Amateur-built T-51 MUSTANG KIT N548RR accident near St Francis, Kansas

Probable cause

Foreign debris in the propeller governor, which led to excessive wear in the governor and its subsequent in-flight failure.

NTSB analysis

The pilot had been flying the amateur-built airplane for about 15 minutes at a cruise altitude of between 4,000 and 5,000 ft when he attempted to slow the engine rpm by pulling the propeller control back; however, this had no effect on the engine rpm. The pilot attempted to slow the rpm several times, but the propeller then cycled to "full bite" and remained that way until he performed a wheels-up landing on a rough road.

The airplane had accumulated 50 hours of total flight time at the time of the accident. During a postaccident test run, the engine ran normally. Oil was drained from the propeller gearbox, and it presented a used appearance. The propeller governor was subsequently bench tested and did not meet the manufacturer's test specifications. A disassembly of the governor revealed the presence of foreign debris and wear marks on several parts of the governor. After the governor was cleaned and reassembled, it was bench tested again, and it operated normally. The pilot reported that, after the accident, the airplane was repaired, the engine and a new governor were installed, and the airplane operated without any anomalies. The foreign debris likely caused excessive wear inside the propeller governor, which subsequently led to its in-flight failure.

Text from the NTSB. Open the NTSB docket for CEN13LA346 for the full record.