The pilot was conducting a personal flight in his experimental Long EZ.
While in cruise flight, the airplane “violently began shuddering,” and the pilot immediately shut down the engine and attempted an emergency landing. The airplane was unable to reach the selected runway and landed about 200′ short of the runway threshold in a rough, grassy area in Eufaula, Alabama.
After exiting the airplane, the pilot discovered that a portion of the trailing edge of the wood propeller had separated and penetrated the lower half of the right rudder control surface.
A post-accident examination of the remaining portion of the wood propeller determined that the propeller was manufactured from laminations of defect-free hard maple lumber that showed no signs of decay.
An inspection of the separation surface 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 layers that had failed.
Examination of this bond line showed minimal wood failure that was about 8″ long and between 1/8″ and 1/4″ wide.
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 and assembled using an adhesive that is advertised as “ideal for interior wood application.”
However, the adhesive had not been tested for applications in which extreme temperature fluctuations, pressure, and vibrations would be expected, such as those experienced during airplane operations.
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.
NTSB Identification: ANC18LA008
This November 2017 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.
How can a prop manufacturer settle on an interior-strength approved adhesive?
I agree. I can’t believe the binding agent is not approved by the FAA for this usage. Did they run short and quickly get some more at Home Depot. Sure hope they incurred liability for his aircraft! Something fishy here!
It’s a Homebuilt aircraft, even the owner could have made the prop. The FAA does not regulate them.
It was an experimental prop for an experimental aircraft so it was up to the builder to determine if the prop was suitable for the application. This article does not mention who the prop maker was but I would guess it did not come from any shop that manufactures props approved for certified aircraft. So it comes back to Let The Buyer Beware when going outside the certified aircraft supply chain.
Just for the record you can get the specifics such as the name of the manufacturer on this link to the NTSB:
https://www.ntsb.gov/_layouts/ntsb.aviation/brief2.aspx?ev_id=20171113X84023&ntsbno=ANC18LA008&akey=1
So a well known prop maker for the experimental market (who shall remain nameless here) was essentially using adhesive that could be picked up at the local Home Depot (DAP Weldwood). If word of this gets out they will probably see a big drop in sales.
Kind of a useless report until you go drill into down the NTSB reports to identify the prop manufacturer.