SEA07LA039

The passenger reported that the experimental amateur-built airplane was in cruise flight about 12 miles from the airport when a bird impacted the propeller, and the airplane started shaking and vibrating violently. The flight returned to the airport, and the pilot entered the traffic pattern for landing. The airplane was high and fast on final for runway 30, and when it was about 1/2 to 2/3 of the way down the runway, the pilot decided to go around. When the throttle was advanced, the engine ran rough and did not produce power. During the go around attempt, the airplane entered a stall and subsequently impacted terrain about 500 feet beyond the departure end of the runway. Examination of the wreckage revealed that one blade of the experimental wooden propeller was broken off at the hub, and the other blade was broken off at approximately midspan. Wood fragments identified as being from a propeller blade were found at the accident site. Laboratory examination of the remaining portion of the propeller and the recovered blade fragments indicated the fragments were from the blade that was broken off at the hub, and this blade likely fractured as a result of ground impact. The fracture features found on the blade that separated near midspan were consistent with a traumatic event such as an in-flight bird strike. No obvious signs of bird residue were noted on the propeller, but the loss of the outboard portion of the blade prevented examination of this part of the propeller.

On December 29, 2006, about 1440 Pacific standard time, an Averyt Vans RV-4 amateur-built experimental airplane, N234RV, impacted terrain following a loss of control during a go around at Grants Pass Airport, Grants Pass, Oregon. The airplane was registered to and operated by the pilot. The commercial pilot and the passenger received serious injuries, and the airplane sustained substantial damage. Visual meteorological conditions prevailed and no flight plan was filed for the local personal flight conducted under 14 CFR Part 91. The flight originated at an unknown time from the Grants Pass Airport.

The passenger reported to Federal Aviation Administration (FAA) inspectors and to the airport manager that the flight departed from Grants Pass and proceeded towards the coast. While flying over the Rogue River, about 12 miles from the airport, a bird impacted the propeller, and the airplane started shaking and vibrating violently. The flight returned to the airport, and the pilot entered the traffic pattern for landing. The airplane was high and fast on final for runway 30, and when it was about 1/2 to 2/3 of the way down the runway, the pilot decided to go around. When the throttle was advanced, the engine "performed very badly, misfiring, vibrating, and not producing power." During the go around attempt, the airplane entered a stall and subsequently impacted terrain about 500 feet beyond the departure end of the runway.

During an on scene examination of the wreckage, FAA inspectors noted that one blade of the wooden propeller was broken off at the hub, and the other blade was broken off at approximately midspan. Wood fragments identified as being from a propeller blade were found at the accident site. The fiberglass propeller spinner was not found at the accident site. The propeller was identified as a Pacesetter experimental propeller. At the request of the National Transportation Safety Board (NTSB) investigator in charge (IIC), the remaining portion of the propeller and the blade fragments were sent to the NTSB Materials Laboratory for examination.

The NTSB Materials Laboratory reported that the propeller was made from a series of six laminates, each about 3/4 inch thick, that were glued together and then formed into the shape of the blade. The lab labeled the separation of the blade broken off near midspan as fracture "1" and the separation of the blade broken off at the hub as fracture "2." Fracture "1" was located primarily between 12 to 18 inches from the center of the hub. The two laminate layers on the forward side of the blade were fractured about 16 inches from the center of the hub on a relatively flat plane. Examination of the fracture through these laminates showed pulled out fibers indicative of a tensile fracture region. The remainder of the blade contained multiple fracture planes, with significant splintering, indicative of bending loads. Fracture "1" also progressed through an area of what appeared to be solid epoxy along the leading edge of the blade arm. This epoxy region was fractured near the tensile fracture region in the two forward laminate layers. The overall features of fracture "1" were typical of a bending overstress fracture, with the direction of loading aft on the separated portion of the blade arm.

Fracture "2" was in the blade arm opposite fracture "1" and was closer to the hub. This fracture progressed through the laminate layers within a radial distance of about 2 to 3 inches, and minimal grain splitting or delamination was noted. Detailed visual examination of the individual broken wooden fibers in this fracture showed the presence of tensile fracture with fiber pullout over almost the entire fracture, with the possible exception of an area of compression fracture adjacent to the aft surface of the blade. A central portion of the second and third laminate layers from the aft side of the blade split into the centerline hole and were displaced radially outboard during the fracture process. What appeared to be ground impact damage was noted on the forward face of the propeller adjacent to fracture "2". Examination of the forward side of the blade adjacent to fracture "2" showed damage where it appeared that the forward spinner bulkhead had been pushed aftward into the blade, leaving an impact mark and partially cutting into the forward two laminates.

The lab also examined a large number of pieces of the propeller (probably greater than 100 pieces) that were reportedly recovered from the accident site. Most of these pieces could not be identified as being from any specific location on the propeller. However, 11 of the pieces were positively identified as being from fracture "2", the fracture closer to the hub, based on paint markings, curvature of the exterior surface, or bolt hole features. In addition, these pieces included the inboard end of a leading edge epoxy strip, and it was noted that the inboard end of this strip was present on fracture "1", further confirming that the pieces were from fracture "2."

Neither the pilot nor the passenger responded to written requests from the NTSB IIC for their statements regarding the accident.