Fatal Crash of Experimental Oliver RV-9A Near May, Idaho (N559B)

Accident Overview and Immediate Circumstances On June 19, 2010, at 1103 mountain daylight time, an experimental Oliver RV-9A, N559B, impacted terrain approximately one-quarter mile south of May Airport in May, Idaho. The pilot, who was the sole occupant, sustained fatal injuries. The aircraft, which was owned and operated by the pilot, sustained substantial damage. The flight was a 14 Code of Federal Regulations Part 91 personal operation that departed Challis, Idaho, about 15 minutes before the accident. Visual meteorological conditions prevailed, and no flight plan had been filed. ## Pre-Accident Flight Sequence The pilot and another aviator were returning from a backcountry aerial camping trip. They had landed in McCall, Idaho, on June 18, then proceeded to Johnson Creek Airstrip for the night. On the morning of June 19, they flew to Challis, Idaho, where they remained on the ground for approximately 50 minutes. After taking off from Challis, both pilots climbed over the hills between Challis and May. The other pilot landed first and communicated with the RV-9A pilot via VHF radio regarding the roughness of the May Airport dirt/turf surface. ## Witness Observations The pilot on the ground, accompanied by another person, observed the RV-9A pilot maneuvering over the airfield to visually evaluate the landing surface. The aircraft eventually rolled wings level about 200 feet above ground level (AGL) and proceeded along the south side of the airfield. Witnesses reported that the airplane's forward speed may have slowed before it suddenly rolled to the left and entered a one-half turn spin into the ground. No audible change in engine power or sounds indicating an engine anomaly were reported. ## GPS Data Analysis Data downloaded from a Garmin 696 global positioning system (GPS) unit recovered from the wreckage indicated that the pilot entered a shallow left turn about one and one-quarter miles south of May. He then tightened the turn to circle the town with a diameter of about one-third mile. Subsequently, he decreased his bank angle, resulting in a second left turn with a diameter of about three-quarters of a mile. This path took the aircraft over the western half of May Airport, off the west end, and back to the southern side, where the pilot rolled wings level and paralleled the runway on an easterly heading. Approximately 20 seconds after rolling out of the turn, the airplane descended into the terrain. The total time from the initial left turn to rolling wings level was approximately 240 seconds (4 minutes). After rolling out, the pilot maintained an airspeed between 81 and 83 miles per hour, which was 30 mph over the level flight stall speed of 48 mph. ## Mechanical Examination and Toxicology A post-accident examination of the flight control system and primary structure by a Federal Aviation Administration (FAA) Airworthiness Inspector revealed no evidence of a malfunction or anomaly that would have contributed to the rapid roll and descent. A forensic toxicological examination by the FAA's Civil Aerospace Medical Institute (CAMI) found 0.173 ug/ml of diphenhydramine in the pilot's blood and an undesignated level in his urine. Diphenhydramine is an over-the-counter antihistamine that can cause sedation, tiredness, sleepiness, dizziness, and disturbed coordination. This blood level would be expected to result in impairment, which may have contributed to confusion or spatial disorientation.