Aircraft: Piper Cherokee. Injuries: 1 Fatal, 1 Serious. Location: Provincetown, Mass. Aircraft damage: Destroyed.
What reportedly happened: The non-instrument-rated pilot took off on a dark night from an airport located at the tip of a peninsula.
Analysis of GPS data showed that he turned the airplane toward the destination course before it had reached an altitude of 100 feet. The airplane did not climb, and continued on the heading toward a non-lighted area until it crashed in trees about 900 feet beyond the left boundary of the runway.
The wreckage path orientation and length were consistent with a shallow, powered descent, and signatures observed on the wreckage were consistent with a relatively level impact attitude.
Toxicological analysis detected elevated levels of ethanol in postmortem samples of the pilot’s blood, urine, and brain tissue, the distribution of which was consistent with ingestion. The levels of ethanol present in the pilot’s samples were present in levels known to degrade psychomotor performance.
Toxicological testing also detected an inactive metabolite of cocaine in postmortem samples of the pilot’s urine, but not in samples of blood. This was a likely indication that the pilot had used cocaine, but neither the drug nor its metabolite was active at the time of the accident.
The circumstances of the accident are consistent with the pilot experiencing a form of spatial disorientation known as the somatogravic illusion, in which a pilot misperceives acceleration cues as increasing pitch and makes corrective nose-down inputs. These circumstances include the accelerating phase of flight during takeoff, the dark night lighting conditions associated with an early turn on course, and a non-instrument-rated pilot whose judgment and psychomotor performance were degraded by alcohol consumption.
Probable cause: The pilot’s failure to maintain adequate clearance from trees and terrain during the initial climb. Contributing factors were spatial disorientation due to a vestibular illusion and the pilot’s likely impairment due to alcohol consumption.
NTSB Identification: ERA11FA480
This August 2011 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.