ASN Wikibase Occurrence # 358336
This information is added by users of ASN. Neither ASN nor the Flight Safety Foundation are responsible for the completeness or correctness of this information.
If you feel this information is incomplete or incorrect, you can submit corrected information.
| Date: | Friday 1 September 1995 |
| Time: | 08:30 LT |
| Type: |  Hiller UH-12E |
| Owner/operator: | Bettencourt Flying Service, In |
| Registration: | N4027D |
| MSN: | 5072 |
| Total airframe hrs: | 2749 hours |
| Engine model: | LYCOMING VO-540-C2A |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Dos Palos, CA -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Agricultural |
| Departure airport: | Delhi, CA (0M9) |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
THE PILOT WAS SPRAYING A TOMATO FIELD WHEN A STRONG VIBRATION STARTED THROUGH THE AIRFRAME, FOLLOWED IMMEDIATELY BY A SEVERE YAW. PEDAL INPUT HAD NO EFFECT ON THE YAW AND THE HELICOPTER BEGAN TO SPIN. THE PILOT REDUCED POWER AND LOWERED THE COLLECTIVE TO STOP THE YAW AND THE HELICOPTER LANDED HARD. AN FAA AIRWORTHINESS INSPECTOR EXAMINED THE WRECKAGE AT THE ACCIDENT SITE. ONE TAIL ROTOR BLADE WAS MISSING AND SUBSEQUENTLY FOUND ABOUT 100 FEET AWAY. THE INSPECTOR REPORTED THAT THE TENSION TORSION (TT) PLATES OF THE SEPARATED BLADE WERE BROKEN AT THE HUB ATTACH BOLTS. NO LEADING EDGE DAMAGE WAS OBSERVED ON THE BLADE. THE FRACTURED TT PLATES WERE SENT TO THE NTSB LAB WHERE REPRESENTATIVE PLATE FRACTURES WERE SELECTED FOR DETAILED EXAMINATION. FEATURES TYPICAL OF PROGRESSIVE FATIGUE CRACKING WERE OBSERVED. A MATERIAL ANALYSIS REVEALED THAT THE STRAPS WERE MADE FROM THE MANUFACTURER'S SPECIFIED MATERIAL. NO EVIDENCE OF FOREIGN ELEMENT CONTAMINATION WAS FOUND ON THE FRACTURE FACES. THE TAIL ROTOR TT BAR HAS A 12,500-HOUR LIFE LIMIT AND THE FRACTURED TT BAR HAD ACCUMULATED A TOTAL TIME IN SERVICE OF 3,710 HOURS. NO PRIOR INCIDENTS WERE FOUND IN THE FAA SERVICE DIFFICULTY REPORT DATA BASE.
Probable Cause: the fatigue failure of the tail rotor tension torsion bar plates.
Accident investigation:
 |
|
Sources:
NTSB LAX95LA318
History of this aircraft
Other occurrences involving this aircraft
| 7 January 1983 | N4027D | Private | 0 | Near Vacaville, CA | |
sub |
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 14-Mar-2024 12:26 | ASN Update Bot | Added |
Corrections or additions? ... Edit this accident description
The Aviation Safety Network is an exclusive service provided by:
Quick Links:
| ASN Home | Send Correction / Feedback |
| FSF Home | Disclaimer | Copyright |
| Contact Us | Privacy Policy |
| Press / Media |
CONNECT WITH US:
©2024 Flight Safety Foundation