Accident Summary
A helicopter crashed vertically into a city street during an autorotation following a loss of engine power. The pilot was on his second logged flight since obtaining his rotorcraft rating and was conducting a solo cross-country flight. Witnesses reported hearing the engine misfire before it quit entirely. They observed the main rotor blades coning up and then ceasing rotation completely, after which the helicopter fell straight down to the street below.
Witness Accounts
According to witnesses, the engine produced abnormal sounds before stopping. One witness noted that the rotor blades coned upward and then stopped spinning. No one at the scene was reported to have manipulated the magneto switch after the accident.
Investigation Findings
Investigators found the magneto switch in the off position, with no sign of impact damage to the switch or key. An evaluation of the crash dynamics, force vectors, and structural deformation could not account for the switch position. Examination of the engine and helicopter systems revealed no anomalies that would have prevented normal operation. The engine roughness heard by witnesses, combined with the magneto switch position, suggests that the pilot may have been attempting to diagnose the engine roughness by selectively turning off one magneto at a time and may have inadvertently selected the both-off position. The pilot was seated in the right seat; manipulation of the magneto switch would have required him to remove his hand from the collective, potentially delaying his reaction to the loss of engine power.
Toxicology Report
Toxicology tests detected chlorpheniramine in the pilot's blood at a level several times higher than the expected concentration from a typical maximum single over-the-counter dose. Chlorpheniramine is a sedating antihistamine commonly used for cold and allergy symptoms and is present in many multi-symptom preparations. At typical doses, this medication has measurable adverse effects on performance of complex cognitive and motor tasks. Investigators concluded that it is likely the pilot's performance and judgment were impaired by chlorpheniramine. The Federal Aviation Administration instructs Aviation Medical Examiners that any airman undergoing continuous treatment with sedating antihistaminic drugs must be deferred certification.