History of Flight
On September 5, 2012, about 1500 Pacific daylight time, an experimental Hansen Vans RV-6 airplane, N53MH, nosed over during a forced landing on Oregon Highway 138 near Lemolo Lake, Oregon. The student pilot/owner operated the airplane under 14 CFR Part 91 on a solo flight. The flight had departed Rogue Valley International-Medford Airport (MFR), Medford, Oregon, with planned stops at Klamath Falls Airport (KLM) and Sunriver Airport (S21), before returning to MFR. The first two legs were normal.
While cruising at 10,500 feet, the pilot detected a strange odor and found he could no longer transmit to air traffic control. He changed his transponder code to 7600 (the code for loss of communications) but the post-accident examination found the transponder set to 7670; the investigation did not determine whether the code was mis-set or disturbed during the accident. The controller instructed the pilot to push the IDENT button if he could hear, which the pilot did. Subsequently, the electric gauges became erratic and the instrument panel began smoking.
Concerned about an onboard fire, the pilot initiated a rapid descent. The terrain below was dense forest, but he located a road suitable for a precautionary landing. He noted the narrow road and presence of power lines. Smoke was collecting in the upper cockpit, forcing him to cant and lower his head. After touchdown, the airplane veered left. The pilot applied brakes, but the airplane exited the road, nosed over, and came to rest inverted.
Pilot Information
The pilot held a student pilot/medical certificate issued in June 2011. He reported approximately 100 total flight hours, with about 25 hours in the accident airplane make and model.
Aircraft Information
The airplane was built by a previous owner and first flew in October 2005. It was equipped with a Lycoming O-360 series engine. The engine was overhauled at a total time in service of about 2,142 hours and had accumulated 215 hours since overhaul. The most recent condition inspection was completed on June 6, 2012, at a total time in service of 193 hours. The maintenance records contained no entries related to the electrical/smoke event.
Meteorological Information
Weather near the accident location included scattered clouds at 11,500 feet above ground level with 10 miles visibility.
Wreckage and Impact Information
The accident site was about 77 miles north-northeast of MFR. The airplane came to rest inverted in a grassy ditch adjacent to the road. Tire skid marks about 20 feet long, consistent with the main landing gear, were found prior to where the airplane left the pavement, diverging at an angle of about 30 degrees. The spinner was crushed; the canopy and canopy bow were partly fractured and crushed; the fuselage and empennage were buckled. There was no post-impact fire. The pilot escaped through the fractured canopy.
Additional Information
After recovery, the airplane was examined to locate the electrical problem. The cowlings were removed; the alternator remained attached, the belt was intact, and the battery was secure with no thermal damage. Wiring behind the instrument panel appeared firmly attached, with no smoke or thermal damage. All circuit breakers were closed and fuses intact.
Using an automotive battery (since the airplane's battery did not retain a charge), master relays clicked when the master switch was actuated. However, four devices—turn coordinator, communications radio, auxiliary fuel pump, and voltmeter—did not function, even though 14 volts was measured at their terminals. The voltmeter needle remained below 0 volts. Other components operated normally. The symptoms were consistent with an overvoltage event.
The alternator was an automotive Nippondenso 12-volt type with an integral voltage regulator. A bench test produced over 18 volts (the test bench limit). Disassembly showed no physical or thermal damage to the voltage regulator, which was stamped IN219 12V US 413. The examination did not determine the specific reason(s) for the incorrect high voltage output.
Communications
The pilot was receiving flight following from Seattle Air Route Traffic Control Center and was assigned a discrete transponder code. After losing transmit capability, he changed the code to 7600. The controller recognized it and acknowledged. Examination after the accident found the transponder set to 7670; the investigation could not determine if the pilot mis-set the code or if it was disturbed during the accident.