Pilot Debrief

GRUMMAN ACFT ENG COR-SCHWEIZER G-164A near Wilton, CA — 2012-05-27

Final reportWPR12LA233
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Date
2012-05-27
Location
Wilton, CA, USA
Airport
PVT
Aircraft
GRUMMAN ACFT ENG COR-SCHWEIZER G-164A
Registration
N8380
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Maneuvering

Probable cause

The failure of the hopper gate mechanism and subsequent sulfur fire during a low-level maneuver.

NTSB narrative

The pilot had just completed an aerial application of sulfur dust over a vineyard when the hopper gate closing mechanism failed as he attempted to stop the flow. The sulfur continued to flow from the hopper, so he initiated a steep turn to keep the dust within the confines of the vineyard. As he rolled out of the turn, the plume of sulfur ignited and a fire began within the hopper. He performed a forced landing into a residential driveway and the airplane sustained substantial damage during the ground roll. The airplane was configured to minimize the hazards of inadvertent fire during sulfur dusting operations; however, the evasive flight maneuver performed by the pilot may have brought the uninterrupted flow of sulfur dust into contact with hot engine exhaust. An alternative ignition source may also have been provided by a spark from the failed gate mechanism. The gate mechanism sustained thermal damage, which prevented an accurate assessment of its failure mode.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have checked the hopper gate mechanism before flight.

NTSB coding

Evidence available

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

Docket documents8

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