SEA97LA117 · Hiller UH-12E
Hiller UH-12E · Accident: rotor failure/malfunction while maneuvering
From Walla Walla Regional Airport (ALW) to an unrecorded destination
Event
- NTSB case
- SEA97LA117
- 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
- 1 · 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
- N3005J
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Walla Walla Regional Airport (ALW), Walla Walla, WATo 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
- Maneuvering · aerial application
- 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
- Substantial
Cause areas
- Rotor system, main rotor › Fatigue
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
A witness reported that as he was watching the helicopter maneuver for the aerial application flight, one of the main rotor blades separated from the helicopter. The helicopter then nosed down and collided with the terrain. Examination of the separated sections of the main rotor blade found that the origin area contained a few crack arrest positions and small ratchet marks, indicating that fatigue cracking initiated from multiple locations. The thickness of the larger spar was measured and found to be slightly below the specified manufacturer's measurements. Scratches or scoring marks, similar to a sanded appearance, were noted on the lower surface where the thickness was reduced. The thickness of the spar wall continued to decrease further outboard of the fracture. Corrosion was also visible. The applicable Airworthiness Directive (AD) requires performance of inspections per the Service Bulletin (SB) to prevent main rotor blade failure due to cracking of the spar or delamination of the trailing edge skin from the spar. The SB specifies the different types of inspections to be accomplished, the intervals for accomplishment of the inspections, and how the inspections are to be performed to detect for cracks or delamination. The SB indicates that a chemical compound is to be used to strip the paint from the surface to accomplish the inspection. Maintenance records indicate that inspections were performed, however, no cracks were detected.
Probable cause
The main rotor blade separated due to fatigue. Factors were: an Airworthiness Directive was not properly performed, and inadequate inspection of the main rotor blades.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA97LA117
- Event ID
- 20001208X08030
- Case number
- SEA97LA117
- 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: f561f32e26cb3dcb40bc08420d96e9f2dbe39a4738d48a31f1391a49e14e4623; retrieved 2026-09-20T22:57:28.640Z.