# NTSB ANC20CA018: Cessna 172, N817PS, Palmer, AK, February 6, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Data collection · Final report - Date: February 6, 2020, 12:30 local (21:30 UTC) - Place: Palmer, AK - Coordinates: 61.410278, -148.086669 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.4103&lon=-148.0867&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Low altitude operation/event](https://openairdocs.org/ntsb-events/220) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report July 27, 2020 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - NTSB case key (mKey): 100923 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC20CA018 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/100923/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=100923 - Page: https://openairdocs.org/ntsb/ANC20CA018 ## Probable cause The pilot's failure to maintain clearance from snow-covered terrain while maneuvering at low altitude. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Attention/monitoring: monitoring environment](https://openairdocs.org/ntsb-findings/02021545): Personnel issues › Psychological · Pilot (probable cause); cases with it: [Cessna 172F, 1 case](https://openairdocs.org/ntsb-findings/02021545/cases.md?model=2072414), [All aircraft, 809 cases](https://openairdocs.org/ntsb-findings/02021545/cases.md) - [Performance/control parameters: altitude](https://openairdocs.org/ntsb-findings/01062012): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Cessna 172F, 3 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md?model=2072414), [All aircraft, 1,310 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md) - [Object/animal/substance: snow/ice](https://openairdocs.org/ntsb-findings/03022060): Environmental issues › Physical environment · Effect on personnel (probable cause); cases with it: [Cessna 172F, 1 case](https://openairdocs.org/ntsb-findings/03022060/cases.md?model=2072414), [All aircraft, 67 cases](https://openairdocs.org/ntsb-findings/03022060/cases.md) - [Perception/orientation/illusion: visual illusion/disorientation](https://openairdocs.org/ntsb-findings/02022015): Personnel issues › Psychological · Pilot; cases with it: [Cessna 172F, 1 case](https://openairdocs.org/ntsb-findings/02022015/cases.md?model=2072414), [All aircraft, 51 cases](https://openairdocs.org/ntsb-findings/02022015/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-low-alt flying: Low altitude operation/event](https://openairdocs.org/ntsb-events/220) (defining event); cases with it: [Cessna 172F, 1 case](https://openairdocs.org/ntsb-events/220/sequence.md?model=2072414), [All aircraft, 780 cases](https://openairdocs.org/ntsb-events/220/sequence.md) - [Maneuvering-low-alt flying: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Cessna 172F, 22 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=2072414), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis According to the pilot, while conducting a low-altitude pass over a frozen, snow-covered lake in his wheel-equipped airplane, he misjudged the airplane's height above the lake. The landing gear contacted snow, and subsequently, the left wing and propeller struck the ground, and the airplane came to rest upright. The left wing sustained substantial damage. The pilot reported there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. The pilot added that the accident may have been prevented if he had done a better job of evaluating the flight scenario and had properly addressed the risks involved with low-level flight over a snow-covered landscape, including the importance of recognizing visual illusions and depth perception issues associated with those conditions. ## Factual narrative According to the pilot, while conducting a low altitude pass over a frozen, snow-covered lake in his wheel-equipped airplane, he misjudged the airplane's height above the ground. The airplane's landing gear contacted the snow and the airplane descended. Subsequently, the left wing and propeller struck the ground and the airplane came to rest upright on the snow-covered terrain, sustaining substantial damage to the left wing. The pilot stated there were no preaccident mechanical malfunctions or anomalies that would have precluded normal operation. In the recommendation section of the NTSB Accident/Incident Reporting Form 6120.1, the pilot stated that the accident may have been prevented if he had done a better job of evaluating the flight scenario and had properly addressed the risks involved with low level flight over a snow covered landscape. In addition to, the visual illusions associated with those conditions. ## Aircraft - Registration: [N817PS](https://openairdocs.org/aircraft/N817PS), registered now, S/N 17252705, built 1965 (OpenAirDocs) - Reported make and model: Cessna 172 (F) - Registry model: [Cessna 172F](https://openairdocs.org/model/cessna-172f) (registry code 2072414) (OpenAirDocs) - Registry engine: [Continental 0-300 series](https://openairdocs.org/engine/continental-0-300-series) (registry code 17022, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 17252705 - Year built: 1965 - Engines: Continental O-300 SER 145 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, January 28, 2020 - Departed: MRI, Anchorage, AK - Destination: MRI, Anchorage, AK - Equipment: Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; injuries: none; flight instructor, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review February 3, 2020; seat: left; restraint: lap only; flight hours: 714 total, 180 in this make and model, 619 as pilot in command, 80 in the last 90 days, 21 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: 4,800 ft broken - Temperature: 30 °F, dew point 27 °F - Altimeter: 29.76 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 20200206000299A](https://openairdocs.org/incident/20200206000299A), Feb 6, 2020: Cessna 172F, Lake George, AK, Substantial damage. On 02/06/2020 at 1130 local the aircraft departed merrill field to overfly knix glacier with the pilot, and the pilot's wife's uncle and cousin. The aircraft… ## Docket (1 files) The files NTSB released with the investigation on March 20, 2020, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=100923. 581 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 581 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40481420&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF 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.