ASN Wikibase Occurrence # 372422
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| Date: | Wednesday 12 August 1987 |
| Time: | 16:20 LT |
| Type: |  Bell 206B |
| Owner/operator: | Houston Helicopters |
| Registration: | N33PW |
| MSN: | 2223 |
| Year of manufacture: | 1977 |
| Total airframe hrs: | 4468 hours |
| Engine model: | Allison 250-C20B |
| Fatalities: | Fatalities: 0 / Occupants: 4 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Pledger, TX -
 United States of America
|
| Phase: | En route |
| Nature: | Unknown |
| Departure airport: | Bay City, TX |
| Houston, TX | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
WHILE CRUISING AT 900' AGL, THE PLT NOTED A HVY SHUDDER FLWD BY A GRINDING NOISE, LOUD 'BANG' & A LOW ROTOR RPM SIGNAL. HE MADE AN AUTOROTATION TO A ROAD, BUT DRG TOUCHDOWN, THE MAIN ROTOR BLADES FLEXED DWN & SEVERED THE TAIL BOOM. AN EXAM REVEALED THE MAIN PWR (SHORT) SHAFT HAD FAILED DUE TO MISALIGNMENT & HI TEMPS RESULTING FROM THE MISALIGNMENT. FURTHER INV SHOWED THAT THE MISALIGNMENT WAS THE RESULT OF A FAILURE OF THE PYLON ISOLATOR MOUNT DUE TO DEBONDING BETWEEN THE UPPER PLATE & THE RUBBER DAMPER ELEMENT. DEBONDING OCCURRED AFTER PROLONGED EXPOSURE OF THE ISOLATOR MOUNT TO OIL & GREASE WHICH CHEMICALLY DETERIORATED THE BOND. THERE WAS EVIDENCE THE DETERIORATION HAD OCCURRED OVER A LONG PERIOD OF TIME. THE UNIT HAD BEEN INSPECTED PERIODICALLY, BUT THE IMPENDING FAILURE OF THE BOND HAD NOT BEEN DETECTED.
Probable Cause:
Accident investigation:
 |
|
Sources:
NTSB FTW87FA198
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 26-Mar-2024 16:52 | ASN Update Bot | Added |
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