What happened
On August 16, 2010, an experimental Clark RV-6A, registration N621AL, nosed over onto its back at Nampa Municipal Airport in Nampa, Idaho. The aircraft, which had received its airworthiness certificate only five days prior, was being used by the pilot for high-speed taxi test runs in preparation for his first flight of the day.
During the first taxi run on runway 29, witnesses observed the aircraft reaching groundspeeds between 40 and 60 knots. As the aircraft reached approximately two-thirds down the runway, a significant nose wheel shimmy developed. Witnesses noted the pilot attempted to mitigate the shimmy by slightly raising and lowering the aircraft's nose.
The pilot then reversed course to perform a second test run on runway 11. As the aircraft accelerated to approximately 50 knots, the nose wheel shimmy reoccurred. Shortly after, the aircraft became airborne, reaching a height of three to five feet. The nose then lowered, striking the runway and initiating a porpoising sequence. The aircraft's nose wheel struck the runway surface three times; on the third impact, the nose gear strut collapsed. The aircraft slid along the runway, with the main gear tires skidding as if brakes were applied, before departing the right side of the runway and nosed over in soft terrain.
The pilot, the sole occupant, suffered fatal injuries due to blunt force trauma to the head.