# NTSB ANC21LA056: Cessna 170B, N2746D, North Pole, AK, July 1, 2021 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Class 3 · Limited · Final report - Date: July 1, 2021, 14:00 local (22:00 UTC) - Place: North Pole, AK · 31AK - Coordinates: 64.816936, -147.4168 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=64.8169&lon=-147.4168&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Defining event: [Takeoff: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490) - Highest injury: Serious injuries - Injuries: 4 serious - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Alaska Regional Office - Parties: FAA, Textron Aviation, Inc. - NTSB case key (mKey): 103466 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC21LA056 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103466/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103466 - Page: https://openairdocs.org/ntsb/ANC21LA056 ## Probable cause The pilot’s exceedance of the airplane’s takeoff performance limitations, which prevented the airplane from gaining sufficient altitude to clear the trees off the departure end of the runway. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Performance/control parameters: climb rate](https://openairdocs.org/ntsb-findings/01062035): Aircraft › Aircraft oper/perf/capability · Capability exceeded (probable cause); cases with it: [Cessna 170B, 6 cases](https://openairdocs.org/ntsb-findings/01062035/cases.md?model=2072306), [All aircraft, 265 cases](https://openairdocs.org/ntsb-findings/01062035/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Cessna 170B, 91 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=2072306), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Temp/humidity/pressure: high temperature](https://openairdocs.org/ntsb-findings/03031015): Environmental issues › Conditions/weather/phenomena · Effect on operation; cases with it: [Cessna 170B, 1 case](https://openairdocs.org/ntsb-findings/03031015/cases.md?model=2072306), [All aircraft, 30 cases](https://openairdocs.org/ntsb-findings/03031015/cases.md) - [Object/animal/substance: tree(s)](https://openairdocs.org/ntsb-findings/03022020): Environmental issues › Physical environment · Effect on operation; cases with it: [Cessna 170B, 6 cases](https://openairdocs.org/ntsb-findings/03022020/cases.md?model=2072306), [All aircraft, 933 cases](https://openairdocs.org/ntsb-findings/03022020/cases.md) - [Runway/land/takeoff/taxi surface](https://openairdocs.org/ntsb-findings/03023000): Environmental issues › Physical environment · Effect on operation; cases with it: [Cessna 170B, 2 cases](https://openairdocs.org/ntsb-findings/03023000/cases.md?model=2072306), [All aircraft, 253 cases](https://openairdocs.org/ntsb-findings/03023000/cases.md) - [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Cessna 170B, 15 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=2072306), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Preflight or dispatch event](https://openairdocs.org/ntsb-events/030); cases with it: [Cessna 170B, 3 cases](https://openairdocs.org/ntsb-events/030/sequence.md?model=2072306), [All aircraft, 355 cases](https://openairdocs.org/ntsb-events/030/sequence.md) - [Takeoff: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490) (defining event); cases with it: [Cessna 170B, 6 cases](https://openairdocs.org/ntsb-events/490/sequence.md?model=2072306), [All aircraft, 1,309 cases](https://openairdocs.org/ntsb-events/490/sequence.md) ## Analysis During the takeoff of the personal flight, the airplane was unable to gain enough altitude to clear the trees off the departure end of the runway. Subsequently, the airplane impacted the trees and came to rest inverted, and a postaccident fire ensued, which destroyed the airplane. The pilot told the responding law enforcement officer that he thought that the wind had shifted during the takeoff and that the airplane lost lift at the end of the runway. A postaccident examination of the airplane revealed no evidence of preaccident mechanical malfunctions or failures that would have precluded normal operation. At the time of the accident, the airplane was departing from a grass/turf-covered runway, during a hot summer day, with full main fuel tanks, with a total of four occupants on board, and an estimated density altitude of 2,186 ft above mean sea level. The pilot reported that the airplane was about 13 pounds more than its maximum gross takeoff weight. The airplane owner’s manual indicated that at a maximum gross weight the airplane would need an estimated takeoff distance of 2,250 ft to clear a 50-ft obstacle. The accident site is a 2,400 ft long, by 100 ft wide, turf-covered site. The airplane manufacturer added that the turf runway would likely add to the distance needed for the takeoff. Thus, given the conditions of the accident, the pilot likely exceeded the airplane’s takeoff performance limitations, which resulted in the airplane not attaining the altitude needed to clear the tree line during takeoff and the subsequent impact with trees. ## Factual narrative On July 1, 2021, about 1400 Alaska daylight time, a Cessna 170B airplane, N2746D, was destroyed when it was involved in an accident near North Pole, Alaska. The pilot and three passengers were seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The airplane departed from Dalrymple’s Airport (31AK,) Fairbanks, Alaska. The pilot reported that the airplane was about 13 pounds more than its maximum gross takeoff weight. After completing the preflight check, the pilot initiated the takeoff roll with "1 notch” of flaps deployed. During the takeoff roll, when the airplane’s speed was about 40 to 45 mph, the pilot added a ”2nd notch” of flaps and climbed the airplane to tree top level “after using 1,000 ft of runway.” The pilot was unable to increase airspeed or altitude “without overly increasing the angle of attack” and noticed the airplane was not going to clear the trees off the end of the runway. He deployed full flaps, slowed the airplane to about 40 mph, and the airplane “settled in between trees” about 200 ft beyond the end of the runway. The airplane came to rest upright in a wooded area off the departure end of the runway with the nose of the airplane pointed back toward the runway. A postcrash fire ensued. A witness reported that she observed the airplane take off and climb to an altitude of about 100 ft above the trees at the departure end of the runway. The airplane then made a sharp left turn, the left wing impacted a tree, and the airplane descended into terrain. She further stated that the airplane’s nose did not drop during the left turn. The witness added that the airplane sounded normal throughout the takeoff and accident sequence with no unusual sounds and that the engine appeared to be operating. A law enforcement officer who responded to the accident reported that the pilot stated that he was not sure what happened during takeoff. The pilot thought that the wind had shifted, and that the airplane lost lift at the end of the runway. Postaccident examination of the airplane revealed no evidence of preaccident mechanical malfunctions or failures that would have precluded normal operation. The estimated density altitude for 31AK at the time of the accident was 2,186 ft above mean sea level. The airplane owner’s manual indicated that the airplane would need an estimated takeoff distance of 2,250 ft to clear a 50-ft obstacle. AK31 is a 2,400 ft long, by 100 ft wide, turf-covered site. The airplane manufacturer added that the turf runway would likely add to the distance needed for the takeoff. The Federal Aviation Administration (FAA) Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25B) discussed the effects of weight on an aircraft and stated in part the following: The pilot should always be aware of the consequences of overloading. An overloaded aircraft may not be able to leave the ground, or if it does become airborne, it may exhibit unexpected and unusually poorflight characteristics. If not properly loaded, the initial indication of poor performance usually takes place during takeoff. Excessive weight reduces the flight performance in almost every respect. For example, the most important performance deficiencies of an overloaded aircraft are: • Higher takeoff speed • Longer takeoff run • Reduced rate and angle of climb… • Reduced maneuverability • Higher stalling speed… • Excessive weight on the nose wheel or tail wheel The pilot must be knowledgeable about the effect of weight on the performance of the particular aircraft being flown. Preflight planning should include a check of performance charts to determine if the aircraft’s weight may contribute to hazardous flight operations. Excessive weight in itself reduces the safety margins available to the pilot and becomes even more hazardous when other performance-reducing factors are combined with excess weight. The FAA published Density Altitude (FAA-P-8740-2). This document stated that “Density altitude is formally defined as ’pressure altitude corrected for nonstandard temperature variations’.” The document also stated in part the following: The formal definition of density altitude is certainly correct, but the important thing to understand is that density altitude is an indicator of aircraft performance. The term comes from the fact that the density of the air decreases with altitude. A ’high’ density altitude means that air density is reduced, which has an adverse impact on aircraft performance…. Whether due to high altitude, high temperature, or both, reduced air density (reported in terms of density altitude) adversely affects aerodynamic performance and decreases the engine’s horsepower output. ## Aircraft - Registration: [N2746D](https://openairdocs.org/aircraft/N2746D), registered now, S/N 25288, built 1952 (OpenAirDocs) - Reported make and model: CESSNA 170B - Registry model: [Cessna 170B](https://openairdocs.org/model/cessna-170b) (registry code 2072306) (OpenAirDocs) - Registry engine: [Continental 0-300 series](https://openairdocs.org/engine/continental-0-300-series) (registry code 17022, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 25288 - Year built: 1952 - Airframe hours: 3856 - Engines: Lycoming IO-360-N1A 180 horsepower reciprocating - Damage: Destroyed - Fire: On-Ground - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, January 12, 2021 - Destination: 4AK5, Mankomen Lake, AK - Airport: 31AK, Dalrymple'S, runway 6, 2,400 × 100 ft, grass/turf - Equipment: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 63; injuries: serious; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review June 1, 2016; seat: left; restraint: 3-point; flight hours: 3,400 total, 400 in this make and model, 3,400 as pilot in command, 40 in the last 90 days, 15 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 150° at 3 knots - Visibility: 8 statute miles - Lowest ceiling: none - Temperature: 82 °F, dew point 41 °F - Altimeter: 29.90 inHg - Observed at: PAFB, 5 nm away - METAR: PAFB 012158Z 15003KT 8SM CLR 28/05 A2990 RMK AO2A SLP126 T02780053 ## 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 20210701014139A](https://openairdocs.org/incident/20210701014139A), Jul 1, 2021: Cessna 170B, North Pole, AK, Destroyed. After beginning the slightly downwind (3 mph) takeoff roll, the pilot became airborne and indicated the aircraft was tree top level near mid-field. Density… ## Other investigations on N2746D (2) 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. - [NTSB ANC92LA066](https://openairdocs.org/ntsb/ANC92LA066), May 4, 1992: Cessna C-170B (N2746D), Talkeetna, AK, substantial damage. Probable cause: LOSS OF CONTROL ON LANDING ROLL DUE TO THE PILOT'S FAILURE TO MAINTAIN PROPER ALIGNMENT, RESULTING IN COLLISION WITH TERRAIN DURING AN UNCONTROLLED GROUND LOOP/SWERVE. A FACTOR RELATING TO THE… - [NTSB OAK74DVD42](https://openairdocs.org/ntsb/OAK74DVD42), Jun 22, 1974: Cessna 170 (N2746D), Novato, CA, substantial damage ## Docket (7 files) The files NTSB released with the investigation on January 30, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103466. 2.7 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13817497&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Witness roc (item 2, PDF, 1 page, 26 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15016185&FileExtension=pdf&FileName=Record%20of%20Conversation%20-%20Mrs%20Kardash-Rel.pdf - Ast report narrative (item 3, PDF, 1 page, 118 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13848839&FileExtension=pdf&FileName=AST%20Report%20Narrative-Rel.pdf - Performance (item 4, PDF, 2 pages, 187 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13838629&FileExtension=pdf&FileName=Performance-Rel.pdf - Textron email (item 5, PDF, 1 page, 132 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13852450&FileExtension=pdf&FileName=Textron%20ROC-Rel.pdf - Engine inspection (item 6, PDF, 1 page, 112 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13818025&FileExtension=pdf&FileName=IO-360-M1A%20engine%20inspection_Redacted-Rel.pdf - Statement of party representatives to NTSB investigation (item 7, PDF, 1 page, 230 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13838493&FileExtension=pdf&FileName=Textron%20-%20Party%20Form%20ANC21LA056_Redacted-Rel.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.