Beech 35 N7956M accident near Caldwell, Idaho

Probable cause

The total loss of engine power due to the separation of the wastegate exhaust elbow.

NTSB analysis

Shortly after takeoff, about 400 ft above ground level (agl), the engine began to run rough followed by a noticeable power loss. Smoke began to fill the cockpit, which appeared to be coming from the lower left firewall area. The engine continued to lose power and the pilot switched the fuel source to the right main fuel tank; however, there was no change, the engine lost total power, and the propeller stopped turning. The pilot made the decision to return to the runway; as the airplane neared the ground, it stalled, bounced, and then impacted the runway and the VASI/PAPI light structure.

A postaccident examination of the airplane revealed the wastegate exhaust elbow separated from the wastegate and the tail pipe causing exhaust gas to melt the magneto P-leads, which resulted in a loss of engine power. The exhaust system was further examined, and the “V-band” clamp torque was verified to be at least 40-inch pounds (the appropriate amount); however, the tail pipe was not secure to the turbocharger despite the “V-band” clamp being torqued to the proper value. Visual inspection of the exhaust system components did not reveal any other anomalies, and the reason for the exhaust elbow separation could not be determined.

Text from the NTSB. Open the NTSB docket for WPR20LA033 for the full record.