Bell UH-1B N89NW
28 July 1992 · Hayfork, California, United States · Minor injuries
Summary
On 28 July 1992 at about 15:00 local time, a Bell UH-1B registered N89NW, operated by Northwest Helicopters, Inc., was involved in an accident near Hayfork, California, United States. One person was on board and one had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.
The record
- Date
- at 15:00
- Classification
- Accident
- Location
- Hayfork, California, United States
- Coordinates
- 40.5005, -123.1899
- Aircraft
- Bell UH-1B
- Registration
- N89NW
- Category
- Helicopter
- Engines
- 1
- Operator
- Northwest Helicopters, Inc.
- Operating rule
- Part 133: Rotorcraft Ext. Load
- Purpose of flight
- Other Work Use
- Phase of flight
- Not recorded
- Aircraft damage
- Substantial
- Weather
- VMC
- Light
- Day
- NTSB number
- LAX92LA319
People
1 person had minor injuries.
| On board | Died | Serious | Minor | Uninjured |
|---|---|---|---|---|
| 1 | 0 | 0 | 1 | 0 |
Probable cause
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.
Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.
Read the full NTSB narrative
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.
Quoted verbatim from the NTSB record.
Other Bell UH-1B accidents
| Date | Aircraft | Location | Operator | Outcome | Died |
|---|---|---|---|---|---|
| 22 Apr 1992 | Bell UH-1B | La Belle, Florida, United States | Colony Services, Inc. | Serious injuries | - |
| 12 Mar 1991 | Bell UH-1B | Vero Beach, Florida, United States | Colony Services, Inc. | Minor injuries | - |
| 23 Sep 1993 | Bell UH-1B | Pierce, Idaho, United States | Clearwater Management Co. Inc. | No injuries | - |
| 21 May 1991 | Bell UH-1B | Dog Fish Bay, Alaska, United States | - | Fatal | 1 |
| 22 May 1991 | Bell UH-1B | Smith Cove, Alaska, United States | Northwest Helicopter, Inc. | Minor injuries | - |
| 24 Sep 1993 | Bell UH-1B | Detroit Lake, Oregon, United States | Northwest Helicopters, Inc | Serious injuries | - |
Other accidents in this area
| Date | Aircraft | Location | Operator | Outcome | Died |
|---|---|---|---|---|---|
| 22 Feb 1992 | Piper PA-28R-201T | Ludlow, California, United States | Higgins, Melvin W & Jean | Minor injuries | - |
| 22 Feb 1992 | Beechcraft C-23 | Fullerton, California, United States | Eldon R. Howe | No injuries | - |
| 23 Feb 1992 | Cessna 150 | San Jose, California, United States | Veda Corporation | Minor injuries | - |
| 23 Feb 1992 | Cessna 182N | San Ardo, California, United States | Soil Service, Inc. | No injuries | - |
| 25 Feb 1992 | Grumman G-164B | Dixon, California, United States | Sunrise Duster, Inc. | No injuries | - |
| 25 Feb 1992 | Bellanca 7ECA | Apple Valley, California, United States | Chester Waite | Serious injuries | - |