# NTSB SEA01LA139: Pilatus PC-6/B2-H4, N2TS, Great Falls, MT, July 21, 2001 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 21, 2001, 13:31 local (19:31 UTC) - Place: Great Falls, MT - Coordinates: 47.510032, -111.269905 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=47.5100&lon=-111.2699&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report August 26, 2003 - Report: Approved by Office Director - Parties: Federal Aviation Administration - NTSB case key (mKey): 52799 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA01LA139 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/52799/pdf - Page: https://openairdocs.org/ntsb/SEA01LA139 ## Probable cause Pilot's failure to maintain directional control of the aircraft while landing. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of control - on ground/water, landing - directional control - not maintained, pilot in command (cause) - ground loop/swerve - Gear collapsed, landing - roll - landing gear,main gear - overload ## Analysis According to a written report submitted by the operator, the pilot was landing the tail-wheel equipped airplane on runway 03. Shortly after touchdown, during the roll-out, the pilot manually unlocked the airplane's tail wheel. Upon releasing the tail-wheel lock, "...directional control of the airplane was lost." The airplane subsequently ground looped resulting in substantial damage to the right wing. The 1257 METAR observation at Great Falls reported winds from 070 degrees at 6 knots. The accident report submitted by the operator indicated that there were no mechanical malfunctions or failures with the aircraft that may have contributed to the accident. ## Factual narrative On July 21, 2001, at 1331 mountain daylight time, a Pilatus PC-6, airplane, N2TS, sustained substantial damage during the landing roll-out at Great Falls International Airport, Great Falls, Montana. The airplane is registered to N Bar Ranch, LLC, and was being operated as a visual flight rules (VFR) personal/pleasure flight under the provisions of Title 14, CFR Part 91, when the accident occurred. The airline transport pilot, and two passengers aboard the airplane, were not injured. Visual meteorological conditions prevailed and no flight plan was filed for the cross-country flight. The flight originated from a private airstrip near Wolf Creek, Montana, approximately 15 minutes prior to the accident. According to a written report submitted by the operator, the pilot was landing the tail-wheel equipped airplane on runway 03. Shortly after touchdown, during the roll-out, the pilot manually unlocked the airplane's tail wheel. Upon releasing the tail-wheel lock, "...directional control of the airplane was lost." The airplane subsequently ground looped resulting in substantial damage to the right wing. The 1257 METAR observation at Great Falls reported winds from 070 degrees at 6 knots. The accident report submitted by the operator indicated that there were no mechanical malfunctions or failures with the aircraft that may have contributed to the accident. ## Aircraft - Registration: [N2TS](https://openairdocs.org/deregistered/N2TS-2006-03-08), registration cancelled 2006-03-08, S/N 936, built 2000 (OpenAirDocs) - Reported make and model: Pilatus PC-6/B2-H4 - Registry model: [Pilatus PC-6/B2-H4](https://openairdocs.org/model/pilatus-pc-6-b2-h4) (registry code 7090215) (OpenAirDocs) - Registry engine: [Pratt & Whitney PT6A series](https://openairdocs.org/engine/pratt-whitney-pt6a-series) (registry code 52032, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 936 - Airframe hours: 119.5 - Engines: P&W Canada PT6A-27 550 horsepower turbo prop - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Thomas M. Siebel - Registered owner: N Bar Ranch LLC, C/O Dearborn Ranch - Airworthiness certificate: Standard, Normal - Last inspection: Annual, May 1, 2001, 43.3 hours before - Departed: PVT, Wolf Creek, MT - Destination: GTF, Great Falls, MT - Airport: GTF, Great Falls Intl, runway 030, 10,500 × 150 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 48; injuries: none; commercial, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 3, valid medical--no waivers/lim.; last flight review February 21, 2001; seat: left; flight hours: 2,850 total, 50 in this make and model, 2,080 as pilot in command, 110 in the last 90 days, 40 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 52° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 77 °F, dew point 52 °F - Altimeter: 29.90 inHg - Observed at: GTF ## 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 20010721025059A](https://openairdocs.org/incident/20010721025059A), Jul 21, 2001: Pilats PC6, Great Falls, MT, No damage. (-23) Pilot stated loss of directional control during landing roll. 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.