WPR20CA298

NTSB accident investigation · Cessna 208 · Whitmore, AZ · September 7, 2020

Accident · No injuriesClass 4 · Data collectionFinal report
Date
September 7, 2020, 13:00 local (20:00 UTC)
Place
Whitmore, AZ
Injuries
8 uninjured
Damage
Substantial damage
Phase of flight
Landing
Aircraft
N186GCCessna 208
Defining event
Landing-landing roll: Sys/Comp malf/fail (non-power)
Weather
Visual (VMC) · Day
Status
Completed
Report
Approved by Office Director
Investigation class
Class 4 - Basic report with no Prelim publish
NTSB office
Western Pacific Region
Parties
FAA - FSDO
FAA report
20200907014369A
Case key
101931

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

A loss of directional control during landing due to a flat main landing gear tire, which resulted in a lateral runway excursion and impact 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.

Landing gear system: tubeAircraft › Aircraft systems · Unknown/Not determinedCessna 208B: 1 caseAll aircraft: 19 casesProbable cause
Performance/control parameters: directional controlAircraft › Aircraft oper/perf/capability · Attain/maintain not possibleCessna 208B: 8 casesAll aircraft: 3,958 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

**This report was modified on December 5, 2024. Please see the docket for this accident to view the original report.** The pilot reported that, during the landing ground roll, the airplane started to veer left. He applied right rudder input, but the airplane continued to “drag” left. As the pilot repositioned his feet to apply the brakes, the airplane “turned harder to the left,” exited the runway, and impacted terrain. The right wing was substantially damaged. The pilot thought that “a left main tire malfunction on or before landing” had occurred. An examination of the left wheel and tire assembly (by the Federal Aviation Administration) found that the valve stem to the tire inner tube had completely sheared off and was located inside the tire. No other damage to the inner tube was noted, and no other anomalies were observed within the assembly. The operator’s director of maintenance reported no preimpact mechanical malfunctions or failures that would have precluded normal operation. A video recording of the accident landing (taken by a passenger in the first row of passenger seats) indicated that, based on the sound recorded, the left main landing gear tire became flat immediately after main gear touchdown. The left flat tire would have increased the drag between the tire and the runway surface, resulting in a left-turning tendency and a loss of directional control. In addition, a photograph taken during the on-scene investigation showed a double track on the runway starting near the location where the left main tire touched down. The double track was likely caused by the rubber in the left and right sidewalls of the tire contacting the runway after the center of the tire deflated. The left main landing gear tire was installed on the airplane 3 days before the accident. The tire could have become flat if it had been improperly installed or had a material defect. It is also possible that the tire became flat because it hit something not heard or seen on the video of the landing. In addition, another photograph taken during the on-scene investigation showed that the valve stem of the tire inner tube was sheared, indicating that the tire could have become flat because the valve (within the valve stem) had failed. The failure mode for the left main landing gear tire could not be determined based on the available evidence. Nevertheless, the evidence was sufficient to show that the reason for the airplane’s loss of lateral directional control was the flat left main tire.

Aircraft

Registration
N186GC
Reported as
Cessna 208 (B)
Category
Airplane
Serial number
208B2161
Built
2009
Airframe hours
8,044.3
Engine
Pratt & Whitney Canada PT6A-114A, 675 horsepower, turbo prop
Damage
Substantial damage
Flight
Other work use · Part 135
Operator
Grand Canyon Airlines
Registered owner
Zuni Llc
Airworthiness certificate
Standard, Normal
Last inspection
AAIP · August 22, 2020 · 35.8 hours before
Departed
KBVU · Boulder City, NV
Destination
Same as departure
Airport
1Z1 · Grand Canyon Bar Ten Airstrip, runway 34, 4,600 × 40 ft, asphalt
Equipment
Electronic primary flight display, Angle of attack indicator, Onboard weather, ADS-B, 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
57
Injuries
None
Certificate
Commercial
Airplane ratings
Multi-engine land, Single-engine land
Instrument ratings
Airplane
Medical
Class 1, With waivers/limitations
Last flight review
August 25, 2020
Seat
Left
Restraint
5-point
Flight hours
1,460 total · 600 in this make and model · 1,210 as pilot in command · 216 in the last 90 days · 70 in the last 30 days · 3 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Wind
350° at 6 knots, gusting 14
Visibility
10 statute miles
Lowest ceiling
None
Temperature
102 °F, dew point 32 °F
Altimeter
30.02 inHg
Observed at
KAZC, 43 nm away

Docket · 10

The files NTSB released with the investigation on July 12, 2021, on NTSB’s docket system: statements, records, photos and specialists’ reports. 12.5 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.