Page:CAB Accident Report, United Airlines Flight 21.pdf/37

 the west runway because of the load of ice he was carrying. He estimated that he was in the icing condition for 24 minutes during which time he continuously operated his de-icing equipment. The de-icer boots operated effectively, breaking the ice off the boot itself while rough ice accumulated on the wing behind the boot. He stated that while descending through the overcast, he was using 30 inches of manifold pressure and 2300 rpm with an indicated air speed of 120 miles per hour when normally the indicated air speed would be between 150 and 160 miles per hour. After lowering his landing gear and flaps to full down position, he increased his manifold pressure to 37 inches, using his motors until within 200 feet of the runway, at which time he dove onto the field in a steep glide. Captain Couples definitely placed the landing speed at 90 miles per hour as called out by his first officer, and was of the opinion that the air speed indicators were functioning in a normal manner. Although his windshield was iced over except for a small space cleared by his de-icer while in the overcast, all the ice melted from his windshield beneath the overcast within two minutes. However, his visibility was impaired by a heavy mist.

Captain Couples testified that on examination after landing the leading edges of the boots on the wings were covered by clear ice of ⅜ of an inch to an inch in thickness. One-half of an inch of very rough ice extended back of the de-icer boots for about 4-½ inches. Ice was all over the nose of the ship, except the windshield. About one inch of rough ice was built up back of the de-icer boots on the vertical fin and horizontal tail surfaces. The antennas had ice an inch to an inch and a half in diameter. The pitot tubes were clear of ice. Captain Couples believed that the clear ice which covered the boots had accumulated subsequent to the time the boots were shut