What happened
On March 7, 2017, an unregistered experimental amateur-built Quicksable MXL II crashed during takeoff from Hesperia Airport in Hesperia, California. The pilot, who was operating with an expired student pilot certificate, sustained 1 fatal injury.
Prior to the accident, the pilot had been conducting high-speed taxi tests for approximately two months. During these tests, the aircraft exhibited a tendency to pull to the left. One month before the fatal flight, the pilot performed an initial flight test that resulted in the aircraft striking a hangar and sustaining substantial damage. The pilot spent the following month repairing the aircraft and continuing taxi tests.
On the day of the accident, video footage from an onboard GoPro camera showed the pilot performing a high-speed taxi along runway 21, during which the aircraft veered across the centerline eight times. The pilot then turned the aircraft around and accelerated down runway 3. After rotation, the aircraft climbed to approximately 50 feet above ground level while drifting left. At 100 feet, the aircraft entered a 90-degree left roll. The nose dropped, and the aircraft rolled inverted into the ground. The aircraft, bearing the registration UNREG, came to rest approximately 750 feet beyond the runway 3 threshold.
The investigation
Mechanical examination of the aircraft's tri-bar assembly revealed a significant construction error. A bolt intended to secure the forward left tri-bar downtube to the upper assembly was only partially attached. The downtube was 1 1/4 inch short of full insertion, meaning the bolt was merely resting against the end of the lower tube rather than interlocking the components. This error was obscured by insulating foam. This improper assembly created a differential load between the left and right wing structures, which likely caused the left wing to warp during flight.
Additionally, investigators found that a left side tail brace tube remained bent from a previous accident and had not been replaced.
Toxicology results for the pilot revealed the presence of several substances, including methamphetamine, hydrocodone, diazepam, THC, and amphetamine, as well as ethanol. The pilot also had traces of gabapentin and oxazepam in his system.
Findings
- The pilot failed to identify and correct a construction error in a critical structural component.
- The unsecured structural member created an imbalance and differential load that caused the left wing to warp, leading to a loss of control.
- The pilot's decision-making and judgment were impaired by the combined use of multiple drugs and medications.
- The aircraft was not registered with the FAA and lacked an airworthiness certificate, which would have allowed for an official inspection that might have identified the structural error.