TACHIKI 750 CRUZER N145WT accident near Spanish Fork, Utah

Probable cause

A partial loss of engine power due to an obstructed catalytic converter, which most likely resulted from the pilot’s failure to properly repair or replace it after it was likely damaged during a previous incident. Contributing to the accident was the pilot’s failure to maintain adequate airspeed during the forced landing, which led to an exceedance of the airplane’s critical angle-of-attack and an aerodynamic stall.

NTSB analysis

The pilot departed on the local accident flight after having repaired his airplane following a landing incident that occurred 18 months earlier. Shortly after departure, he observed a partial loss of engine power and was unable to maintain altitude. He immediately returned to the airport, but, while maneuvering toward the runway, he made a tight left turn, which likely resulted in an exceedance of the airplane’s critical angle of attack and an accelerated stall. The airplane entered a nose-down dive and impacted a rooftop.

Postaccident examination of the airframe did not reveal any preimpact mechanical anomalies that could have precluded the pilot from controlling the airplane. Examination of the engine revealed that most of the internal components were likely operational at the time of impact. However, the catalytic converter contained several broken pieces of ceramic substrate that had separated during the previous accident. As there were no other preimpact mechanical anomalies with the engine, it is likely that broken substrate blocked the engine exhaust gas path following combustion, which resulted in a partial loss of engine power during the accident flight.

The pilot straightened the bent exhaust tailpipe after the landing incident and re-welded the catalytic converter. However, he did not inspect, repair, or replace the catalytic converter before the accident flight even after debris was emitted from the tailpipe on subsequent engine starts.

Text from the NTSB. Open the NTSB docket for WPR22LA080 for the full record.