NTSB Factual Report

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 root to the wingtip. The crushing was mostly observed on the upper edge of the leading edge and extending aft to the wing spar. The right wing was mostly intact, and exhibited leading edge crushing along its span from the wing root to the wingtip. Crushing oriented on an approximate 20 degree angle was observed from just inboard of the wing landing light outboard to the wingtip. The stall warning switch was intact and undamaged. Electrical continuity from the stall switch to the wing root was established using an ohm meter. The vertical stabilizer and rudder were intact and undamaged.

Flight control continuity was established throughout the airplane to all primary flight control surfaces.

Loose items removed from the airframe (luggage, clothes, flight bag, brochures, signs, chairs) were weighed using an analog scale. The combined weight of all of the items was found to be about 231 pounds.

The gascolator (airframe fuel strainer) was disassembled. No debris was noted within the gascolator bowl and gascolator screen.

Examination of the recovered Lycoming O-360-A1P engine, serial number L-41652-36E revealed that it remained attached to the engine mount and firewall structure, which was separated from the airframe. All engine accessories remained attached to the engine, except for the carburetor. The alternator was partially displaced from its mount. All four cylinders were examined internally using a lighted borescope. All four cylinders, piston heads, and valves were unremarkable. The engine crankshaft was rotated by hand using a hand tool attached to a rear accessory mount pad. Rotational continuity was established throughout the engine and valve train. Thumb compression and suction was noted on all four cylinders.

Both magnetos remained attached to the engine and were subsequently removed. The left magneto drive shaft was rotated by hand. Impulse coupling engagement was noted, and spark was produced on all four terminals. The right magneto drive shaft was rotated by hand, and spark was observed on all four terminals.

The carburetor was intact and displaced from the engine. Impact related damage was noted to the carburetor mount. The throttle and mixture control arms were moved freely by hand from stop to stop. The carburetor fuel screen was free of debris. The carburetor was disassembled and the internal float bowl was free of debris. The metal floats were intact. The venturi was intact.

The propeller was separated from the engine crankshaft just aft of the propeller mount flange. Both propeller blades remained attached to the propeller hub assembly. One of the two propeller blades exhibited leading edge polishing near the propeller blade tip along with chord-wise scratches on the forward side of the propeller blade. The other propeller blade exhibited leading edge polishing and chord-wise scratches from about mid-span to the blade tip. Both propeller blades exhibited a slight aft bend originating from just outboard of the blade root.

No evidence of preimpact mechanical malfunction was noted during the examination of the recovered airframe and engine.

A Garmin GPSmap 396 hand-held GPS and Garmin GPSmap 696 were located within the main wreckage, and subsequently shipped to the National Transportation Safety Board Vehicle Recorders Laboratory, Washington, D.C. for further examination.

The Garmin GPSMAP 396 was found in good condition. Power was applied to the unit using NTSB laboratory equipment. Device startup was consistent with normal operation. No data related to the accident flight was recovered from Garmin GPSmap 396.

The Garmin 696 unit was in good condition. Power was applied to the unit using NTSB laboratory equipment. Device startup was consistent with normal operation, and data was recovered for the accident flight.

Review of the recovered data from the accident airplane's Garmin 696 revealed that the flight track originated from the departure airport, and followed Interstate 25 north to Interstate 80, where the track transitioned to a west, northwest heading, paralleling the interstate. The data depicted that the airplane ascended to an altitude of about 8,600 feet, and then 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 plot was located about 0.3 miles south of the accident site at a recorded altitude of 8,533 feet.

For further information, see the Global Positioning System Devices Report in the public docket for this accident.

NTSB Probable Cause

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