WPR12LA096 · Arrow Falcon Exporters, Inc. OH-58A
Farm Aviation Arrow Falcon Exporters, Inc. OH-58A · Accident: system/component malfunction/failure (non-power) during takeoff
From Brawley, CA to Brawley, CA
Event
- NTSB case
- WPR12LA096
- 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
Arrow Falcon Exporters, Inc. OH-58A
- Aircraft type
- Arrow Falcon Exporters OH-58
- 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
- N902SF
- Operator
- Farm Aviation
- Onboard fatalities
- Unknown
- Route
- From Brawley, CATo Brawley, CA
- 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
- Takeoff
- 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
- System/component malfunction/failure (non-power)
- 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
- Aircraft › Aircraft propeller/rotor
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
During takeoff, the pilot pulled up on the collective, and the main rotor mast fractured near the point where it extends from the transmission; the pilot then aborted the takeoff. The fracture was located below the threads for the mast nut and above the bearing journal for the upper mast bearing. Postaccident examination of the fracture surface revealed multiple fatigue cracks that initiated at the outer diameter of the mast and extended through about 50 percent of the mast's cross section. The fatigue initiation areas and the through-the-wall portion of the fatigue were heavily corroded with extensive pitting and dark deposits visible. A dark oily material was found on the mast's outer surface near the fracture, and the mast's surface was severely corroded on both sides of the fracture. Analysis of samples of the dark oily material suggests that it was a mixture of lubricating oil and water.
When the mast is installed on the helicopter, the location where the corrosion and fracture occurred is hidden. To fully inspect the area, the mast assembly must be removed from the helicopter and completely disassembled. Maintenance records indicated that the most recent overhaul of the main rotor mast was completed 2,499 hours before the accident, about 99 hours beyond the helicopter manufacturer's recommended time between overhaul of 2,400 hours.
The NTSB has previously investigated a similar main rotor mast failure on the same make and model helicopter; in that case, the most recent overhaul of the main rotor mast was completed 1,486 hours before the accident. As a result of these events, in February 2012, the manufacturer issued an alert service bulletin that reduced the main rotor mast overhaul interval from 2,400 hours to 1,200 hours. Additionally, in July 2012, the Federal Aviation Administration issued Airworthiness Directive (AD) 2012-14-11, applicable to Arrow Falcon Exporters, Rotorcraft Development Corporation, and San Joaquin Helicopters model OH-58A, OH-58A+, and OH-58C helicopters. The AD requires operators of those helicopters to, within 30 days, overhaul the helicopters’ main rotor mast assemblies.
Probable cause
The failure of the main rotor mast due to fatigue cracks that originated from corrosion pits. Contributing to the accident was the operator’s failure to adhere to the manufacturer’s recommended overhaul interval for the main rotor mast.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR12LA096
- Event ID
- 20120209X13451
- Case number
- WPR12LA096
- 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: local date, investigation status, coordinates. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 2012-01-21.
- API snapshot SHA-256: ddb0c92f5be02d822ca455991fb84c0d20dc894d73eaa8c4ccb2ef0ffddf35cb; retrieved 2026-09-15T17:12:54.307Z.