Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Brawley, California 92227
Friday, January 20, 2012 19:00 PST
NTSB Narrative Summary Released at Completion of Accident
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.
NTSB Probable Cause Narrative
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.
Event Information
| Type of Event | Accident |
| Event Date | 1/20/2012 |
| Event Day of the Week | Friday |
| Time of Event | 1900 |
| Event Time Zone | Pacific Standard Time |
| Event City | Brawley |
| Event State | CALIFORNIA |
| Event Country | -- |
| Zipcode of the event site | 92227 |
| Event Date Year | 2012 |
| Event Date Month | 1 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 325935N |
| Event Location Longitude | 1153101W |
| Event Location Airport | -- |
| Event Location Nearest Airport ID | -- |
| Indicates whether the acc/inc occurred off or on an airport | Off Airport/Airstrip |
| Distance from airport in statute miles | -- |
| Degrees magnetic from airport | -- |
| Airport Elevation | -- |
| Weather Briefing Completeness | -- |
| Investigator's weather source | Weather Observation Facility |
| Time of the weather observation | 1853 Pacific Standard Time |
| Direction of event from weather observation facility (degrees) | 200 |
| Weather Observation Facility ID | IPL |
| Elevation of weather observation facility | -54 |
| Distance of event from weather observation facility (units?) | 10 |
| Time Zone of the weather observation | PST |
| Lighting Conditions | Night |
| Lowest Ceiling Height | -- |
| Lowest Non-Ceiling Height | -- |
| Sky/Lowest/Cloud Conditions | Clear |
| Sky Condition for Lowest Ceiling | None |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | 15 |
| Dew Point at event time (in degress fahrenheit) | 1 |
| Wind Direction (degrees magnetic) | -- |
| Variable Wind Indicator | Variable |
| Wind Speed (knots) | -- |
| Wind Velocity Indicator | Light and Variable |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | 29.98 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | -- |
| Event Highest Injury | None |
| On Ground, Fatal Injuries | -- |
| On Ground, Minor Injuries | -- |
| On Ground, Serious Injuries | -- |
| Injury Total Fatal | -- |
| Injury Total Minor | -- |
| Injury Total None | 1 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 30328 |
| NTSB Notification Source | -- |
| NTSB Notification Date | -- |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Sep 26 2012 3:14PM |
| User who most recently changed record | reej |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N902SF |
| NTSB Number | WPR12LA096 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 137: Agricultural |
| Type of Flight Plan filed | None |
| Flight plan Was Activated? | -- |
| Damage | Substantial |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | Arrow Falcon Exporters, Inc. |
| Aircraft Model | OH-58A |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 70-15406 |
| Certified Max Gross Weight | -- |
| Aircraft Category | Helicopter |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | -- |
| Cabin Crew Seats | -- |
| Passenger Seats | -- |
| Total number of seats on the aircraft | 4 |
| Number of Engines | 1 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | -- |
| Date of Last Inspection | -- |
| Airframe hours since last inspection | -- |
| Airframe Hours | -- |
| ELT Installed | No |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | FARM AVIATION INC |
| Aircraft Owner Street Address | 1053 N EASTERN AVE |
| Aircraft Owner City | BRAWLEY |
| Aircraft Owner State | CA |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 92227-1719 |
| Operator is an individual? | No |
| Operator Name | FARM AVIATION INC |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | Yes |
| Operator Street Address | 1053 N EASTERN AVE |
| Operator City | BRAWLEY |
| Operator State | CA |
| Operator Country | USA |
| Operator Zip code | 92227-1719 |
| Operator Code | -- |
| Owner has at least one certificate | Yes - certificate holder |
| Other Operator of large aircraft? | No |
| Certified for Part 133 or 137 Operation | Agriculture |
| Operator Certificate Number | -- |
| Indicates whether an air carrier operation was scheduled or not | -- |
| Indicates Domestic or International Flight | -- |
| Operator carrying Pax/Cargo/Mail | -- |
| Type of Flying (Per_Bus / Primary) | Aerial Application |
| Second Pilot on Board | No |
| Departure Point Same as Event | Yes |
| Departure Airport Code | -- |
| Departure City | Brawley |
| Departure State | CA |
| Departure Country | USA |
| Departure Time | 1900 |
| Departure Time Zone | PST |
| Destination Same as Local Flt | dest & departure same, accident can occur anywhere |
| Destination Airport Code | -- |
| Destination City | Brawley |
| Destination State | CA |
| Destination Country | USA |
| Specific Phase of Flight | -- |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Aug 8 2012 12:28PM |
| User who most recently changed record | coos |
| Since inspection or accident | -- |
| Event Location Runway Number and Location | N/A |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |