Page:CAB Accident Report, United Airlines Flight 21.pdf/65

 minimums prescribed by the Civil Aeronautics Administration when its Flight Operations Manual directs its pilots and dispatchers as follows:

"'... The approved minimums ... are not intended as a guide for regular operations or to influence the reason and judgement of flight operations personnel. The approved minimums are intended to the dispatch and landing of flights when all factors are favorable, and the operation can be accomplished safely and conservatively ...'"

The unpredictability of icing conditions and the fact that such conditions may be hazardous under some circumstances and not under others, and the effect to be given to such conditions in conjunction with other circumstances such as the length and state of the runways and the conditions of wind direction and velocity, all make necessary a reliance upon human judgment acting upon all of the facts and circumstances available at the time. The Civil Air Regulations with respect to the flight and landing of aircraft under such conditions and the Flight Operations Manual of United necessarily require the exercise of such a judgment by the airline personnel.

The dispatcher in the present instance was aware that an icing condition existed in the overcast above the airport. In addition to reports of pilots and the weather observations which he had received during the afternoon, he had the information given to him by Airway Traffic Control at 5:24, that a flight in descending through the overcast had picked up 1-½ inches of ice at the 4000 to 3000-foot level. The dispatcher testified that he did not at the time consider this condition to be more than a light icing condition, since the report did not indicate the period of time in which this airplane had accumulated the ice (Captain Couples, the pilot of the airplane referred to, testified that he was in the overcast for about 25 minutes) and since he had obtained further information from the pilot of United's Trip 19,