# NTSB CEN18LA357: Grumman G164, N956X, Opelousas, LA, August 29, 2018

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: August 29, 2018, 11:30 local (16:30 UTC)
- Place: Opelousas, LA
- Coordinates: 30.540832, -92.203613
- Nearby events: https://openairdocs.org/map.md?lat=30.5408&lon=-92.2036&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Defining event: [Maneuvering: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report November 19, 2019
- Report: Approved by Office Director
- NTSB office: Central Region
- Parties: FAA Flight Standards District Office
- NTSB case key (mKey): 98188
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN18LA357
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/98188/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=98188
- Page: https://openairdocs.org/ntsb/CEN18LA357

## Probable cause

The loss of two securing bolts that allowed the left magneto to move around, which disrupted the spark timing and resulted in the engine losing total power.

## Findings

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

- [Ignition system: magneto/distributor](https://openairdocs.org/ntsb-findings/01057414): Aircraft › Aircraft power plant · Inoperative (probable cause); cases with it: [Grumman G-164A, 2 cases](https://openairdocs.org/ntsb-findings/01057414/cases.md?model=3952704), [All aircraft, 101 cases](https://openairdocs.org/ntsb-findings/01057414/cases.md)
- [Terrain: wet/muddy terrain](https://openairdocs.org/ntsb-findings/03021035): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Grumman G-164A, 2 cases](https://openairdocs.org/ntsb-findings/03021035/cases.md?model=3952704), [All aircraft, 110 cases](https://openairdocs.org/ntsb-findings/03021035/cases.md)

## Sequence of events

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

- [Maneuvering: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Grumman G-164A, 11 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=3952704), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md)
- [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Grumman G-164A, 12 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=3952704), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md)
- [Landing: Nose over/nose down](https://openairdocs.org/ntsb-events/096); cases with it: [Grumman G-164A, 11 cases](https://openairdocs.org/ntsb-events/096/sequence.md?model=3952704), [All aircraft, 2,287 cases](https://openairdocs.org/ntsb-events/096/sequence.md)

## Analysis

The private pilot was practicing crop-dusting maneuvers when the engine lost total power; he performed a forced landing in an open, muddy field. The airplane nosed over and sustained substantial damage. Postaccident examination of the engine revealed that two of three bolts that secured the left magneto had come loose and were missing. The safety wire was broken, and the Sims coupling was heavily damaged. The magneto could easily be moved around, which disrupted the spark timing and resulted in a total loss of power.

## Factual narrative

On August 29, 2018, about 1130 central daylight time, a Grumman G-164A airplane, N956X, experienced a total loss of engine power while maneuvering over an open field near Opelousas, Louisiana. The pilot subsequently made an off-airport forced landing in the field. The private pilot was not injured. The airplane sustained substantial damage to the top wings and vertical stabilizer. The airplane was registered to Acadian Dusters LLC, Church Point, Louisiana, and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions were reported at the accident site about the time of the accident, and no flight plan had been filed. The local flight originated from Church Point about 1100. According to the pilot's accident report, he was practicing crop dusting maneuvers when the engine lost all power. Being at low altitude, the pilot made a forced landing in an open muddy rice field, and the airplane nosed over. Post-accident examination of the engine revealed that two bolts that secure the left magneto had come loose and were missing. This disrupted the spark timing, resulting in a complete power loss. The magneto was identified as an American Bosh SB9RU-3 magneto, serial number BB3829, that was installed on January 13, 1998. A Federal Aviation Administration inspector examined the airplane. In his e-mail, he reported finding two of the three bolts for the left magneto had come out. The safety wire was also broken. He stated the left magneto was barely holding on. The Sims coupling was heavily damaged as well. He could easily move the magneto around.

## Aircraft

- Registration: [N956X](https://openairdocs.org/deregistered/N956X-2020-09-04), registration cancelled 2020-09-04, S/N 507, built 1968 (OpenAirDocs)
- Reported make and model: Grumman G164 (A)
- Registry model: [Grumman G-164A](https://openairdocs.org/model/grumman-g-164a) (registry code 3952704) (OpenAirDocs)
- Registry engine: [Pratt & Whitney R-985 series](https://openairdocs.org/engine/pratt-whitney-r-985-series) (registry code 52008, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 507
- Year built: 1968
- Airframe hours: 12058
- Engines: Pratt & Whitney R985-14B 450 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, August 8, 2018
- Departed: 6LA5, Church Point, LA
- Destination: 6LA5, Church Point, LA
- Equipment: Stall warning system

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 35; injuries: none; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review April 14, 2017; seat: single; restraint: 4-point; flight hours: 208 total, 15 in this make and model, 208 as pilot in command, 55 in the last 90 days, 35 in the last 30 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 240° at 5 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 86 °F, dew point 70 °F
- Altimeter: 30.10 inHg
- Observed at: KOPL, 10 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 20180829012539A](https://openairdocs.org/incident/20180829012539A), Aug 29, 2018: Grumman G-164A, Opelousas, LA, Substantial damage. Pilot took off from Church Point Flyers Strip to practice part 137 flying on his farmland. About an hour later, on his return to Church Point Flyers Strip…

## Other investigations on N956X (1)

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.

- [NTSB FTW75FRD47](https://openairdocs.org/ntsb/FTW75FRD47), May 9, 1975: Grumman G-164A (N956X), Morse, LA, substantial damage

## Docket (3 files)

The files NTSB released with the investigation on October 3, 2018, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=98188. 3.8 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 3.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40467170&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF
- E-mail from FAA Inspector (item 2, .PDF, 79 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40467171&FileExtension=.PDF&FileName=E-mail%20from%20FAA%20Inspector-Master.PDF
- Report Photos (item 3, .PDF, 3 photos, 651 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40467172&FileExtension=.PDF&FileName=Report%20Photos-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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