Page:CAB Accident Report, United Airlines Flight 21.pdf/73

 the airplane just before the crash whether a power failure occurred. In any event, we can conclude definitely from the character of these maneuvers that if a failure occurred, it could not have been the right engine, with which Captain Scott had experienced some difficulty at LaGuardia Field, for if that engine had caused the stall, the airplane would have whipped off to the right instead of to the left.

The only evidence in the record which suggests that one motor might have failed at that time is the statement of one witness, an airline pilot, who thought that the maneuver performed by the airplane resembled a stall aggravated by the use of the opposing motor. However, this witness was not able to hear the motors and, as previously shown, the same maneuver could have been caused by an ordinary power-on stall. Although no witness was able to state definitely that both engines responded to the application of power, one witness, an airline mechanic who heard the burst of power, testified that he was certain that he would have detected the failure of one engine.

Moreover, the inspection and the condition of the engines upon disassembly disclosed no evidence from which it could be concluded that either engine was not functioning effectively immediately prior to the impact. The two most probable causes of a momentary refusal of an engine to take the sudden opening of the throttle are icing of the carburetors and normal cooling of the motors during a glide. The tear-down of the engines did not disclose any evidence of carburetor ice in either of the motors and, in addition, it may be assumed that Captain Scott was applying some heat to his carburetors in accordance with airline procedure. There is no evidence which would indicate that the carburetor de-icer in use by United is not effective, and