On July 28, 2022, at 1438 central daylight time, a Piper PA-32RT-300T, N3027J, was substantially damaged when it was involved in an accident near Dallas, Texas. The pilot sustained serious injuries. The airplane was operated under Title 14 Code of Federal Regulations (CFR) Part 91 as a personal flight. The pilot reported to air traffic control (ATC) that the airplane had a rough running engine and declared an emergency. ATC then provided flight radar vectors to Dallas Executive Airport (RBD), Dallas, Texas. The pilot advised ATC that he would be unable to reach RBD, and he was going to land in trees. The airplane landed about 0.5 miles southwest of RBD and was substantially damaged when it impacted trees and terrain. Postaccident examination of the airplane revealed that the engine was equipped with a dual magneto, in which the left and right magnetos were housed in a single casing. The magneto case had a yellow tag affixed to it with the following information: Continental Motors, Inc., type: D6LN-3000, part number: 10-682560-13 serial number: G199915GR. The magneto case also had a blue tag affixed to it with identifying information of a 14 CFR Part 145 repair station. Postaccident examination of the magneto revealed all four of the magneto case screws were loose before the case was opened. Grounding of the magneto halves and its capacitors occurred through the magneto case. Upon opening the case, the cam follower for the right side of the magneto assembly was melted, which would not provide clearance for the contact point. The left side of the magneto assembly did not exhibit melting or electrical arcing, and its contact point clearance was 0.008 in. According to the magneto manufacturer’s maintenance information, the contact point clearance is specified as 0.016 +/-0.002 in. The magneto capacitors that were installed at the time of the accident were tested and found to be within the magneto manufacturer’s specifications. The magneto case was reassembled in preparation for an initial bench test of the magneto. During the test, there was no ignition on the right side and very intermittent, almost nonexistent, ignition from the left side. The test leads were then swapped so that the left side was operating off the right capacitor and the right side was operating off the left capacitor; no ignition was produced. Examination of the magneto afterward revealed that the left-side cam follower began to melt. In preparation of a second bench test, the magneto’s left-side contact point clearance was then re-gapped to 0.018 and good test capacitors were used with test leads bypassing the installed capacitors. During the test, the ignition from the left side of the magneto functioned normally. In preparation for a third bench test, the test capacitors that were used for the second bench test were disconnected and the leads from the original capacitors from the time of the accident were reconnected. During the test, intermittent ignition was produced again. When a separate ground lead was connected directly to the left-side capacitor to bypass the magneto case, the ignition from the left side of the magneto functioned normally. The right-side capacitor was then tested in the same manner, and the ignition from the right side functioned normally. When the direct ground wire was removed, ignition was almost nonexistent, and arcing was observed melting the cam follower. The left capacitor was then removed from the magneto case and corrosion was noted on the inner and outer portions of the case, which provided a ground to the capacitor. Teledyne Continental Service Bulletin (SB) 651 provides capacitor information and installation for D-2000 and D-3000 series magnetos, which states the following warning: “High resistance or discontinuity between the capacitor and the remainder of the magneto will result in destruction of the contact assembly, loss of ignition, and loss of engine power.” The SB further states: “When a magneto is removed from an engine for replacement, its capacitors are sometimes left on the engine with the separated harness. If the reason for the original magneto's removal originated in the capacitor circuit, but the capacitors are not changed, the same symptoms can be expected to recur with the replacement magneto.” “If either the ground return path or the flag terminal lead path presents high resistance, arcing will occur at the points. Arcing causes the points to overheat, which also overheats the spring to which one of the points is attached. The nylon cam follower then melts where it bears against the hot spring.” The airplane tachometer indication at the time of the accident was 2,876.6 hours. A review of maintenance records showed that the last annual inspections of the airframe and engine were dated July 2, 2021, with a tachometer time of 2,876.3 hours. An invoice to the pilot from a maintenance facility, dated May 22, 2021, with a tachometer time of 2,876.2 hours, showed that the magneto was removed and replaced for a 500-hour inspection. There were no corresponding entries, as required by regulation, in the engine logbook for the magneto removal and installation. An Airworthiness Approval Tag, Federal Aviation Administration Form 8130-3, for the magneto’s 500-hour inspection by the repair station identified by the blue tag affixed to the magneto case, stated that the installer must comply with SB651.