Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Hayfork, California 96041
Tuesady, July 28, 1992 8:00 PDT
NTSB Narrative Summary Released at Completion of Accident
THE PILOT HAD JUST DROPPED OFF A LOAD OF LOGS AND WAS EN ROUTE BACK TO THE CUTTING AREA WHEN HE HEARD A LOUD BANG CONCURRENT WITH A LEFT YAW AND A RAPID LOSS OF ROTOR SPEED. THE PILOT ENTERED AN AUTOROTATION AND COLLIDED WITH TREES DURING THE DESCENT. EXAMINATION REVEALED THAT THE MAIN ROTOR DRIVE SHAFT HAD FAILED. EXAMINATION OF THE SHAFT REVEALED EVIDENCE OF A LOSS OF GREASE FROM THE SHAFT'S BOOT, WHICH RESULTED IN AN OVERHEATING CONDITION AND CATASTROPHIC FAILURE OF THE UNIT. THE 'O' RING, WHICH PROVIDES THE GREASE SEAL FOR THE SHAFT BOOT, WAS FOUND DEFORMED WITH EVIDENCE THAT GREASE HAD BEEN SLUNG FROM THE BOOT. THE MAIN ROTOR DRIVE SHAFT HAD BEEN REMOVED FOR MAINTENANCE AND REPLACED THREE DAYS AND 6 HOURS PRIOR TO THE ACCIDENT. THE MAINTENANCE INSTRUCTIONS CALL FOR A NEW 'O' RING TO BE INSTALLED WHEN THE DRIVE SHAFT AND BOOT ARE REASSEMBLED. ACORDING TO THE BELL LABORATORY, THE 'O' RING APPEARED TO HAVE NOT BEEN REPLACED.
NTSB Probable Cause Narrative
THE FAILURE OF THE MAIN ROTOR DRIVE SHAFT DUE TO THE IMPROPER INSTALLATION BY COMPANY MAINTENANCE PERSONNEL OF AN 'O' RING SEAL, WHICH ALLOWED THE PACKING GREASE TO ESCAPE AND CAUSED THE OVER TEMPERATURE FAILURE OF THE DRIVE SHAFT. A FACTOR IN THE ACCIDENT WAS THE LACK OF SUITABLE TERRAIN IN WHICH TO PERFORM AN AUTOROTATION.
Event Information
| Type of Event | Accident |
| Event Date | 7/28/1992 |
| Event Day of the Week | Tuesday |
| Time of Event | 800 |
| Event Time Zone | Pacific Daylight Time |
| Event City | HAYFORK |
| Event State | CALIFORNIA |
| Event Country | -- |
| Zipcode of the event site | 96041 |
| Event Date Year | 1992 |
| Event Date Month | 7 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | |
| Event Location Longitude | |
| 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 | 0 |
| Degrees magnetic from airport | 0 |
| Airport Elevation | -- |
| Weather Briefing Completeness | Unknown |
| Investigator's weather source | Pilot |
| Time of the weather observation | 0 |
| Direction of event from weather observation facility (degrees) | 0 |
| Weather Observation Facility ID | |
| Elevation of weather observation facility | 0 |
| Distance of event from weather observation facility (units?) | 0 |
| Time Zone of the weather observation | |
| Lighting Conditions | Day |
| Lowest Ceiling Height | 0 |
| Lowest Non-Ceiling Height | 0 |
| Sky/Lowest/Cloud Conditions | Clear |
| Sky Condition for Lowest Ceiling | None |
| Visibility Runway Visual Range (Feet) | 0 |
| Visibility Runway Visual Value (Statute Miles) | 0 |
| Visibility (Statute Miles) | 20 |
| Air Temperature at event time (in degrees celsius) | 27 |
| Dew Point at event time (in degress fahrenheit) | -- |
| Wind Direction (degrees magnetic) | 0 |
| Variable Wind Indicator | Variable |
| Wind Speed (knots) | 0 |
| Wind Velocity Indicator | Light and Variable |
| Wind Gust Indicator | Unknown |
| Wind Gust (knots) | 0 |
| Altimeter Setting at event time (in. Hg) | 29 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | Unknown |
| METAR weather report | -- |
| Event Highest Injury | Minor |
| On Ground, Fatal Injuries | 0 |
| On Ground, Minor Injuries | 0 |
| On Ground, Serious Injuries | 0 |
| Injury Total Fatal | -- |
| Injury Total Minor | 1 |
| Injury Total None | -- |
| Injury Total Serious | -- |
| Injury Total All | 1 |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 2684 |
| NTSB Notification Source | -- |
| NTSB Notification Date | Jul 28 1992 12:00AM |
| NTSB Notification Time | 1015 |
| Fiche Number and/or location -used to find docket information | 47484 |
| Date of most recent change to record | Dec 11 2000 3:05PM |
| User who most recently changed record | dbo |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N89NW |
| NTSB Number | LAX92LA319 |
| Missing Aircraft Indicator | N |
| Federal Aviation Reg. Part | Part 133: Rotorcraft Ext. Load |
| Type of Flight Plan filed | None |
| Flight plan Was Activated? | -- |
| Damage | Substantial |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | BELL |
| Aircraft Model | UH-1B |
| Aircraft Series Identifier | UH-1B |
| Aircraft Serial Number | 62-4576 |
| Certified Max Gross Weight | 8500 |
| Aircraft Category | Helicopter |
| Aircraft Registration Class | U.S. Registered/U.S. Soil |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | -- |
| Cabin Crew Seats | -- |
| Passenger Seats | -- |
| Total number of seats on the aircraft | 2 |
| Number of Engines | 1 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | 100 Hour |
| Date of Last Inspection | Jul 27 1992 12:00AM |
| Airframe hours since last inspection | 6 |
| Airframe Hours | 5496 |
| ELT Installed | Yes |
| ELT Activated | No |
| ELT Aided Location of Event Site | No |
| ELT Type | -- |
| Aircraft Owner Name | NORTHWEST HELICOPTERS, INC. |
| Aircraft Owner Street Address | 7822 OLD HWY 99 SE |
| Aircraft Owner City | OLYMPIA |
| Aircraft Owner State | WA |
| Aircraft Owner Country | |
| Aircraft Owner Zipcode | 98501 |
| Operator is an individual? | -- |
| Operator Name | NORTHWEST HELICOPTERS, INC. |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | Yes |
| Operator Street Address | 7822 OLD HWY 99 SE |
| Operator City | OLYMPIA |
| Operator State | WA |
| Operator Country | |
| Operator Zip code | 98501 |
| Operator Code | WYFL |
| Owner has at least one certificate | Yes - certificate holder |
| Other Operator of large aircraft? | No |
| Certified for Part 133 or 137 Operation | External Load |
| Operator Certificate Number | -- |
| Indicates whether an air carrier operation was scheduled or not | Unknown |
| Indicates Domestic or International Flight | Unknown |
| Operator carrying Pax/Cargo/Mail | Unknown |
| Type of Flying (Per_Bus / Primary) | Other Work Use |
| Second Pilot on Board | No |
| Departure Point Same as Event | Yes |
| Departure Airport Code | |
| Departure City | |
| Departure State | |
| Departure Country | |
| Departure Time | 720 |
| 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 | Maneuvering |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Jan 2 2001 10:35AM |
| User who most recently changed record | dbo |
| Since inspection or accident | -- |
| Event Location Runway Number and Location | 0 |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |