GAA15CA282

NTSB accident investigation · Cessna 170B · Arctic Village, AK · September 24, 2015

Accident · Minor injuriesData collectionFinal report
Date
September 24, 2015, 13:00 local (21:00 UTC)
Place
Arctic Village, AK
Injuries
1 minor, 1 uninjured
Damage
Substantial damage
Phase of flight
Takeoff
Aircraft
N2528CCessna 170B
Defining event
Takeoff: Aerodynamic stall/spin
Weather
Visual (VMC) · Day
Status
Completed · report December 3, 2015
Report
Approved by Office Director
NTSB office
General Aviation Accidents
Parties
FAA Fairbanks FSDO
FAA report
20150924016519A
Case key
92082

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

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Probable cause

The pilot exceeded the critical angle of attack during takeoff, which resulted in an aerodynamic stall and a collision with terrain.

Findings · 2

NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.

Use of equip/info: aircraft controlPersonnel issues › Task performance · PilotCessna 170B: 91 casesAll aircraft: 9,295 casesProbable cause
Performance/control parameters: angle of attackAircraft › Aircraft oper/perf/capability · Not attained/maintainedCessna 170B: 5 casesAll aircraft: 990 casesProbable cause

Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.

Analysis

The pilot reported that after taking off from a frozen gravel bar by a river in remote wilderness, the airplane stalled. The left main landing gear struck the edge of the cut bank and the left wing impacted the ground. The fuselage then impacted the top of the bank and spun counterclockwise. The pilot stated that the left wing was separated from the fuselage and the fuselage had sustained substantial damage. The pilot reported there were no pre-impact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.

Factual narrative

The pilot reported that after taking off from a frozen gravel bar by a river in remote wilderness, the airplane stalled. The left main landing gear struck the edge of the cut bank and the left wing impacted the ground. The fuselage then impacted the top of the bank and spun counterclockwise. The pilot stated that the left wing was separated from the fuselage and the fuselage had sustained substantial damage. The pilot reported there were no pre-impact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation. The pilot reported as a safety recommendation, "I would take off empty or with minimal known weight to ensure that the aircraft would perform as planned. I could then land to reload, or if partially loaded, fly to another gravel bar that was longer, and stage from there, returning to the point of origin empty, and then continue to shuttle gear and people. That first flight would have been better planned without another person on board, not just due to weight, but due to risk to that person." ADDITIONAL INFORMATION Alaska Off Airport Flight Operations The Alaskan Aviation Safety Foundation has published a safety briefing Off Airport Landings. This safety briefing discusses off airport takeoff and landing operations. This safety briefing states in part; When flying very low and slow on takeoff or landing approach, do not fly over an abrupt drop-off such as a cut bank or steep lake shore. You can abruptly lose ground effect and begin to settle. This safety briefing also lists considerations when selecting off airport takeoff and landing sites and states in part; Airplane load: Obviously, ever gram counts. Density altitude: You don't have to go into the mountains to get a change in density altitude. Ground drag: A thawed gravel bar, even a dry one, presents considerably more drag than a frozen one. Departure obstacles: An obvious thing, but if you've been flying off river bars in ground effect, it's easy to underestimate the additional space needed to clear a 15 foot obstacle.

Aircraft

Registration
N2528C
Reported as
Cessna 170B (UNDESIGNAT)
Category
Airplane
Serial number
26172
Built
1954
Airframe hours
2,653
Engine
Lycoming O-320-D1A, 160 horsepower, reciprocating
Damage
Substantial damage
Flight
Personal · Part 91
Airworthiness certificate
Standard, Normal
Last inspection
Annual · January 7, 2015
Departed
FAI · Fairbanks, AK
Destination
FAI · Fairbanks, AK

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
57
Injuries
Minor
Certificate
Private
Airplane ratings
Single-engine land
Medical
Class 3, Without waivers/limitations
Last flight review
July 8, 2014
Seat
Left
Restraint
4-point
Flight hours
355 total · 110 in this make and model · 316 as pilot in command

Weather

Conditions
Visual (VMC) · Day
Wind
60° at 5 knots
Visibility
10 statute miles
Lowest ceiling
1,700 ft overcast
Temperature
21 °F, dew point 12 °F
Altimeter
29.84 inHg
Observed at
PARC, 78 nm away

Docket · 2

The files NTSB released with the investigation on November 10, 2015, on NTSB’s docket system: statements, records, photos and specialists’ reports. 3.2 MB in all.

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.