Accident Overview
A rented airplane crashed into a lake shortly after takeoff from a mountain resort airport. The pilot, who had obtained his fixed-wing private pilot certificate two weeks earlier, was flying a local sightseeing trip with three passengers. The airplane was found in a takeoff and initial climb configuration. No preimpact mechanical malfunctions or failures were identified.
Circumstances of the Flight
The pilot rented the airplane and flew 47 miles to the mountain resort airport, where he landed and met his future in-laws. After loading three of them onboard, he departed for a local sightseeing trip around the lake. The accident occurred during the initial climb from takeoff on runway 16, based on the aircraft's recording hour meter and stopped electric clock. The performance data indicated the airplane would have climbed to between 400 and 500 feet above ground level at the accident location. The elapsed time on the recording hour meter did not support a conclusion that the pilot completed a run-up or had any appreciable ground run time prior to the accident takeoff.
Airport and Terrain
The lake is in an oval-shaped mountain valley 25 miles long by 15 miles wide, surrounded by mountains that rise 3,000 to 4,000 feet above the water's surface. The town and airport are at the northwest end of the lake. The town borders the airport to the north, and mature pine trees 50 to 60 feet in height surround the field, providing obstacles for approaches or departures except on runway 16/34. The airport manager stated that due to terrain, obstacles, and the proximity of the noise-sensitive town to the north, pilots typically land on runway 34 and take off on runway 16. While he could not be certain, the manager believed the airplane departed on runway 16. The location of the wreckage would be consistent with an upwind to crosswind turn point for runway 16.
Impact and Wreckage
There were no witnesses to the accident. A passing motorist saw the tail of the aircraft sticking out of the lake and notified authorities. Crush lines on the recovered wreckage indicated that it impacted the water right wing low with a pitch attitude in excess of 45 degrees nose down. The aircraft was found in a takeoff and initial climb configuration.
Weather and Wind Conditions
Between 1500 and 1600, the airport's automatic weather observation station recorded winds from 289 degrees at 9 mph with peak gusts to 23 mph. The system only records the highest peak wind gust during the hour-long observation period, not the time of the peak. Surface winds are affected by friction and Coriolis deflection, which produce an average increase in wind speed of 10 mph at the boundary between the surface layer and the free flow layer above, typically about 400 feet above ground level. Coriolis deflection causes the wind direction to change clockwise at the boundary, with a typical change of 10 to 20 degrees. Katabatic wind effects in mountainous areas can result in rapidly moving air masses that may flow over lower layers. The takeoff roll on runway 16 would have been with a right quartering tailwind, which moved closer to a direct tailwind and increased in speed as the aircraft climbed through 400 feet. Considering the recorded peak wind speed, it is likely the aircraft encountered a rapid change in wind velocity by as much as 25 to 30 mph.
Pilot Experience and Density Altitude
The pilot obtained his fixed-wing private certificate two weeks prior to the accident, and this was his first flight with passengers. During training, he had only one flight involving a high-density altitude airport, with the balance conducted at airports with elevations less than 1,000 feet mean sea level. The density altitude at the accident site was 5,400 feet. The flaps-up stall speed at zero degrees of bank is 44 knots indicated airspeed (KIAS) and 47 KIAS with 30 degrees of bank. Normal initial climb segment airspeed is 74 KIAS at 5,000 feet mean sea level.