# NTSB ANC21LA017: Maule M-6-235, N56517, Tyonek, AK, February 13, 2021 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 4 · Limited · Final report - Date: February 13, 2021, 13:00 local (22:00 UTC) - Place: Tyonek, AK · Capps Glacier - Coordinates: 61.336392, -152.01643 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.3364&lon=-152.0164&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing: Loss of control on ground](https://openairdocs.org/ntsb-events/230) - Highest injury: Minor injuries - Injuries: 2 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 4 - Basic report with no Prelim publish - NTSB office: Alaska Regional Office - Parties: FAA - NTSB case key (mKey): 102639 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC21LA017 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102639/pdf - Page: https://openairdocs.org/ntsb/ANC21LA017 ## Probable cause The pilot’s selection of unsuitable terrain for landing, which resulted in the airplane encountering deep snow and coming to rest inverted. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Performance/control parameters: landing flare](https://openairdocs.org/ntsb-findings/01062041): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Maule M-6-235, 1 case](https://openairdocs.org/ntsb-findings/01062041/cases.md?model=5460160), [All aircraft, 1,285 cases](https://openairdocs.org/ntsb-findings/01062041/cases.md) - [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Maule M-6-235, 4 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=5460160), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Maule M-6-235, 7 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=5460160), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Runway/land/takeoff/taxi surface: snow/slush/ice covered surface](https://openairdocs.org/ntsb-findings/03023015): Environmental issues › Physical environment · Effect on operation; cases with it: [Maule M-6-235, 1 case](https://openairdocs.org/ntsb-findings/03023015/cases.md?model=5460160), [All aircraft, 219 cases](https://openairdocs.org/ntsb-findings/03023015/cases.md) - [Runway/land/takeoff/taxi surface: soft surface](https://openairdocs.org/ntsb-findings/03023020): Environmental issues › Physical environment · Effect on operation; cases with it: [Maule M-6-235, 1 case](https://openairdocs.org/ntsb-findings/03023020/cases.md?model=5460160), [All aircraft, 264 cases](https://openairdocs.org/ntsb-findings/03023020/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing: Miscellaneous/other](https://openairdocs.org/ntsb-events/900); cases with it: [Maule M-6-235, 1 case](https://openairdocs.org/ntsb-events/900/sequence.md?model=5460160), [All aircraft, 1,556 cases](https://openairdocs.org/ntsb-events/900/sequence.md) - [Landing: Loss of control on ground](https://openairdocs.org/ntsb-events/230) (defining event); cases with it: [Maule M-6-235, 5 cases](https://openairdocs.org/ntsb-events/230/sequence.md?model=5460160), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) - [Landing: Nose over/nose down](https://openairdocs.org/ntsb-events/096); cases with it: [Maule M-6-235, 3 cases](https://openairdocs.org/ntsb-events/096/sequence.md?model=5460160), [All aircraft, 2,287 cases](https://openairdocs.org/ntsb-events/096/sequence.md) ## Analysis The pilot initially reported that before landing on a snow-covered glacier, he intended to fly a low pass over the snow-covered site and briefly touchdown to determine the condition of the snowpack, a maneuver commonly known as dragging the landing site. He said that during a second downhill pass over the site, he inadvertently allowed the tailwheel-ski equipped airplane to slow while attempting to “set the track more fully”. He added that, he mis-judged the snow depth and allowed the airplane to slow too much. Subsequently, the ski tips dug into the snow and the airplane came to rest inverted. The airplane sustained substantial damage to the fuselage, the wings, and the empennage. The pilot initially reported there were no preimpact mechanical failures or malfunctions with the airframe and engine that would have precluded normal operation. The pilot later reported that he believed the brake calipers had obstructed the movement of the skis. Two witness marks were observed on the skis that indicated the brake calipers had impacted the skis. A Federal Aviation Administration (FAA) aviation safety inspector (airworthiness) examined the airplane and stated that there were no preimpact mechanical failures or malfunctions found with the airplane. Based on the available evidence, it is likely that the damage to the skis from the brake calipers were from impact damage. ## Aircraft - Registration: [N56517](https://openairdocs.org/aircraft/N56517), registered now, S/N 7450C, built 1983 (OpenAirDocs) - Reported make and model: MAULE M-6-235 - Registry model: [Maule M-6-235](https://openairdocs.org/model/maule-m-6-235) (registry code 5460160) (OpenAirDocs) - Registry engine: [Lycoming IO-540 series](https://openairdocs.org/engine/lycoming-io-540-series) (registry code 41530, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 7450C - Year built: 1983 - Airframe hours: 2363.9 - Engines: LYCOMING IO-540-W1A5 235 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Paul Andrews - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 28, 2020 - Departed: BCV, Birchwood, AK - Destination: Same as departure - Equipment: Handheld GPS, Electronic multifunction display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 53; injuries: minor; private; airplane ratings: single-engine sea, single-engine land; medical: class 3, without waivers/limitations; last flight review September 28, 2020; seat: left; flight hours: 1,998 total, 1,998 as pilot in command, 10 in the last 90 days, 6 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 30° at 5 knots - Visibility: 10 statute miles - Temperature: 16 °F, dew point 7 °F - Altimeter: 29.83 inHg - Observed at: PANC, 58 nm away - METAR: PANC 132153Z 03005KT 10SM FEW110 M09/M14 A2983 RMK AO2 SLP106 T10941139 ## 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 20210213000539A](https://openairdocs.org/incident/20210213000539A), Feb 13, 2021: Maule M-6-235, Tordrillo Mtns, AK, Substantial damage. Pilot was attempting a landing on a glacier with deep snow pack with a ski equipped aircraft. Pilot made one pass as to "drag" the selected landing spot to… 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.