Pilot Debrief

BELL HELICOPTER TEXTRON CANADA 206 L4 near Houston, TX — 2016-04-25

Final reportCEN16LA168
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Date
2016-04-25
Location
Houston, TX, USA
Airport
8TS4
Aircraft
BELL HELICOPTER TEXTRON CANADA 206 L4
Registration
N435AE
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Takeoff roll

Probable cause

The pilot's failure to maintain directional control during takeoff in varying wind conditions, which resulted in a hard landing.

NTSB narrative

The commercial pilot was departing for a positioning flight from a helipad bordered on three sides by buildings and parking structures. The pilot reported that, after lifting off, as he translated the helicopter from behind one of the buildings and into the prevailing wind, the nose began yawing right. He applied full left pedal, but the helicopter may have fully rotated once while moving back toward the helipad before the rotation stopped. The low rotor speed warning sounded, and the helicopter then began rotating rapidly right. The pilot lowered the collective and maneuvered toward the helipad. He subsequently raised the collective while at 25 ft above ground level, but the helicopter landed hard. A postaccident examination of the helicopter revealed no preimpact mechanical failures or malfunctions that would have precluded normal operation. A loss of tail rotor effectiveness can be encountered while hovering under certain wind conditions, which may be encountered unexpectedly near buildings due to rapidly changing wind conditions. However, the pilot's report that the low rotor speed warning sounded and engine data provided by the operator indicated that the main rotor speed decayed during the takeoff with a corresponding decrease in the tail rotor speed. A significant reduction in the tail rotor speed could result in an uncommanded yaw and a loss of directional control. The investigation was unable to determine if the pilot's loss of directional control was due solely to the decrease in rotor speed during takeoff, the varying wind conditions, or a combination of both.

Analysis

Primary failure mode
Loss of control
First missed decision gate
Pilot could have aborted takeoff when yawing began at 75 feet agl.

NTSB coding

Evidence available

  • 8 docket documents
View NTSB final reportView NTSB docket

Docket documents8

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