Lemolo Lake, OR, USA
N53MH
HANSEN HANSEN-VANS RV-6
The student pilot/owner of the experimental, amateur-built airplane was conducting a long cross-country solo flight, and he completed the first two legs uneventfully. He reported that, when the airplane was in cruise flight at 10,500 ft on the final leg of the trip, he began experiencing radio problems, followed shortly by other electrical problems and smoke in the cockpit. Due to concerns about an on-board fire, he opted to conduct a precautionary landing on a road. During the landing roll, the airplane exited the paved surface, nosed over, and then came to rest inverted. Postaccident examination of the airplane did not reveal any indications of smoke or thermal damage. However, four electrically powered devices, including the voltmeter, were found to be inoperative. Although a visual examination of the alternator, which was a 12-volt automotive-grade unit with an integral voltage regulator, found no evidence of electrical arcing or thermal damage, a functional check revealed that the continuous-regulated voltage output was greater than 18 volts. The alternator and regulator were disassembled, and no internal mechanical anomalies were identified. The electrical anomalies described by the pilot and noted during the tests and examinations, particularly the failed voltmeter, were consistent with an overvoltage event due to the failure of the automotive voltage regulator, which would have resulted in the smoke in the cockpit. Although the engine likely would have continued to run with the noted electrical system anomalies, the pilot had no way of knowing whether the observed smoke and electrical anomalies would result in additional problems or an onboard fire; therefore, his decision to conduct a forced landing was appropriate.
HISTORY OF FLIGHTOn 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 the provisions of Title 14 Code of Federal Regulations Part 91, as a solo flight. The student pilot received serious injuries, and the airplane sustained substantial damage to the tail section. Visual meteorological conditions prevailed for the flight that had departed the Rouge Valley International – Medford Airport (MFR), Medford, Oregon, at an undetermined time. A visual flight rules (VFR) flight plan had been filed for the flight. According to the pilot, his flight originated at Rogue Valley International-Medford Airport (MFR), with planned stops at Klamath Falls Airport (KLM), Klamath Falls, Oregon, and Sunriver Airport (S21), Sunriver, Oregon, and a return back to MFR. The first two legs of the flight were normal. After departing from S21, while cruising at an altitude of 10,500 feet, the pilot detected a strange odor, and then determined that he was no longer able to transmit to air traffic control. He changed his transponder code to indicate that he had lost communications, and heard the controller instruct him to push the IDENT button if he could hear the controller. The pilot complied, the controller acknowledged, and then the "electric gauges" became erratic. The pilot stated that the instrument panel then began smoking. The pilot initiated a rapid descent because he was concerned about an onboard fire, and wanted to land as soon as possible. The terrain below him was dense forest, but the pilot located a road that he considered suitable for a precautionary landing. He set up for a landing, but noted that he had to cant and lower his head, since smoke was collecting in the upper region of the cockpit. He also noted that the road was narrow, and that power lines were present. After the airplane touched down, it began to veer to the left. The pilot applied the brakes, but the airplane continued to the left; it exited the road, where it nosed over and came to rest inverted. The airplane was recovered to a secure location for subsequent examination. PERSONNEL INFORMATIONAccording to information provided by the pilot, he had approximately 100 total hours of flight experience, including approximately 25 hours in the accident airplane make and model. His most recent FAA student pilot/medical certificate was issued in June 2011. AIRCRAFT INFORMATIONAccording to information in the airplane maintenance records provided by the pilot, the airplane was built by a previous owner, and first flew in October 2005. The airplane was equipped with a Lycoming O-360 series engine. The maintenance records and pilot-provided information indicated that the engine was overhauled when it had a total time in service of about 2,142 hours, and had accumulated a total time in service since overhaul of 215 hours. The airplane's most recent condition inspection was completed on June 6, 2012, and the records indicated that at that time, the airplane had a total time in service of 193 hours. The maintenance records did not contain any entries that could be associated with the electrical/smoke event. METEOROLOGICAL INFORMATIONAccording to information provided by the pilot, the weather conditions near the accident location included scattered clouds at 11,500 feet above ground level, with 10 miles visibility. AIRPORT INFORMATIONAccording to information in the airplane maintenance records provided by the pilot, the airplane was built by a previous owner, and first flew in October 2005. The airplane was equipped with a Lycoming O-360 series engine. The maintenance records and pilot-provided information indicated that the engine was overhauled when it had a total time in service of about 2,142 hours, and had accumulated a total time in service since overhaul of 215 hours. The airplane's most recent condition inspection was completed on June 6, 2012, and the records indicated that at that time, the airplane had a total time in service of 193 hours. The maintenance records did not contain any entries that could be associated with the electrical/smoke event. WRECKAGE AND IMPACT INFORMATIONThe accident site was situated about 77 miles north-northeast of MFR, the flight's point of origin, and intended destination. The airplane came to rest inverted in a grassy ditch that was adjacent to the road that the pilot had used for landing. Tire skid marks about 20 feet long, and consistent with the two main landing gear, were located just prior to where the airplane exited the paved road surface. The skid marks diverged from the roadway at an angle of about 30 degrees. The spinner was crushed, and the canopy and canopy bow were partly fractured and crushed. The fuselage and empennage sections were buckled. There was no post-impact fire. The pilot escaped the cockpit through the fractured canopy. ADDITIONAL INFORMATIONSubsequent to its recovery, the airplane was examined in an attempt to locate the source of the electrical problems. The engine upper and lower cowlings were removed, and the electrical system forward of the firewall was examined. The alternator remained attached to the engine crankcase, and the alternator belt was intact and in place. The battery remained properly secured to the firewall, and all electrical cables were intact and free of damage. No indication of smoke or thermal damage was observed. The wiring behind the instrument panel was examined. All wires appeared firmly attached to their respective posts on each electrically driven instrument, and no indication of smoke or thermal damage was observed. All circuit breakers were in the closed (non-activated) position, and all fuse links were intact. The airplane 12-volt battery did not retain a charge, so an automotive battery was utilized to perform some system tests. Using that power source, the master relays audibly clicked when the airplane master switch was actuated. However, four electrically-powered devices did not function, even though a potential difference of 14 volts was measured across their respective input terminals. The devices included the turn coordinator, communications radio, auxiliary fuel pump, and voltmeter. The voltmeter indicator needle did not move from its non-powered position (just below 0 volts) when the 12 volts from the external battery were applied. The voltmeter scale maximum was 16 volts. All remaining electrical components, including the flap motor, transponder, GPS receiver, and temperature gauge, appeared to function normally. The symptoms described by the pilot, and the deficiencies noted during the test, were all consistent with an overvoltage event in the electrical system. The alternator was an automotive version, with no identifying information or placards. The alternator had an integral voltage regulator, and no other voltage regulator was installed on the airplane. The alternator was removed from the airplane and retained for possible additional examination. The alternator was a Nippondenso 12-volt automotive-grade alternator; it was examined under the supervision of the National Transportation Safety Board in Puyallup, Washington. The visual examination of the alternator revealed no evidence of damage, electrical arcing, or thermal damage. The alternator drive shaft rotated freely with no binding or rotational resistance. A functional bench test was performed. It was noted that the alternator produced a continuous voltage in excess of 18 volts, which was the test bench instrumentation's maximum upper limit. Following the bench test, the alternator was disassembled; the voltage regulator showed no evidence of physical or thermal damage, and the manufacturing stamp confirmed that it was a 12-volt regulator; the following information was stamped on the voltage regulator IN219 12V US 413. The examination did not determine the specific reason(s) for the incorrect high voltage output. COMMUNICATIONSThe pilot was utilizing flight following services provided by Seattle Air Route Traffic Control Center (SEA ARTCC), and was assigned a discrete transponder code. Once the pilot determined that he was not able to transmit to SEA ARTCC, he either partially or fully changed the transponder code to "7600," which is the designated code to indicate a loss of radio communications capability. The controller recognized and understood the meaning of the new code, but examination of the airplane after the accident found the transponder set to "7670." The investigation did not determine whether the pilot mis-remembered or mis-set the code, or whether the transponder code was disturbed during or after the accident sequence.
An overvoltage event due to the failure of the automotive voltage regulator, which resulted in electrical anomalies and smoke in the cockpit and a subsequent forced off-airport landing.
Source: NTSB Aviation Accident Database
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