CHI06GA174 · Bell UH-1H
Bell UH-1H · Accident: airframe, component or system failure en route
From Chicago Fire Department Air Sea Rescue Heliport (LL35) to Chicago Fire Department Air Sea Rescue Heliport (LL35)
Event
- NTSB case
- CHI06GA174
- 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
Bell UH-1H
- Aircraft type
- Bell UH-1
- 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
- N681FD
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Chicago Fire Department Air Sea Rescue Heliport (LL35), Chicago, ILTo Chicago Fire Department Air Sea Rescue Heliport (LL35), Chicago, IL
- 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
- 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
- Airframe, component or system 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
- Company maintenance personnel › Maintenance, inspection, inadequate
- Miscellaneous rotorcraft › Separation
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
The public-use helicopter was responding to an emergency when it had a vibration and yawed to the right during cruise flight. It subsequently had a loss of tail rotor thrust. The pilot reduced engine power and made an autorotation to a park along the lakeshore. During landing flare, the helicopter yawed left as the pilot increased collective prior to touchdown. He stated that the touchdown "seemed smooth" and was made on the aft-portion of the skids, but as the helicopter slowed the left yaw tendency increased. The helicopter rolled over and came to rest inverted at the completion of the run-on landing. Examination of the helicopter revealed that the number-one tail rotor driveshaft hanger assembly had separated, resulting in a discontinuity of the tail rotor driveshaft. The machine bolt that held the assembly together was not installed with the required cotter pin. Further examination of the hanger assembly revealed that the splined areas did not contain grease. The remaining tail rotor driveshaft hanger bearings were properly greased and assembled. The mechanic who worked on the helicopter reported that due to other workload items, the previous tail rotor driveshaft inspection was interrupted several times before he was able to complete all of the required tasks. To avoid inter-mixing the driveshaft components, he temporarily reassembled the hanger assemblies before working on other projects. His intention was to disassemble each hanger bearing when he had the opportunity to complete the inspection. The mechanic stated that he must have forgotten to disassemble, inspect, and grease the number one hanger assembly. At the time of the accident, the number one hanger assembly had accumulated about 33 hours since the inspection.
Probable cause
The in-flight separation of a tail rotor driveshaft hanger bearing due to inadequate maintenance performed by maintenance personnel. Contributing to the accident was the inability to maintain directional control due to the lack of tail rotor thrust.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI06GA174
- Event ID
- 20060711X00918
- Case number
- CHI06GA174
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- 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, coordinates. 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: f82544336faf05e51722332c5ca2e7cafdbdd4b315ee2007830fc3a7ee5fad79; retrieved 2026-09-18T21:14:58.648Z.