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WPR11LA379 · Bell 47G-3B-2

14 Aug 2011 · Los Banos, CA, United States

Double Springs Helicopters Bell 47G-3B-2 · Accident: collision during takeoff/landing

From Los Banos, CA to Los Banos, CA

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Event

NTSB case
WPR11LA379
Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
Accident
InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
Completed
API-reported fatalities
0 · all aircraft and ground
Ground fatalities
Unknown
OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
General aviation
WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
Visual Meteorological Cond

Bell 47G-3B-2

Aircraft type
Bell 47
Category
Helicopter
RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
N475AL
Onboard fatalities
Unknown
Route
From Los Banos, CATo Los Banos, CA
Aircraft age
Not recorded
Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
Part 137: Agricultural
Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
Takeoff
Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
Collision during takeoff/landing
DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
Substantial

Cause areas

  • Aircraft › Aircraft power plant
  • Aircraft › Aircraft propeller/rotor
  • Personnel issues › Task performance

Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.

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.

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.

Verbatim NTSB analysis and probable cause from the NTSB dataset

Sources

NTSB record WPR11LA379
Event ID
20110814X84838
Case number
WPR11LA379
Dataset
full-current
Source SHA-256
5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
  • Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
  • Filled from the NTSB case API where the bulk record had no value: investigation status, coordinates. Values present in the bulk record are kept.
  • The date is the local date, which is the same as the UTC date the NTSB stores.
  • API snapshot SHA-256: 98a1b5b762364c8fb6518634342e91c385a6aee20fb6650acfaa0a77e68b26ad; retrieved 2026-09-15T16:36:27.164Z.