CEN19LA216

The commercial pilot of the experimental airplane reported that he was unable to enter the destination airport airspace, so he remained outside of the airspace at a reduced power setting. After adjusting the mixture control, the engine experienced a complete loss of power and the propeller stopped rotating. About 1,600 ft above ground level (agl), the pilot initiated a steep dive to increase airspeed and attempt to get the propeller to windmill and the engine to restart; however, the propeller would not rotate, so he pulled out of the dive about 300 ft agl and aligned with traffic on an interstate for a forced landing. During the landing, the right wing contacted a truck and the airplane sustained substantial damage to the wings and fuselage. A postaccident engine test run revealed no anomalies, and the test was unable to determine why the propeller would not windmill above the published speed. The atmospheric conditions at the time of the accident were conducive to the accumulation of carburetor icing at glide and cruise power settings. The pilot did not use the carburetor heat during the reduced engine power operation; therefore, it is likely that the carburetor accumulated ice, which resulted in the total loss of engine power.

On July 8, 2019, at 1600 central daylight time, a Knight-Wilcox Varieze experimental airplane, N112EZ, made a forced landing to an interstate and collided with a vehicle near Kaneville, Illinois. The pilot sustained minor injuries and the airplane sustained substantial damage. The vehicle occupant was uninjured. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions existed near the accident site and a visual flight rules (VFR) flight plan was not filed. The flight departed Waukegan National Airport (UGN), Waukegan, Illinois, at 1537, and was en route to Aurora Municipal Airport (ARR), Aurora, Illinois. After the accident the pilot stated that he was descending toward the destination airport and contacted the ARR air traffic control (ATC) tower. The controller advised the pilot that the ARR airspace was operating under instrument flight rules (IFR) due to low visibility and haze. The pilot remained north of the ARR airspace and requested a special VFR clearance, which was denied by ATC due to an inbound IFR flight. He stated that while holding outside of ARR airspace with a reduced power setting, about 1,900 rpm, and the carburetor heat off, he reduced the mixture control about one inch of travel and the engine experienced a total loss of power and the propeller completely stopped rotating. While about 1,600 ft above ground level (agl), the pilot initiated a steep dive to increase airspeed and allow the propeller to rotate and the engine to restart. During the maneuver, he added carburetor heat but the propeller would not rotate so he pulled out of the dive about 300 ft agl and determined the interstate was the best place for a forced landing. After aligning with the west bound lane, he glided the airplane over several cars and maneuvered for an opening between vehicles where he could land the airplane. During the landing the right wing contacted a pickup truck in the far right lane, the airplane veered right, the landing gear collapsed, and the pilot was unable to maintain directional control. The airplane rotated 360° and came to rest in the grass median – see figure 1. Figure 1 – Airplane in grass median (Courtesy of Chicago WGN9) The weather conditions reported about the time of the accident included outside air temperature of 83° F, dew point 52° F, and about 34% relative humidity. The carburetor icing probability chart included in the airplane flight manual and the Federal Aviation Administration Special Airworthiness Information Bulletin No. CE-09-35, Carburetor Icing Prevention, indicated that the airplane was operating in an area that was associated with a risk of carburetor ice accumulation at glide and cruise power settings. The pilot was using the Foreflight application on his tablet to record the flight data. According to the data provided, during the steep dive the airplane reached an airspeed about 189 mph.According to the Varieze airplane flight manual, the propeller minimum wind-milling speed is 70 mph. If the propeller is stopped, the propeller restart speed in a steep dive is 150 mph. The responding Federal Aviation Administration (FAA) inspector reported that the airplane was recovered to a local hangar where an engine functional test run was conducted. The functional test run was successful and no engine anomalies were noted. The test was unable to determine why the propeller would not rotate during the steep dive. Additionally, the pilot reported that two days before the accident while flying the airplane in cruise flight, the carburetor accumulated ice and the engine ran rough. He stated that after applying carburetor heat the engine stumbled but returned to full power after the carburetor ice was cleared.