Pilot Debrief

BELL 47G-3B-2 near Los Banos, CA — 2011-08-14

Final reportWPR11LA379
Sign in to save
Date
2011-08-14
Location
Los Banos, CA, USA
Aircraft
BELL 47G-3B-2
Registration
N475AL
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Takeoff roll

Probable cause

The pilot’s inadequate preflight, and contamination of both the engine compressor section and the main rotor blades, which resulted in reduced performance of the engine and rotor system.

NTSB narrative

During an agricultural application flight, the helicopter had just departed from the elevated landing pad when it experienced a loss of lift, which the pilot thought was a loss of engine power. The pilot attempted to arrest the descent but was unsuccessful before the helicopter hit the trees. Examination of the engine revealed no pre-impact mechanical malfunctions that would have prevented normal operations. Postaccident examination noted that the compressor vanes and both main rotor blades were layered with a substance that had the consistency of peanut butter. As a result of the contamination, the compressor would not operate at its optimum level, which affected the power output performance of the engine. The material on the main rotor blades would also have affected the helicopter’s lift performance. The examination did not reveal what the substance was, but the airplane flew through agricultural products, which may have led to the substance building up on the blades and compressor over time. Had the pilot done a preflight inspection, he may have noticed the contamination in the engine compressor section and the main rotor blades. Because the helicopter was departing from an elevated land platform, after liftoff, the helicopter was immediately out of ground effect, which resulted in an immediate descent that the pilot was unable to arrest.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have conducted a preflight inspection for contamination.

NTSB coding

Evidence available

  • 4 docket documents
View NTSB final reportView NTSB docket

Docket documents4

Related mishaps