History of Flight
On November 16, 2012, at about 0726 mountain standard time, a Cirrus Aircraft SR22, registration N800RW, was substantially damaged following a parachute-assisted descent near Show Low, Arizona. The pilot, who was also the owner, received minor injuries. The personal flight originated from Animas Airpark, Durango, Colorado, around 0600, with an intended destination of Nogales International Airport, Arizona. The flight was conducted under instrument flight rules.
According to the pilot, while cruising at 12,000 feet mean sea level, air traffic control cleared the flight to 14,000 feet for terrain clearance. Shortly before reaching the new altitude, the pilot heard a loud "pop." About four minutes later, an oil pressure annunciation appeared, indicating 47 psi at the bottom of the normal range. Within another minute, oil pressure dropped to zero. The pilot shut down the engine and advised ATC, requesting vectors to the nearest airport. ATC directed him toward Show Low Regional Airport. During descent, the pilot realized he could not reach the airport and decided to deploy the ballistic parachute when over suitable terrain, estimating deployment between 1,000 and 2,000 feet above ground level. The airplane impacted a field while swinging left under the parachute, bounced at least once, and came to rest upright. The pilot shut down the airplane, exited, and contacted assistance via satellite telephone. He and the airplane were located about two hours later after he re-inflated the parachute and used his personal mobile phone.
Aircraft Information
The airplane, manufactured in 2005, was equipped with a Continental Motors IO-550 series engine and the Cirrus Airframe Parachute System. In February 2009, a Forced Aeromotive Technologies supercharger was installed per supplemental type certificate SA10925SC. The most recent annual inspection was completed in July 2012, after which the airplane had accumulated about 60 hours. At the time of the accident, total time on the airframe and engine was about 1,150 hours.
Meteorological Information
Weather recorded at Show Low Regional Airport at 0735 included calm winds, visibility 10 miles, clear skies, temperature 1°C, dew point -5°C, and an altimeter setting of 30.25 inHg.
Wreckage and Impact
The landing site was in remote terrain. The right main landing gear had fracture-separated; the nose and left main gear remained attached but displaced. Propeller damage was minor, consistent with a non-rotating impact. The airplane was otherwise intact except for parachute deployment disruptions. After the pilot documented the scene, wind inflated the parachute, dragging the airplane about 100 feet. The pilot left for assistance; on return with first responders, the airplane had been dragged further and inverted. Law enforcement cut the parachute bridle straps.
FAA inspectors noted significant oil streaking on the left side and aft lower fuselage. Examination of the inverted engine revealed substantial oil inside the cowling. The oil line supplying the supercharger bearing had fracture-separated from the supercharger at the nipple fitting. Avionics data download corroborated the pilot's account.
Additional Information: Supercharger Design and Maintenance
The supercharger, mounted to the aft engine section, was belt-driven and lubricated by pressurized engine oil sprayed via a nozzle. The nozzle connected to the oil system through fittings and a flexible hose. A standard AN816-6-2D aluminum nipple fitting was installed into the nozzle. The STC installation instructions required using two wrenches to achieve a leak-proof joint, but did not specify torque values. The instructions for continued airworthiness required nozzle removal and cleaning at each annual inspection, but did not mention the two-wrench requirement or torque values. No guidance existed on sealant use.
Maintenance records showed a new supercharger drive seal and nozzle cleaning on July 11, 2012, during the annual inspection. On October 3, 2012, a mechanic removed and reinstalled the supercharger after factory repair. The mechanic stated he used two wrenches to tighten the oil line fitting and did not apply sealant. Examination of the fractured nipple showed fatigue cracking that originated at multiple thread root valleys, with no material or mechanical defects. The crack progressed through about 95% of the cross section before ductile overstress separation. CT scans revealed 3–4 threads engagement. Remnants of yellow thread sealant were observed at the fracture interface. Red RTV silicone was found on the nipple segment attached to the oil line, with a pattern suggesting a washer had been present, although no washer was found in the wreckage. The STC documentation did not call for a washer or external sealant.