Pilot Debrief

MESSERSCHMITT-BOELKOW-BLOHM BO-105S near Thibodaux, LA — 2009-09-06

Final reportCEN09LA571
Sign in to save
Date
2009-09-06
Location
Thibodaux, LA, USA
Airport
L83
Aircraft
MESSERSCHMITT-BOELKOW-BLOHM BO-105S
Registration
N131EH
Category
Helicopter
Highest injury
Minor
Fatalities
0
Phase of flight
Hover

Probable cause

The pilot's inability to maintain control due to the mechanic's inadvertent switching of two cyclic control tubes of different lengths during maintenance.

NTSB narrative

While in a 3-foot hover the helicopter began an uncommanded roll to the right. The pilot unsuccessfully attempted to arrest the roll by applying full left cyclic. Moments later the right landing skid made contact with the ground, followed by the main rotor blades. The helicopter came to rest in a right-side-low, upright position and the pilot was able to exit unassisted. The purpose of the flight was to perform an operational flight check of maintenance performed to the cyclic control system. The investigation revealed that the mechanic who had performed the maintenance had inadvertently switched two cyclic control tubes, of different lengths, during reassembly. This resulted in an out-of-rig condition in the cyclic control system. No other preimpact anomalies were noted with the helicopter's flight control system.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Mechanic could have correctly reassembled the cyclic control tubes.

NTSB coding

Evidence available

  • Photos
  • 3 docket documents
View NTSB final reportView NTSB docket

Docket documents3

Related mishaps