WPR12CA025

NTSB accident investigation · Cessna 172K · Florence, MT · October 30, 2011

Accident · No injuriesData collectionFinal report
Date
October 30, 2011, 16:20 local (22:20 UTC)
Place
Florence, MT
Injuries
3 uninjured
Damage
Substantial damage
Phase of flight
Maneuvering
Aircraft
N7276GCessna 172K
Defining event
Maneuvering-low-alt flying: Low altitude operation/event
Weather
Visual (VMC) · Day
Status
Completed · report January 18, 2012
Report
Approved by Office Director
NTSB office
Western Pacific Region
Parties
FAA FSDO
FAA report
20111030024669A
Case key
82215

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's failure to maintain clearance from a power line during a low-level flight along a river. Contributing to the accident was the pilot's decision to fly at a low altitude.

Findings · 3

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.

Perception/orientation/illusion: perceptionPersonnel issues › Psychological · PilotAll aircraft: 61 casesProbable cause
Object/animal/substance: wireEnvironmental issues › Physical environment · Response/compensationAll aircraft: 588 casesProbable cause
Info processing/decision: decision making/judgmentPersonnel issues › Action/decision · PilotAll aircraft: 3,098 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

After a series of takeoffs and landings at several nearby airports, the pilot was returning to his home airport and descended to a low level to follow a river. The pilot reported that the conditions were turbulent for most of the day but that, during that low-altitude leg, the airplane seemed to perform abnormally. While still airborne, a passenger observed that the brake line that was attached to the right main landing gear strut was severed. As a result, the pilot conducted a precautionary landing at a nearby airport. The pilot and passengers observed multiple damage sites on the airplane but, since no one was present at that airport, they reboarded and departed for the home airport where they landed uneventfully. A postaccident investigation revealed that the airplane struck and severed one of several electrical power lines that spanned the river. The wire height at mid river was about 30 to 40 feet above the water. The propeller, cowling, exhaust stack, right wing (multiple places), right wing strut, right main gear brake line, right landing gear wheel fairing, right fuselage, and vertical stabilizer were damaged by the wire strike, and the rear window was punctured. The pilot stated that he did not see any wires and that he was not aware of the wire strike until he examined the airplane after the precautionary landing. Neither the pilot nor the passengers incurred any injuries.

Factual narrative

The pilot departed, conducted a touch-and-go at one airport, landed at another, and then flew north to a third airport, where another touch-and-go was conducted. The airplane then headed south towards the home airport, and the pilot descended to low level and followed a river for a portion of that flight leg. The pilot reported that the conditions were turbulent for most of the day, but during that low-altitude leg, the airplane behavior seemed abnormal. While still airborne, a passenger observed that the brake line that was attached to the right main landing gear strut was severed. As a result, the pilot conducted a precautionary landing at a nearby airport. The pilot and passengers observed multiple damage sites on the airplane, but since no one was present at that airport, they reboarded and departed for the home airport, where an uneventful landing was made. Investigation revealed that the airplane struck and severed one of several electrical power lines, which spanned the river. Those lines were strung between two poles, one on each side of the river. Both poles were set back from the river edge, and the west pole was situated in a loose stand of trees. The approximate wire span was 464 feet, and the wire height at mid river was approximately 30 to 40 feet above the water. Airplane damage from the wire strike included the propeller, cowling, exhaust stack, right wing (multiple places), right wing strut, right main gear brake line, right landing gear wheel fairing, right fuselage, and vertical stabilizer. In addition, the rear window was punctured. The pilot stated that he did not see any wires, and that he was not aware of the wire strike until he examined the airplane after the precautionary landing. Neither the pilot nor the passengers incurred any injuries.

Aircraft

Registration
N7276G
Reported as
Cessna 172K (K)
Category
Airplane
Serial number
17258976
Airframe hours
3,553
Engine
Lycoming O-320, 150 horsepower, reciprocating
Damage
Substantial damage
Flight
Personal · Part 91
Operator
North Star Aviation
Registered owner
North Star Aviation
Airworthiness certificate
Standard, Normal
Last inspection
100 hour · September 29, 2011
Departed
MSO · Missoula, MT
Destination
6S5 · Hamilton, MT
Airport
6S5 · Ravalli County

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
38
Injuries
None
Certificate
Private
Airplane ratings
Single-engine land
Medical
Class 3, Without waivers/limitations
Last flight review
January 4, 2010
Seat
Left
Flight hours
126 total · 20 in this make and model · 89 as pilot in command · 6 in the last 90 days · 3 in the last 30 days

Weather

Conditions
Visual (VMC) · Day
Wind
110° at 3 knots
Visibility
10 statute miles
Lowest ceiling
None
Temperature
54 °F, dew point 30 °F
Altimeter
30.06 inHg
Observed at
MSO, 20 nm away

Docket · 13

The files NTSB released with the investigation on December 6, 2011, on NTSB’s docket system: statements, records, photos and specialists’ reports. 6.4 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.