Tl Ultralight Sro STINGSPORT N177N accident near Piru, California

Probable cause

The pilot’s failure to recover from a stall, which resulted in a spin. Contributing to the accident was the instructor’s inadequate remedial action.

NTSB analysis

The flight instructor and commercial pilot were conducting a flight review during daytime visual flight rules conditions. Multiple witnesses near the accident site reported observing the accident airplane descending in a nose-low attitude while spinning. Witness reports, findings from the wreckage examination and recovered GPS data are consistent with the airplane entering a stall as part of the flight review and a subsequent spin. A postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The airplane was equipped with dual flight controls; however, it could not be determined which pilot was manipulating the controls at the time of the accident nor could it be determined why neither pilot was able to recover from the spin.

The airplane was also equipped with a rescue ballistic parachute system. The arming handle was found fractured from the cabin roof due to a force on the handle that loaded the adhesive joint in peel mode. The arming pin was not engaged within the arming handle and exhibited a permanent bend. Fretting wear deposits were present on the retaining pin shank, suggesting that the pin was most likely engaged within the handle a significant portion of the time when the airplane was in motion. It could not be determined if the arming pin was removed before the flight or at some point during the flight. The parachute was not deployed.

Medical record review revealed that the left seat pilot had significant preexisting heart disease. However, due to the limitations of the available medical evidence, the investigation could not determine if the pilot had an acute cardiac event during the flight that degraded his ability to operate the aircraft. Toxicology tests for the pilot were positive for Metoprolol, Ticlopidine, and Valsartan, which are commonly used to treat high blood pressure and angina, to control heart rate in some arrhythmias, and to reduce the risk of stroke.

Toxicology testing for the flight instructor, who was seated in the right seat, revealed evidence of previous marijuana use; however no active compound was detected in the postmortem blood, thus it is unlikely that he was experiencing acute impairment from marijuana at the time of the accident.

Text from the NTSB. Open the NTSB docket for WPR12FA295 for the full record.