CORNING, CA, USA
N6002N
Cessna 210M
The pilot reported an in-flight electrical problem to air traffic control and requested a descent for an immediate landing at the next airport. The airplane was seen descending and emanating smoke from the cabin until it crashed about 12 miles from the airport. Examination of the airplane revealed evidence of an in-flight fire. The interior of the airplane's cabin had evidence of fire on the flight controls and heavy smoke accumulation. Portions of the airplane's windshield were no longer translucent due to sooting on the interior surfaces. The source of fire was traced to a 100-amp inductive noise filter mounted directly to the airplane's firewall. There was evidence of an electrical insulation failure between an electrical terminal and the steel case of the filter. The filter was not marked as an FAA approved part and was not listed in the manufacturer's parts catalog. The airplane's electrical system had been altered with installation of a filter on the alternator output 3.5 years before the accident. There was no circuit protection or isolation mount for the 100-amp filter. The repair station that performed the work did not file an FAA Form 337. The airplane had a history of maintenance performed on the electrical system since the installation of the filter. The maintenance also included the completion of annual inspections and one repair station had replaced the 100-amp filter with another used filter.
HISTORY OF FLIGHT On July 22, 1996, at 1035 hours Pacific daylight time, a Cessna 210M, N6002N, crashed in level cultivated terrain near Red Bluff, California, after the pilot reported an electrical problem. The airplane was destroyed and the certificated pilot and sole occupant received fatal injuries. The airplane was being operated by the pilot/owner as a personal flight. The flight originated in Visalia, California, about 0900 and was destined for Aurora, Oregon. Visual meteorological conditions prevailed at the time. The pilot was in radio and radar contact with the Oakland Air Route Traffic Control Center (ARTCC), and was receiving visual flight rules (VFR) traffic advisories. At 1032:31, the pilot reported to the ARTCC sector controller he had an electrical problem and indicated he "needed to descend into Red Bluff." According to radar data, the airplane's position was about 20 miles south of the Red Bluff Airport and at 8,600 feet msl. At 1732:38, the ARTCC local controller acknowledged the pilot's transmission and told the pilot the altimeter was 29.99 inHg and the Red Bluff Airport was at his 12 o'clock 19.5 miles. The pilot acknowledged the local controller and there were no further radio transmissions from the pilot to ARTCC. Radar data also revealed the Cessna 210 mode C transponder beacon code ceased at 1733:11 and a primary return was then received. The airplane then descended over 7,000 feet in less than 4 miles and the airplane impacted the ground about 12 miles south of the Red Bluff Airport. Radar contact with the accident airplane was lost at 1735:24. A California Highway Patrol (CHP) Officer was positioned about 1 mile south of the accident. The officer witnessed the accident airplane over fly his position. The officer told FAA inspectors that the airplane was trailing smoke and paper-like debris. PERSONNEL INFORMATION The pilot held a private pilot certificate, which was last issued on December 22, 1991, with the addition of a instrument rating for single engine airplanes. The most recent third-class medical certificate was issued to the pilot on December 19, 1994, and contained the limitation that correcting lenses be worn for distant vision and corrective lenses must be carried for near vision. Review of the pilot's logbook revealed the pilot accomplished a biennial flight review on March 24, 1995, in a Cessna 172. AIRCRAFT INFORMATION The airplane was manufactured on August 3, 1978, and had accumulated a total time in service of 996 hours. Examination of the maintenance records revealed that the most recent annual inspection was accomplished on May 22, 1996, 34 flight hours before the accident. In a written statement, the pilot's wife said that on June 28, 1996, she and her husband smelled something burning while on the first leg of a cross-country flight from Anchorage, Alaska, to Redman, Oregon. The burning odor dissipated after a minute and the couple attributed the odor to over flying something burning. She further reported that "The automatic direction finder (ADF) was not tracking" and the "loran did not pick up a signal." On the second day of the trip, June 29, 1996, the pilot's wife stated her husband indicated the switches of the audio panel were "very hot to touch." She felt the switches and the panel and found them to be hot. While approaching another overnight stop, the couple discovered the Loran was malfunctioning. The unit would accept coordinates, but would not pick up a signal. The next day, June 30, 1996, the couple found the audio panel was again hot. They removed their headsets and noticed static noise coming from the overhead speaker. After arriving in Redmond, the pilot and his wife drove to a hotel. The following day the pilot contacted a local fixed base operator (FBO) to arrange the repair to the airplane. The FBO informed the pilot they were not capable of performing work on the Loran. On July 10, 1996, the pilot flew the airplane to Portland International Airport, Portland, Oregon, for repair. According to the pilot's wife, the pilot told the FBO in Portland of the problems with the airplane's avionics and the burning odor. On July 11, 1996, the FBO informed the pilot that they had found a short circuit. The FBO suggested the audio panel be replaced, and that they could have everything working in time for the pilot's planned flight to California on July 16, 1996. WRECKAGE AND IMPACT INFORMATION The airplane came to rest in a recently planted almond tree orchard at north latitude 39 degrees 58.152 minutes and west longitude 122 degrees 12.378 minutes. The initial impact point was marked by a 5-foot wide by 16-foot long by 17-inch deep ground scar. An 18-foot-long ground disturbance was found on the left side of the wreckage path adjacent to the initial impact point. The shape of the disturbance corresponded to the shape of one of the airplane's wings. Two of the three propeller blades were found attached to the propeller hub on the rim of the first ground scar. The third blade was found buried in the soil at the bottom of the ground scar. The blades exhibited chordwise scratches and leading edge nicks. The separated blade was bent forward at the tip then bent back 6 inches from the tip. The airplane's fuselage, wings, and engine were found along a northwesterly wreckage path that extended about 530 feet. From the initial impact point the following components were found at: 212 feet on a 329 degree magnetic radial for the wings; the fuselage at 311 feet on a 318 degree magnetic radial; and the engine 530 feet on a 338 degree magnetic radial. There was scattered debris throughout the wreckage path, most of which was located close to the fuselage and wings. Fragments of the windshield were examined. The plexiglass material was found smoked on the internal surfaces. A piece of the windshield was placed in a fence post and photographed. It was noted that the windshield was no longer translucent and the horizon was not visible when viewed through the plexiglass. The glare shield, both control yokes, parts of the front seat belts, the right and left doors, and right front passenger seat were separated from the fuselage and were found melted and sooted. The upholstered door panels and right front seat were partially sooted and melted above a line that extended from the forward lower corner of the door to the lower rear corner of the window. The right front seat upholstery was melted in areas that faced forward towards the instrument panel. The webbing from the front seat belts was found partially melted and the buckles were found sooted. The control yokes were also melted. The airplane's windshield canvas cover was found wrapped around the rudder pedals. Holes were found burnt through the canvas in the areas in contact with the metal of the pedals. Examination of the instrument panel revealed most of the instruments had separated. The panel was reconstructed and the instruments forward of the pilot had evidence of heat distress, and in some cases, the plastic housings were melted at the aft end of the instrument closest to the fire wall. The avionics stack located in the center of the instrument panel separated as a unit. The radio mounts were bent parallel to each other. No evidence was found of internal component heating or sooting during an examination of the radios. The overhead console that houses the radio speaker was found melted and sooted on the side exposed to the cockpit. No evidence was found of fire on the side that faces away from the cockpit, nor was there any evidence of malfunction found with the speaker or rheostat attached to the overhead console. The engine cowling was found separated from the fuselage. The primer paint was found discolored and sooted in the area above the battery aft to the dzus fasteners which attach the cowling to the fuselage above the firewall. A segment of the firewall located behind the battery was found buckled and bent. The metal exhibited black, blue, and light tan colors. There were three holes found in the segment that had burrs on the cockpit side of the firewall. A Hisonic 100-amp filter was found in the debris scattered near the fuselage. The filter was contained in a metallic case. The rear cover was missing, exposing burnt potting material. The ferrite core was visible along with heavy gage copper wire, which was found melted. One of the filter's two terminals was missing. A hole was found in the metallic case in the area where the terminal is mounted. The metal edges of the hole was melted. The case also exhibited a blue color in the area of the missing terminal. The filter case had four mounting holes, with one having a threaded blind rivet attached. The diameter of the rivet was similar to the diameter of the holes found in the segment of the burned and discolored firewall. The orientation of the of the filter mounting holes matched the geometric pattern of the holes found on the firewall, placing the missing terminal in the blue/black colored area. There was no evidence of heat shadowing on the firewall from the mounting of the filter. There was no evidence of additional circuit protection found for the RFI filter, or any evidence found of an isolation mount between the RFI unit and the firewall. The battery separated and was found in the wreckage path between the fuselage and the engine. The top aft corner of the battery case was melted in the area closest to the firewall. One of the battery cables was found. The cable's insulation was melted exposing the individual wire strands. One end of the cable was attached to a terminal and the other end was broken at various lengths of the individual strands. The broken strands exhibited evidence of necking at the break. MEDICAL AND PATHOLOGICAL INFORMATION A post mortem examination was conducted by Tehama County Coroner's Office with specimens retained for toxicological examination. The specimens were shipped to the FAA Civil Aeromedical Institute (CAMI) in Oklahoma City, Oklahoma, for analysis. According to CAMI, the specimens were not suitable for carbon monoxide and cyanide analysis. The toxicological analysis for drugs was reported as negative. Ethanol was detected in muscle tissue specimens, but was not detected in kidney tissue specimens. According to CAMI, the ethanol detected was most likely produced postmortem. FIRE ASPECTS There was no evidence of postimpact fire found in the wreckage other than that to the windshield cover found touching the rudder pedals. TESTS AND RESEARCH Hisonic 100-Amp RFI Filter The airplane was repaired by Sarasota Avionics, Sarasota, Florida, on July 22, 1992. A discrepancy was documented on Sarasota Avionics work order #8269 indicating the PM 2000 was noisy. The company replaced the power wire to the unit with a shielded wire, which according to the work order, eliminated all noise except for alternator whine. The work order indicated they checked an existing noise filter and found it was "good," but was ineffective in the audio range. The work order states, "Alternator needs additional filter when one can be located that will do the job." According to the airplane's maintenance records, the Hisonic 100-amp RFI filter was installed on the alternator output by Sarasota Avionics on November 18, 1992. After the installation the work was signed off as inspected "in accordance with current Regulators of the Federal Aviation Agency." The airplane was then returned to service by Sarasota Avionics. Review of the aircraft file, maintained by the FAA Aircraft Registration Branch, did not reveal the filing of an FAA Form 337, "Major Alteration or Repair" for the Hisonic 100-amp RFI installation on the alternator output. An examination of an exemplar Hisonic 100-amp RFI did not reveal the letters "FAA-PMA" as required by 14 CFR Part 45.15(a). According to Cessna Aircraft Company, the filter is not listed in their parts manuals. On July 8, 1994, the airplane was being serviced by Channel Islands Aviation, Camarillo, California. A discrepancy on work order #7403 indicated the noise filter was broken. The corrective action indicated a "used good filter" was installed. ELECTRICAL ENGINEERING EVALUATION The Safety Board submitted the Hisonic 100-amp RFI filter with an exemplar filter and the segment of the firewall to an independent electrical engineer for evaluation. The electrical engineer concluded that there was an electrical insulation failure between one of the terminals and the steel case of the RFI filter. The electrical engineer stated in his report, "The insulation failure resulted in a series of arcing events between the aircraft alternator bus and the case of the RFI filter. The heating associated with the arcing was augmented by the resistive heating in the stainless steel firewall material which was delivering the fault current to the aircraft ground. The absence of an adequate ground on the filter allowed the fault current to stray through the highly resistive steel components of the aircraft heating some of these components as the current found its way to the aircraft negative supply. The heating was sufficient to melt solder which held the cover of the RFI 100 in place on the case, and cause plastic materials to smolder and eventually ignite." ADDITIONAL INFORMATION The wreckage was released to the representatives of the owner on July 24, 1996, with three components retained for further examination. The three components were sent to the owner's representative on March 24, 1997, via Federal Express priority overnite shipment.
improper installation of an electrical component, during an alteration of the aircraft electrical system; and subsequent electrical insulation failure, which resulted in electrical shorting, arcing, and an electrical fire. Factors relating to the accident were: inadequate maintenance record keeping (by not filing FAA Form 337), smoke in the cabin, and the resultant restriction of the pilot's vision, which impeded his ability to control the airplane as it neared the ground.
Source: NTSB Aviation Accident Database
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