FTW83FU003

After assembling his ultralight, the plt received dual instruction in a 2 place model. After his 2nd dual flt, he told his instructor (CFI) he had soloed his vehicle. The CFI cautioned him against further solo flts until he was qualified &emphasized the need to wear a helmet. 3 days later, witnesses saw the vehicle cruising at aprx 300 to 500 ft AGL when itsuddenly rolled right & entered a steep nose down attitude & crashed. None of the witnesses could verify the eng status before impact. Neither of the prop blades had rotational damage, but 1 blade broke when it hit the ground. The eng was started with fuel remaining in the fuel tank & operated normally. The ignition switch was mounted on the control stick next to the twist grip throttle & was found in the off position. The eng was equipped with a centrifugal clutch & could not be started by a windmilling prop. The plt was not wearing a helmet & had suffered extensive head injuries. His CFI had warned him that his spoiler lines were too tight & could result in unwanted spoiler action wtih aft stick movement.