# NTSB FTW04LA056: Pitts S-1S, N9AQ, Burleson, TX, January 3, 2004 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: January 3, 2004, 12:40 local (18:40 UTC) - Place: Burleson, TX - Coordinates: 32.531665, -97.308052 - Nearby events: https://openairdocs.org/map.md?lat=32.5317&lon=-97.3081&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report March 30, 2004 - Report: Approved by Office Director - Parties: Fort Worth Flight Standards District Office - NTSB case key (mKey): 58578 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW04LA056 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/58578/pdf - Page: https://openairdocs.org/ntsb/FTW04LA056 ## Probable cause The separation of the right main gear wheel, during landing, due to the improper maintenance by unknown maintenance personnel on the right main landing gear assembly. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, landing - maintenance,installation - improper, unknown (contributing factor) - landing gear,wheel - separation (cause) ## Analysis While landing at a private airstrip, the right main gear separated from the aircraft. Shortly after touchdown, the right gear strut dug into the grass for approximately 75 feet before the aircraft nosed over and came to rest inverted. Inspection of the amateur-built aircraft revealed that there was an old crack on the flange where it was welded to the axle nut. A new fracture had propagated from the ends of this crack around the lower axle shaft bolt, causing the other 3 remaining bolts to fracture and separate. Examination also revealed that the axle shaft had been cut off next to the backing plate flange and an axle shaft similar to what is used on a Cessna spring gear was bolted to the flange with four quarter-inch bolts. The FAA Inspector found the separated wheel with a piece of the flange still attached to it by one of the bolts. The flange was able to swivel around the bolt, suggesting that the bolt (and the 3 other bolts) was improperly torqued. ## Factual narrative On January 3, 2004, at 1240 central standard time, a Pitts S-1S experimental amateur-built airplane, N9AQ, was substantially damaged following the separation of the right main landing gear wheel while landing on a private airstrip near Burleson, Texas. The airplane was registered to and operated by the pilot under Title 14 Code of Federal Regulations Part 91. The private pilot, sole occupant of the airplane, was not injured. The flight departed from the Spinks Airport (FWS) near Fort Worth, Texas with the Rafter J. Airport (3TX9) near Burleson, Texas, as its intended destination. Visual meteorological conditions prevailed, and a flight plan was not filed for the local flight. The 259-hour pilot, with approximately 17 hours in the accident aircraft, stated that he made a normal approach and landing on the 2,800 feet long by 50 feet wide private turf airstrip. Shortly after ground contact, the right main wheel separated from the aircraft. The right gear strut dug into the grass for approximately 75 feet before the aircraft nosed-over coming to rest in an inverted position. The aircraft sustained damage to the propeller, engine, landing gear, vertical stabilizer, and the upper wing surface. A witness standing beside the runway, reported that the approach and landing "appeared normal." However, when the right main gear touched the ground, it separated from the aircraft. Afterwards, the right main gear strut drug the nose of the aircraft into the ground and flipped inverted. According to the FAA Inspector, who responded to the accident site, an old crack was present on the flange where it was welded to the axle nut. A new fracture propagated from both ends of this crack around the lower axle shaft bolt, causing the other 3 remaining bolts to fracture and separate. The FAA Inspector added that the deformity of the flange in the area of the new fracture and the failure of the remaining axle shaft bolts indicated that the gear was subjected to a hard landing and/or substantial side loads prior to, or during the accident landing. The FAA Inspector also found the separated wheel with a piece of the flange still attached to it by one of the bolts. The flange was able to swivel around the bolt. The Inspector added that this condition suggested that the bolt (and the 3 other bolts) was improperly torqued. The amateur built Pitts S-1S, serial number 568-H, has accumulated a total airframe time of 1,486.8 hours. The most recent annual inspection was completed on June 22, 2003, 26 hours before the accident. The Lycoming engine, model IO-360-A1B, has 2425.8 hours total time. There has been 247.8 hours since the engine's last overhaul. ## Aircraft - Registration: [N9AQ](https://openairdocs.org/aircraft/N9AQ), registered now, S/N 568-H, built 1975 (OpenAirDocs) - Reported make and model: Pitts S-1S - Registry model: [Pitts S-1C](https://openairdocs.org/model/pitts-s-1c) (registry code 72202LV) (OpenAirDocs) - Registry engine: [Lycoming I0360 series](https://openairdocs.org/engine/lycoming-i0360-series) (registry code 41515, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 568-H - Airframe hours: 1486.8 - Engines: Lycoming IO-360-A1B 200 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Joe A. Scott - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Annual, June 22, 2003, 26 hours before - Departed: FWS, Burleson, TX - Destination: 3TX9, Burleson, TX - Airport: 3TX9, Rafter J Airport, runway 15, 2,800 × 50 ft, grass/turf ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 43; injuries: none; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; last flight review January 3, 2004; seat: center; flight hours: 259 total, 17 in this make and model, 172 as pilot in command, 9 in the last 90 days, 9 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 170° at 20 knots - Visibility: 10 statute miles - Lowest ceiling: 12,000 ft overcast - Temperature: 64 °F, dew point 46 °F - Altimeter: 30.10 inHg ## 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 20040103000369A](https://openairdocs.org/incident/20040103000369A), Jan 3, 2004: Amtr S1C, Fort Worth, TX, Substantial damage. (-23) Inspector's statement: my name is willis h. power; I'm employed as an aviation safety inspector at the forth Worth flight standards district office. On… 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.