History of Flight
On October 15, 2015, at about 1300 eastern daylight time, an amateur-built Titan Tornado airplane, registration N4070F, was substantially damaged when it was involved in an accident near Mitchells, Virginia. The pilot was not injured. The airplane was operating as a Title 14 Code of Federal Regulations Part 91 personal flight.
According to the pilot, after performing a preflight inspection and receiving weather from the Warrenton-Fauquier Airport (HWY) automated weather observation system, he departed from runway 33 at about 1235. After departure, he turned the airplane to 240° and climbed to about 2,000 feet mean sea level (msl). He flew outbound for about 35 minutes before turning back to HWY. He climbed to 2,500 feet msl, and about 5 minutes after turning back, the engine suddenly lost power and ran rough, and he could not maintain level flight. The Coffeewood Correctional Center was at his 4 o'clock position, and he believed it presented the best available landing site, so he turned toward it. He maneuvered to line up with the entrance road to the prison.
An automobile was entering the prison on the road in front of the airplane, so the pilot glided over the car and then made a very quick descent to the road surface to avoid striking powerlines. After touchdown, he attempted to stay on the roadway, but the airplane could not follow a dogleg to the left. The airplane departed the pavement on the right side of the road, struck a shallow drainage ditch, struck the prison fence with its right wingtip, spun 180°, and came to rest with the left wing against the fence.
Aircraft and Engine Information
The airplane was equipped with an air-cooled, 4-cylinder, naturally aspirated, 85-horsepower Jabiru 2200A engine in a pusher configuration, driving a Prince Aircraft 2-bladed carbon fiber propeller. The most recent condition inspection was completed on June 28, 2015. At the time of the accident, the airplane had 388 total hours of operation, and the engine had 136.3 total hours.
Wreckage and Impact Information
Examination of the accident site revealed that the airplane traveled about 223 feet after leaving the roadway on a heading of about 108° before striking the perimeter fence and coming to rest. The airframe was substantially damaged: wingtips showed impact damage, the right main landing gear separated from its mounting, the stabilator was bent, and the nosewheel wheel pant had separated.
Postaccident examination of the engine revealed significant damage to the No. 3 cylinder. The cylinder head dome had multiple impact areas, and the exhaust valve head was missing. The piston had broken up, with pieces lying in the bottom of the cylinder. The No. 3 connecting rod was connected to the crankshaft but showed bending. Part of a piston ring was found in the muffler.
The exhaust valve had separated at the stem. The remaining stem appeared straight with no scoring on the outer diameter. Progressive crack arrest marks consistent with fatigue cracking were visible on the fracture surface and had progressed through most of the valve stem. Multiple thumbnail-shaped patterns with ratchet marks indicated multiple-initiation fatigue cracking. No defects or pre-existing damage were observed at the initiation site of the main fatigue cracking.
After rocker shaft removal, both valves moved freely in their guides. The intake valve stem was bent, with cracking visible on the outer diameter and material flaking off, revealing shiny silver metal. Similar cracking was observed in the exhaust valve head end near the fracture surface, but without the flaking. Metallurgical cross-sections revealed numerous cracks in the exhaust valve stem near the fracture surface, one extending through almost half the diameter; oxidation products inside indicated the cracks were present during engine operation at high temperatures.
A distinct layer was observed on the external surface of both valves. Hardness testing and spectroscopy confirmed the valves were made of 214N stainless steel with a nitrogen-rich layer. The damage to the No. 3 cylinder head, piston, and sparkplug was likely secondary to the exhaust valve separation.
Additional Information
The accident engine (S/N 22A2371) was manufactured in Australia on September 3, 2006, and purchased second-hand by the pilot to replace a previous Jabiru 2200 engine that had a valve failure at 269.7 hours. The pilot installed the accident engine on May 4, 2013; it had previously accrued about 9 hours on a Kolb airplane. The pilot had installed cooling ducts and EGT probes; he used the color of spark plugs to monitor performance. He installed a ROTEC ignition system on September 22, 2015 (5.2 hours before failure). He had used 93 octane Mogas (lead- and ethanol-free) and had used Decalin fuel additive for a period but discontinued it. Jabiru stated that fuel additives were not allowed.
The source references similar valve failures documented by the UK AAIB, NTSB (case ERA12TA542), and ATSB. Jabiru reported that valve failures were virtually always exhaust valves, often associated with overheating. Jabiru implemented several safety improvements, including redesigned valve trains and revised maintenance requirements, and reported a decrease in valve failures after 2018.