Accident Overview
On August 7, 2015, at 1910 eastern daylight time, an experimental, amateur-built Zenith 601HD, registration N740JB, sustained substantial damage during a forced landing after takeoff from Stuart Powell Field (DVK) in Danville, Kentucky. The pilot, who was also the owner and builder, was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local test flight conducted under 14 CFR Part 91.
Pilot and Aircraft Information
The pilot held a sport pilot certificate with a rating for airplane single-engine land and reported 124 total hours of flight experience, with 5 hours in the accident airplane make and model. The aircraft was issued an FAA airworthiness certificate in July 2014 and was powered by a Chevrolet Corvair 100-horsepower 6-cylinder engine equipped with a ground-adjustable, two-bladed composite propeller.
Pre-Accident Events
After trailering the airplane to the airport and assembling it, the pilot taxied several times to become accustomed to the flight controls. Nothing felt out of place, so he elected to take off. The departure runway was 5,000 feet long, and the takeoff roll used approximately 2,500 feet prior to rotation.
Accident Sequence
The airplane climbed to about 350 feet above ground level before its handling characteristics felt "mushy," the climb stopped, and the airplane entered a descent the pilot could not arrest. He maneuvered away from houses toward an open field but struck wires, trees, and terrain before reaching the field. The pilot reported that the engine was producing full power, but the airplane would neither climb nor maintain altitude.
Post-Accident Findings
A Federal Aviation Administration inspector examined the engine, propeller, and associated logbooks. The engine's camshaft had been changed, which may have affected timing, and the propeller logbook showed the pilot had adjusted blade pitch to 9 degrees. The pilot later checked the timing and found it correct. He consulted with builders of the same model, who suggested incorrect propeller pitch.
The engine kit manufacturer noted that a static rpm of 3,800 at 12 degrees and 3,200 at 9 degrees (as measured by the pilot before the flight) were contrary to known performance, suggesting misreading of the protractor adjustment tool. The manufacturer indicated that a static rpm of 3,800 should have been a red flag, and that the accident airplane's performance was consistent with a blade angle of around 2 to 4 degrees. A pitch of 7 degrees with a properly running engine would result in a ground roll of about 500 feet.
Regulatory Guidance
FAA Advisory Circular 90-89A, the Amateur-Built Aircraft and Ultralight Flight Testing Handbook, emphasizes that test flying is a critical undertaking requiring thorough planning, skill, and common sense. It provides guidance on preparing for each phase of production, including taxi tests, flight testing, and emergency procedures, and suggests that test pilots be rated, current, and competent in the same category and class as the aircraft being tested.