Cirrus SR22 N800RW accident near Show Low, Arizona

Probable cause

The fatigue failure of an improperly installed nipple in the oil system of a supplemental type certificate-installed supercharger, which resulted in a complete loss of engine oil during cruise climb.

NTSB analysis

While the airplane was in a cruise climb from 12,000 to 14,000 ft mean sea level, the pilot/owner of the airplane heard a loud "pop," and, about 4 minutes later, he observed an oil pressure annunciation on the primary flight display. Within 1 minute, the pilot saw that the engine had completely lost oil pressure, so he shut down the engine and advised an air traffic controller of the situation. He then asked for and received vectors to the nearest airport, but, during the descent, he recognized that the airplane would be unable to reach the airport. Shortly thereafter, he advised the controller that he would deploy the airplane's ballistic parachute when the airplane was over suitable terrain. After the pilot deployed the parachute, the airplane impacted a field and came to rest upright.

Postaccident examination of the airplane revealed that a nipple in the flexible oil line used to provide engine oil to an aftermarket engine supercharger had failed due to fatigue, which resulted in a complete loss of engine oil. The fatigue crack had multiple initiation sites that were not the result of any manufacturing or material defects. Evidence indicates that a washer was present on the nipple threads between the nipple and the oil nozzle at one time. The washer initially prevented proper thread engagement and sealing of the joint between the nipple and the nozzle. To seal the joint, the nipple was then overtorqued, which resulted in the fatigue crack initiation. Engine vibration caused the flexible oil line to impose cyclic loads on the nipple, which, over time, failed due to fatigue.

Although the supercharger installation was approved under a Federal Aviation Administration supplemental type certificate (STC), the installation was not in accordance with the STC installation and maintenance instructions or standard maintenance practices. Although review of the supercharger STC installation and maintenance instructions revealed that they did not contain detailed information for installing the oil nozzle or nipple, the lack of this information did not appear to directly contribute to the improper installation of the supercharger on the accident airplane. It could not be determined when or by whom the improper installation was accomplished.

Text from the NTSB. Open the NTSB docket for WPR13LA043 for the full record.