-4-
About this time, the captain instructed the first officer to go back and observe the right engine. While the first officer was out of his seat, the right engine began to backfire and the captain then shut down the engine and feathered the propeller. The aircraft was approximately 50 nautical miles east-northeast of Malmstrom AFB and had flown approximately 12 miles past the Geraldine Airport[1] at Geraldine, Montana. The captain reversed course to return toward Malmstrom AFB and began a gradual descent of from 100 to 200 feet per minute. He recalled seeing the Geraldine Airport and believed he was 300 to 1100 feet above the terrain at the time. The captain said that when the right propeller was feathered, the left engine was set at 2,100 r.p.m. and the aircraft was in a slight descent at an airspeed of from 100 to 105 knots. The cowl flaps of the left engine were then placed in trail position. Prior to shut down of the No. 2 engine, the cowl flaps were left at the closed position, oil pressures remained at approximately 50 psi, and cylinder head temperatures remained at approximately 200°C.
As the aircraft approached Geraldine westbound, two witnesses in the area observed it. (See Attachment I.) One witness stated his attention was drawn to a low flying aircraft about 300 feet above the ground l/4 to 1/2 mile away flying in a west-northwest direction. He observed the right propeller turning slowly. The second witness observed the aircraft with a feathered right propeller flying at less than 500 feet above the ground Headed "3 a little north of west."
After flying westbound past the Geraldine Airport, of which the captain was aware, he said power was increased to 2,550 r.p.m. on the left engine. When the airspeed dropped to 100 knots, he descended the aircraft to a lower altitude because he believed ground effect[2] would help him maintain altitude. At the same time, the terrain appeared lower to the northwest so he turned in that direction. When the airspeed dropped to below 100 knots, the captain went to "full power." Airspeed dissipated through 95 knots and altitude could not be maintained with full power. Therefore, the captain began to make several turns to avoid the rolling terrain. At this time, the captain said the left inlet oil temperature gauge indicated approximately 130°C., cylinder temperature 200°C., and airspeed had dropped to 90 knots.
Several witnesses observed the aircraft following its course change to a northwest direction after passing Geraldine. (See Attachment I.) One witness, located approximately four miles northwest of Geraldine, observed the aircraft pass above him. It was approximately 250 feet above the ground with a feathered right propeller. Thinking the aircraft was about to crash, the witness climbed from the rock crusher he was operating and followed the aircraft for about three miles in his pickup truck before losing sight of it. Another witness observed the aircraft with the right propeller feathered flying north-northwest at an estimated altitude of 50 to 100 feet. These and other witnesses describe the aircraft as making turns, some as steep as 45 degrees.
- ↑ Geraldine Airport, located one statute mile south of the city of Geraldine, Montana, has an east-west hard surfaced, 2,900-foot runway at an elevation of 3,180 feet m.s.l. There are no approach obstructions and the airport is situated on level terrain 37 nautical miles east-northeast of Malmstrom AFB. The runway had been extended from 2,500 feet to 2,900 feet and resurfaced the day before the accident. The shortest landing distance permitted by Civil Aeronautics Manual 42 for N 67941, under the existing conditions, was approximately 3,380 feet.
- ↑ The effect of the ground or surface in turning the down-wash, or induced flow from the wings or rotor of an aircraft hovering or flying near it, thus reducing induced drag and increasing lift.
