SEA98LA124 · Hiller UH-12E
Hiller UH-12E · Accident: rotor failure/malfunction during initial climb
Event
- NTSB case
- SEA98LA124
- 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
- 0
- 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
- General aviation
- 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
Hiller UH-12E
- Aircraft type
- Hiller UH-12
- 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
- N5360V
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From not recordedTo not recorded
- 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
- Part 137: Agricultural
- 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
- Initial climb
- 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
- Rotor failure/malfunction
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Destroyed
Cause areas
- Other maintenance personnel › Maintenance, compliance with ad, not followed
- Rotor system, main rotor blade spar › Fatigue
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot reported that he had just taken off to the south. About 30 seconds into the flight, a control paddle departed the helicopter, and control was lost. The helicopter crashed in a cornfield and rolled inverted, after which the pilot exited. Post-crash examination revealed that a flight control rotor blade departed the helicopter. The spar from the blade separated from a fatigue crack, which originated near one of the outboard retention bolt holes and propagated nearly all of the way around the spar on both sides. The NTSB materials laboratory determined that the fatigue cracking initiated from corrosion pitting. FAA Airworthiness Directives in effect at the time of the accident required inspection of the spar tube, cuff, and bolt holes every 100 hours to detect corrosion and cracking in accordance with a Hiller service bulletin. This service bulletin required a visual inspection for corrosion of the inside surface of the cuff and the inner and outer surfaces of the spar tube. This visual inspection was to be followed by a dye-penetrant inspection of the spar and the cuff to detect any cracks. Although logbook entries (of less than four months and 70 hours time in service before the accident) cited compliance with the relevant AD and service bulletin, no evidence was found of dye penetrant residue, zinc chromate primer, or the required sealant material during NTSB materials laboratory testing.
Probable cause
Fatigue of the control rotor blade spar and failure of the maintenance inspector to follow the procedures set forth in the airworthiness directive.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA98LA124
- Event ID
- 20001211X10706
- Case number
- SEA98LA124
- 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. 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: 0839acfc41053f1205a74b266ef29105668c6c6ee4a1449e235633ae178b6ffa; retrieved 2026-09-21T20:47:08.547Z.