Page:CAB Accident Report, United Airlines Flight 21.pdf/69

 According to the testimony of the pilots, it appears that in landing on the northwest runway a drag approach is made with gear down, three-quarter flaps, and about 25 percent horsepower. We have previously discussed the stall characteristics of a DC-3 airplane. The stall characteristics of this airplane with gear down and three-quarter flaps and with 25 percent horsepower position are intermediate between those with cruising power and with power off, corresponding more closely to those obtaining in the case of a stall with cruising power on, giving slight warning to the pilot and being accompanied by a violent rolling motion to one side or the other.

The tests previously referred to, conducted by Captain Thompson on an iced-up DC-3, were made with approximately this setting and, although not carried to the stall point, indicate that when ice is present the approach to the stall is accompanied by little or no warning except for a slight sluggishness of the aileron control and a tendency for the airplane to wobble. In addition, there is some indication that under this condition the stability of the aircraft is not very positive and the stick forces and movements required to alter the attitude of the airplane are slight; although this is not conclusively established inasmuch as longitudinal stability is very sensitive to the location of the center of gravity and the center of gravity at the time of the accident is not precisely known. Thus, under all circumstances surrounding Captain Scott's approach to the northwest runway, it would require even greater attention and skill than is usually the case to effect a safe landing.

Careful inquiry was made in order to determine whether a fire in the cockpit or other parts of the airplane might have occurred to divert the