# NTSB LAX96LA291: Boeing A75N1, N68251, Tracy, CA, July 29, 1996 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 29, 1996, 06:15 local (13:15 UTC) - Place: Tracy, CA - Coordinates: 37.730365, -121.420516 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.7304&lon=-121.4205&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report December 16, 1996 - Report: Approved by Office Director - NTSB case key (mKey): 29524 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX96LA291 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29524/pdf - Page: https://openairdocs.org/ntsb/LAX96LA291 ## Probable cause A loss of engine power due to the disengagement of the crankshaft gear from it's hub due to the overload shear of the eight retaining screws. ## 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, cruise - engine assembly,timing gear - sheared (cause) - engine assembly,timing gear - disengaged (cause) - ignition system,magneto - disengaged - Forced landing, emergency descent/landing - On ground/water encounter with terrain/water, landing - roll - terrain condition - ditch ## Analysis The pilot reported that the engine quit while he was en route to a job and he landed in an alfalfa field. The aircraft collided with a ditch which was obscured by the crops. A postcrash fire erupted and consumed the aircraft. The aircraft was examined by an FAA airworthiness inspector. He reported that the engine crankshaft would rotate; however, no corresponding valve action was noted on any cylinder. The inspector observed a disassembly of the engine and reported that the eight screws which secure the crankshaft hub to the crankshaft gear had sheared. The crankshaft gear rotates all accessory drive gears, including the magnetos. ## Factual narrative On July 29, 1996, at 0615 hours Pacific daylight time, a Boeing A75-N1, N68251, collided with a ditch during a forced landing near Tracy, California. The forced landing was precipitated by a total loss of engine power. The aircraft was operated by Trinkle & Boys of Tracy, and was on an aerial application flight under 14 CFR 137 of the Federal Aviation Regulations. Visual meteorological conditions prevailed and no flight plan was filed. The aircraft was demolished in the impact and postcrash fire sequence. The certificated commercial pilot was not injured. The flight originated at a private agricultural airstrip near Tracy at 0600 on the morning of the accident and was loaded with sulfur for application to a nearby field. The pilot reported that the engine quit while he was en route to a job and he landed in an alfalfa field. The aircraft collided with a ditch which was obscured by the crops. A postcrash fire erupted and consumed the aircraft. The aircraft was examined by an FAA airworthiness inspector. He reported that the engine crankshaft would rotate; however, no corresponding valve action was noted on any cylinder. The inspector observed a disassembly of the engine and reported that the eight screws which secure the crankshaft hub to the crankshaft gear had sheared. The crankshaft gear rotates all accessory drive gears, including the magnetos. ## Aircraft - Registration: [N68251](https://openairdocs.org/deregistered/N68251-2004-05-26), registration cancelled 2004-05-26, S/N 75-7976, built 1943 (OpenAirDocs) - Reported make and model: Boeing A75N1 (A75-N1) - Registry model: [Boeing A75N1(PT17)](https://openairdocs.org/model/boeing-a75n1-pt17) (registry code 1380134) (OpenAirDocs) - Registry engine: [Wright 975E&F-2&3](https://openairdocs.org/engine/wright-975e-f-2-3) (registry code 67015, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 75-7976 - Airframe hours: 3779 - Engines: Wright R-975-11 440 horsepower reciprocating - Damage: Destroyed - Fire: On-Ground - Flight: Aerial application, Part 137 - Registered owner: Trinkel & Boys - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, June 26, 1996, 85 hours before ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 49; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: center; flight hours: 4,700 total, 1,030 in this make and model, 4,450 as pilot in command, 150 in the last 90 days, 85 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 20 statute miles - Lowest ceiling: none - 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 19960729026049A](https://openairdocs.org/incident/19960729026049A), Jul 29, 1996: Boeing A75N1, Tracy, CA, Destroyed. (.4)The pilot reported that the engine quit while he was en route to a job and he landed in an alfalfa field. The aircraft collided with a ditch which was… 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.