GAA19CA098

NTSB accident investigation · Cessna 170 · Riggins, ID · December 16, 2018

Accident · No injuriesData collectionFinal report
Date
December 16, 2018, 12:00 local (19:00 UTC)
Place
Riggins, ID
Injuries
1 uninjured
Damage
Substantial damage
Phase of flight
Takeoff
Aircraft
N4385BCessna 170
Defining event
Takeoff: Loss of control in flight
Weather
Visual (VMC) · Day
Status
Completed · report September 26, 2019
Report
Approved by Office Director
NTSB office
General Aviation Accidents
Parties
FAA
FAA report
20181216022219A
Case key
98778

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

On this page

Probable cause

The pilot's improper preflight performance planning and his subsequent failure to attain sufficient speed for the airplane to climb with a tailwind.

Findings · 4

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.

Performance/control parameters: climb rateAircraft › Aircraft oper/perf/capability · Not attained/maintainedCessna 170B: 6 casesAll aircraft: 265 casesProbable cause
Object/animal/substance: tree(s)Environmental issues › Physical environment · Contributed to outcomeCessna 170B: 6 casesAll aircraft: 933 cases
Wind: tailwindEnvironmental issues › Conditions/weather/phenomena · Response/compensationCessna 170B: 12 casesAll aircraft: 594 cases
Planning/preparation: performance calculationsPersonnel issues › Task performance · PilotCessna 170B: 2 casesAll aircraft: 114 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 of the ski-equipped airplane reported that he aborted his first attempt to take off, and during his second takeoff attempt with a tailwind, shortly after rotation, the airplane settled back onto the snow-packed runway. He added that the airplane lifted off again, but when it was about 5 ft above the ground and near the end of the runway, a wind gust pushed the airplane down onto the runway. Subsequently, the airplane overran the runway, and the right wing impacted a tree. The pilot did not know the wind direction and speed because the airport did not have a windsock or weather reporting station. The airplane sustained substantial damage to the wings. The pilot reported that there were no preimpact mechanical failures or malfunctions with the airplane that would have precluded normal operation. The pilot chose to depart to the north due to rising terrain and tall trees on the south end of runway. The pilot further reported he had landed and taken off from this airport previously without incident. The airport elevation was about 7,600 ft, and the runway was 1,800 ft long. The airplane owner's manual recommended a takeoff distance of 3,420 ft at 7,000 ft elevation and 40°F with zero wind velocity and from a hard level surface. The manual also stated that, under the most favorable condition of smooth, packed snow at 30°F, the takeoff distance for a ski-equipped airplane was about 10% greater than that for a wheel-equipped airplane. Per a supplemental type certificate (STC), the airplane underwent an engine conversion to a 180-horsepower, constant-speed propeller engine. No takeoff performance data were provided on the STC.

Factual narrative

The pilot of the ski-equipped airplane reported that he aborted his first attempt to take off, and during his second takeoff in a tailwind, shortly after rotation, the airplane settled back onto the snow-packed runway. He further reported that the airplane lifted off again, but about 5 feet above the ground and near the end of the runway, a wind gust pushed the airplane down onto the runway. The airplane overran the runway and the right wing impacted a tree. The wind direction and speed were not discernable due to the lack of a windsock or weather reporting station. The airplane sustained substantial damage to the wings. The pilot reported that there were no preimpact mechanical failures or malfunctions with the airplane that would have precluded normal operation. The pilot chose to depart to the north due to raising terrain and tall trees on south end of runway. The airport elevation was approximately 7,600 feet with the runway length of 1,800 feet. The airplane owner's manual performance information for zero wind velocity and hard level surface recommends 3,260 feet for take of distance at 7,000 feet elevation, 40 degrees F. and flaps in the up configuration. With flaps at 20 degrees, the owner's manual recommends 3,420 feet for take of distance at 7,000 feet elevation and 40 degrees F. The owner's manual also identifies performance information for a skiplane under the most favorable condition of smooth packed snow at temperatures of approximately 30 degrees F, the skiplane take-off distance is approximately 10% greater than that shown for the landplane. However, via the Supplimental Type Certificate (STC) process the airplane did undergo an engine conversion to the 180 hp and constant speed propeller. No take-off performance data was identified on the STC. The pilot further reported he had landed and taken-off from this airport previously without incident.

Aircraft

Registration
N4385B
Reported as
Cessna 170 (B)
Category
Airplane
Serial number
26729
Built
1956
Airframe hours
6,729.8
Engine
Lycoming O-360-4A4, 180 horsepower, reciprocating
Damage
Substantial damage
Flight
Positioning · Part 91
Airworthiness certificate
Special, Restricted (Special); Standard, Normal
Last inspection
Annual · August 29, 2018
Departed
KMYL · McCall, ID
Destination
PVT · Riggins, ID
Flight plan
Company VFR
Airport
PVT · Buffalo Hump (Concord) private, runway 01, 1,800 × 50 ft, snow
Equipment
Stall warning system

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
64
Injuries
None
Certificates
Flight instructor, Commercial
Airplane ratings
Single-engine sea, Single-engine land, Multi-engine land
Instrument ratings
Airplane
Medical
Class 2, With waivers/limitations
Last flight review
June 14, 2018
Seat
Front
Restraint
3-point
Flight hours
21,500 total · 2,000 in this make and model · 21,200 as pilot in command · 137 in the last 90 days · 15 in the last 30 days

Weather

Conditions
Visual (VMC) · Day
Wind
290° at 8 knots
Visibility
10 statute miles
Lowest ceiling
8,500 ft overcast
Temperature
43 °F, dew point 28 °F
Altimeter
29.97 inHg
Observed at
KGIC, 28 nm away

Docket · 2

The files NTSB released with the investigation on March 12, 2019, on NTSB’s docket system: statements, records, photos and specialists’ reports. 3.8 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.