Individually Owned: 151,845
Corporate Owned: 143,699
Aircraft Accident/Incident Report
Happy Camp, California 96039
Friday, August 4, 2006 19:47 PDT
NTSB Narrative Summary Released at Completion of Accident
The helicopter experienced an in-flight separation of a tail rotor blade and subsequent separation of the tail rotor gearbox and remaining tail rotor blades while conducting fire suppression operations for the United States Forest Service (USFS). A witness located near the accident site reported that he observed the helicopter over the dip site when the witness heard a "loud bang." He observed the helicopter flying over a stone riverbed toward a bridge when he noticed a large piece fall off the helicopter, later identified as the tail rotor gearbox with three of the four tail rotor blades attached to the hub. The helicopter pitched nose low at an approximate 45-degree nose down attitude while rotating around its vertical axis before impacting the side of the river/shoreline. The tail rotor blade associated with the red spindle separated from the tail rotor. The red tail rotor spindle failed due to a fatigue fracture in the spindle. Among three machined grooves, located on the spindle under a spacer, the fatigue initiated in the groove located closest to the blade (the outboard groove). Fatigue initiated at a single origin associated with a shot-peen pit. Circumferential scratches were observed in the groove areas and on the adjacent journal surface; however, the fatigue crack origin was not associated with these scratches. The journal diameter was also undersize by 0.007 inch, and fretting was observed on the journal surface. The origin was not associated with any particular scratch or other apparent material defect. The groove peak between the middle and inboard grooves was sheared at the trailing side of the red spindle and displaced toward inboard, damage consistent with a tail rotor strike. The total time of the spindle could not be determined as it was not a life-limited component that required serial number and time tracking. The tail rotor assembly underwent an overhaul about 233.6 hours prior to the accident. During the overhaul, the spindles are to be inspected via fluorescent penetrant; however, the overhaul manual did not require the removal of the spacer that covered the groove area where the fatigue cracking initiated unless the spacer was damaged or worn beyond its approved limits. According to the operator, the spacer was not routinely removed at overhaul unless it was damaged or out of dimensional tolerance.
NTSB Probable Cause Narrative
The fatigue failure of tail rotor blade spindle, which resulted in the separation of the blade and tail rotor gearbox.
Event Information
| Type of Event | Accident |
| Event Date | 8/4/2006 |
| Event Day of the Week | Friday |
| Time of Event | 1947 |
| Event Time Zone | Pacific Daylight Time |
| Event City | Happy Camp |
| Event State | CALIFORNIA |
| Event Country | -- |
| Zipcode of the event site | 96039 |
| Event Date Year | 2006 |
| Event Date Month | 8 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 413939N |
| Event Location Longitude | 1232654W |
| 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 | Witness |
| Time of the weather observation | |
| Direction of event from weather observation facility (degrees) | -- |
| Weather Observation Facility ID | -- |
| Elevation of weather observation facility | -- |
| Distance of event from weather observation facility (units?) | -- |
| Time Zone of the weather observation | -- |
| Lighting Conditions | Day |
| Lowest Ceiling Height | -- |
| Lowest Non-Ceiling Height | -- |
| Sky/Lowest/Cloud Conditions | -- |
| Sky Condition for Lowest Ceiling | -- |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | -- |
| Air Temperature at event time (in degrees celsius) | 32 |
| Dew Point at event time (in degress fahrenheit) | -- |
| Wind Direction (degrees magnetic) | -- |
| Variable Wind Indicator | Variable |
| Wind Speed (knots) | 5 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Gusting |
| Wind Gust (knots) | 8 |
| Altimeter Setting at event time (in. Hg) | -- |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | -- |
| Event Highest Injury | Fatal |
| On Ground, Fatal Injuries | -- |
| On Ground, Minor Injuries | -- |
| On Ground, Serious Injuries | -- |
| Injury Total Fatal | 2 |
| Injury Total Minor | -- |
| Injury Total None | -- |
| Injury Total Serious | -- |
| Injury Total All | 2 |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 21855 |
| NTSB Notification Source | FAA |
| NTSB Notification Date | Aug 4 2006 12:00AM |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | DMS |
| Date of most recent change to record | Jul 25 2007 12:22PM |
| User who most recently changed record | NTSB\lema |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | Sacramento FSDO |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N6156U |
| NTSB Number | LAX06GA254 |
| Missing Aircraft Indicator | Y |
| Federal Aviation Reg. Part | Part 91: General Aviation |
| Type of Flight Plan filed | Company VFR |
| Flight plan Was Activated? | Yes |
| Damage | Substantial |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | Aviation International Rotors |
| Aircraft Model | CH-54A |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 66-18410 |
| Certified Max Gross Weight | 42000 |
| 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 | 2 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | AAIP |
| Date of Last Inspection | Jul 1 2006 12:00AM |
| Airframe hours since last inspection | 19.1 |
| Airframe Hours | 6191.6 |
| ELT Installed | Yes |
| ELT Activated | No |
| ELT Aided Location of Event Site | No |
| ELT Type | -- |
| Aircraft Owner Name | Heavy Lift Helicopters Inc. |
| Aircraft Owner Street Address | 13463 Nomwaket Road |
| Aircraft Owner City | Apple Valley |
| Aircraft Owner State | CA |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 92308 |
| Operator is an individual? | No |
| Operator Name | Department of Agriculture, U.S. Forest Service |
| Operator Same as Owner? | No |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | No |
| Operator Street Address | -- |
| Operator City | Washington |
| Operator State | DC |
| Operator Country | USA |
| Operator Zip code | -- |
| Operator Code | -- |
| Owner has at least one certificate | -- |
| Other Operator of large aircraft? | -- |
| Certified for Part 133 or 137 Operation | External Load |
| 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) | -- |
| Second Pilot on Board | Yes |
| Departure Point Same as Event | No |
| Departure Airport Code | 36S |
| Departure City | Happy Camp |
| Departure State | CA |
| Departure Country | USA |
| Departure Time | 1912 |
| Departure Time Zone | PDT |
| Destination Same as Local Flt | dest & departure same, accident can occur anywhere |
| Destination Airport Code | -- |
| Destination City | -- |
| Destination State | -- |
| Destination Country | -- |
| Specific Phase of Flight | Emergency descent/landing |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Jul 9 2007 11:56AM |
| User who most recently changed record | STAM |
| Since inspection or accident | Time of Accident |
| Event Location Runway Number and Location | NA |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |