Marshall

The Cessna had departed about 3 minutes prior on a scheduled passenger flight and the Piper was en route to a remote hunting camp when the two airplanes collided at an altitude about 1,760 ft mean sea level over a remote area in day, visual meteorological conditions. The airline transport pilot and two passengers onboard the Cessna and the commercial pilot and the passenger onboard the Piper were fatally injured; both airplanes were destroyed. Post accident examination revealed signatures consistent with the Cessna's outboard left wing initially impacting the Piper's right wing forward strut while in level cruise flight. Examination revealed no mechanical malfunctions or anomalies that would have precluded normal operation of either airplane. Neither pilot was in communication with an air traffic control facility and they were not required to be. A performance and visibility study indicated that each airplane would have remained a relatively small, slow-moving object in the other pilot's window (their fuselages spanning less than 0.5° of the field of view, equivalent to the diameter of a penny viewed from about 7 ft away) until about 10 seconds before the collision, at which time it would have appeared to grow in size suddenly (the "blossom" effect). From about 2 minutes before the collision, neither airplane would have been obscured from the other airplane pilot's (nominal) field of view by cockpit structure, although the Cessna would have appeared close to the bottom of the Piper's right wing and near the forward edge of its forward wing strut. The Cessna was Automatic Dependent Surveillance-Broadcast (ADS-B) Out equipped; the Piper was not ADS-B equipped, and neither airplane was equipped with any cockpit display of traffic information (CDTI). CDTI data would have presented visual information regarding the potential conflict to both pilots beginning about 2 minutes 39 seconds and auditory information beginning about 39 seconds before the collision, providing adequate time for the pilots to react. The see-and-avoid concept requires a pilot to look through the cockpit windows, identify other aircraft, decide if any aircraft are collision threats, and, if necessary, take the appropriate action to avert a collision. There are inherent limitations of this concept, including limitations of the human visual and information processing systems, pilot tasks that compete with the requirement to scan for traffic, the limited field of view from the cockpit, and environmental factors that could diminish the visibility of other aircraft. Given the remote area in which the airplanes were operating, it is likely that the pilots had relaxed their vigilance in looking for traffic. The circumstances of this accident underscore the difficultly in seeing airborne traffic by pilots; the foundation of the "see and avoid" concept in VMC, even when the cockpit visibility offers opportunities to do so, and particularly when the pilots have no warning of traffic in the vicinity. Due to the level of trauma sustained to the Cessna pilot, the autopsy was inconclusive for the presence of natural disease. It was undetermined if natural disease could have presented a significant hazard to flight safety.

The commercial pilot was positioning the airplane from the departure airport to another airport. The flight took place on a dark night with overcast skies, and no discernible horizon. The pilot departed and climbed to a cruise altitude between 1,200 and 1,400 feet msl. About 4 miles south of the departure airport, the airplane collided with an east-west ridge at 1,200 feet msl. The ridgeline is perpendicular to the direct route of flight between the departure and destination airports, and rises from west to east with a summit elevation of 1,714 feet msl. The departure airport was a newly commissioned airport 3 miles east-northeast of the old airport. The accident flight was the pilot's second trip to the new airport, and his first night departure from either the old or new airport. Direct flight from the new airport to the destination airport requires a higher altitude to clear the ridgeline than does a direct flight from the old airport. A direct flight from the old airport crosses the same ridgeline farther to the west, where the elevation of the ridge is less than 500 feet msl.

The pilot landed at Watertown, loaded and off-loaded cargo, and departed without getting out of the airplane. A witness reported seeing the airplane over the runway at an altitude of about 50 feet agl. The airplane was described to be bouncing and buffeting. Another witness reported the weather as overcast with occasional snow flakes. The airplane then descended, impacted the terrain and exploded. Post accident inspection revealed a 1/2 to 3/4 inch thick ridge of rime ice along the leading edge of the left horizontal stabilizer. Pieces of arc shaped ice were located along the wreckage path. Inspection of the wreckage failed to reveal any preimpact failure/malfunction of the engine or airframe which would have prevented flight.

The pilot stalled the airplane while making a steep turn to avoid high voltage power lines. The airplane caught fire on impact and the air taxi pilot subsequently died of extensive thermal injuries. The pilot was flying in formation with another aircraft at low altitude. When the power lines were sighted the other aircraft successfully pulled up and avoided the wires. The accident pilot turned steeply and lost control of the aircraft before crashing.

Flight 318 departed Dallas, Texas, on a VFR Flight Plan at 1310, on time, for Atlanta, Georgia, with a scheduled stop at Shreveport, Louisiana. The crew consisted of Captain Douglas B. yolk, First Officer James P. Stewart and Stewardess Joanne Carlson; there were 17 passengers including one infant. The aircraft’s gross weight on departure from Dallas was 24,099 pounds, which was within the allowable weight of 25,200 pounds, and the center of gravity was within the prescribed limits. Flight 318 proceeded normally and at 1352 reported to the company station at Longview, Texas, that it was then west of Gladewater, Texas. Longview gave the flight the latest Shreveport weather which was dark scattered clouds at 1,000 feet, ceiling estimated 4,000 feet broken clouds, overcast at 20,000 feet, visibility 10 miles, thunderstorms, light rain showers, wind south 10. Remarks were thunderstorms south, occasional lightning cloud to cloud south. The flight was also advised by the company’s Longview operator that he had been watching thunderstorms east and southeast of the Longview field and suggested that the flight stay well to the north. Flight 318 answered “OK.” At 1408, in the vicinity of Marshall, Texas, the flight made a routine radio contact with Delta’s Shreveport station, during which it was given the Shreveport altimeter setting of 29.78. At this time the flight advised it was changing over to the Shreveport Control Tower frequency. At about 1412, four minutes later, Flight 318 called the Shreveport Control Tower, which cleared it to make a right-hard turn for landing approach to Runway 13 and gave the wind as southeast 10 miles per hour, Flight 318 acknowledged this message and requested the Shreveport weather which was transmitted as dark scattered clouds at 1,000 feet, ceiling estimated 4,000 feet, overcast at 20,000 feet, visibility 10 miles, thunderstorm, light rain shower. The tower also advised of a thunderstorm approximately 15 miles west of Shreveport. This transmission also was acknowledged by the flight. At 1416 the Shreveport Control Tower asked Flight 318 to give a position report. No reply was received, and a number of unsuccessful attempts were then made to contact the flight. At 1428 the tower was advised that an aircraft had crashed near Marshall, Texas. A passenger was seriously injured while 19 other occupants were killed. The aircraft was destroyed.

The crew left Sedalia AFB on a local instrument training mission. Enroute, both wings failed and the aircraft crashed in a field located east of Marshall. Both pilots were killed. It is believed that both wings failed due an overstress situation caused by a possible inappropriate attitude of the aircraft during flight.