On January 28, 2023, about 1310 eastern standard time, a Mooney M20C, N5587Q, was destroyed when it was involved in an accident in Calhoun, Georgia. The pilot was seriously injured, and the flight instructor-rated passenger received minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The flight departed from Tom B David Field Airport (CZL), Calhoun, Georgia for a local flight with the pilot acting as the pilot-in-command. According to the pilot, before takeoff he performed a preflight check and runup; the oil pressure, oil temperature, and suction were normal. When checking the magnetos, the right magneto dropped 150 rpm. They leaned the fuel mixture and ran the engine up to about 1,700 rpm for about 1 minute. They did this a couple of times until both magnetos dropped 125 rpm. They conducted a couple more magneto checks, and each resulted in both magnetos dropping 125 rpm with normal engine operation. After the preflight runup was completed, they proceeded to runway 17. Full throttle was applied, the oil temperature and pressure were in the green, and the engine sounded normal. Just after liftoff, the pilot retracted the landing gear and a few moments later, while they were about 70 ft above the runway, there was a popping noise, the engine lost power, the engine rpm went to nearly zero, and they began to lose altitude. They had not cleared the south end of the runway, so they lowered the landing gear and the pilot pitched down and started descending. The airplane touched down at the very end of the runway and the pilot applied the wheel brakes. There was not enough runway remaining for them to stop, and the airplane skidded off the end of the runway into the grass and slid into an earth embankment. The airplane then went airborne briefly, rotated 90º to the left and then came to rest after a few hundred feet. At this point, the flight instructor unbuckled his lap belt and saw flames near the pilot’s feet. The flight instructor then advised the pilot of the fire, they both egressed, and moved away from the airplane in a westerly direction in case there was an explosion. According to a witness who was moving airplanes in a hangar about 4,000 ft from runway 17, he heard “sputtering” around the time that the airplane passed him, but it did not sound like a complete engine failure. The landing gear was retracted and then extended when the engine roughness and loss of power occurred. He then ran to the end of the row of hangars and observed the airplane hit the displaced threshold. He heard the tires chirp at impact. The airplane then bounced back into the air, touched down again, then skidded through the grass and hit an embankment about 100 ft off the end of the runway. The airplane momentarily became airborne once again, then cartwheeled into the ground and came to rest. Both pilots were out of the airplane when he arrived at the airplane, which was becoming engulfed in flames. Examination of the displaced threshold revealed the presence of four propeller strike marks, the spacing of which indicated that the propeller was rotating on impact. Examination of the wreckage revealed that the cabin had been destroyed by the fire. Flight control continuity was established from the flight control surfaces to the cabin. The fuel selector valve was in the right-wing fuel tank position, and when an air source was applied to the port on the fuel selector for the right tank, no blockages were discovered. Examination of the 4-cylinder, horizontally opposed, air-cooled, carbureted engine revealed that the No. 3 bottom spark plug was not in the spark plug hole and was hanging from the ignition cable. The No. 3 bottom spark plug hole thread insert (Helicoil) was partially pulled from the spark plug hole, with the lower three threads displaying an absence of rust. The threads above the lower three threads were rusty, and the bottom portion of the Helicoil was still intact. No other anomalies were discovered that would have resulted in a preimpact failure or malfunction that would have precluded normal operation. Review of maintenance records revealed that the most recent engine overhaul was completed on March 9, 1993, about 30 years before the accident. The most recent annual inspection was completed on December 1, 2022. Review of the logbook entry for the annual inspection indicated that the engine had accumulated 838.24 hours of time in service. The entry indicated that during the annual, the spark plugs had been “removed, cleaned, inspected and installed.” As of the last entry in the engine logbook, dated January 14, 2023, the engine had accumulated 839.24 hours since that overhaul. This last entry stated that the No. 2 cylinder spark plug was replaced. The pilot stated this maintenance was a result of the engine running rough during a magneto check. The investigation was not able to determine if the No. 3 spark plug was removed and reinstalled at that time.