Saturday, December 05, 2020

Loss of Control on Ground: Cessna 170B, N4476B; Accident occurred December 28, 2019 at Missoula International Airport (KMSO), Montana

Aviation Accident Final Report - National Transportation Safety Board

Additional Participating Entity:
Federal Aviation Administration / Flight Standards District Office; Helena, Montana

Investigation Docket - National Transportation Safety Board:

Montana Flying Service LLC
Location: Missoula, Montana 
Accident Number: WPR20CA053
Date & Time: December 28, 2019, 13:45 Local
Registration: N4476B
Aircraft: Cessna 170 
Aircraft Damage: Substantial
Defining Event: Loss of control on ground
Injuries: 2 None
Flight Conducted Under: Part 91: General aviation - Instructional


The pilot, who was receiving instruction for his tailwheel endorsement, reported that, during the takeoff roll, the airplane began to veer left. He applied corrective control inputs, and the flight instructor called for him to abort the takeoff, but the airplane ground looped and departed the runway. The airplane sustained substantial damage to the right wing and aileron. The instructor reported that the event happened too fast for him to correct the diversion and that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The pilot receiving instruction's failure to maintain directional control during the takeoff roll, which resulted in a runway excursion and ground-loop, and the flight instructor's failure to adequately monitor the pilot.


Aircraft Directional control - Not attained/maintained
Personnel issues Monitoring other person - Instructor/check pilot
Personnel issues Aircraft control - Student/instructed pilot

Factual Information

History of Flight

Takeoff Loss of control on ground (Defining event)
Takeoff Attempted remediation/recovery
Takeoff Runway excursion

Flight instructor Information

Certificate: Commercial; Flight engineer; Flight instructor
Age: 63, Male
Airplane Rating(s): Single-engine land 
Seat Occupied: Right
Other Aircraft Rating(s): Helicopter 
Restraint Used: 4-point
Instrument Rating(s): Airplane; Helicopter
Second Pilot Present: Yes
Instructor Rating(s): Airplane single-engine; Helicopter 
Toxicology Performed: No
Medical Certification: Class 2 With waivers/limitations
Last FAA Medical Exam: January 23, 2019
Occupational Pilot: No 
Last Flight Review or Equivalent: June 18, 2019
Flight Time: 2607 hours (Total, all aircraft), 474 hours (Total, this make and model), 1708 hours (Pilot In Command, all aircraft), 19.8 hours (Last 90 days, all aircraft), 4.5 hours (Last 30 days, all aircraft), 0.8 hours (Last 24 hours, all aircraft)

Pilot Information

Certificate: Commercial; Flight instructor; Private
Age: 68, Male
Airplane Rating(s): Single-engine land; Multi-engine land
Seat Occupied: Left
Other Aircraft Rating(s): None
Restraint Used: 4-point
Instrument Rating(s): Airplane 
Second Pilot Present: Yes
Instructor Rating(s): Airplane single-engine 
Toxicology Performed: No
Medical Certification: BasicMed None 
Last FAA Medical Exam: June 14, 2019
Occupational Pilot: No
Last Flight Review or Equivalent: June 14, 2019
Flight Time: 1071.5 hours (Total, all aircraft), 2.7 hours (Total, this make and model), 980.7 hours (Pilot In Command, all aircraft), 3.2 hours (Last 90 days, all aircraft), 0.8 hours (Last 30 days, all aircraft), 0.8 hours (Last 24 hours, all aircraft)

Aircraft and Owner/Operator Information

Aircraft Make: Cessna 
Registration: N4476B
Model/Series: 170 B 
Aircraft Category: Airplane
Year of Manufacture: 1955
Amateur Built: No
Airworthiness Certificate: Normal
Serial Number: 26820
Landing Gear Type: Tailwheel 
Seats: 4
Date/Type of Last Inspection: December 3, 2019
Annual Certified Max Gross Wt.: 2200 lbs
Time Since Last Inspection: 4 Hrs
Engines: 1 Reciprocating
Airframe Total Time: 3967.9 Hrs as of last inspection
Engine Manufacturer: Continental
ELT: C126 installed, not activated Engine Model/Series: O-300-A
Registered Owner:
Rated Power: 145 Horsepower
Operator: On file
Operating Certificate(s) Held: None

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual (VMC)
Condition of Light: Day
Observation Facility, Elevation: 3206 ft msl 
Distance from Accident Site: 0 Nautical Miles
Observation Time: 20:53 Local
Direction from Accident Site: 0°
Lowest Cloud Condition: Clear
Visibility: 10 miles
Lowest Ceiling: Overcast / 5000 ft AGL
Visibility (RVR):
Wind Speed/Gusts: / 
Turbulence Type Forecast/Actual:  /
Wind Direction: 
Turbulence Severity Forecast/Actual: /
Altimeter Setting: 30.15 inches Hg 
Temperature/Dew Point: -1°C / -8°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Missoula, MT (MSO)
Type of Flight Plan Filed: None
Destination: Missoula, MT (MSO)
Type of Clearance: None
Departure Time: 
Type of Airspace: Class D

Airport Information

Airport: Missoula Intl MSO
Runway Surface Type: Asphalt
Airport Elevation: 3205 ft msl 
Runway Surface Condition: Dry
Runway Used: 12 IFR 
Approach: None
Runway Length/Width: 9501 ft / 150 ft
VFR Approach/Landing: None

Wreckage and Impact Information

Crew Injuries: 2 None 
Aircraft Damage: Substantial
Passenger Injuries:
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 2 None
Latitude, Longitude: 46.915832,-114.089447(est)

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