Sunday, May 02, 2021

Flight Control System Malfunction/Failure: Denney Kitfox Model 3, N73BH; accident occurred May 02, 2018 at Stovall Ranch Number 4 Airport (6TX9), Marathon, Brewster County, Texas

Accident Site Wreckage. 

Accident Site View of Wings and Damaged Flaperon Attach Points. 

Wing rib reinforcement.

Aviation Accident Final Report - National Transportation Safety Board 

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entity:

Federal Aviation Administration / Flight Standards District Office; Lubbock, Texas

Investigation Docket - National Transportation Safety Board:

Location: Marathon, TX
Accident Number: CEN18LA157
Date & Time: 05/02/2018, 1100 CDT
Registration: N73BH
Aircraft Damage: Substantial
Defining Event: Flight control sys malf/fail
Injuries: 2 Minor
Flight Conducted Under: Part 91: General Aviation - Personal 


The pilot and the passenger were departing on a local personal flight in the experimental amateur-built airplane. The pilot indicated that, during the takeoff climb, about 15 ft above the ground, the airplane violently rolled to the right. He applied full aileron and rudder opposite the direction of the roll, but the airplane continued to roll to the right, struck the ground with the right wing, and then impacted a tree. Postaccident examination of the airplane revealed that three of the four hinges connecting the right flaperon hanger rib were loose. The wooden material of the flaperon was found dry rotted where the hinges connected. The airplane had been flown about 3 hours in the 11 months before the accident. The airplane kit manufacturer had issued a service bulletin in 1991 that identified flaperon hanger rib failures on the model of the accident airplane. The service bulletin recommended the addition of an aluminum reinforcement on each flaperon hanger rib end. The accident airplane did not have the reinforcement installed and thus did not have the benefit of additional reinforcement in the attachment point area of the hinges.

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The failure of the flaperon hinge attachment point during takeoff, which resulted in a loss of airplane control. Contributing to the accident was the lack of reinforcement of the hinge attachment point in accordance with the manufacturer's service bulletin.


Aircraft (general) - Failure
Personnel issues Installation - Owner/builder
Environmental issues Tree(s) - Contributed to outcome

Factual Information

On May 2, 2018, about 1100 central daylight time, an experimental, amateur-built Kitfox III airplane, N73BH, was substantially substantial damaged during a forced landing after takeoff from the Stovall Ranch Airport (6TX9), Marathon, Texas. The airline transport pilot and one passenger sustained minor injuries. The airplane was privately owned and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed throughout the area and no flight plan was filed for the flight. The local flight was originating at the time of the accident.

The pilot reported that during takeoff, about 15 ft above the ground, the airplane rolled violently to the right. He applied full aileron and rudder opposite the direction of the roll, but the airplane continued to roll to the right. The airplane struck the ground with the right wing and then impacted a mesquite tree.

Examination of the wreckage after the accident revealed that 3 of the 4 hinges connecting the right flaperon hangar rib were loose. The wooden (spruce) material of the flaperon appeared to by dry rotted where the hinges attached. According to records provided by the owner, the airplane had last flown about 6 months prior to the accident flight. Records showed that the airplane had about 3 hours of flight time since its most recent conditional airworthiness inspection which was performed on May 23, 2017.

Denny Aerocraft Company Service Bulletin #9, dated September 12, 1991, had identified flaperon hangar rib failures on Kitfox models I, II, and III. The service bulletin recommended the addition of an aluminum reinforcement on each flaperon hanger rib end. The accident airplane did not have the reinforcement installed.

History of Flight

Takeoff Flight control sys malf/fail (Defining event)
Takeoff Collision with terr/obj (non-CFIT)

Pilot Information

Certificate: Airline Transport
Age: 74, Male
Airplane Rating(s): Multi-engine Land; Multi-engine Sea; Single-engine Land; Single-engine Sea
Seat Occupied: Left
Other Aircraft Rating(s): None
Restraint Used:
Instrument Rating(s): Airplane
Second Pilot Present: No
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Sport Pilot None
Last FAA Medical Exam: 03/15/2018
Occupational Pilot: No
Last Flight Review or Equivalent: 05/05/2017
Flight Time:  20000 hours (Total, all aircraft), 130 hours (Total, this make and model), 35 hours (Last 90 days, all aircraft), 29 hours (Last 30 days, all aircraft), 0 hours (Last 24 hours, all aircraft) 

Aircraft and Owner/Operator Information

Aircraft Make: HARTLINE J BON
Registration: N73BH
Aircraft Category: Airplane
Year of Manufacture: 1991
Amateur Built: Yes
Airworthiness Certificate: Experimental
Serial Number:1000 
Landing Gear Type: Tricycle
Date/Type of Last Inspection: 05/23/2017, Condition
Certified Max Gross Wt.:
Time Since Last Inspection: 3 Hours
Engines:  Reciprocating
Airframe Total Time: 1184.6 Hours at time of accident
Engine Manufacturer: Rotax
ELT: Not installed
Engine Model/Series: 912
Registered Owner: BOURGEOIS BARRY S
Rated Power: 65 hp
Operator: On file
Operating Certificate(s) Held: None

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: KE38
Distance from Accident Site: 100 Nautical Miles
Observation Time: 1055 CDT
Direction from Accident Site: 180°
Lowest Cloud Condition: Clear
Visibility:  10 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 21 knots / 34 knots
Turbulence Type Forecast/Actual: / None
Wind Direction: 230°
Turbulence Severity Forecast/Actual:
Altimeter Setting: 30.05 inches Hg
Temperature/Dew Point: 27°C / -1°C
Precipitation and Obscuration:
Departure Point: Marathon, TX (6TX9)
Type of Flight Plan Filed: None
Destination: Marathon, TX (6TX9)
Type of Clearance: None
Departure Time:1100 CDT 
Type of Airspace: Class E

Airport Information

Airport: Stovall Ranch Airport (6TX9)
Runway Surface Type: N/A
Airport Elevation: 3010 ft
Runway Surface Condition: Vegetation
Runway Used: N/A
IFR Approach: None
Runway Length/Width:
VFR Approach/Landing: Forced Landing

Wreckage and Impact Information

Crew Injuries: 1 Minor
Aircraft Damage: Substantial
Passenger Injuries: 1 Minor
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 2 Minor
Latitude, Longitude: 29.855000, -102.791667 (est)

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