ASN Wikibase Occurrence # 370374
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| Date: | Thursday 19 February 2004 |
| Time: | 18:59 LT |
| Type: |  Eurocopter AS 350B |
| Owner/operator: | Heli Usa Inc |
| Registration: | N358NT |
| MSN: | 1016 |
| Year of manufacture: | 1978 |
| Total airframe hrs: | 4426 hours |
| Engine model: | Turbomeca Aeriel 1B |
| Fatalities: | Fatalities: 0 / Occupants: 6 |
| Aircraft damage: | Minor |
| Category: | Serious incident |
| Location: | Las Vegas, NV -
 United States of America
|
| Phase: | En route |
| Nature: | Unknown |
| Departure airport: | Grand Canyon-National Park Airport, AZ (GCN/KGCN) |
| Las Vegas-McCarran International Airport, NV (LAS/KLAS) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The helicopter experienced an in-flight loss of tail rotor control due to the fatigue fracture and failure of the tail rotor pitch change lever (SN MA 3671). The purpose of this part is to translate forward and aft movement from the tail rotor controls to change the pitch of the tail rotor. The operator had removed the component from the helicopter prior to the arrival of Federal Aviation Administration inspectors, and so the condition of the part as installed could not be determined. Following the incident, the operator discovered a crack on an additional lever (SN MA 3010) in their fleet. The Safety Board Materials Laboratory determined that the fatigue cracks in the two levers were not due to material or manufacturing defects, but were caused by improper installation of the component on the tail rotor gear box. Service Bulletin (SB) No. 65.00.42 was issued in response to cracks found in other levers where the cracks were determined to have been caused by improper installation of the tail rotor gear box pitch control lever bolt. The condition of the incident lever and the second one were found to be identical to the prior cases that triggered the issuance of the service bulletin. The tail rotor gearbox assembly had 3,148.5 hours. The lever is an on-condition part, which is inspected during overhaul of the tail rotor gear box. The overhauls are completed at a normal interval of 3,000 hours; the manufacturer allows a tolerance of 10 percent over the recommended overhaul schedule. When the tail rotor gearbox assembly was submitted for overhaul, a tail rotor pitch change lever different from the one involved in the incident was submitted for inspection. There are no tracking requirements on this part and the time and history of the tail rotor pitch change lever involved in the incident could not be determined.
Probable Cause: the tail rotor pitch change lever failed in fatigue due to improper installation by company maintenance personnel.
Accident investigation:
 |
|
Sources:
NTSB LAX04IA133
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 25-Mar-2024 10:01 | ASN Update Bot | Added |
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