# NTSB MIA91LA101: Air Tractor AT-401, N73135, Avon, MS, March 15, 1991

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: March 15, 1991, 15:00 local (21:00 UTC)
- Place: Avon, MS
- Coordinates: 33.229438, -91.040496 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=33.2294&lon=-91.0405&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 1 serious
- Status: Completed, report February 8, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 32834
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA91LA101
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/32834/pdf
- Page: https://openairdocs.org/ntsb/MIA91LA101

## Probable cause

LOSS OF ENGINE POWER FOR UNDETERMINED REASONS DURING A TURN WHILE ON AN AERIAL APPLICATION FLIGHT.  CONTRIBUTING TO THE ACCIDENT WAS FAILURE OF THE LEFT MAGNETO DUE TO FAILURE OF A PHENOLIC GEAR WHICH DRIVES THE ROTATING MAGNET.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Loss of engine power, maneuvering - turn to reverse direction
  - ignition system,magneto - inoperative (contributing factor)
  - reason for occurrence undetermined (cause)
- Forced landing, descent - emergency
- In flight collision with terrain/water, landing - flare/touchdown
  - terrain condition - none suitable
- Nose over, landing - flare/touchdown

## Analysis

DURING A TURN FOR A SPRAY PASS, THE PLT STATED THAT THE ENG QUIT.  HE THEN OPENED THE CHEMICAL DUMP VALVE & LANDED THE ACFT PERPENDICULAR TO PLOWED ROWS IN A FIELD.  THE ACFT THEN NOSED OVER AFTER TOUCHDOWN & THE PLT WHO WAS UNCONSCIOUS, WAS CUT FREE FROM HIS SEATBELT & SHOULDER HARNESS.  EXAM OF THE ACFT AT THE ACCIDENT SITE REVEALED THAT THE MAGNETO SWITCH WAS POSITIONED TO 'BOTH.'  THE ACFT WAS RECOVERED & THE ENG WAS STARTED & OPERATED NORMALLY WITH THE MAGNETO SWITCH POSITIONED TO THE BOTH POSITION HOWEVER WHEN THE MAGNETO SWITCH WAS POSITIONED TO THE LT POSITION, THE ENG QUIT.  THE LT MAGNETO WAS REMOVED FOR DISASSEMBLY.  EXAM OF THE LT MAGNETO REVEALED THAT A PHENOLIC GEAR WHICH DRIVES THE ROTATING MAGNET WAS DAMAGED WHICH PREVENTED THE MAGNETO FROM PRODUCING SPARK.  NO DETERMINATION COULD BE MADE AS TO THE REASON FOR THE LOSS OF ENG POWER.

## Aircraft

- Registration: [N73135](https://openairdocs.org/aircraft/N73135), registered now, S/N 401-0671, built 1987 (OpenAirDocs)
- Reported make and model: Air Tractor AT-401
- Registry model: [Air Tractor AT-401](https://openairdocs.org/model/air-tractor-at-401) (registry code 0390204) (OpenAirDocs)
- Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 401-0671
- Airframe hours: 1675
- Engines: P&W R1340-AN1 600 horsepower reciprocating
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: Longwood Flying Service, Inc.
- Registered owner: Longwood Flying Service, Inc.
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, November 27, 1990, 50 hours before

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 59; commercial, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; flight hours: 16,225 total, 670 in this make and model, 14,900 as pilot in command, 50 in the last 90 days, 35 in the last 30 days, 6 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 360° at 5 knots, gusting 10
- Visibility: 5 statute miles
- Temperature: 64 °F

## 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 19910315006629A](https://openairdocs.org/incident/19910315006629A), Mar 15, 1991: Airtrc AT401, Avon, MS, Substantial damage. Engine quit during a spray run turn around. Landed across rows in plowed field. Nosed over. Left mag was defective.

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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