Amateur-built Lancair ES N44AZ accident near Prescott, Arizona

Probable cause

A partial loss of engine power due to an over-temperature event, which thermally damaged the blade tips of the turbocharger wheel and resulted in a slowing or stoppage in the rotation of the turbocharger.

NTSB analysis

The airline transport pilot was departing in the experimental, amateur-built airplane. During the initial climb, the engine experienced a partial loss of power. The pilot performed a precautionary landing on a taxiway, during which the airplane departed the paved surface and the nose landing gear collapsed.

Postaccident examination of the engine turbocharger revealed reddish-white discoloration of the turbine wheel, which suggested excessive engine exhaust gas temperature. Likewise, discoloration observed on the turbine end shaft journal was consistent with high temperature. The combination of high exhaust temperature and the rotational speed of the turbine wheel likely caused the blade material to creep and the wheel diameter to increase until the blade tips rubbed against the turbine housing. This eventually caused blade tip failures, which resulted in a rotating imbalance. It is likely that the combination of wheel rubbing and imbalance and caused the turbocharger to slow or stop, which in turn resulted in the loss of engine power. The reason for the excessive engine temperature could not be determined during the investigation based on the available information.

Text from the NTSB. Open the NTSB docket for WPR16LA088 for the full record.