Sunday, May 02, 2021

Flight Control System Malfunction/Failure: de Havilland DH-4, N32517; accident occurred May 02, 2020 at Bowling Green–Warren County Regional Airport (KBWG), Kentucky


Aviation Accident Final Report - National Transportation Safety Board

Additional Participating Entity: 
Federal Aviation Administration / Flight Standards District Office; Louisville, Kentucky

Investigation Docket - National Transportation Safety Board:

Location: Bowling Green, KY
Accident Number:ERA20CA168 
Date & Time: 05/02/2020, 0700 CDT
Registration: N32517
Aircraft Damage: Substantial
Defining Event: Flight control sys malf/fail
Injuries: 1 None
Flight Conducted Under: Part 91: General Aviation - Flight Test 


The pilot reported that, during the first flight test of the antique airplane, which was in the process of being restored, he had difficulty controlling the airplane in the roll axis. After takeoff, he noticed that the airplane required some right aileron to keep the wings level. After turning crosswind, the problem worsened, and required that he apply more pressure to the control stick (in the right aileron direction). As he turned downwind, he used nearly full right aileron to maintain control, and the force on the control stick was so high that he was unable to hold it with one hand. When he removed his left hand from the control stick to adjust the throttle, the airplane would roll toward the left. As the airplane approached the base leg, the pilot was unable to keep the wings level; the airplane entered a slip and he was unable to prevent the airplane from turning left. The airplane descended, touched down in the grass to the right of the runway, and came to rest nose down.

Examination of the airplane revealed that the aileron control system was continuous. However, due to the airplane damage, the rigging of the aileron system could not be evaluated.

The airplane sustained substantial damage to the forward fuselage, lower wing, and horizontal stabilizer.

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
A primary control (aileron) system anomaly that progressively worsened during a test flight that resulted in a loss of control. The reason for the anomaly was not determined due to impact damage. 


Aircraft Aileron control system - Malfunction
Aircraft Lateral/bank control - Attain/maintain not possible
Not determined (general) - Unknown/Not determined

Factual Information

History of Flight

Takeoff Flight control sys malf/fail (Defining event)

Pilot Information

Certificate: Private
Age: 73, Male
Airplane Rating(s): Single-engine Land
Seat Occupied: Center
Other Aircraft Rating(s): None
Restraint Used:
Instrument Rating(s): Airplane
Second Pilot Present: No
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 3 With Waivers/Limitations
Last FAA Medical Exam: 03/22/2019
Occupational Pilot: No
Last Flight Review or Equivalent: 01/10/2019
Flight Time:  946 hours (Total, all aircraft), 309 hours (Total, this make and model), 946 hours (Pilot In Command, all aircraft), 16 hours (Last 90 days, all aircraft), 3 hours (Last 30 days, all aircraft), 0.3 hours (Last 24 hours, all aircraft)

Aircraft and Owner/Operator Information

Aircraft Make: DAYTON-WRIGHT
Registration: N32517
Model/Series: DH-4
Aircraft Category: Airplane
Year of Manufacture: 1918
Amateur Built:No 
Airworthiness Certificate: Experimental; Special Flight
Serial Number: 12459
Landing Gear Type: Tailwheel
Seats: 2
Date/Type of Last Inspection: 01/25/2020, Annual
Certified Max Gross Wt.: 4297 lbs
Time Since Last Inspection: 5 Hours
Engines: 1 Reciprocating
Airframe Total Time: 5 Hours at time of accident
Engine Manufacturer: Lincoln
ELT: Not installed
Engine Model/Series: Liberty V12
Registered Owner: Saving Liberty Dh4 Llc
Rated Power: 400 hp
Operator: Saving Liberty Dh4 Llc
Operating Certificate(s) Held: None

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: BWG, 537 ft msl
Distance from Accident Site: 0 Nautical Miles
Observation Time: 0653 CDT
Direction from Accident Site: 279°
Lowest Cloud Condition: Clear
Visibility:  10 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: Calm /
Turbulence Type Forecast/Actual:
Wind Direction:
Turbulence Severity Forecast/Actual:
Altimeter Setting: 30.12 inches Hg
Temperature/Dew Point: 13°C / 11°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Bowling Green, KY (BWG)
Type of Flight Plan Filed: None
Destination: Bowling Green, KY (BWG)
Type of Clearance: None
Departure Time: 0652 CDT
Type of Airspace: Class E

Airport Information

Airport: Bowling Green-Warren County Rg (BWG)
Runway Surface Type: Grass/turf
Airport Elevation: 547 ft
Runway Surface Condition: Dry; Vegetation
Runway Used: 03
IFR Approach: None
Runway Length/Width: 6501 ft / 150 ft
VFR Approach/Landing: Forced Landing; Traffic Pattern 

Wreckage and Impact Information

Crew Injuries: 1 None
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 None
Latitude, Longitude: 36.964444, -86.419722 (est)


  1. Pilot had 309 hours this make and model? Damn!

  2. Glad the pilot wasn't hurt, but dang that is a real D4 with a Liberty V12 engine. At first glance I thought it was just a homebuilt replica, but it is the real deal. I am glad the pilot wasn't hurt, but I hope the plane can be rebuilt, not many of these WW1 birds left, and even less still flying.

  3. Such a shame. I think this was the plane that Robertson Aircraft bought out of surplus and used for the first air mail flights St. Louis-Chicago ...flown by a young pilot named Lindbergh.