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Sixty-four U. S. Army personnel boarded at Daggett and were briefed by a stewardess regarding emergency exit locations, emergency equipment and procedure. The aircraft required no servicing or maintenance and there were no carry-over maintenance items reported. Takeoff gross weight was computed to be 116,520 lb. This weight and the center of gravity (c.g.) were both within prescribed limits.
Flight 3880 departed Daggett at 1345 under an Instrument Flight Rules (IFR) flight plan to Manhattan, Kansas, with an estimated time en route of 4 hours and 30 minutes. The flight proceeded without incident and at 1720, in the vicinity of Edina, Kansas, canceled its IFR flight plan with Kansas City Air Route Traffic Control Center The let-down was made in clear weather and the aircraft entered normal lefthand traffic pattern for a VFR approach to runway 21 at the Manhattan Municipal Airport. This runway is 5,500 feet long, 100 feet wide, and the final elevation is 1,060 feet m.s.l. The FAA Flight Service Station located on the airport[1] reported the surface wind as west-northwest six knots and the altimeter settling 29.97 inches. The skies were clear and the visibility 15 miles.
According to the captain, who was flying the aircraft from the left pilot seat the flight entered an extended downwind leg at an altitude of 2,500 feet m.s.l. The aircraft was turned onto a left base leg for runway 21 at which time the before landing checklist was completed; landing gear extended, flaps set to 60 percent and 2400 r.p.m. selected for all propellers. A left turn onto the final approach was completed at an altitude of approximately 900 feet above ground level (a.g.l.) at an airspeed of 140 knots. During the final portion of the approach 100 percent flaps were extended, and the airspeed was reduced to 120 knots.
At an altitude estimated to approximately 170 feet a.g.l., the right wing down, the aircraft yawed to the right, and a higher than normal rate of descent was noticed. The captain stated that his first impression was that the aircraft had entered a down draft but would fly out of it momentarily. However, the descent continued and the control forces became greater. Realizing that this was an abnormally high rate of descent he added “. . . considerable . . ." power to all four engines. Immediately following the power application, control forces became stronger and the rate of descent increased alarmingly. Within seconds the aircraft struck the ground.
The flight engineer recalled that after increasing the r.p.m. to 2400 on all four propellers during the approach, the No. 3 propeller surged to about 2475 r.p.m. He thereupon placed the No. 3 propeller control switch in the manual position and increased r.p.m. to 2400, then repositioned the switch to automatic. The r.p.m. remained nearly steady with only slight fluctuations. His attention was next drawn towards other duties in preparation for landing. During this time he felt the aircraft sink, followed by an application of high engine power. He quickly returned his attention to the panel but could only remember seeing the engines manifold pressures at approximately 50 inches hg prior to ground impact.
The observer/pilot, who was standing between the captain's and first officer's seats, recalled that shortly after entering the final approach he observed the propeller r.p.m. increase approximately 100 r.p.m. and then return to the original setting of 2400 r.p.m. This fluctuation occurred three times. Then, following extension of full flaps, he observed the captain reduce power to approximately
- ↑ There ls no airport traffic control tower at Manhattan Municipal Airport.
