1:48PM |
| User who most recently changed record | lema |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | Federal Aviation Adminstration - Columbus FSDO |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N554CP |
| NTSB Number | CHI06GA241 |
| 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 | None |
| Aircraft Manufacturer's Full Name | McDonnell Douglas Helicopters |
| Aircraft Model | 369E |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 0542E |
| Certified Max Gross Weight | 3000 |
| Aircraft Category | Helicopter |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | -- |
| Cabin Crew Seats | -- |
| Passenger Seats | -- |
| Total number of seats on the aircraft | 4 |
| Number of Engines | 1 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | 100 Hour |
| Date of Last Inspection | Aug 1 2006 12:00AM |
| Airframe hours since last inspection | 41.4 |
| Airframe Hours | 6639.7 |
| ELT Installed | No |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | City of Columbus Police Department |
| Aircraft Owner Street Address | 120 Marconi Boulevard |
| Aircraft Owner City | Columbus |
| Aircraft Owner State | OH |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 43215 |
| Operator is an individual? | No |
| Operator Name | City of Columbus Police Department |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | Yes |
| Operator Street Address | 120 Marconi Boulevard |
| Operator City | Columbus |
| Operator State | OH |
| Operator Country | USA |
| Operator Zip code | 43215 |
| Operator Code | -- |
| Owner has at least one certificate | None |
| Other Operator of large aircraft? | No |
| 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 | No |
| Departure Point Same as Event | Yes |
| Departure Airport Code | OH52 |
| Departure City | Columbus |
| Departure State | OH |
| Departure Country | USA |
| Departure Time | 1600 |
| Departure Time Zone | EDT |
| Destination Same as Local Flt | dest & departure same, accident can occur anywhere |
| Destination Airport Code | OH52 |
| Destination City | Columbus |
| Destination State | OH |
| Destination Country | USA |
| Specific Phase of Flight | Emergency descent/landing |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Nov 12 2008 1:32PM |
| User who most recently changed record | lema |
| 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 | -- |