On July 4, 1987, an Aerospatiale AS-355-F1 (registration N5796M) operated by Petroleum Helicopters,inc. was involved in an aviation accident near Venice, LA. Investigators recorded the probable cause as: The failure to install the retaining bolts securing the vibration absorber assembly during maintenance, leading to its in-flight separation and contact with the main rotor system. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 2 related events involving the same aircraft type or operator are linked below.
A helicopter experienced an in-flight separation of the vibration absorber assembly after retaining bolts were not installed during maintenance, leading to contact with the main rotor system, loss of control, and subsequent terrain impact.
Incident Overview
A helicopter broke apart in flight after a loud bang, according to witnesses. The aircraft subsequently impacted terrain (water). Examination of the wreckage indicated that the vibration absorber assembly had separated from the helicopter and contacted the main rotor system, resulting in loss of aircraft control.
Maintenance Findings
One of the mechanics who performed maintenance on the main rotor head reported uncertainty about the installation of the retaining bolts that secure the vibration absorber assembly to the aircraft. Metallurgical analysis of the assembly revealed that the retaining bolts were not installed at impact.
Sequence of Events
Witnesses observed the helicopter come apart in flight after hearing a loud 'boom'. The vibration absorber assembly's separation and contact with the main rotor system led to loss of control. The helicopter subsequently made contact with the terrain, which was water.
Probable cause
The failure to install the retaining bolts securing the vibration absorber assembly during maintenance, leading to its in-flight separation and contact with the main rotor system.
What happened in the 4 Jul 1987 Aerospatiale AS-355-F1 accident near Venice, LA?
A helicopter experienced an in-flight separation of the vibration absorber assembly after retaining bolts were not installed during maintenance, leading to contact with the main rotor system, loss of control, and subsequent terrain impact.
What aircraft was involved and where did it happen?
The accident on 4 Jul 1987 involved an Aerospatiale AS-355-F1, registration N5796M, operated by Petroleum Helicopters,inc., at Venice, LA.
What was the probable cause of the accident?
The failure to install the retaining bolts securing the vibration absorber assembly during maintenance, leading to its in-flight separation and contact with the main rotor system.
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