WPR11FA188

The pilot’s failure to maintain airplane control and to recover from an aerodynamic stall, which resulted in a spin.

Two airplanes of the same make and model were repositioning together to the same destination and were flying about 1 mile apart from one another. The pilot of the lead airplane reported that shortly after departure, they encountered some light rain, but saw no evidence of ice. As both airplanes approached a mountain pass near the accident site, they encountered light snow with a cloud ceiling of about 1,200 feet above ground level and 3 to 4 miles visibility. The lead pilot heard a blind transmission from the pilot of the accident airplane saying he was "on the edge of a stall." No further radio transmissions were received from the accident pilot. The lead pilot stated that at the time of the radio transmission, he had no evidence of icing on his airplane or anything abnormal about the flight characteristics of his airplane. Witnesses located near the accident site reported observing the two airplanes and that the second airplane, which was about 1/2 to 1 mile behind the first airplane, appeared to be "wobbling" back and forth before it suddenly nosed downward into terrain. Review of weather conditions near the time of the accident revealed no potential for icing below about 11,000 feet. Review of the recovered data from the accident airplane's GPS revealed that the airplane began a descent in the last 3 minutes 57 seconds of recorded data. The data showed an increase in groundspeed for the immediate 44 seconds following the start of the descent from 78 knots to 85 knots; however, the groundspeed then decreased to about 53 knots over the following 2 minutes 56 seconds. The last recorded data point was located about 0.3 mile south of the accident site and about 50 feet above ground level. Wreckage and impact signatures were consistent with a stall and subsequent spin with a right-wing, nose-low impact. Postaccident examination of the airframe, flight control system, and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. Toxicology tests on the pilot were positive for quinine, commonly found in tonic water and occasionally used to treat leg cramps, and sertraline, an antidepressant, which is commonly marketed as Zoloft, and its metabolite, desmethylsertraline. Review of the pilot's medical records revealed that the pilot did not report the usage of these medications on his most recent medical certification application. The degree of the pilot’s cognitive impairment from these medications could not be determined.

HISTORY OF FLIGHT On April 6, 2011, about 0905 mountain daylight time, an Aviat Aircraft, Inc., A-1C-180, N28WY, sustained substantial damage when it impacted terrain about 11 miles east of Laramie, Wyoming. The commercial pilot, sole occupant of the airplane, was fatally injured. The airplane was registered to and operated by Alpine Aviation, Alpine, Wyoming, under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the cross-country positioning flight, which originated from Fort Collins, Colorado, about 0800 with an intended destination of Alpine. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot of the lead airplane reported that the pilot of the accident airplane and himself were repositioning two Aviat Aircraft, Inc., A-1C-180 airplanes from Florida to Alpine. He said that prior to departure the morning of the accident they looked at the weather and felt confident about the flight to Alpine, noting that some areas would possibly be marginal visual flight rules (VFR) conditions. The pilot stated that following an uneventful departure from Fort Collins, Colorado, the flight remained close to Interstate 80 throughout the flight. He noted that shortly after departure, they encountered some light rain, but no evidence of ice. As both airplanes approached the mountain pass to the east of Laramie, Wyoming, they encountered light snow with a cloud ceiling of about 1,200 feet above ground level (agl) and 3 to 4 miles visibility. The pilot estimated that around this time, he heard a transmission in the blind from the pilot of the accident airplane saying he was "on the edge of a stall." No further radio transmissions were received from the pilot of the accident airplane. The pilot further stated that at the time of the radio transmission, he had no evidence of icing on his airplane or anything abnormal about its flight characteristics. A witness located on Interstate 80 at milepost 336 observed two airplanes flying on a northwesterly heading at a low altitude, noting that the airplane in trail was shaking in an abnormal fashion. PERSONNEL INFORMATION The pilot, age 73, held a commercial pilot certificate with airplane single-engine land, airplane single-engine sea, and instrument airplane ratings. A second-class airman medical certificate was issued on March 9, 2011, with no limitations stated. The pilot reported on his most recent medical certificate application that he had accumulated 4,500 total flight hours. Review of the pilot's logbook revealed that as of the most recent entry dated March 28, 2011, he had accumulated a total of 4,307.2 flight hours. AIRCRAFT INFORMATION The two-seat, high-wing, fixed-gear airplane, serial number (S/N) 310, was manufactured in 2010. It was powered by a Lycoming O-360-A1P engine, serial number L-41652-36E, rated at 180 horse power, with a Hartzell two bladed adjustable pitch propeller. The airplane was also equipped with 8.50x6 tires and an Airglass cargo pod. The airplane’s logbook records were not located during the course of the investigation. METEOROLOGICAL INFORMATION An NTSB staff meteorologist prepared a factual report for the area and timeframe surrounding the accident. A National Weather Service (NWS) Surface Analysis Chart, issued at 0900 depicted a low pressure center in central Colorado. Station models in the region depicted calm and light winds with variable directions. At 0853, the weather reporting station at Laramie Regional Airport, Laramie, Wyoming, reported wind from 230 degrees at 7 knots, visibility of 10 miles or greater, ceiling overcast at 4,900 feet, temperature 2 degrees Celsius, dew point temperature -6 degrees Celsius, and an altimeter setting 29.89 inches of mercury. Weather observations retrieved from the Wyoming Department of Transportation (WyDOT) weather station WY28, located about 1 mile to the northwest of the accident site at an elevation of approximately 8,570 feet revealed that at 0905, recorded data indicated moderate snow, temperature 25 degrees Fahrenheit, dew point 24.6 degrees Fahrenheit, 97 % relative humidity, and visibility of 0.78 miles. Information on quality assurance of the data retrieved from WY28 and instrument operation was not obtained. A North American Mesoscale (NAM) model sounding indicated no potential for icing below about 11,000 feet. The majority of the troposphere below 500 hPa was stable or conditionally unstable. At 0530, a Terminal Aerodrome Forecast (TAF) issued for Laramie, Wyoming, forecasted for between 0600 and 1000: wind from 310 degrees at 12 knots, visibility 4 miles, light snow, scattered clouds at 2,000 feet, ceiling overcast at 4,000 feet. For further information, see the weather study in the public docket for this accident. WRECKAGE AND IMPACT INFORMATION Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the airplane came to rest on its left side about 300 feet north of Interstate 80. All major structural components were present at the accident site. The right wing was partially separated, and the engine was crushed aft into the fuselage. The wreckage was recovered to a secure location for further examination. MEDICAL AND PATHOLOGICAL INFORMATION The Albany County Coroner's Office conducted an autopsy on the pilot on April 6, 2011. The cause of death was reported as "rapid deceleration tear of the aorta." The FAA's Civil Aeromedical Institute (CAMI) in Oklahoma City, Oklahoma, performed toxicology tests on the pilot. According to CAMI's report, carbon monoxide, cyanide, volatiles, and drugs were tested, and had positive results for: Desmethylsertraline detected in Liver 0.27 (ug/mL, ug/g) Desmethylsertraline detected in Blood Quinine detected in Blood Sertraline detected in Liver 0.107 (ug/mL, ug/g) Sertraline detected in Blood Review of the autopsy, FAA Airman Medical records, toxicology test, and interviews with the pilot's primary physician were reviewed by the NTSB Chief Medical Officer. Quinine was identified in the blood, as was sertraline (marketed under the trade name Zoloft; 0.107 ug/mL) and its primary metabolite desmethylsertraline (0.27 ug/mL). Quinine is an antimalarial medication that is also present in tonic water and marketed over the counter to prevent leg cramps. At usual doses, it has no significant effect on performance and carries no Food and Drug Administration (FDA) warnings. Sertaline (Zoloft) is an antidepressant medication in the class known as “selective serotonin re-uptake inhibitors (SSRIs).” Its therapeutic range is considered 0.010 ug/ml to 0.200 ug/ml and it carries a FDA warning: "may impair mental and/or physical ability required for the performance of potentially hazardous tasks (e.g., driving, operating heavy machinery)." The pilot’s primary physician was also his aviation medical examiner and reported that he was unaware of the pilot’s use of the medication. TESTS AND RESEARCH Examination of the recovered airframe revealed that the left and right wings were separated from the fuselage by wreckage recovery personnel to facilitate wreckage recovery. The fuselage was mostly intact and undamaged aft of the cabin area. The flap handle was observed in a position consistent with 30-degrees of flaps. The elevator trim was observed in a position of slightly nose down. The fuel selector valve was in the "ON" position. The carburetor heat handle was in the extended position, consistent with being "ON." Battery power was applied to the stall warning horn and an audible tone was heard. The throttle handle was in the full forward, or maximum power position. The left wing was mostly intact, and exhibited leading edge crushing along its span from the wing