WPR10CA164 · Eurocopter AS 350 B3
Omniflight Helicopters Eurocopter AS 350 B3 · Accident while maneuvering
From La Paz Regional Hospital Heliport (AZ47) to La Paz Regional Hospital Heliport (AZ47)
Event
- NTSB case
- WPR10CA164
- 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
- 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
Eurocopter AS 350 B3
- Aircraft type
- Eurocopter AS-350
- 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
- N4282
- Operator
- Omniflight Helicopters
- Onboard fatalities
- Unknown
- Route
- From La Paz Regional Hospital Heliport (AZ47), Parker, AZTo La Paz Regional Hospital Heliport (AZ47), Parker, AZ
- 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 91: General Aviation
- 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 · hover
- Defining eventThe 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
- Miscellaneous/other
- 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
- Personnel issues › Task performance
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot of the helicopter told the lead mechanic that the main rotor blade needed to be balanced. Two mechanics showed up on the morning of the accident and installed the balancing equipment. A test flight was flown. The two men performed the necessary work, which required a second adjustable wrench on the top of the rotor head to hold the bolt while the nut below was removed and later torqued back on. When the work was finished, the men gathered their tools. The pilot asked the lead mechanic if they had gathered all their tools and the mechanic replied "yes." The three men got on the helicopter for a test hover to check their work. As the main rotor speed reach 100 percent, the three occupants heard a "bang." As the helicopter hovered, the two mechanics thought the balancing equipment readings were worse than the first flight, and the vibrations in the aircraft had increased. The pilot landed the helicopter so that the mechanics could make additional adjustments. The mechanics discovered that they were missing the adjustable wrench that had been used on the top of the main rotor head. Postaccident examination revealed that one main rotor blade, the tail boom, and the lower vertical stabilizer had received damage from the unaccounted for wrench.
Probable cause
The mechanics' failure to account for all the tools following a maintenance procedure and the pilot's failure to perform a preflight check before a maintenance test flight.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR10CA164
- Event ID
- 20100320X84445
- Case number
- WPR10CA164
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
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: 97ee886c84a668e6c0a45d7f6a703b30045b66a8a0924c24adc406a809f7bbfa; retrieved 2026-09-15T13:45:56.819Z.