Flight History
On February 17, 2008, at 1638 Pacific standard time, an experimental Wilson Vans RV-7, registration N331KM, experienced a loss of engine power and collided with trees approximately 1.7 miles northwest of Nevada City, California. The private pilot operated the airplane under Part 91. The pilot was killed, and the airplane was substantially damaged. Visual meteorological conditions prevailed, and no flight plan was filed. The personal flight originated at Nevada County Air Park in Grass Valley, California, at about 1610.
At 1637, another pilot (N6375Q) was in communication with the accident pilot and made a mayday distress call on guard frequency (121.5 MHz) on behalf of the accident pilot. The accident pilot had earlier made a distress call on the Nevada County Air Park common traffic advisory frequency (CTAF), stating that the engine had quit and he could not restart it.
A second pilot, airborne at 5,500 feet MSL, reported that the accident pilot said he could not restart the engine despite trying everything and that he was going down. The witness observed the airplane in a controlled descent into an area of large trees.
The wreckage came to rest inverted on the ground, with leading edge damage to the wings and broken pine branches nearby. Witnesses and sheriff's deputies noted a distinct smell of fuel. Photographs taken immediately after the accident showed the fuel pump switch in the 'on' position.
Pilot and Aircraft Information
The 57-year-old pilot held a private pilot certificate dated May 9, 2005, and a third-class medical certificate from August 2007. His logbook showed 871.6 hours in single-engine airplanes as of February 14, 2008. He had logged 42.2 hours in RV-6A and RV-7 aircraft since November 8, 2007, with 27.3 hours in the accident airplane.
The two-seat, low-wing, fixed landing gear experimental airplane was constructed by the pilot. It was powered by an experimental Xtreem 360 engine (model IO-360-B1AA4) equipped with a Hartzell constant-speed propeller. The engine was first test-run on November 12, 2007, and again on December 10, 2007. A Special Airworthiness Certificate was issued on December 13, 2007.
On January 4, 2008, at 13.0 total engine hours, the engine-driven fuel pump was removed and replaced. The pilot had earlier expressed concerns to a colleague about a fuel leak around the pump. After replacing the pump, the pilot could not get the engine to run and enlisted a mechanic friend to assist. During the post-accident examination, the hobbs hour meter showed 29.1 hours.
Engine and Fuel Pump Examination
The NTSB examined the engine and airplane on March 27, 2008, at a facility in Pleasant Grove, California. The number 2 cylinder fuel injection line was slightly crimped, and both leads for the number 1 cylinder were severed. The oil level was four quarts. All four spark plugs exhibited a whitish-gray color on the electrodes, with similar gaps and no mechanical damage. The engine rotated by hand with thumb compression on all cylinders. Throttle, propeller, and mixture controls moved without binding.
Electrical power was applied to the airplane, and the electric fuel boost pump was energized. All electrical switches were damaged but could function if held in the 'on' position. Fuel from an external can was plumbed into the fuel selector valve. The boost pump momentarily produced over 30 psi on the fuel pressure gauge. The engine started using the ignition switch and external power but stopped after a few seconds. It ran continuously at about 1,100 rpm only when the boost pump was held in the 'on' position.
The engine-driven fuel pump was removed. The pump arm was not aligned squarely with the pump centerline. Disassembly revealed a crack on the pump arm below the pivot hole. The lever arm pad face showed wear on the center and left side. The pump components were sent to the NTSB Materials Laboratory.
Microscopic examination showed the crack face had fine granular features near the edges, consistent with a hardened case, and smooth features in the core. The crack extended through about 75 percent of the lever arm cross section. When the lever arm was reinserted into the pump casting, it showed lateral bending deformation of about 0.25 inch. Scanning electron microscopy revealed striations typical of fatigue cracking, originating below the surface of the hardened case at the edge of a channel, approximately 0.3 inches from the attachment pin hole. The edges showed granular features typical of a hardened case, with ductile dimple bands adjacent. The fatigue crack originated from the ductile dimple band region. The core exhibited mechanical damage from relative movement and ductile dimple features from overstress separation.
The manufacturer of the fuel pump stated that if the push rod is not aligned under the lever arm during installation, the lever arm can bend or crack when bolts are torqued. Such a crack may not be visually detectable.
Medical Information
An autopsy on February 20, 2008, listed the cause of death as multiple blunt force trauma. Forensic toxicology tested negative for carbon monoxide, cyanide, ethanol, and listed drugs. Quinine and ibuprofen were detected in the pilot’s blood.