Cirrus SR22 N333LZ accident near Mercer, Tennessee

Probable cause

A partial loss of engine power due to foreign object debris contamination of the left turbocharger wastegate. Contributing to the accident was the pilot’s failure to divert to the nearest airport.

NTSB analysis

While climbing to cruise altitude during a cross-country flight, the pilot advised the air traffic controller that the airplane was experiencing engine issues associated with manifold pressure and requested to divert to an airport where the airplane was maintained; however, this was not the nearest airport. The pilot further stated that he was not declaring an emergency. The controller cleared the airplane to the requested airport with a descent to 3,000 ft msl at the pilot’s discretion, and subsequently transferred communications to the controller at the diversion airport. The controller advised the pilot that he needed to maintain 2,500 ft msl, which was the minimum vectoring altitude (MVA). The airplane gradually descended below the MVA, and the controller advised the pilot that a closer airport was located on his right side (about 10 nm); however, the pilot continued to the diversion airport (about 27 nm). When the controller asked if the pilot was going to use the airframe parachute, the pilot indicated that he was attempting to land in a field. The airplane impacted trees and came to rest in a field about 10 miles from the diversion airport.

Data retrieved from the airplane’s Recoverable Data Module (RDM) revealed that the manifold air pressure (MAP) limit was exceeded about 10 minutes into the flight, reaching a peak recorded value of 53.9 inches. The maximum normal operating range for MAP for the airplane according to the pilot operating handbook (POH) was 36.5 inches. The MAP fluctuated from the time of the exceedance until the end of the data, about 19 minutes later.

Examination of the engine revealed that the left turbocharger waste gate contained a small metal fragment wedged between the housing and the valve, which was about 75% closed. Metallurgical examination of the fragment revealed it was consistent with stainless steel. Review of the airplane’s maintenance records revealed that the left turbocharger was replaced 3 months before the accident during the most recent annual inspection. It is likely that the maintenance performed on the airplane during the inspection resulted in foreign object deposited into the exhaust system and jammed the waste gate, resulting in an overboost of the turbocharger and partial loss of engine power.

Text from the NTSB. Open the NTSB docket for ERA21FA263 for the full record.