# NTSB DEN99LA100: Butler SX-300, N120J, Hill Afb, UT, June 12, 1999 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 12, 1999, 12:00 local (18:00 UTC) - Place: Hill Afb, UT - Coordinates: 41.119785, -111.979263 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=41.1198&lon=-111.9793&mi=10 - Phase of flight: [Taxi](https://openairdocs.org/ntsb-phases/250) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report October 13, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 46518 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN99LA100 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/46518/pdf - Page: https://openairdocs.org/ntsb/DEN99LA100 ## Probable cause A failure of the left main landing gear attachment for undetermined reasons. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Gear collapsed, taxi - from landing - landing gear,main gear attachment - failure,total (cause) - reason for occurrence undetermined (cause) ## Analysis While taxiing following landing at the end of a cross-country flight, the left main landing gear collapsed when the pilot turned the airplane. Examination determined the strut's outer trunion flange had cracked and broke free from its attach bolt. This action had apparently taken place several days before the accident when the pilot related he had heard a loud 'bang/thump' but could not find the origin. ## Factual narrative On June 12, 1999, at 1200 mountain daylight time, a Butler SX-300 homebuilt experimental aircraft, N120J, sustained substantial damage when the left main landing gear collapsed during taxi from landing at Hill AFB, Ogden, Utah. The commercial pilot and sole occupant was not injured. Visual meteorological conditions prevailed for this air show flight operating under Title 14 CFR Part 91 and no flight plan was filed. The flight departed Salt Lake City, Utah, earlier in the day. The pilot said he was taxiing the aircraft to the ramp following landing and the left main landing gear collapsed when he made a turn. According to the Federal Aviation Administration (FAA) Inspector who examined the aircraft following the accident, the pilot had landing gear problems a few days before the accident. The pilot related to the FAA inspector that he had heard a loud "bang/thump" from the landing gear but could not find the origin. In a post-accident examination, the FAA inspector examined the left landing gear and determined the strut's outer trunnion flange had cracked and broke free from its attachment bolt. The inspector said this action allowed the strut to rotate forward. With this rotation, the actuator ram threaded rod end bent, then snapped free from the self-aligning anti-friction rod end assembly. The strut continued forward and impacted the fuselage causing damage to a structural bulkhead. Both sides of the empennage sustained damage and exhibited wrinkled skin panels. ## Aircraft - Registration: [N120J](https://openairdocs.org/aircraft/N120J), registered now, S/N 60, built 1988 (OpenAirDocs) - Reported make and model: BUTLER SX-300 - Registry model: [Butler John R SX 300](https://openairdocs.org/model/butler-john-r-sx-300) (registry code 05612VN) (OpenAirDocs) - Registry engine: [Lycoming IO-540 series](https://openairdocs.org/engine/lycoming-io-540-series) (registry code 41530, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 60 - Airframe hours: 906 - Engines: Lycoming AEIO540L 300 horsepower reciprocating - Damage: Substantial damage - Flight: Part 91 - Registered owner: John R. Butler - Airworthiness certificate: Special, Experimental (Special) - Last inspection: AAIP, June 27, 1998, 50 hours before - Departed: SLC, SALT LAKE CITY, UT - Destination: HIF, OGDEN, UT - Airport: HIF, Hill Air Force Base, runway 14, 13,500 × 200 ft, concrete ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 74; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 19,414 total, 900 in this make and model, 14,400 as pilot in command, 20 in the last 90 days, 10 in the last 30 days, 8 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 4 knots - Visibility: 7 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 50 °F - Altimeter: 30.00 inHg - Observed at: HIL ## 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 19990612006829A](https://openairdocs.org/incident/19990612006829A), Jun 12, 1999: Amtr SX300, Ogden, UT, Substantial damage. Acft was involved in an air show when its left main landing gear collapsed on landing. (From .19) on June 12, 1999, at 1200 mountain daylight time, a butler… ## Other investigations on N120J (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 CEN12CA121](https://openairdocs.org/ntsb/CEN12CA121), Jan 3, 2012: Butler John R SX 300 (N120J), Truth or Consequences, NM, substantial damage. Probable cause: The pilot did not maintain airplane control during takeoff due to his distraction with the improperly secured canopy, which he forgot to latch. 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.