# NTSB SEA95LA161: Air Tractor AT-301, N3660U, Havre, MT, July 24, 1995 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 24, 1995, 17:15 local (23:15 UTC) - Place: Havre, MT - Coordinates: 48.559696, -109.729682 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=48.5597&lon=-109.7297&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report April 29, 1996 - Report: Approved by Office Director - NTSB case key (mKey): 42203 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA95LA161 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/42203/pdf - Page: https://openairdocs.org/ntsb/SEA95LA161 ## Probable cause the loss of power due to a failure of the cylinder head exhaust valve rocker box. The tall crop encountered during the forced landing is a factor. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - mech failure/malf, maneuvering - aerial application - engine assembly,cylinder - fatigue (cause) - Forced landing, emergency descent/landing - In flight collision with terrain/water, emergency descent/landing - terrain condition - crop (contributing factor) - terrain condition - high vegetation (contributing factor) ## Analysis During an aerial application flight, the aircraft experienced a complete loss of engine power. Almost immediately after the loss of power, one of the aircraft's wings caught in the tall barley the pilot was spraying. After catching the wing, the aircraft cartwheeled and came to rest in an inverted position. Examination of the engine revealed that a rocker box had sustained a fatigue fracture at the point where the rocker pivot bolt passes through the box. ## Factual narrative On July 24, 1995, approximately 1715 mountain daylight time, an Air Tractor AT-301, N3660U, impacted the terrain and nosed over while maneuvering over an open field north of Havre, Montana. The airline transport pilot, who was the sole occupant of the aircraft, was not injured, but the aircraft sustained substantial damage. The aerial application flight, which departed Havre Airport about 20 minutes earlier, was being operated in visual meteorological conditions at the time of the accident. No flight plan had been filed, and there was no ELT activation. According to the pilot, the aircraft's engine experienced a total power loss, which was followed almost immediately by a wing tip being caught by the tall barley he was spraying. After catching the wing, the aircraft cartwheeled and came to a rest inverted in the field. Investigation revealed that an exhaust valve rocker box had failed at the point where the rocker pivot bolt passes through the box. An NTSB metallurgist made a visual inspection of the fracture surface and stated that it appeared to show evidence of fatigue. ## Aircraft - Registration: [N3660U](https://openairdocs.org/deregistered/N3660U-2009-06-23), registration cancelled 2009-06-23, S/N 301-0337, built 1981 (OpenAirDocs) - Reported make and model: AIR TRACTOR AT-301 - Registry model: [Air Tractor AT-301](https://openairdocs.org/model/air-tractor-at-301) (registry code 0390103) (OpenAirDocs) - Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 337 - Airframe hours: 3439 - Engines: P&W R-1340-AN1 600 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Registered owner: Darrold K. Hutchinson - Airworthiness certificate: Special, Restricted (Special) - Last inspection: 100 hour, June 1, 1995, 11 hours before - Departed: HVR, UT ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 43; airline transport, flight engineer, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: front; flight hours: 5,347 total, 920 in this make and model, 4,335 as pilot in command, 307 in the last 90 days, 100 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 60 statute miles - Lowest ceiling: none - Temperature: 70 °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 19950724045279A](https://openairdocs.org/incident/19950724045279A), Jul 24, 1995: Airtrc AT301, Havre, MT, Substantial damage. Lost power on spray run. Wing caught in tall barley. Cartwheeled. Rocker arm boss failed in fatigue. 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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.