Convair 240 accident at Near Springfield, Missouri, 20 Mar 1955

Accident narrative

On March 20, 1955, American Airlines Flight 711, a Convair 240, crashed in an open field approximately one and a quarter miles north-northwest of the Municipal Airport at Springfield, Missouri. The accident occurred at 2236. Eleven of the 32 passengers, the first officer, and the stewardess were fatally injured. The captain and all but one of the surviving passengers were seriously injured. The aircraft was destroyed by the impact.

**The flight**

Flight 711 was a scheduled service from Newark, New Jersey, to Tulsa, Oklahoma, with several intermediate stops. Following a scheduled crew change at Chicago, Captain John Pripish, First Officer Glenn E. Walker, and Stewardess Rita M. Madaj took over the flight. It proceeded normally to St. Louis, landing at 2100. Captain Pripish had flown into Springfield about 55 times; First Officer Walker had recently been recalled from furlough, and this was his first flight after completing his checkout requirements.

At St. Louis, the crew was briefed on weather conditions for the next stop, Springfield, which forecast low ceilings and visibility. The flight departed at 2136, more than an hour behind schedule, on an Instrument Flight Rules (IFR) clearance to the Springfield VOR station via Victor Airway 14. Company records indicated the aircraft was loaded below its maximum allowable weight.

**The approach**

At 2218, the flight contacted Springfield Approach Control and estimated it would reach the Springfield VOR at 2233. The controller provided the 2208 weather observation, reporting an overcast ceiling, 10 miles visibility, and a west wind at 12 knots. The flight stated its intention to land and was cleared for a standard range approach, with instructions to report over the range station and when starting the procedure turn.

Shortly after, the flight asked for clearance to descend. With no other traffic in the area, the controller cleared Flight 711 for an approach and to descend whenever it wished. At 2229, the controller transmitted the latest weather: a 500-foot overcast ceiling, 8 miles visibility, and very light drizzle. The flight advised it would make a circling approach to runway 31.

The crew reported, "American 711, over the Omni at 34, proceeding to the field. Approximately two minutes later, an explosion was seen and heard north-northwest of the airport.

**What the investigation found**

The aircraft struck the ground in a muddy, cultivated field at an altitude of 1,250 feet mean sea level, on a heading of 220 degrees magnetic. It had cleared several trees bordering the field, the top of one being 27 feet higher than the initial impact point 200 feet beyond it. This indicated the aircraft was descending at about 1,600 feet per minute. The landing gear was fully retracted and the flaps were extended about 19 degrees.

Examination of the wreckage revealed no evidence of structural failure, fatigue cracking, or malfunctioning controls prior to impact. Both engines were developing appreciable and nearly equal power, which was normal for a Convair circling to land. The aircraft's altimeters were set and indicating correctly.

Air Defense Radar sequence photographs captured the flight's progress. The radar plots showed the aircraft passed slightly north of the Springfield VOR station, then turned left toward the airport. The approved VOR instrument approach from St. Louis required an aircraft to turn right at the VOR, establish an outbound track of 13 degrees, execute a procedure turn, and then follow an inbound track of 193 degrees.

A company witness stated his belief that the approach executed was a safe and reasonable interpretation of the VOR procedure, considering the degree of turn from the airway, the distance involved, and the en route altitude. Conversely, a Civil Aeronautics Administration agent stated the radar track was not consistent with the procedure's requirements. He testified that the full procedure is expected to be completed in instrument conditions to permit a safe descent in a known area and afford the crew time for final cockpit checks. Captain Pripish, who survived but could not remember the accident due to severe injuries, stated his interpretation of the procedure would not permit eliminating the outbound heading and procedure turn if instrument conditions prevailed.

Surviving passengers described the flight as smooth. The "Fasten Seat Belt" sign was on, and the stewardess had checked their belts. Two passengers noted the aircraft descended into the clouds, obscuring ground lights until they broke out below the overcast. A passenger seated in the front aisle heard one of the pilots cry out in an excited, warning voice, "My God, we are going to hit the ground." An instant roar of engine power followed, almost simultaneously with the impact. Ground witnesses who saw the aircraft flying below the clouds toward the airport all believed it was unusually low, though the engine sound appeared normal.

The Board's weather analysis indicated the top of the overcast was 3,000 feet, with a solid base about 500 feet above the surface. The Board believed these conditions likely prevailed at the VOR station, meaning the entire prescribed instrument procedure should have been made. While it was possible the crew established visual contact at the VOR and proceeded visually, the Board considered this not probable at the required altitude.

The investigation noted that the aircraft was flown visually below the overcast for several miles, nearly on the required 193-degree inbound radial, and in a normal configuration for an approach. The pilot's exclamation just before impact indicated the crew was unaware of their low altitude and descent. The Board believed it was probable the pilots were devoting their attention outside the cockpit toward distant airport lights while flying over flat, dark, sparsely lighted terrain in somewhat restricted visibility. The Board noted that such conditions can create a sensory illusion, giving flight crews an erroneous impression of altitude or the illusion that the aircraft is flying horizontally when the nose is actually pitched up or down.

**Probable cause**

The Board determined that the probable cause of this accident was "a descent to the ground while approaching the airport caused by the crew's inattention to their flight instruments and a possible sensory illusion giving them an erroneous impression of the attitude of the aircraft."