Air Safety Institute Safety Spotlight
A cold lesson about icing
On February 7, 2004, the instrument-rated pilot of a Piper Arrow crashed just short of the runway at the Tri-County Regional Airport in Lone Rock, Wisconsin. The airplane was destroyed, but fortunately the pilot and his two passengers received only minor injuries. During the pilot's preflight briefing, he was advised of airmets for both IFR conditions and icing along his route from Racine to Lone Rock. He was also given a pilot report for light rime icing in the vicinity of Madison.
After departing Racine, he climbed to 4,000 feet--above the cloud layer. As he approached his destination, he entered instrument meteorological conditions, and ice began to accumulate on the wings. He requested a higher altitude in an attempt to avoid the ice, but because he was near his destination, he was cleared to descend to 3,200 feet--an altitude that kept him in the clouds.
On the first instrument approach to Lone Rock, the pilot couldn't find the airport because of recent snow and his unfamiliarity with the area. During a second approach, he entered visual meteorological conditions. The pilot cancelled IFR and entered the pattern for Runway 36, but on short final with 25 degrees of flaps and airspeed of just under 85 mph, the airplane began to drift left. The pilot applied full power to abort the landing, but the Arrow rolled inverted and crashed. After the accident, the pilot observed rime ice on the leading edges of the wings.
The NTSB determined the cause of this accident to be the pilot's continued flight into icing conditions, resulting in ice accretion on the wing--and his failure to maintain airspeed, resulting in a stall.
The pilot had received his instrument rating seven weeks before the accident. At the time of the accident, he had logged two and one-half hours of instrument time, including a half-hour in the past 30 days.
The Pilot's Handbook of Aeronautical Knowledge states that in-flight "ice formation will alter the shape of the airfoil and adversely affect all aspects of airplane performance and control. As the ice forms on the airfoil, especially the leading edge, the flow of air over the wing is disrupted." This disruption can increase the stall speed of the aircraft.
This pilot was faced with a dilemma--climb out of the ice and possibly divert to another airport, or descend and follow ATC's instructions. After the accident, the pilot said that he should have been more assertive with ATC in his attempt to avoid the icing conditions.
For more information about icing and wing contamination, see the AOPA Air Safety Foundation's Safety Hot Spot. Also, to learn how ATC can help in an emergency, take ASF's interactive online course Say Intentions.
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