Approach and Control Communication
A commercial pilot with two passengers was arriving at the destination airport in a light twin-engine airplane on a business flight. The air traffic tower controller advised the pilot to follow a slower airplane that was on base leg. Subsequently, the controller asked the accident pilot if he could reduce speed "a little bit." The pilot responded that he was slowing down. Less than a minute later, the controller cleared the pilot to land, and the pilot acknowledged the landing clearance—his last radio transmission.
The controller stated that he did not visually see the accident airplane other than on the radar scope but did observe a plume of smoke on the final approach course for the active runway.
Witness Observations
Ground witnesses reported seeing the airplane flying slowly with its wings wobbling. It then turned right and dove into the ground. The majority of the airplane was consumed by a post-crash fire.
Investigation Findings
Inspection of the flight controls and engines found no evidence of any preimpact mechanical problems. Low-speed flight reduces the margin between a safe operating speed and an aerodynamic stall. Wing wobble at low speeds is often an indicator of an incipient aerodynamic stall.
Toxicology and Pilot Impairment
Toxicological samples from the pilot’s blood detected diphenhydramine (a sedating antihistamine commonly known by the trade name Benadryl) at a level consistent with recent use of at least the maximum over-the-counter dose. Diphenhydramine is used over-the-counter for allergies and as a sleep aid and has been shown to impair the performance of complex cognitive and motor tasks at typical doses. The FAA does not specifically prohibit the use of diphenhydramine by pilots, though Federal Air Regulation 91.17 states, in part: "No crewmember may act, or attempt to act as a crewmember of a civil aircraft...while using any drug that affects the person's faculties in any way contrary to safety..."