ANC21LA056 · Cessna 170B
Cessna 170B · Accident: collision during takeoff/landing
From an unrecorded airport to Mankomen Lake Airport (4AK5)
Event
- NTSB case
- ANC21LA056
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- Event fatalities
- Unknown
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Cessna 170B
- Aircraft type
- Cessna 170
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N2746D
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From not recordedTo Mankomen Lake Airport (4AK5), Mankomen Lake, AK
- Aircraft age
- About 69 years (built 1952)
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Takeoff
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Collision during takeoff/landing
- Also codedOther events the NTSB coded in the sequence, such as a wire strike after a loss of power. Flight Findings uses them for its kinds of event. Glossary
- Tree(s)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Destroyed
Cause areas
- Aircraft › Aircraft oper/perf/capability
- Personnel issues › Action/decision
- Personnel issues › Task performance
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
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.
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.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ANC21LA056
- Event ID
- 20210713103466
- Case number
- ANC21LA056
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, cause areas. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: b39a6d4c0cd95d0b0e166f03ae3592bb1894ec73dc40209347aa845493628fcb; retrieved 2026-09-16T14:17:04.338Z.