# NTSB CEN14LA450: Air Tractor AT-401, N91968, Natchez, LA, August 24, 2014

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: August 24, 2014, 17:30 local (22:30 UTC)
- Place: Natchez, LA
- Coordinates: 30.606666, -92.951667 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=30.6067&lon=-92.9517&mi=10
- Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping)
- Defining event: [Takeoff: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report January 14, 2015
- Report: Approved by Office Director
- NTSB office: Central Region
- Parties: FAA Baton Rouge FSDO
- NTSB case key (mKey): 89941
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN14LA450
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/89941/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=89941
- Page: https://openairdocs.org/ntsb/CEN14LA450

## Probable cause

The loss of power due to the failure of the No. 2 exhaust valve and rocker boss during takeoff.

## Findings

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

- [Engine (reciprocating): recip eng cyl section](https://openairdocs.org/ntsb-findings/01058530): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Air Tractor AT-401, 2 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md?model=0390204), [All aircraft, 373 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md)
- [Engine (reciprocating): recip eng cyl section](https://openairdocs.org/ntsb-findings/01058530): Aircraft › Aircraft power plant · Damaged/degraded (probable cause); cases with it: [Air Tractor AT-401, 2 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md?model=0390204), [All aircraft, 373 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md)

## Sequence of events

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

- [Takeoff: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Air Tractor AT-401, 4 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=0390204), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md)
- [Post-impact: Fire/smoke (post-impact)](https://openairdocs.org/ntsb-events/170); cases with it: [Air Tractor AT-401, 1 case](https://openairdocs.org/ntsb-events/170/sequence.md?model=0390204), [All aircraft, 354 cases](https://openairdocs.org/ntsb-events/170/sequence.md)

## Analysis

The pilot reported that during climbout for an agricultural flight, about 75 feet above the runway, he heard a loud "pop," and the engine started to lose power. He dumped the 250 gallons of chemical that weighed about 2,000 pounds. The airplane continued to lose altitude, and the pilot executed a forced landing to a cotton field. A postimpact engine fire ensued, consuming the airplane. An examination of the engine revealed that the No. 2 cylinder exhaust rocker boss was cracked, which likely allowed oil to escape, which led to the loss of engine power and the subsequent fire.

## Factual narrative

On August 24, 2014, about 1730 central daylight time, an Air Tractor AT-401, N91968, was destroyed by a post-impact ground fire after a forced landing due to a loss of engine power near Natchez, Louisiana. The pilot was not injured. The airplane was registered to and operated by Red River Dusting Inc. under the provisions of the 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed at the time of the accident. No flight plan was filed. The airplane was departing from a private grass airstrip near Natchez, Louisiana, at 1730 on a local flight. The pilot reported that during climbout about 75 above the runway, he heard a loud "pop" and the engine started to lose power. He dumped the 250 gallons of chemical that weighed about 2,000 pounds. The airplane continued to lose altitude. He executed a forced landing to a cotton field, and during the landing roll, the airplane hit a ditch which spun the airplane around. A post impact engine fire ensued and the airplane was consumed by fire. The pilot reported that the No. 2 cylinder "swallowed the exhaust valve" and broke the top of the jug. An examination of the engine revealed that the No. 2 cylinder exhaust rocker boss was cracked. The 600-horsepower radial engine had a total of 11,534 hours of operation. The time since the last inspection was 229 hours, and the time since the last overhaul was 1,314 hours.

## Aircraft

- Registration: [N91968](https://openairdocs.org/deregistered/N91968-2018-01-10), registration cancelled 2018-01-10, S/N 401-0942, built 1994 (OpenAirDocs)
- Reported make and model: AIR TRACTOR INC 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: 401-0942
- Year built: 1994
- Airframe hours: 7846
- Engines: Pratt & Whitney R-1340-S3H1-G 600 horsepower reciprocating
- Damage: Destroyed
- Fire: On-Ground
- Flight: Aerial application, Part 137
- Operator: Red River Dusting Inc
- Registered owner: Red River Dusting Inc
- Airworthiness certificate: Special, Restricted (Special); Standard, Utility
- Last inspection: Annual, May 9, 2014
- Departed: RRDI, Natchez, LA
- Destination: RRDI, Natchez, LA
- Airport: RRDI, Private Airstrip, runway 36, 3,000 × 100 ft, grass/turf
- Equipment: Stall warning system

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 47; injuries: none; commercial; airplane ratings: single-engine land; medical: class 2, without waivers/limitations; last flight review January 11, 2013; seat: single; restraint: 4-point; flight hours: 6,904 total, 2,591 in this make and model, 100 in the last 90 days, 30 in the last 30 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 60° at 4 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 93 °F, dew point 72 °F
- Altimeter: 29.89 inHg
- Observed at: IER, 5 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 20140824015459A](https://openairdocs.org/incident/20140824015459A), Aug 24, 2014: Air Tractor Inc AT-401, Natchitoches, LA, Destroyed. On climb out pilot experienced large ?pop? And smoke from engine. Started back to strip, dumped load and crashed. Pilot got out and plane caught fire.

## Other investigations on N91968 (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 FTW00LA074](https://openairdocs.org/ntsb/FTW00LA074), Jan 25, 2000: Air Tractor AT-401 (N91968), Rayville, LA, substantial damage. Probable cause: The loss of engine power due to a crack in the #6 cylinder. A factor was the lack of suitable terrain for the forced landing.

## Docket (4 files)

The files NTSB released with the investigation on October 3, 2014, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=89941. 3.8 MB in all.

- NTSB 6120-1 Pilot Report (item 1, .PDF, 3.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40417326&FileExtension=.PDF&FileName=NTSB%206120-1%20Pilot%20Report-Redacted.PDF
- Photo 1 – View of burned airplane in the cotton field (item 2, .PDF, 57 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40417327&FileExtension=.PDF&FileName=Photo%201%20%E2%80%93%20View%20of%20burned%20airplane%20in%20the%20cotton%20field-Master.PDF
- Photo 2 – View of radial engine (item 3, .PDF, 61 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40417328&FileExtension=.PDF&FileName=Photo%202%20%E2%80%93%20View%20of%20radial%20engine%0D%0A-Master.PDF
- Photo 3 – View of cracked cylinder (item 4, .PDF, 88 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40417329&FileExtension=.PDF&FileName=Photo%203%20%E2%80%93%20View%20of%20cracked%20cylinder-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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