NTSB Factual Report

On November 11, 2017, about 0935 central standard time (CST), a Cloud Jeffery Ferrell Long EZ airplane, N754T, landed short of the runway during a forced landing at Wheedon Field (KEUF), Eufaula, Alabama. The private pilot and passenger were not injured, and the airplane was substantially damaged. The flight was being operated as a 14 Code of Federal Regulations (CFR) Part 91 visual flight rules personal flight. Visual meteorological conditions prevailed, and no flight plan was filed. The flight departed Marianna Municipal Airport (KMAI), Marianna, Florida, about 1000 eastern standard time, and was destined for Falcon Field (KFFC), Atlanta, Georgia. However, due to deteriorating weather conditions en route, the destination was changed to KEUF. No flight plan had been filed.

According to a statement from the pilot, while flying about 7,500 ft msl, about 9 miles northeast of KEUF, "suddenly and without warning the aircraft violently began shuddering." The pilot immediately shut down the engine and turned the airplane towards KEUF. During the turn, he noticed the right rudder control surface was damaged. Due to winds and orientation to the runway when the engine was shut down, the airplane was unable to reach the runway and landed about 200 ft prior to the runway edge in a rough, grassy area. Upon exiting the airplane, the pilot discovered a portion of the trailing edge of the propeller had separated and penetrated the lower half of the right rudder control surface, which resulted in substantial damage. The separated portion of the propeller was not located.

The wood propeller, manufactured by Ed Sterba Propellers, was removed from the aircraft and sent to the US Department of Agriculture's Forest Products Laboratory in Madison, Wisconsin, for examination under the NTSB supervision. The examination determined that the propeller was manufactured from laminations of defect-free hard maple lumber that was absent of any decay. An inspection of the separation surface, using a low magnification hand lens, indicated that the individual layers of the propeller were laminated together using an adhesive that resulted in a light-colored bond line. The failure surface included an exposed portion of the bond line between two wood laminae that had failed. Examination of this bond line showed minimal wood failure about eight inches in length and between 1/8" and 1/4" wide. It was noted that the amount of cured adhesive observed varied considerably along the length of the failure surface's bond line, with an area of the bond line having minimal adhesive coverage.

According to the propeller manufacturer, the propeller was carved by hand using hard maple lumber. The adhesive used was Weldwood® Plastic Resin Glue. Weldwood is a ureaformaldehyde product that is advertised as "ideal for interior wood application." In a letter to the NTSB from DAP Products Inc., the adhesive manufacturer, it was stated "DAP has not qualified this product for use on any aircraft component such as hand-carven wooden propeller, nor has it been tested for applications where extreme temperature fluctuations, pressure and vibration would be expected."

The closest official weather observation station is Columbus Airport (KCSG), Columbus, Georgia, which is located about 35 miles northeast of the accident site. At 0851, a METAR was reporting, in part, wind 090° at 11 knots; visibility 10 statute miles; clouds and ceiling clear; temperature 50° F; dew point 39° F; altimeter 30.35 inches of Mercury.

NTSB Probable Cause

The in-flight separation of a portion of the propeller, which subsequently penetrated the right rudder, as a result of the failure of the bond line between two of the propeller’s wood layers. Contributing to the failure of the propeller was the manufacturer’s use of an inappropriate bonding agent.