The pilot reported that, during the first flight test of the antique Dayton-Wright DH-4, which was in the process of being restored, he had difficulty controlling the airplane in the roll axis.
After takeoff from the airport in Bowling Green, Kentucky, 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.
The airplane sustained substantial damage to the forward fuselage, lower wing, and horizontal stabilizer.
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.
Probable Cause: 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.
To download the final report. Click here. This will trigger a PDF download to your device.
This May 2020 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
When building or restoring an aircraft or doing a preflight, don’t just move the stick or wheel.
Verify that the surfaces move in the correct direction and amount.
A lone builder can move the stick to an extreme and lock it in position. The use tools to measure the free on all surfaces. See if the surface can move with the stick locked.
Two different qualified people should verify the initial rigging.
Great advice, Jim, with emphasis on “Verify that the surfaces move in the correct direction”
Aircraft and lives have been lost because the controls, typically ailerons, were hooked up “backwards,” such that a control input to the right initiated a roll to the left. This can be very confusing to the pilot, and lead to an accident. It’s happened to all types of aircraft…GA, military, and airline. Murphy lives in the workshop.
Thank you! Even professional shops and factories have mistakes and errors. Sometimes as simple as forgetting to grease a nosewheel strut. Sometimes failing to properly torque and mark a wing or engine bolt.