Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Hanford, California 93230
Thursday, June 23, 2011 4:00 PDT
NTSB Narrative Summary Released at Completion of Accident
The pilot reported that during a preflight inspection he observed a small oil leak originating where the tail rotor drive shaft attaches to the transmission. He said that, following a discussion with his boss, they decided to reposition the helicopter from a vehicle-mounted platform onto the ground so they could perform a more detailed examination of the oil leak. The pilot stated that following a normal engine start, he began to lift the helicopter off the platform and heard a "growling" sound originating from the transmission followed by an immediate loss of tail rotor control. The pilot said that the helicopter immediately began to rotate to the right as he rolled the throttle off and lowered the collective. Subsequently, the helicopter landed hard onto the ground adjacent to the truck and platform. Postaccident examination of the helicopter revealed that the tail rotor gear shaft was separated from the tail rotor drive shaft coupling.
Metallurgical analysis of the fracture surface of the tail rotor gear shaft revealed that the fracture was consistent with fatigue cracking that emanated from multiple origins at the root portion of a thread on the threaded portion of the shaft. The fatigue crack origin exhibited signatures consistent with being open for an extended period of time compared to the other regions of the fracture face; the amount of time could not be determined. The fatigue crack eventually propagated around the gear shaft as torsional fatigue. No maintenance records for the helicopter were recovered during the course of the investigation, and therefore the amount of flight time on the tail rotor gear shaft was undetermined.
NTSB Probable Cause Narrative
The separation of the tail rotor drive gear shaft due to torsional fatigue of its threaded portion, which resulted in a loss of tail rotor control.
Event Information
| Type of Event | Accident |
| Event Date | 6/23/2011 |
| Event Day of the Week | Thursday |
| Time of Event | 400 |
| Event Time Zone | Pacific Daylight Time |
| Event City | Hanford |
| Event State | CALIFORNIA |
| Event Country | -- |
| Zipcode of the event site | 93230 |
| Event Date Year | 2011 |
| Event Date Month | 6 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 361900N |
| Event Location Longitude | 1193739W |
| 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 | 353 Pacific Daylight Time |
| Direction of event from weather observation facility (degrees) | 60 |
| Weather Observation Facility ID | HJO |
| Elevation of weather observation facility | 240 |
| Distance of event from weather observation facility (units?) | 5 |
| Time Zone of the weather observation | PDT |
| 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) | 23 |
| Dew Point at event time (in degress fahrenheit) | 8 |
| Wind Direction (degrees magnetic) | 330 |
| Variable Wind Indicator | Wind direction could be determined |
| Wind Speed (knots) | 8 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | 29.78 |
| 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) | 29726 |
| NTSB Notification Source | FAA Operations Center |
| NTSB Notification Date | -- |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Apr 19 2012 12:30PM |
| User who most recently changed record | johb |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N99579 |
| NTSB Number | WPR11LA282 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 91: General Aviation |
| Type of Flight Plan filed | None |
| Flight plan Was Activated? | -- |
| Damage | Substantial |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | HILLER |
| Aircraft Model | UH12E |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 1733 |
| Certified Max Gross Weight | 3100 |
| 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 | 3 |
| Number of Engines | 1 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | 100 Hour |
| Date of Last Inspection | Jun 14 2011 12:00AM |
| Airframe hours since last inspection | -- |
| Airframe Hours | 10485 |
| ELT Installed | No |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | Central Valley Aviation Inc. |
| Aircraft Owner Street Address | -- |
| Aircraft Owner City | Selma |
| Aircraft Owner State | CA |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 93662 |
| Operator is an individual? | No |
| Operator Name | Central Valley Aviation Inc. |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | Yes |
| Operator Street Address | -- |
| Operator City | Selma |
| Operator State | CA |
| Operator Country | USA |
| Operator Zip code | 93662 |
| 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) | Positioning |
| Second Pilot on Board | No |
| Departure Point Same as Event | Yes |
| Departure Airport Code | -- |
| Departure City | Hanford |
| Departure State | CA |
| Departure Country | USA |
| Departure Time | 400 |
| Departure Time Zone | PDT |
| Destination Same as Local Flt | dest & departure same, accident can occur anywhere |
| Destination Airport Code | -- |
| Destination City | Hanford |
| Destination State | CA |
| Destination Country | USA |
| Specific Phase of Flight | -- |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Mar 22 2012 1:23PM |
| User who most recently changed record | stam |
| 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 | -- |