Air Safety Institute Safety Spotlight
Aviation ice capades
Many parts of the country are entering the throes of winter, and poor surface conditions can make ground operations challenging. All of the following accidents occurred in January 2004; fortunately, no one was injured.
On January 3, the pilot of a Cessna 172 attempted to land on a snow-covered runway at Hayfork Airport in Hayfork, California. The pilot had noticed tire tracks on the runway, and proceeded to perform a short-field landing. After landing, snow accumulated in front of the nosewheel, 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 to be the pilot's 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 nosewheel 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 six to eight inches of snow on the ground.
The NTSB determined the cause of this accident to be the encounter with the unknown snowdrifts during landing. A contributing factor was the failure of the airport to issue a notice to airmen about the runway conditions.
Finally, on January 17, a Cessna 310R hit a snowbank following a loss of directional control during landing at St. Clair County Airport in Port Huron, Michigan. The pilot had listened to the airport's AWOS, which included a notam reporting braking action measurements of 33, 35, and 36 MU with light snow, and received the same notam from air traffic control; neither indicated any rapidly changing conditions. 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 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 the snowbank, causing the airplane to swing around. The nose then hit the same snowbank, collapsing the nose gear. The original notam included the 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 to be the loss of directional control as a result of reduced braking performance because of a snow-covered runway.
For more information on how to operate on less-than-ideal surfaces, and how to better interpret braking action reports, read ASF's Safety Brief, Cold Facts: Braking Action Reports.
Kristen Hummel manages the GA accident database for the AOPA Air Safety Foundation. She holds a commercial pilot certificate with multiengine and instrument ratings.
By Kristen Hummel