Accident Overview
On October 15, 2017, at approximately 1000 mountain daylight time, an experimental amateur-built Barber Turbine Cubs PA-18, registration N181TJ, nosed over during a precautionary landing near Skull Valley, Utah. The private pilot and passenger were not injured. The airplane sustained substantial damage to both wings and the empennage. The flight was conducted under 14 CFR Part 91 as a personal flight. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated from West Jordan, Utah, about 0915.
Pilot Report
The pilot reported completing a thorough pre-flight inspection, including sumping the fuel tanks for water, which revealed no contamination. The cabin heat was on for the entire flight due to an outside air temperature of 41°F. During the flight, the pilot performed a low-altitude pass at about 250 to 300 feet above ground level. When applying power to initiate a climb, the engine stumbled slightly and hesitated. The pilot applied carburetor heat due to concerns about carburetor ice and then increased power to full, but the engine hesitated again. The pilot elected to execute a precautionary landing on an open salt flat area.
The pilot conducted a tail-low wheel landing. Upon touchdown, the airplane nosed over and came to rest inverted. After exiting, the pilot noted that both main wheel brakes were engaged. Neither the pilot nor the passenger had applied pressure to the heel brake pedals during the landing sequence. A photo provided by the pilot's mechanic showed tire tracks about 20 to 25 feet in length, consistent with both main landing gear tires.
Wreckage Examination
The airplane was equipped with two brake master cylinders connected to a central reservoir located beneath the front seat. Examination of the recovered wreckage revealed that the left and right brake master cylinders remained secured to their mounts. When actuated by hand, the right brake pedal needed minimal input to engage the brake, while the left brake pedal required significant movement. Both main landing gear wheels rotated freely without restriction. The hydraulic reservoir cap was removed, and residual hydraulic fluid was observed in the reservoir cavity. The vented cap was free of debris. Evidence indicated that hydraulic fluid drained from the reservoir through the vent while the airplane was inverted.
The engine and all accessories remained secure to their mounts. Fuel lines were intact with no leaks or kinks. Throttle, mixture, and carburetor heat control continuity was established. The wooden propeller was attached to the crankshaft, but one blade had separated at the hub. Rotational continuity was established throughout the engine and valve train.
The carburetor was equipped with a temperature probe. One of two wires was separated from the crimped side of an electrical connector, with missing shielding and no wire visible in the connector. The carburetor was removed and examined; the throttle and mixture levers moved freely, and the accelerator pump functioned normally. Disassembly showed the internal floats were intact and moved freely, and the needle valve and seat were intact.
Additional Findings
The airplane was equipped with a Dynon FlightDEK-D180, which functioned when power was applied, but the carburetor air inlet temperature display was inoperative. No evidence of any preexisting mechanical malfunction that would have precluded normal engine operation was found.
The Federal Aviation Administration published Special Airworthiness Information Bulletin (SAIB) CE-09-35 on June 30, 2009, regarding carburetor ice prevention. The conditions encountered in this accident (ambient temperature 41°F, dew point 23°F) were in the area of icing at glide and cruise power.