Amateur-built SD-1 TG accident near Spanish Fork, Utah, September 6, 2013

The NTSB's narrative final · quoted from the NTSB record

The owner/builder reported that the accident flight was the fourth test flight for the experimental airplane. One of the three ground crewmembers reported that, for this flight, the pilot wanted to test the airplane's G limits, perform stalls, and conduct touch-and-go takeoffs and landings. While the pilot was flying the airplane in the traffic pattern, two of the ground crewmembers observed the airplane perform an unscheduled roll. About 1 minute later, they observed the airplane perform a second roll. One of the ground crewmembers reported that, about midway through the second roll, the pilot lost airplane control, and the ballistic parachute subsequently deployed with the airplane traveling at a high rate of speed; almost immediately after deployment, the parachute separated from the airframe. The airplane then spun toward the ground and was destroyed by impact forces. The Pilot's Operating Handbook (POH) contained a warning that aerobatics and intentional spins were prohibited. The POH also indicated that the minimum deployment altitude for the parachute was 210 ft and recommended that the parachute be deployed at the lowest airspeed possible and not above 150 mph; the airplane was operating at the airport's traffic pattern altitude of about 1,000 ft above ground level when the parachute deployed. The airplane's never-exceed speed was 131 mph; the airplane's actual speed at the time of the parachute's deployment could not be determined. Although the airplane was likely traveling within the speed and altitude specified for parachute deployment, the pilot was performing a prohibited roll when it deployed. All of the parachute system's hardware was accounted for during the postaccident examination of the system. The examination of the three parachute lines that were attached to the fuselage per the kit specifications revealed that two of the lines had been cut and that the third line exhibited overstress fractures. It is likely that the lines were severed when the parachute was deployed during the roll and that the remaining line then failed due to overload. Due to the severity of the damage and fragmentation of the airframe, it could not be determined if the pilot intentionally deployed the parachute following the loss of control during the roll maneuver or if a malfunction occurred that caused the parachute to deploy unintentionally. Once the parachute separated, the airplane was likely uncontrollable. Although postaccident toxicological tests detected chlorpheniramine, a sedating antihistamine, in the pilot's cavity, it is unlikely that the pilot was impaired at the time of the accident.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.

Other NTSB records under N123SD the same tail number, which may have belonged to a different aircraft at the time