Diamond Aircraft Ind Inc DA 20 C1 N979DC accident near Shipshewana, Indiana

Probable cause

The total loss of engine power due to impact ice obstructing the primary air induction system, which resulted from the student pilot’s failure to operate the alternate air control. Contributing to the accident was the student pilot’s lack of knowledge about using the alternate air control during an engine power loss.

NTSB analysis

The student pilot reported that he was practicing solo ground reference maneuvers about 1,600 ft above ground level when the engine began operating erratically. He further stated that the airplane might have entered an aerodynamic stall. He advanced the throttle to full forward, but the engine did not respond and subsequently experienced a total loss of power. He attempted to restart the engine by completing the emergency procedures that he remembered. The engine "turned over" but did not restart. He then prepared for a forced landing to a nearby field. During the base-to-final turn, he lost control of the airplane, and it descended to the ground. The airplane impacted the field and continued into a propane tank and then a house where it came to rest.

A postaccident examination of the airplane revealed that most of the induction air filter was obstructed by ice; no other anomalies were noted. The engine was test run with and without the ice in the air filter, and the engine produced full power under both conditions. The alternate air lever, which selects a second induction air intake in case the primary air intake (air filter) becomes restricted, was found in the "off" position. The aircraft flight manual states that, in the event of an in-flight engine failure, the alternate air control should be opened (or "on"). A Federal Aviation Administration advisory circular warns pilots of induction system icing known as "impact ice," which can build up on components like the air filter when moisture-laden air is near freezing. Based on the near-freezing outside air temperature and clouds in the area in which the flight was operating and the lack of any apparent engine malfunctions, it is likely that the primary air induction system became obstructed with impact ice during the flight.

When asked about the airplane's alternate air lever, the student pilot indicated that he was unfamiliar with the lever and did not know its intended use. If the student pilot had opened the alternate air control during the initial power loss, it is likely that engine power would have been restored.

Text from the NTSB. Open the NTSB docket for CEN15LA106 for the full record.