ASN Wikibase Occurrence # 150331
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| Date: | Monday 18 September 1995 |
| Time: | 09:40 LT |
| Type: |  PADC/MBB Bo 105C |
| Owner/operator: | Petroleum Helicopters, Inc. |
| Registration: | N91070 |
| MSN: | S145 |
| Year of manufacture: | 1974 |
| Total airframe hrs: | 8285 hours |
| Engine model: | ALLISON 250-C20 |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | near Lafayette, LA -
 United States of America
|
| Phase: | En route |
| Nature: | Unknown |
| Departure airport: | (KLFT) |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
While over 'Fast Lane,' a visual check point on the highway approach to the Lafayette Regional Airport, the helicopter 'abruptly and violently pitched nose down.' It took both pilots pulling aft on the cyclic to level the helicopter. Once control was re-established, the PIC saw that the 'hyd block' light was illuminated and the Mast Moment Indicator (MMI) limit light was on steady. The helicopter was landed without further incident. Examination and testing of the Tandem Hydraulic Unit found the System 1 hydraulic pump leaking internally. A nick and an abrasion were found in the edge of its longitudinal control slider. Metallic chips were found in the hydraulic high and low pressure filters, and one chip was found in a groove of the longitudinal control slider. The electrical portion of the 'jam-proof system,' which should activate the back-up hydraulic system two in case of a control slider jamming, only worked randomly. The connector was heavily corroded and the magnetic core of the solenoid valve had an internal short circuit.
Probable Cause: a short in the 'jam proof system' solenoid valve which prevented activation of the backup hydraulic system and resulting in a cyclic hardover. Factors were the contaminated hydraulic fluid and the resulting jammed actuator (longitudinal control slider).
Accident investigation:
 |
|
Sources:
NTSB FTW95IA397
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 23-Oct-2012 11:52 | TB | Added |
| 11-Oct-2016 16:55 | TB | Updated [Source] |
| 21-Dec-2016 19:28 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 10-Dec-2018 20:03 | TB | Updated [Aircraft type, Narrative] |
| 09-Apr-2024 11:51 | ASN Update Bot | Updated [Time, Cn, Operator, Other fatalities, Phase, Departure airport, Destination airport, Source, Narrative, Category, Accident report] |
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