Accident Narrative
On April 15, 2009, at approximately 1000 mountain standard time, a Cessna 152, registration N6285M, operated by Air Safety Flight Academy under 14 Code of Federal Regulations Part 91, sustained substantial damage after impacting a fence during a forced landing near Glendale Municipal Airport in Glendale, Arizona. The flight instructor and his student pilot received minor injuries. The local instructional flight had departed from Glendale Municipal Airport around 0830 under visual meteorological conditions. No flight plan was filed.
According to the flight instructor, he and the student had completed a series of flight maneuvers. While returning to the airport, the engine began running rough. The instructor applied carburetor heat and slightly leaned the mixture, which temporarily resolved the roughness. As the airplane neared the airport, the engine roughness returned and progressively worsened. The instructor applied carburetor heat and requested priority to land. Shortly thereafter, the engine sputtered briefly and stopped. Unable to restart the engine, the instructor initiated a forced landing onto a grassy field. During the landing roll, the airplane struck a chain link fence, resulting in a bent and wrinkled right wing and a bent aft nose wheel.
Post-Accident Examination
An examination of the airplane was conducted under the supervision of a Federal Aviation Administration (FAA) inspector. The propeller was replaced to facilitate an engine run, but despite several attempts, the engine would not operate. The magnetos were removed for inspection. Both magneto impulse couplings were snapped multiple times, and neither magneto produced spark.
Both magnetos were placed on a test stand and run at various speeds but failed to produce spark. Disassembly of the left magneto revealed that the condenser was within manufacturer limits and the points were set correctly. However, inspection and testing of the coil indicated a complete failure of the secondary coil. The coil also exhibited thermal discoloration near the rotating magnet.
The right magneto was disassembled and inspected. It also displayed thermal discoloration, but to a lesser degree. Testing of the primary and secondary coils showed no anomalies. Internal timing revealed that the "EGap" was set incorrectly. The points were off center and not opening completely. Further inspection indicated that the lead connector from the magneto's coil to the points was loose. After retiming the magneto to manufacturer specifications and reinstalling the lead on the points, the magneto operated normally on the test stand.
Maintenance History
A review of the engine maintenance logbook showed that on April 13, 2009, at a tachometer time of 3,107.5 hours, a 100-hour inspection was performed. The company maintenance work order for that inspection indicated that a 12-month magneto inspection was completed and that "serviceable" magnetos with new contact points, capacitors, and gaskets were reinstalled. The tachometer reading at the time of the accident was 3,110.5 hours.