Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Brentwood, California 94513
Sunday, July 3, 2011 6:30 PDT
NTSB Narrative Summary Released at Completion of Accident
During an aerial application flight, the helicopter's main rotor mast separated, and the helicopter fell from a height of about 30 feet and impacted terrain. Postaccident examination of the wreckage found that the mast had fractured below the point where it extended from the transmission and just above the mast seal retainer plate. Examination of the fracture surfaces revealed that an area of fatigue extended about 95 degrees around the mast’s circumference. The remaining portions of the fracture were identified as low cycle fatigue and overload. The fracture had multiple origins at corrosion pitting on the threads of the mast. The source of the corrosion could not be determined.
Maintenance records indicated that the most recent overhaul of the main rotor mast assembly was completed 1,486 hours before the accident. At that time, a magnaflux inspection was performed on the main rotor mast with no discrepancies noted. The records indicate that, during reassembly, a sealant was applied to the threads for corrosion protection.
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.
A second mast failure on a helicopter of the same make and model series occurred on January 20, 2012, in Brawley, California (WPR12LA096). In February 2012, the helicopter manufacturer issued an alert service bulletin that reduced the main rotor mast overhaul interval from 2,400 hours to 1,200 hours. 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 required, within 30 days, overhaul of the main rotor mast assemblies of these helicopters.
NTSB Probable Cause Narrative
The failure of the main rotor mast due to fatigue cracking originating from corrosion pits.
Event Information
| Type of Event | Accident |
| Event Date | 7/3/2011 |
| Event Day of the Week | Sunday |
| Time of Event | 630 |
| Event Time Zone | Pacific Daylight Time |
| Event City | Brentwood |
| Event State | CALIFORNIA |
| Event Country | -- |
| Zipcode of the event site | 94513 |
| Event Date Year | 2011 |
| Event Date Month | 7 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 375422N |
| Event Location Longitude | 1214007W |
| 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 | 653 Pacific Daylight Time |
| Direction of event from weather observation facility (degrees) | 206 |
| Weather Observation Facility ID | LVK |
| Elevation of weather observation facility | 400 |
| Distance of event from weather observation facility (units?) | 17 |
| Time Zone of the weather observation | PDT |
| Lighting Conditions | Day |
| 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) | 16 |
| Dew Point at event time (in degress fahrenheit) | 12 |
| 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) | 29.76 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | -- |
| Event Highest Injury | Serious |
| On Ground, Fatal Injuries | -- |
| On Ground, Minor Injuries | -- |
| On Ground, Serious Injuries | -- |
| Injury Total Fatal | -- |
| Injury Total Minor | -- |
| Injury Total None | -- |
| Injury Total Serious | 1 |
| Injury Total All | 1 |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 30410 |
| NTSB Notification Source | FAA ROC |
| NTSB Notification Date | -- |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Oct 29 2012 3:04PM |
| User who most recently changed record | snyg |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N6264D |
| NTSB Number | WPR11LA303 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 137: Agricultural |
| Type of Flight Plan filed | Unknown |
| Flight plan Was Activated? | No |
| Damage | Substantial |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | ARROW FALCON EXPORTERS INC |
| Aircraft Model | OH-58C |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 69-16118 |
| 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 | Annual |
| Date of Last Inspection | Dec 2 2010 12:00AM |
| Airframe hours since last inspection | -- |
| Airframe Hours | 5030 |
| ELT Installed | No |
| ELT Activated | No |
| ELT Aided Location of Event Site | No |
| ELT Type | Unknown |
| Aircraft Owner Name | COOKSEY DOFF W |
| Aircraft Owner Street Address | -- |
| Aircraft Owner City | BRENTWOOD |
| Aircraft Owner State | CA |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 94513-3815 |
| Operator is an individual? | No |
| Operator Name | Aerial Control |
| Operator Same as Owner? | No |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | No |
| Operator Street Address | -- |
| Operator City | Brentwood |
| Operator State | CA |
| Operator Country | USA |
| Operator Zip code | 94513 |
| 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 | Brentwood |
| Departure State | CA |
| Departure Country | USA |
| Departure Time | 610 |
| Departure Time Zone | PDT |
| Destination Same as Local Flt | dest & departure same, accident can occur anywhere |
| Destination Airport Code | -- |
| Destination City | Brentwood |
| Destination State | CA |
| Destination Country | USA |
| Specific Phase of Flight | -- |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Aug 7 2012 5:55PM |
| User who most recently changed record | coos |
| Since inspection or accident | Last Inspection |
| Event Location Runway Number and Location | N/A |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |