Many parts of the country are well into the throes of winter and poor surface conditions can make ground operations extremely challenging. All of the following accidents occurred in 2004; fortunately no one was injured.
On January 3, the pilot of a Cessna 172 attempted to land on a snow-covered runway at the Hayfork Airport in Hayfork, California. Upon completing a fly-over, the pilot noticed tire tracks on the runway, and proceeded to perform a short-field landing. After landing, snow accumulated in front of the nose wheel, causing the 172 to nose over. The propeller and both wings struck the ground, causing substantial damage.
The NTSB determined the cause of this accident was the pilot's inadequate in-flight decision to land on a snow-covered runway without ascertaining the depth of the snow.
On January 10, a Cessna 150 was substantially damaged when it nosed over after hitting a snowdrift during a night landing at Princeton-Kauffman Memorial Airport in Princeton, Missouri. The pilot said that after a normal approach and landing, "the main wheels seemed to slow, pulling the nose wheel down." He then lost control and veered to the left and the airplane flipped tail over nose at the edge of the runway. When the pilot exited the plane, he noticed 6 to 8 inches of snow on the ground.
The NTSB determined the cause of this accident was the encounter with the unknown snowdrifts during landing. A contributing factor was the failure of the airport to issue a notam about the runway conditions.
Finally, on January 17, a Cessna 310R hit a snow bank following a loss of directional control during landing at the St. Clair County Airport in Port Huron, Michigan. En route to the airport the pilot listened to the AWOS report, which included a notam reporting braking action measurements of 33, 35, and 36 MU with light snow. The pilot received the same notam from air traffic control. Neither indicated any rapidly changing conditions.
The pilot reported that after landing, the aircraft never gained any traction, and slid to the left side of the runway. The left main gear hit a snow bank, causing the airplane to swing around. The nose then hit the same snow bank and the nose gear collapsed. The original notam included remarks "one-half inch loose snow over patchy ice, compacted snow and ice all surfaces, executive ramp closed."
The NTSB determined the cause of this accident was the loss of directional control as a result of reduced braking performance because of a snow-covered runway.
According to the Aeronautical Information Manual, "MU (friction) values range from 0 to 100 where zero is the lowest friction value and 100 is the maximum friction value obtainable. For frozen contaminants on runway surfaces, a MU value of 40 or less is the level when the aircraft braking performance starts to deteriorate and directional control begins to be less responsive. The lower the MU value, the less effective braking performance becomes and the more difficult directional control becomes."
For more information on how to operate on less than ideal surfaces, and how to better interpret braking action reports, read the AOPA Air Safety Institute's Safety Brief, Cold Facts: Braking Action Reports .
Accident reports can be found in ASI's accident database.
Posted Thursday, January 19, 2006 9:55:12 AM