# NTSB FTW98LA360: Cessna 170, N2574V, Boulder, CO, August 16, 1998 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: August 16, 1998, 16:30 local (22:30 UTC) - Place: Boulder, CO - Coordinates: 39.989913, -105.090682 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.9899&lon=-105.0907&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 3 minor - Status: Completed, report January 28, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 43768 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW98LA360 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/43768/pdf - Page: https://openairdocs.org/ntsb/FTW98LA360 ## Probable cause The pilot's intentional ground loop and his inadequate compensation for the wind condition. A contributng factor was crosswinds. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - On ground/water encounter with terrain/water, landing - flare/touchdown - weather condition - crosswind (contributing factor) - compensation for wind conditions - inadequate, pilot in command (cause) - ground loop/swerve - intentional, pilot in command (cause) - terrain condition - runway ## Analysis As the pilot approached the airport for a full stop landing, he heard the pilot of another airplane, which was landing on runway 8 report that he had a tail wind during his landing sequence. The pilot 'noticed the wind sock on the east end of the runway was standing straight out in a direction that appeared to be 180 degrees.' The pilot landed on runway 26, but reported having difficulty keeping the airplane aligned with the centerline. He said 'I didn't feel at the time I stood any chance of gaining airspeed to execute a climb.' He performed a ground loop rather then go in the lake on the west end of the runway. One witness reported that immediately after the accident they noticed that the wind was coming from the northeast. The winds at the nearest reporting station, 9 nautical miles southeast, were 180 degrees and 13 knots at 1549 and at 1655, the winds were 150 degrees and 11 knots gusting to 20 knots. ## Factual narrative On August 16, 1998, approximately 1630 mountain daylight time, a Cessna 170, N2574V, was substantially damaged following an intentional ground loop initiated by the pilot at Boulder Municipal Airport, Boulder, Colorado. The private pilot and his two passengers received minor injuries. The airplane was being operated by the pilot under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the personal cross-country flight which originated from Ogallala, Nebraska, approximately 2 hours before the accident. A VFR flight plan had been filed. The pilot reported that as he approached Boulder Municipal Airport (elevation 5,288 feet, density altitude 7,807 feet) for a full stop landing, he heard the pilot of another airplane which was landing on runway 8 report that he had a tail wind during his landing. The pilot said that he "noticed the wind sock on the east end of the runway was standing straight out in a direction that appeared to be 180 degrees." The pilot landed on runway 26, but reported having difficulty keeping N2574V aligned with the centerline. He said, "I immediately determined to execute a go around. I had trimmed nose up for landing so I was attempting to get the nose down but was also buffeted by very turbulent winds [coming] over the hangers to the south." The pilot said that he believed it was safer to perform a ground loop then to go in the lake at the west end of the runway. He said, "I didn't feel at the time I stood any chance of gaining airspeed to execute a climb." One witness reported that immediately after the accident, they noticed that the wind was coming from the northeast. The winds at Jefferson County Airport (BJC), which is 9 nm southeast of Boulder Municipal Airport, were 180 degrees and 13 knots at 1549. At 1655, the winds at BJC were 150 degrees and 11 knots gusting to 20 knots. ## Aircraft - Registration: [N2574V](https://openairdocs.org/deregistered/N2574V-2001-01-20), registration cancelled 2001-01-20, S/N 18111 (OpenAirDocs) - Reported make and model: Cessna 170 - Registry model: [Cessna 170](https://openairdocs.org/model/cessna-170) (registry code 2072302) (OpenAirDocs) - Category: Airplane - Serial number: 18111 - Airframe hours: 5688 - Engines: Continental C145-2 145 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Eric D. Twombly - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 6, 1997, 126 hours before - Departed: OGA, OGALLALA, NE - Destination: 1V5 - Flight plan: VFR - Airport: 1V5, Boulder Municipal, runway 26, 4,100 × 75 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 47; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; seat: left; flight hours: 1,068 total, 1,025 in this make and model, 1,003 as pilot in command, 47 in the last 90 days, 30 in the last 30 days, 6 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 150° at 11 knots, gusting 20 - Visibility: 50 statute miles - Lowest ceiling: 20,000 ft broken - Temperature: 81 °F, dew point 52 °F - Altimeter: 30.00 inHg - Observed at: BJC, 9 nm away ## 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 19980816021079A](https://openairdocs.org/incident/19980816021079A), Aug 16, 1998: Cessna 170, Boulder, CO, Substantial damage. Acft encountered a crosswind on landing and attempted to go around, acft did not maintain the necessary altitude or airspeed, the pilot purposely ground looped… 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.