Primary finding
Probable cause
Maintenance personnel’s improper installation of the muffler attachment hardware, which resulted in the muffler separating in flight, thermal damage that interrupted the magnetos’ function, and the subsequent total loss of engine power.
Investigator assessment
Analysis narrative
The private pilot and flight instructor were conducting a cross-country instructional flight. During departure and while climbing through 2,800 ft mean sea level, the pilot and instructor noticed multiple avionics malfunctions and initiated a turn back toward the airport. While the airplane was turning, the engine lost all power, and the pilots noted indications of a fire. Because they were unable to find a suitable area for a forced landing, the pilot activated the airplane's parachute system. The airplane descended under the parachute into a parking lot, and the main wing spar sustained substantial damage. Examination of the engine revealed that the engine exhaust muffler attachment hardware was not secured correctly, which allowed the exhaust collector to freely rotate. A hole near the lower right engine cowling was consistent with escaping hot exhaust gas. Several components in the right forward side of the firewall were thermally damaged, and both magneto p-leads were shorted against the engine's metal mount frame. The thermal damage interrupted both magnetos' function, which resulted in the loss of engine power. During a pre-buy inspection of the airplane, the No. 1 cylinder base O-ring was replaced. The work order, dated 3 days before the accident, required removal of the muffler. During the muffler reinstallation, maintenance personnel likely did not correctly install the attachment hardware, which resulted in the muffler separating in flight, thermal damage that interrupted the magnetos' function, and the subsequent loss of engine power.
Source record
Factual narrative
On September 30, 2018, about 1121 central daylight time, a Cirrus SR22 airplane, N818GM, impacted terrain following a total loss of engine power near Addison Airport (ADS), Dallas, Texas. The pilot and flight instructor were not injured, and the airplane was substantially damaged. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91 as an instructional flight. Day visual meteorological conditions prevailed for the flight, which departed ADS about 1115, with a destination of Waco Regional Airport (ACT), Waco, Texas. While on departure climbing through 2,800 ft mean sea level, the pilot and flight instructor noticed multiple avionics malfunctions and turned back toward ADS. During this turn, the engine lost total power and indications of a fire were noticed. When the flight instructor and pilot recognized the airplane was not within gliding distance of ADS or a suitable forced landing area, the pilot initiated the Cirrus Airframe Parachute System (CAPS). The airplane descended under parachute into a parking lot and the main spar was damaged. Accident site examination revealed a hole near the lower right engine cowling from a burn through. Examination at the recovery facility revealed two of the three sets of hardware were missing from the muffler attach point. The remaining bolt, washers, spring and castellated nut remained attached, but no cotter pin was installed. Without the muffler attachment hardware, the exhaust collector was free to rotate. The hole in the lower right engine cowling was consistent with escaping hot exhaust gas. Various components in the right forward side of the firewall were thermally damaged. Numerous white areas consistent with electrical arcing were present, including both magneto p-leads shorted against the metal engine mount frame. Although both magneto p-leads were shorted, the two magnetos were not damaged. After the magneto p-leads were disconnected, the magnetos produced sparks at all ignition leads when the engine was manually rotated. During a pre-buy inspection of the airplane, a report prepared by the maintenance provider listed issues discovered and corrective actions performed. Two of the entries were "#1-cylinder base o-ring is seeping" and "replaced #1-cylinder base o-ring P/N 641066 IAW TCM IO-550-N MN CH17-3". The work order to replace the cylinder o-ring, dated three days prior to the accident, required removal and reinstallation of the muffler.