WPR09FA398

The pilot's failure to maintain adequate airspeed while maneuvering in the traffic pattern, which resulted in an aerodynamic stall/spin. Also causal was the failure of the left magneto due to improper assembly of the drive gear during installation on the engine, and the improper internal timing of the right magneto due to inadequate maintenance that reduced the ability of the magneto to produce an adequate spark, resulting in a partial loss of engine power.

The accident flight was to be a local area personal flight. After fueling the airplane, the pilot and passenger departed. A ground witness who is a pilot and former Federal Aviation Administration controller was in an automobile located near the destination airport and observed the airplane make a high and fast approach to runway 21. Unable to land, the pilot executed a go-around. The airplane returned for a second approach to runway 21, which was again flown high and fast and terminated in another go-around. The witness described the airplane's climb and left crosswind turn at the departure end of the runway with a pitch attitude of 45 degrees nose up and the airplane's left bank angle about 60 degrees. The witness stated that he lost sight of the airplane and came upon the crash site next to the road on which he was traveling. The airplane was oriented in a northerly direction. The witness reported that the wind, which he estimated at 5 knots, was also coming from a northerly direction. The accident airplane was found on near level soil about 1/4-mile southeast of the departure end of runway 21. The airplane was in a nose-down attitude, with the engine buried in the sandy soil to an estimated 1-foot depth at about a 45 degree angle. Crush deformation and ground scars were consistent with a stall/spin loss of control. The pilot's route of flight between the departure airport and the destination could not be determined; however, a more or less direct flight would be about 30 minutes. Except for the magnetos, examination of the wreckage disclosed no evidence of a preimpact mechanical malfunction or failure in the airframe or core engine components. Both magnetos had been displaced from their respective mounting pads. When the left magneto was removed, investigators noted that the castellated nut, washer, and cotter pin that secure the magneto drive gear and impulse coupler were missing. The respective threads on the shaft were undamaged, indicating that the nut was not mechanically forced off of the shaft but that it backed off during operation. The nut and associated washer were found in the oil sump, but the cotter pin was not located. The magneto drive gear that attaches to the subject magneto shaft, which is an engine part and must be installed onto the magneto when it is installed on the engine, exhibited no visible witness marks on the inside bore. Witness marks would have been present if the cotter pin had been in place and worked its way out of the castellated nut and shaft during operation of the engine. The rear of the engine case within the accessory section, which corresponds to the location of the magneto drive gear, exhibited a rotational burnishing signature consistent with having prolonged contact with the subject gear while the engine was operating. In addition to these observations, metal particles were found in the oil filter, all of which indicate that the airplane was operated with the improperly assembled drive gear for a sustained period of time. The left magneto sustained impact damage that precluded functional testing. The right magneto “E-gap” was found to be excessively out of the manufacturer’s specifications during the examination; however, the magneto produced a weak spark during hand rotation of the drive. The internal magneto timing was 34 degrees ± 1.5 degrees. According to the magneto manufacturer, ± 5 degrees is the normal allowable range for internal timing. With the timing noted during the examination, the right magneto would produce a spark, but it would be very weak and negatively affect the power production of the engine. The maintenance history documents multiple instances of magneto maintenance, removal and replacement, and timing adjustments--particularly to the left magneto--during the 2-year period between the engine’s overhaul and installation in August 2007 and the accident. In general, the historical review found that the magneto timing had to be adjusted at roughly 50-hour intervals, which is indicative of the operator’s maintenance personnel chasing the internal magneto timing issues by timing the magneto to the engine instead of resolving the internal malfunction. An August 8, 2009, entry in the flight department rental log sheet for the accident airplane lists a pilot report of an rpm drop of 225 when the left magneto was tested during the runup procedure before a flight. According to the Cessna Pilot's Operating Handbook for this airplane, the maximum allowed rpm drop on either magneto is 125. Review of the aircraft and maintenance department records found no corresponding maintenance record in response to the pilot-reported discrepancy. It is likely that the internal timing issues found with both magnetos resulted in weak ignition spark outputs that would negatively affect the power production of the engine but not necessarily produce a condition, such as prolonged roughness, that would alert the pilot to a potentially serious problem. Since the pilot flew about 30 minutes to the vicinity of the airport, the castellated nut securing the drive gear to the magneto shaft in the left magneto probably loosened sufficiently to free the gear from engagement on the shaft. Once the gear was liberated, the left magneto would not have functioned, leaving the weak right magneto as the only source of ignition spark, which would have presented itself as a serious partial loss of power. During the pilot’s ensuing attempts to land at the airport, he inadvertently stalled the airplane while maneuvering in the pattern.

History of Flight On August 16, 2009, about 1121 Pacific daylight time, a Cessna 152, N67361, descended into terrain about 1/4-mile southeast of the Hesperia Airport, Hesperia, California. The airplane was registered to and operated by M.Y. AIR, a flight school based in Redlands, California. Visual meteorological conditions prevailed at the time of the personal flight, and no flight plan had been filed. The airplane was substantially damaged, and the private pilot and passenger were killed. The flight was performed under the provisions of 14 Code of Federal Regulations Part 91, and it originated from Redlands about 1040. M.Y. AIR's manager reported to the National Transportation Safety Board investigator that he holds a certified flight instructor (CFI) certificate. The manager stated that on August 13, 2009, he provided recurrent flight training to the accident pilot. The dual instructional flight lesson was performed in N67361, and it lasted about 1.1 hours. The purpose of the lesson was to provide the pilot recurrent training. The flight school's records indicate that, thereafter, the accident pilot flew N67361 for 1.3 and 1.0 hours on August 14 and 15, respectively. On August 16, the pilot reported that he intended to rent the airplane again for another local area flight. The flight school's scheduling records indicate the pilot blocked out the airplane between 0900 and 1200. After the pilot acquired fuel, he and his passenger departed in the airplane. The Federal Aviation Administration (FAA) coordinator reported that no evidence of a flight plan was found for the accident flight. No report of any distress call was received by FAA air traffic facilities. The pilot's route of flight between Redlands and Hesperia has not been determined. A ground-based witness in an automobile, located near the Hesperia Airport, reported to the Safety Board investigator that he observed an airplane, which matched the make and model of the accident airplane. According to the witness, the airplane made a high and fast approach to runway 21. Unable to land, the airplane's pilot made a go around. The airplane returned for a second approach to runway 21, which was again flown high and fast. Thereafter, the pilot initiated another go-around. The witness described the airplane's climb and left low altitude crosswind leg turn into the traffic pattern as being unusual, in that the airplane's pitch attitude was upward about 45 degrees, and the airplane's left bank angle was about 60 degrees. Also, the airplane turned left for the left-hand traffic pattern very soon after overflying the departure end of runway 21. The witness stated that he lost sight of the airplane seconds later when he drove into an area where his view became obstructed by ground obstacles. A few minutes later the witness observed the crashed airplane next to the road on which he was driving. The airplane was oriented in a northerly direction. The witness reported that the wind, estimated at 5 knots, was also coming from a northerly direction. (The witness was a former FAA controller and pilot.) Personnel Information According to FAA airman and medical record files, the 41 year old pilot held a private pilot certificate with an airplane single engine land rating, which was issued November 13, 1992. The most recent Third class medical certificate was issued on August 8, 2007, without limitations. The pilot is a Japanese national and in response to a request from the investigation the Japan Transport Safety Board reported that the pilot did not hold a Japan airman certificate. An examination of the pilot's personal flight record logbook indicates he began taking flying lessons in September, 1992. He was issued a private pilot certificate in November, 1992, at a total time of about 59 hours. With the exception of one duel lesson in a Piper PA-28, all of the pilot's recorded flying was accomplished in Cessna 150, 152, and 172 models of airplanes, and in the southern California geographic area. Regarding the pilot's more recent flying activity, on August 13, 2007, he received a 1.1-hour-long combined flight review and Cessna 172 checkout. The CFI providing the instruction was affiliated with M.Y. AIR. Thereafter, the pilot flew 8 additional times during the remainder of the month for a total of 3.3 hours. The pilot's next flight occurred on August 11, 2008. On this date he again flew with the same CFI in the accident airplane. The flight review lasted 1.2 hours. Thereafter, the pilot flew the airplane 6 times for a total of 4.7 hours. The pilot's next flight occurred on August 13, 2009. On this date he again flew with the same CFI in the accident airplane. The flight review lasted 1.1 hours. Thereafter, the pilot flew the airplane on August 14 and 15 for a total of 2.3 hours. The accident occurred the following day after flying for 0.7 hours. By August 16, 2009, the pilot's total time was about 193.3 hours, of which 51.0 hours were acquired receiving duel flight instruction. Aircraft Information The following information was obtained through a review of the aircraft maintenance records, interviews with the operator’s maintenance personnel, and the operator's flight department records. The aircraft was a Cessna 152, serial number 15281779, which was manufactured in 1978. As of the accident, the airframe had accrued a total time in service of 8344.6 hours. The most recent annual inspection was endorsed as completed on December 9, 2008, 297 hours prior to the accident. The most recent 100-hour inspection was completed on June 21, 2009, 93 hours prior to the accident. The engine installed in the airframe was a Lycoming O-235-L2C, serial number L-15117-15. The engine was overhauled on August 9, 2007, and installed in the airframe on August 14, 2007. At overhaul, the engine total time in service was 8,507.6 hours. At the accident, the engine total time in service was 9,446.8 hours, with 939.2 hours of operation accrued since major overhaul. A document titled "Aircraft Maintenance History" can be found in the public docket for this accident and it summarizes the significant maintenance actions on the engine over a two year period from its August 2007 overhaul and installation in the airframe until the accident on August 16, 2009. In pertinent part, this history documents multiple instances of magneto maintenance, change outs, and timing adjustments, particularly to the left magneto. In general, the review found that the magneto timing had to be adjusted at roughly 50-hour intervals. An August 8, 2009, entry in the flight department rental log sheet for this aircraft lists a pilot squawk of a rpm drop of 225 when the left magneto was tested during the run-up procedure before a flight. According to the Cessna POH for this airplane, the maximum allowed rpm drop on either magneto is 125. Review of the aircraft and maintenance department records found no corresponding maintenance record in response to this pilot discrepancy. On August 20, the individual in charge of the operator's maintenance shop was interviewed concerning the magneto drop pilot write-up. He stated that he cannot explain why there is no entry in the aircraft logs for the work that was accomplished. He stated that in response to this reported magneto drop, the spark plugs were removed, gapped, and tested. According to the interviewee's statement, most of the top and all of the bottom plugs were lead fouled. He stated that he is not certain, but the plugs may also have been replaced. The engine timing also checked and confirmed at 20 degrees BTDC on both magnetos. Airport Information The Hesperia airport is a non-towered public airport at an elevation of 3,390 feet msl. It has one asphalt runway, 03 - 21, that is 3,910 feet long and 50 feet wide. Meteorological Information The closest official weather observation station is the Victorville, California, airp