# NTSB WPR12LA233: Grumman Acft ENG Cor-Schweizer G-164A, N8380, Wilton, CA, May 27, 2012

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: May 27, 2012, 08:15 local (15:15 UTC)
- Place: Wilton, CA
- Coordinates: 38.337776, -121.235557 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=38.3378&lon=-121.2356&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Defining event: [Maneuvering-low-alt flying: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report November 26, 2012
- Report: Approved by Office Director
- NTSB office: Western Pacific Region
- Parties: Federal Aviation Administration FSDO
- ADs cited in the narratives: [AD 48-34-02](https://openairdocs.org/ad/48-34-02) (OpenAirDocs)
- NTSB case key (mKey): 83762
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR12LA233
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/83762/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=83762
- Page: https://openairdocs.org/ntsb/WPR12LA233

## Probable cause

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

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Equipment/furnishings: agricultural/external load sys](https://openairdocs.org/ntsb-findings/01022551): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Grumman Acft ENG Cor-Schweizer G-164A, 1 case](https://openairdocs.org/ntsb-findings/01022551/cases.md?model=3952801), [All aircraft, 14 cases](https://openairdocs.org/ntsb-findings/01022551/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Maneuvering-low-alt flying: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Grumman Acft ENG Cor-Schweizer G-164A, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=3952801), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md)
- [Maneuvering-low-alt flying: Hazardous material leak/spill](https://openairdocs.org/ntsb-events/450); cases with it: [Grumman Acft ENG Cor-Schweizer G-164A, 1 case](https://openairdocs.org/ntsb-events/450/sequence.md?model=3952801), [All aircraft, 12 cases](https://openairdocs.org/ntsb-events/450/sequence.md)
- [Maneuvering-low-alt flying: Abrupt maneuver](https://openairdocs.org/ntsb-events/270); cases with it: [Grumman Acft ENG Cor-Schweizer G-164A, 1 case](https://openairdocs.org/ntsb-events/270/sequence.md?model=3952801), [All aircraft, 346 cases](https://openairdocs.org/ntsb-events/270/sequence.md)
- [Maneuvering-low-alt flying: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150); cases with it: [Grumman Acft ENG Cor-Schweizer G-164A, 2 cases](https://openairdocs.org/ntsb-events/150/sequence.md?model=3952801), [All aircraft, 504 cases](https://openairdocs.org/ntsb-events/150/sequence.md)
- [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Grumman Acft ENG Cor-Schweizer G-164A, 12 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=3952801), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md)
- [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Grumman Acft ENG Cor-Schweizer G-164A, 20 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=3952801), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)

## Analysis

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.

## Factual narrative

HISTORY OF FLIGHT On May 27, 2012, about 0815 Pacific daylight time, a Grumman G-164A, N8380, experienced an in-flight fire to its chemical dispersal system near Wilton, California. The airplane was operated by Harding Flying Service, and was engaged in agricultural aerial application operations under the provisions of 14 Code of Federal Regulations Part 137. The certificated commercial pilot was not injured, the airplane sustained substantial damage during the accident sequence, and was consumed by post impact fire. The local flight departed from a private airstrip near Clarksburg about 0730. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot reported that he had just completed a pass over a vineyard where he was applying sulfur dust. As he pulled the hopper gate lever to stop the flow, the lever went limp. 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 behind the airplane and he heard a popping sound from the hopper, which was now on fire. He performed a forced landing into a residential driveway, and during the ground roll, the main landing gear became embedded in soft dirt, and the airplane nosed over. The majority of the airplane's non-steel components were consumed by fire. The airplane's maintenance records were examined by an inspector from the Federal Aviation Administration. According to the records, the airplane had undergone an annual inspection, which was completed on January 16, 2012. At that time, the airplane had amassed 12,376 flight hours since its manufacture in 1971. The FAA inspector stated that the airplane was in compliance with Airworthiness Directive 48-34-02, which defines the inclusion of specific aircraft features designed to decrease the hazards from fire during dusting operations involving the use of sulfur. The gate mechanism was the original factory installed system. Examination of the hopper gate mechanism, located under the cabin floor, revealed that the hinge of the gate interconnect tube had separated from the gate lever. The hinge bolt remained in place, and attached to the remnants of the hinge. The mechanism had sustained thermal damage, which prevented an accurate assessment of its fracture features. Review of the FAA Service Difficulty Report and Airworthiness Directive databases did not reveal any documentation of prior instances of this failure.

## Aircraft

- Registration: [N8380](https://openairdocs.org/deregistered/N8380-2018-03-08), registration cancelled 2018-03-08, S/N 874, built 1971 (OpenAirDocs)
- Reported make and model: GRUMMAN ACFT ENG COR-SCHWEIZER G-164A
- Registry model: [Grumman Acft ENG Cor-Schweizer G-164A](https://openairdocs.org/model/grumman-acft-eng-cor-schweizer-g-164a) (registry code 3952801) (OpenAirDocs)
- Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 874
- Airframe hours: 12376
- Engines: Pratt and Whitney R1340 SERIES 600 horsepower reciprocating
- Damage: Substantial damage
- Fire: In-Flight
- Flight: Aerial application, Part 137
- Operator: Harding, Harry Nelson, doing business as Harding Flying Service
- Registered owner: Avery Walter DBA
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, January 16, 2012, 56 hours before
- Departed: PVT, Clarksburg, CA
- Destination: PVT, Wilton, CA
- Airport: PVT, Clarksburg

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 54; injuries: none; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review June 1, 2010; seat: single; flight hours: 3,300 total, 2,000 in this make and model, 3,200 as pilot in command, 100 in the last 90 days, 30 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 180° at 6 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 55 °F, dew point 46 °F
- Altimeter: 30.12 inHg
- Observed at: KMHR, 15 nm away

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 20120527009959A](https://openairdocs.org/incident/20120527009959A), May 27, 2012: Grumman Acft Eng Cor-Schweizer G-164A, Wilton, CA, Substantial damage. The pilot was closing the gate of the hopper at the end of an sulphur dust application pass when he felt a "snap" and felt the gate handle go slack. He pulled…

## Docket (8 files)

The files NTSB released with the investigation on October 3, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=83762. 4.4 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 262 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40376327&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF
- Photo 1 – Exemplar Gate Control Lever (item 2, .PDF, 98 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40376329&FileExtension=.PDF&FileName=Photo%201%20%E2%80%93%20Exemplar%20Gate%20Control%20Lever-Master.PDF
- Photo 2 – Gate Control Torque Tube Fitting (item 3, .PDF, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40376330&FileExtension=.PDF&FileName=Photo%202%20%E2%80%93%20Gate%20Control%20Torque%20Tube%20Fitting-Master.PDF
- Photo 3 – Torque Tube Hinge Tab (item 4, .PDF, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40376331&FileExtension=.PDF&FileName=Photo%203%20%E2%80%93%20Torque%20Tube%20Hinge%20Tab-Master.PDF
- Photo 4 - Torque Tube Hinge (item 5, .PDF, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40376332&FileExtension=.PDF&FileName=Photo%204%20-%20Torque%20Tube%20Hinge-Master.PDF
- Airframe Logbook Excerpts (item 6, .PDF, 248 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40376334&FileExtension=.PDF&FileName=Airframe%20Logbook%20Excerpts-Redacted.PDF
- FAA Airworthiness Directive 48-34-02 (item 7, .PDF, 30 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40376335&FileExtension=.PDF&FileName=FAA%20Airworthiness%20Directive%2048-34-02-Master.PDF
- Evidence Control Form (item 8, .PDF, 78 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40376336&FileExtension=.PDF&FileName=Evidence%20Control%20Form-Master.PDF

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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