Champion 7GCBC N3464D accident near Eatonville, Washington

Probable cause

The pilot’s exceedance of the airplane’s critical angle of attack while maneuvering to avoid trees, which resulted in an aerodynamic stall.

NTSB analysis

The pilot planned to depart on his fourth flight of the day. Witnesses reported that the engine run-up, departure, and climbout were normal. When the airplane reached about 500 ft above ground level and was about 0.5 nautical miles (nm) south of the runway, the airplane entered an abrupt left bank, which was immediately followed by a spin before it impacted the ground in a nose-low attitude.

Postaccident examination of the engine and flight controls did not reveal any preimpact mechanical anomalies. Witness reports indicated that the engine power was smooth and continuous and then ceased just before the airplane impacted trees. As the propeller damage signatures showed limited to no rotation at the time of impact, the pilot likely reduced the throttle during the descent. In addition, the gascolator sump valve was found in the open position. However, a witness did not observe any fuel leaking from the airplane during taxi or takeoff; thus, the sump valve position was likely a result of the impact.

An examination of the engine controls revealed that the mixture control cable had separated at the carburetor. A metallurgical examination did not yield sufficient evidence, on its own, to determine whether the separation occurred prior to the accident. While there was evidence that the mixture cable attachment was worn and may have been slipping before the accident flight, the fracture surfaces showed overstress fracture features that could have occurred during the accident. If the fracture had occurred before the accident, it likely would have required at least one instance of aggressive use of the controls to cause the initial buckling of the control cable. However, evidence showed the pilot was able to adjust engine power during the descent, which suggests the cable failure likely occurred during the impact, and not before.

The airplane’s precise fuel quantity at the time of the accident could not be determined, as the pilot also used a personal fuel trailer that did not contain any fuel records. Fuel receipts indicated that the pilot had most recently refueled the airplane at a nearby airport three months prior to the accident. Fuel performance computations showed that he likely filled the tanks to their total capacity during his last refueling, which would have left him with about 18 gallons of fuel on the day of the accident. This was sufficient to complete the estimated 30-minute scenic flight but would have placed the airplane about 40 lbs over its gross weight.

The airplane was in a nose-high attitude about 10 ft above trees and approaching rising terrain when it stalled. The airplane impacted the ground after the pilot attempted to avoid the trees by entering a rapid left bank and a pitch attitude that exceeded the airplane’s critical angle of attack, which resulted in an aerodynamic stall and a loss of control.

Text from the NTSB. Open the NTSB docket for WPR24FA226 for the full record.