Aircraft: Cessna Skymaster. Injuries: 1 Fatal. Location: Casper, Wyo. Aircraft damage: Destroyed.
What reportedly happened: The 61-year-old pilot, who was the owner of the airplane, held multiple ratings and had logged 4,582 hours, including 687.3 hours in the Skymaster. Additionally, he recorded 644.7 hours of actual instrument time and 648.9 hours of night time.
According to the pilot’s logbook his most recent instrument approaches, a total of 10, had been completed in a simulator on Feb. 15, 2011.
On the day of the accident, he received two pre-departure weather briefings, both of which reported that snow showers were expected over most of the state. During the second briefing, he was advised that adverse weather conditions, including mountain obscuration, moderate icing, moderate turbulence, and low-level wind shear, existed throughout the planned route of flight. The pilot took off.
As the airplane neared its destination, the approach controller issued the pilot vectors to the final ILS approach course. The approach controller noticed the airplane at 6,900 feet MSL, which was 300 feet below the minimum vectoring altitude for the approach. The controller issued the pilot a low altitude alert. The pilot climbed the airplane back to 7,200 feet MSL.
The approach controller transferred control of the flight over to the tower controller.
A few minutes later the tower controller saw that the airplane was about a quarter mile right of the inbound approach course. The controller then issued the pilot missed approach instructions, advising him to fly the runway heading and to climb and maintain 8,000 feet MSL.
The tower controller then transferred the pilot back to the approach controller, who advised the pilot that the runway visual range had decreased below that required for the approach. The pilot then elected to be vectored back to the final approach course to hold on the localizer until the weather improved.
While issuing the vectors to the localizer, the approach controller observed the airplane flying an inappropriate heading. He issued a revised heading to the pilot to get him back to toward the localizer. The controller noticed the airplane begin the right turn toward the assigned heading, and shortly thereafter, descend 1,200 feet below its assigned altitude. The controller issued another low altitude alert.
There were no further radio communications with the pilot. The airplane crashed eight nautical miles northeast of the airport, slightly left of the missed approach course, in a left-wing-low, steep nose-down attitude.
About two minutes before the accident, the destination airport reported a half mile visibility in moderate snow and freezing fog, with scattered clouds at 800 feet AGL and an overcast cloud layer at 1,300 feet AGL.
The post-accident review of the weather conditions in the area at the time of the accident indicated that the pilot was operating in instrument meteorological conditions favorable for structural icing at a moderate to severe level.
Investigators determined it was likely the pilot failed to maintain adequate airspeed due to structural icing, which resulted in a loss of airplane control and subsequent impact with terrain.
Probable cause: The pilot’s failure to maintain airspeed and airplane control while maneuvering in low visibility and icing conditions.
NTSB Identification: WPR12FA040
This November 2011 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.