WPR13LA043

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.

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.

HISTORY OF FLIGHT On November 16, 2012, about 0726 mountain standard time, a Cirrus Aircraft SR22, N800RW, was substantially damaged when the airplane descended to the ground under parachute near Show Low, Arizona, after the engine experienced a complete loss of oil pressure during cruise flight. The pilot/owner received minor injuries. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and the flight was operating on a Federal Aviation Administration (FAA) instrument flight rules (IFR) flight plan. According to the pilot, he departed Animas Airpark (00C), Durango, Colorado, about 0600, with an intended destination of Nogales International Airport (OLS), Nogales, Arizona. About 2 hours after takeoff, while in cruise flight at 12,000 feet above mean sea level, air traffic control (ATC) cleared the flight to 14,000 feet for terrain clearance purposes. Just before the airplane reached the new assigned altitude, the pilot heard a loud "pop." About 4 minutes later, he received an oil pressure annunciation on the primary flight display. At that time, the indicated oil pressure was about 47 pounds per square inch (psi), which was at the bottom of the normal range. Within 1 minute the pilot saw the oil pressure had decreased to 0 psi, so he shut down the engine, and advised ATC. He asked for vectors to the nearest airport, was advised that Show Low Regional Airport (SOW), Show Low, was the closest, and then turned towards SOW. During the descent, about the same time that ATC advised him that radar contact had been lost, the pilot recognized that he would be unable to reach SOW. He then advised ATC that he would deploy the ballistic parachute when he was over terrain that appeared suitable for a parachute landing. The pilot estimated that he deployed the parachute between 1,000 and 2,000 feet above ground level. The airplane impacted in a field while it was swinging towards the left under the parachute, bounced at least one time, and came to rest upright. The pilot shut down the airplane and exited. He contacted assistance via his satellite telephone. The pilot and airplane were located about 2 hours after the landing, aided by his re-inflation of the parachute and use of his personal mobile (not satellite) telephone. PERSONNEL INFORMATION The pilot held a private pilot certificate with airplane single- and multi-engine, and instrument airplane ratings. He had approximately 1,661 total hours of flight experience, including approximately 1,140 hours in the accident airplane make and model. His most recent flight review was completed in December 2011, and his most recent FAA third-class medical certificate was issued in January 2011. AIRCRAFT INFORMATION FAA records indicated that the airplane was manufactured in 2005, and was purchased new by the pilot. The airplane was equipped with the standard Cirrus Airframe Parachute System (CAPS) and a Continental Motors IO-550 series engine. In February 2009 a Forced Aeromotive Technologies (FAT) supercharger was installed in accordance with supplemental type certificate (STC) SA10925SC. The most recent annual inspection was completed in July 2012, and the airplane had accumulated about 60 hours in service since that inspection. At the time of the accident, the airplane and engine each had a total time (TT) in service of about 1,150 hours. METEOROLOGICAL INFORMATION The 0735 automated weather observation at SOW, located about 8 miles north of the landing site, included calm winds, visibility 10 miles, clear skies, temperature 1 degree C, dew point -5 degrees C, and an altimeter setting of 30.25 inches of mercury. WRECKAGE AND IMPACT INFORMATION The landing site was in remote territory. According to the pilot, after he exited the airplane, he photo-documented the scene. The right main landing gear was fracture-separated from the airplane, and the nose and left main landing gear remained attached but were displaced up and right. Propeller damage was minor, consistent with it not rotating during the impact sequence. The airplane was otherwise intact, except for the normal disruptions caused by the parachute deployment. Shortly after the pilot documented the scene, the wind inflated the parachute, and dragged the airplane about 100 feet across the terrain. The pilot left the scene to obtain assistance, and on his return with first responders, discovered that the airplane had then been dragged further by the parachute, and had been inverted, before the parachute deflated and ceased dragging the airplane. The responding law enforcement agency personnel cut the parachute bridle straps to prevent further movement of the airplane. FAA personnel responded to the scene, but NTSB personnel did not. The responding FAA inspectors reported that the exterior surfaces of the left side and aft lower fuselage exhibited significant oil streaking. While the airplane was still inverted, the inspectors decowled the engine, and observed a significant amount of engine oil had been deposited inside the cowling and engine compartment. They observed that the oil line that supplied engine oil to the supercharger bearing for lubrication had fracture-separated from the supercharger at the nipple fitting. FAA personnel removed several avionics units for possible data download by the NTSB recorders laboratory. The airplane was recovered and transported to a secure location for detailed examination. The downloaded data corroborated the information provided by the pilot. ADDITIONAL INFORMATION Supercharger Design and Installation Information The supercharger was mounted to the aft section of the engine, and was driven via a belt by a pulley mounted to an engine accessory drive. The supercharger bearings were lubricated by pressurized engine oil, which was sprayed into the supercharger via a nozzle. The nozzle connected to the engine oil system via a series of fittings and a flexible hose. The nozzle was provided as part of the STC, and threaded directly into the supercharger body. A standard AN816-6-2D aluminum nipple fitting installed into the nozzle, and an MS27226 fitting with a B-nut was used to attach the flexible oil line to the nipple. According to the STC holder, in order to attain a leak-proof joint from the oil line to the supercharger without damaging the supercharger, nozzle, or AN816 nipple, two wrenches had to be used concurrently to properly attach and secure the oil line to the supercharger. This requirement was explicitly specified in the supercharger installation instructions. However, those instructions did not specify the installation torque values for any of those components. The STC instructions for continued airworthiness (ICA) required that the oil nozzle be removed and cleaned in conjunction with every annual inspection. However, the ICA did not contain any information regarding the need to use two wrenches, and did not specify the installation torque values for the nozzle, AN816 nipple, or oil line B-nut fitting. Review of the STC installation and ICA documentation that was current at the time of the accident revealed that neither document set contained any guidance regarding the use of sealant for the nozzle, nipple, or oil line B-nut. Supercharger Maintenance Information The supercharger was installed when the airplane had a TT of 674 hours. According to the maintenance records, a new supercharger "drive seal" was installed, and the oil nozzle was "cleaned, resealed, and torqued" by Arapahoe Aero on 7/11/12. That activity was accomplished in conjunction with the airplane's most recent annual inspection. At that time, the airplane had a TT of about 1,090 hours. The most recent recorded maintenance regarding or affecting the supercharger was conducted by an aircraft mechanic on 10/03/2012. That mechanic was not associated with Arapahoe Aero. The maintenance reco