Page:CAB Accident Report, United Airlines Flight 21.pdf/43

 dislodged when the wing struck the house on Keating Avenue. There was an accumulation of about ⅜ of an inch of rough, granular ice over the nose of the de-icer boot on the horizontal stabilizer extending backward for a distance of one inch on each side. The de-icer boot on the vertical fin was capped with ice about ⅜ of an inch in thickness extending back about ¾ of an inch on each side. The ice accumulation on the fin antenna was reported to have been about 1-½ inches in diameter and on the antenna underneath the center section to have been about ¾ of an inch in diameter. While there is testimony by a passenger that he observed the de-icer boots operating above the overcast, in the clouds and under the clouds, the ice on the leading edge of the de-icer boots showed no evidence of cracking such as would have been present if the de-icer boots had been operated. Moreover, this ice was a type which the boots could have effectively broken off.

It seems clear from the record that Captain Scott had accumulated on his windshield a substantial amount of ice because, after breaking out of the overcast, he told the airport control tower operator that it would be necessary for him to circle the airport in order to get the ice off his windshield. However, there is no evidence from which we can determine as to whether he was successful in doing so. Since the pilot's compartment and nose section of the fuselage were completely demolished, the only part of the windshield remaining for examination was the frame, from which it appeared that the set screws which fasten the sliding panel of the windshield in front of the Captain's seat had been unscrewed.

The detailed inspection of the ice accumulation on the airplane was made about 7:15 p.m., almost 1-½ hours after the accident occurred. Since the temperature during this period remained at or below the freezing point and an inspection of the ice showed no indication of melting, it is reasonable to conclude that no reduction in the ice accumulation on the wreckage occurred between the time when the plane came to rest and the time it was first carefully examined.