SAN DIEGO, CA, USA
N61560
Cessna 172M
During a practice instrument approach on a dark night, the aircraft began losing electrical power. The airplane was over a low cloud layer and the pilot cancelled his IFR clearance, informed ATC that he was losing electrical power and that he would fly back to home base under visual flight rules. He then flew in a southerly direction, following roads until he decided that he had flown far enough to locate his home airport. He was unable to locate the airport, made a 180-degree turn in an attempt to locate another airport, and found that he was unsure of his position. He elected to land on a large well-lit parking lot and collided with concrete barriers during the landing roll. An automotive alternator was found installed on the airplane, with a nonapproved support bracket that allowed for pulley misalignment, slack belt tension, and excessive vibration. The voltage regulator, alternator, and associated wiring harnesses were removed for functional testing. The voltage regulator and the alternator as separate units passed functional tests. The power input connector on the regulator fit loosely and allowed an intermittent electrical connection. Failure of the connection would allow the alternator to cease operating. A month prior to the accident, in response to pilot reports of intermittent low system output, a mechanic removed the alternator for repair. The automotive shop that performed the work found the unit had an acceptable voltage output, but the amperage was low. A diode in the bridge rectifier was replaced and the mechanic reinstalled the alternator on the engine. The mechanic said the alternator had been on the airplane for several years and 'it never occurred to [him] to check the Type Certificate Data Sheet' to ensure the alternator was approved for airplanes.
HISTORY OF FLIGHT On June 20, 1999, at 2220 hours Pacific daylight time, a Cessna 172M, N61560, collided with concrete barriers and nosed over during a precautionary landing on a parking lot at MCAS Miramar, San Diego, California. The precautionary landing was precipitated by a loss of the electrical system. The airplane was operated by Plus One Flyers, Inc., and rented by the pilot for a personal flight under 14 CFR Part 91. The airplane was destroyed, and the instrument rated private pilot received serious injuries. Visual meteorological conditions prevailed for the local area night flight, and an Instrument Flight Rules (IFR) flight plan had been filed. The flight originated at Montgomery Field, San Diego, at 2105, and was scheduled to terminate there. The pilot reported that there were no discrepancies noted with the electrical system during the preflight inspection, or initial portions of the flight. The pilot's intention was to execute the VOR-A with a missed approach into the Oceanside airport, an ILS with a missed approach into McClellan-Palomar airport, and then return to Montgomery Field. The ATC controller cleared the pilot for the VOR-A approach into Oceanside and informed the pilot that he had lost the aircraft's transponder. The controller further indicated that the pilot was to switch to UNICOM for the approach, and when established on the published missed approach procedure to recontact him. The pilot acknowledged the instructions and subsequently observed the high voltage indicator light was illuminated. He informed the controller that his electrical system was failing. ATC then asked if he wanted to continue the approach into Oceanside, and he stated that he did not. In the pilot's written statement he said that he decided not to continue with the approach because he would have had to enter a cloud layer to complete the approach and his electrically powered instruments were failing. He then informed the controller that he would maintain VFR, en route back to Montgomery Field, and to conserve power, he was turning his radio off. The pilot indicated that ATC advised him of his position relative to the Oceanside VOR, and asked if he could see McClellan-Palomar airport. The pilot stated that he could not see the airport, and ATC advised him to remain clear of the Class B airspace. He again stated his intention to return to Montgomery Field, and ATC again advised him that he needed to remain clear of the Class B airspace. A few moments later, the controller lost radio contact with the flight. The controller then made several unsuccessful attempts to contact the pilot. A primary target was observed proceeding on a southbound heading in the vicinity of Miramar, and then the primary target was lost. The pilot reported that he flew in a southerly direction following major roads until he "determined that [he] had flown far enough to locate Montgomery Field, but was unable to locate [Montgomery.]" He made a 180-degree turn and flew north attempting to find the Miramar Marine Corps Air Station. He indicated he was unable to locate Miramar, and was unsure of his position. The pilot reported that instead of flying at a low altitude attempting to find an airport, he chose to land the airplane. He selected a large well-lit parking lot for the precautionary landing. During the landing rollout, the airplane struck a cement blockade and nosed over, coming to rest inverted. AIRCRAFT INFORMATION The Airframe and Powerplant mechanic who performed the last inspection on the airplane, stated that he had worked on this airplane for the last 5 years. He reported that the airplane was brought in for maintenance on May 30, 1999, due to the number 1 Nav-Comm fading out, and the airplane being hard to start. He stated that this was a sign that the charging system was not working properly. He tested the alternator on the airplane and found that the voltage output was okay, but the amperage was low. He then removed the alternator for a bench check. He noted that the alternator was for an automobile and it was located at the front of the engine, hanging from a "rather odd bracket arrangement." He further noted that the bracket was allowing for pulley misalignment, slack belt tension, and vibration. The mechanic took the alternator to an auto electric facility for a bench test. The bench test revealed that one of the diodes for the bridge rectifier current was burned out. This would result in only a partial charge being produced. The facility was asked to repair the alternator. The mechanic picked the alternator up the next day, and was informed that the brushes were worn out, and that one of the support bearings needed replacing. Another bench test was performed and it was found to function properly. The alternator was reinstalled on the airplane, a test run was conducted, and the airplane was returned to service. The mechanic further stated that this alternator had been on the airplane for a number of years and it never occurred to him "to check the Type Certificate Data Sheet" to ensure that it was approved for installation in this airplane. METEOROLOGICAL INFORMATION The weather observation for Oceanside at 2053 reported calm winds with 8 miles visibility, and an overcast ceiling of 1,200 feet. The weather observation for MCAS Miramar at 2256, reported winds from 260 degrees at 4 knots, 10 miles visibility, and clear skies. TEST AND RESEARCH An airframe inspection was conducted at Aircraft Recovery Services, Compton, California, on June 21, 1999, by Safety Board investigators. Technical assistance was provided by a representative from the Cessna Aircraft Company, who was a party to the investigation. Flight control continuity was established from the cockpit to the tail section; however, continuity from the cockpit to the wings was not established due to postimpact damage. No further discrepancies were noted with the airframe. Examination of the electrical system disclosed that the alternator was an automotive type. The only label on the unit was a company sticker for "Broadway Auto Electric," and, "15V40A D5 AF 10300 BA" was stamped into the aluminum housing. Review of various auto parts catalogues disclosed that this stamped number identified the unit as a Ford part number for a 15-volt, 40-amp alternator. The examination further revealed that the alternator mounting bracket was found to have elongated mounting holes. It was also noted by the FAA that there was nonapproved wiring behind the instrument panel. The main ground wire was found chafed in the access hole through the engine baffling. According to the Cessna Parts Manual, a 60-amp alternator is required for the airplane. Using technical data supplied by Cessna concerning the electrical loads of various components on the airplane, a normal electrical load during an IFR night operation was determined to be approximately 39 amps. The alternator was bench tested at Gardena Battery Supply located in Compton, and found capable of producing the required rated capacity of 40 amps. The voltage regulator, alternator, and associated wiring harness were sent to the Wichita FAA-ACO for testing and examination by personnel from the Cessna Single Engine Engineering department, under the auspices of the FAA. The voltage regulator was tested in July 1999, and found to operate properly. It was observed that one of the connectors that supplies the main input voltage to the regulator fit loosely and would produce an intermittent electrical contact with vibration. The voltage regulator and alternator were bench tested as a unit in August 1999, and both components functioned properly. During the testing, the connector wire that was found loose on the regulator was "jiggled" by the engineer conducting the test, which allowed the output from the alternator to be intermittent. The engineer stated that if the connection from the voltage regulator and alternator failed on its own, it would cause the alternator to cease from operating. He further stated that the regulator and alternator supported good operation of the electrical charging system; however the integrity of the associated wiring and connecting terminals that were inspected did not (report appended to file).
The mechanic's improper installation of nonapproved automotive electrical system parts, and his failure to ensure that all electrical connections were secure during the reinstallation, which resulted in the failure of the electrical system. The pilot's becoming lost and disoriented during the subsequent attempt to find an airport on the dark night flight was a factor.
Source: NTSB Aviation Accident Database
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