Amateur-built ZENITH 601 HD N740JB accident near Danville, Kentucky

Probable cause

The pilot's improper adjustment of the propeller blade angle, which resulted in inadequate engine thrust, and his decision to continue the takeoff despite the excessively long takeoff roll.

NTSB analysis

The pilot, who also the owner/builder of the experimental, amateur-built airplane, was conducting the airplane's first test flight. The pilot stated that, during the takeoff roll, the airplane used about half of the runway surface, or five times the distance of a nominal takeoff roll, before becoming airborne. He added that the airplane then climbed to about 350 ft, at which point the flight controls began to feel "mushy." The airplane then entered a descent and impacted wires and trees before coming to rest in an open field. The pilot reported that the engine was producing full power throughout the flight but that the airplane would neither climb nor maintain altitude.

Postaccident examination and testing of the airplane revealed that the pilot had likely misread the propeller adjustment tool when installing and adjusting the pitch of the ground-adjustable propeller and had inadvertently set the blades to an extremely low pitch. The low pitch of the propeller blades resulted in inadequate engine thrust, as evidenced by the long takeoff roll and the airplane's inability to climb.

Text from the NTSB. Open the NTSB docket for ERA15LA304 for the full record.