# NTSB LAX98LA011: Cessna 170A, N9212A, Quincy, CA, October 12, 1997 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: October 12, 1997, 15:00 local (22:00 UTC) - Place: Quincy, CA - Coordinates: 39.943987, -120.95396 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.9440&lon=-120.9540&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 4 uninjured - Status: Completed, report September 4, 1998 - Report: Approved by Office Director - NTSB case key (mKey): 29975 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX98LA011 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29975/pdf - Page: https://openairdocs.org/ntsb/LAX98LA011 ## Probable cause loss of directional control due to a severe tail wheel vibration, which was induced by an improperly installed and adjusted tail wheel assembly. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of control - on ground/water, landing - roll - landing gear,tailwheel assembly - other (cause) - maintenance,installation - improper, other maintenance personnel (cause) - maintenance,adjustment - improper, other maintenance personnel (cause) - landing gear,tailwheel assembly - vibration (cause) - directional control - not possible, pilot in command - ground loop/swerve - On ground/water encounter with terrain/water, landing ## Analysis The pilot reported that the approach, landing flare, and touchdown were normal. He further stated that during the initial ground roll, a very strong tail wheel vibration began, which 'shook the plane and overrode my rudder controls.' The pilot was unable to regain control, and the aircraft veered to the left, then ground looped in a very tight circle. Written statements submitted by the passengers were consistent with the pilot's report. An FAA airworthiness inspector examined the runway and aircraft. He reported that tail wheel scrub marks were present on the runway pavement in a high frequency wave pattern which led to the point of the ground loop. Examination of the aircraft disclosed about 1/8-inch play in the tail wheel bearings. The inspector also reported that the tail wheel was improperly shimmed. Review of the maintenance records disclosed that the tail wheel was replaced 12 days before the accident. Work orders from the repair shop (that installed the unit) noted that the tail wheel assembly was supplied by the owner. The work order noted that the bearings were replaced by the shop at the time of installation. ## Factual narrative On October 12, 1997, at 1500 hours Pacific daylight time, a Cessna 170A, N9212A, ground looped while attempting to land at the Gansner Field Airport, Quincy, California. The aircraft sustained substantial damage and the commercial pilot and three passengers were not injured. The aircraft was owned and operated by the pilot, and was completing a personal cross-country flight from Chico, California. Visual meteorological conditions prevailed and included light and variable wind conditions. In his written statement, the pilot reported that the approach, landing flare, and touchdown were normal. He further stated that during the initial ground roll, a very strong tailwheel vibration began and "shook the plane and overrode my rudder controls." The pilot was unable to regain control and the aircraft veered to the left, then ground looped in a very tight circle. Written statements submitted by the passengers were consistent with the pilot's report. An Federal Aviation Administration airworthiness inspector from the Reno, Nevada, Flight Standards District Office examined the runway and the aircraft. He reported that tail wheel scrub marks were present on the runway pavement in a high frequency wave pattern which led to the point of the ground loop. Examination of the aircraft disclosed about 1/8-inch play in the tail wheel bearings. The inspector also reported that the tail wheel was improperly shimmed. Review of the maintenance records disclosed that the tail wheel was replaced 12 days prior to the accident. The work orders from the repair shop which installed the unit noted that the tail wheel assembly was supplied by the owner. The work order notes that the bearings were replaced by the shop at the time of installation. ## Aircraft - Registration: [N9212A](https://openairdocs.org/aircraft/N9212A), registered now, S/N 18973, built 1949 (OpenAirDocs) - Reported make and model: Cessna 170A - Registry model: [Cessna 170A](https://openairdocs.org/model/cessna-170a) (registry code 2072304) (OpenAirDocs) - Registry engine: [Continental C145 series](https://openairdocs.org/engine/continental-c145-series) (registry code 17012, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 18973 - Engines: Continental O-300 145 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: James R. Forbes - Airworthiness certificate: Standard, Normal - Departed: CIC, CHICO, CA - Destination: 201 - Airport: 2O1, Gasner Field, runway 24, 4,100 × 60 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 68; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; seat: left; flight hours: 2,599 total, 500 in this make and model, 2,426 as pilot in command, 18 in the last 90 days, 6 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Visibility: 30 statute miles - Lowest ceiling: none ## 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 19971012031319A](https://openairdocs.org/incident/19971012031319A), Oct 12, 1997: Cessna 170A, Quincy, CA, Substantial damage. Tailwheel shimmy landing. Lost control. Ground looped. Tailwheel bearings worn out. Wheel improperly shimmed. 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.