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ASN Wikibase Occurrence # 150359
Last updated: 4 June 2021
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Date:22-OCT-2012
Time:06:02
Type:Silhouette image of generic A139 model; specific model in this crash may look slightly different
AgustaWestland AW139
Owner/operator:Era Helicopters Llc
Registration: N385RH
MSN: 41013
Fatalities:Fatalities: 0 / Occupants: 2
Aircraft damage: Substantial
Category:Accident
Location:Houma-Terrebonne Airport -   United States of America
Phase: Taxi
Nature:Ferry/positioning
Departure airport:Houma, LA (KHUM)
Destination airport:Houma, LA (KHUM)
Investigating agency: NTSB
Narrative:
The flight crew was repositioning the helicopter to another landing pad when the accident occurred. According to the flight crew and flight data recorder (FDR) data, as the helicopter was touching down, it began to experience severe vertical vibrations and to oscillate violently. The pilot reported that he lowered the collective but that the vibrations and oscillations intensified. The pilot then increased the collective to lift the helicopter off the ground. The helicopter became airborne, but the violent oscillations and vibrations continued. The pilot initiated a left pedal turn to avoid another helicopter, at which time, the oscillations and vibrations were so severe that the pilots’ headsets came off of their heads. The helicopter entered a spin and impacted the grass hard while moving laterally to the left. The pilots shut down and then exited the helicopter.

The blue main rotor blade damper was replaced the night before the accident. A maintenance test flight was performed following the replacement. The flight crewmembers who flew the test flight reported that there was a slight vibration from the main rotor system and that one of the five main rotor blades had a “slight dip” in its track. There was no record of the main rotor blade out-of-track discrepancy nor of a main rotor track and balance inspection being performed subsequent to this flight. Although an out-of-track blade could cause a persistent vertical vibration, an examination of the main rotor blades, elastomeric bearings, main rotor dampers, main rotor rod ends, main gearbox attachment points and antitorque beam, and automatic flight control system did not reveal any anomalies that could account for the vertical vibrations reported by the flight crew and recorded on the FDR.

Probable Cause: The helicopter’s sudden and severe vertical vibrations during landing, which resulted in a collision with terrain. The reason for the helicopter’s sudden and severe vertical vibrations could not be determined during postaccident examinations.


Sources:

NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20121023X30148&key=1

Location


Revision history:

Date/timeContributorUpdates
25-Oct-2012 06:34 aegir Added
25-Oct-2012 10:23 Alpine Flight Updated [Time, Aircraft type, Operator, Location, Narrative]
29-Oct-2012 04:22 aegir Updated [Source, Narrative]
19-Dec-2012 04:46 TB Updated [Time, Aircraft type, Location, Nature, Narrative]
28-Jun-2015 17:06 Aerossurance Updated [Phase, Departure airport, Source, Narrative]
28-Jun-2015 17:08 Aerossurance Updated [Time, Destination airport]
29-Sep-2016 15:06 Aerossurance Updated [Location, Source]
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
28-Nov-2017 13:45 ASN Update Bot Updated [Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative]

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