CHI06GA241 · McDonnell Douglas Helicopters 369E
City of Columbus Police Department McDonnell Douglas Helicopters 369E · Accident: total loss of engine power (mechanical failure) en route
From Columbus Heliport (OH52) to Columbus Heliport (OH52)
Narrative check · The NTSB narrative appears to contradict this record's flight rules. Values are shown as recorded, not corrected; compare with the narrative.
Event
- NTSB case
- CHI06GA241
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Government
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
McDonnell Douglas Helicopters 369E
- Aircraft type
- McDonnell Douglas 369
- Category
- Helicopter
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N554CP
- Onboard fatalities
- Unknown
- Route
- From Columbus Heliport (OH52), Columbus, OHTo Columbus Heliport (OH52), Columbus, OH
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Public Aircraft Narrative disagrees
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- En route · cruise
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Total loss of engine power (mechanical failure)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Miscellaneous, engine uncontained failure
- Miscellaneous, engine › Fatigue
- Turbine assembly › Failure
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
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.
Probable cause
The uncontained engine failure due to the fatigue failure of the gas producer turbine tie bolt.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI06GA241
- Event ID
- 20060828X01241
- Case number
- CHI06GA241
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (5)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: b05900c57695a99ec6809a9bdc65a3aa81c68cfe3218344efd0923701d9ce722; retrieved 2026-09-22T04:33:09.340Z.
- Corrected after a review of the NTSB narrative, which states these values explicitly: operation. The narrative states "The public-use helicopter was conducting a routine patrol flight"; the operator was the City of Columbus Police Department, so the flight was a public aircraft operation, not Part 91 general aviation.