American Airlines Flight 320

Investigation

Within two hours of the crash, investigators interviewed flight engineer Warren Cook. He told them he had felt that the flight's approach to the airport was routine and when the aircraft hit the water it was completely unexpected. The investigators had to wait to talk to first officer Frank Hlavacek because of his injuries, but several days later he told them that he had been calling out altimeter readings to Captain DeWitt during the descent in 100 ft increments as they approached the runway. He said that he had barely gotten the words out for 500 ft when the plane struck the river. Even though both pilots were interviewed at different times and at different locations, both pilots stated that the aircraft struck the river just as Hlavacek was saying "five hundred feet".

As soon as weather conditions allowed, investigators began the process of recovering the aircraft wreckage. They recovered 25 percent of the plane by February 5, and 50 percent by the next day. On the day after the crash, crews attempted to use salvage cranes to raise the fuselage of the aircraft out of the river, but they were only briefly successful before the wreckage broke apart and most of it fell back into the water. The tail section was recovered on the evening of February 5, and newspapers reported that the damage to that section hinted that the aircraft may have crashed in a "nose up" position, as though the pilots had noticed at the last minute that they were well short of the runway and tried to climb. Divers were deployed to locate missing sections of the aircraft beneath the surface of the water, but the efforts were hindered by high winds, strong river currents, and low visibility in the water. Some pieces of the plane had been swept away by currents and were found as far away as Northport, Long Island, more than 30 mi away. Each piece of the aircraft that was recovered was identified, tagged, cleaned off, and moved to Hangar 9 of the Marine Air Terminal of LaGuardia Airport. The nose section and cockpit of the plane were recovered late on February 7. The cockpit was in relatively good condition; the spring-wound clock on the instrument panel was still working when the section was recovered from the river.

In response to the accident, on February 9, the FAA increased the minimum visibility requirements for Lockheed Electra landings during poor weather conditions. American Airlines and Eastern Airlines, the two airlines that were flying the Electras at that point, described the restrictions as temporary, likely lasting only a few days. Representatives of Lockheed Aircraft Corporation expressed disappointment in the new changes, but said the company would continue to cooperate with the investigation any way it could. The following day, the Agency reversed course, and said that the two airlines flying the Electra could resume flying with the previous visibility requirements.

Final report

The CAB released a final report on the accident on January 10, 1960. The investigation concluded that the crew had been preoccupied with aspects of the flight and had failed to monitor essential flight instruments during the descent, leading to their descending below their intended glide path. Contributing to the accident were factors that included the crew's limited experience with the aircraft type, an unsafe approach technique where the autopilot was used to or almost to ground level, an incorrect setting of one of the altimeters, and a possible misinterpretation of the altimeter and the rate of descent indicators on the aircraft. It also mentioned the poor weather conditions in the approach area and lack of visual references, causing the crew to misinterpret their height and altitude. The board was critical of the airline's lack of a comprehensive simulator training program for its pilots flying the Electra, calling the accident potentially avoidable if such a program had been in place. It also called for new regulations by the FAA to require the installation of a flight data recorder in all large turbine-engine aircraft used in air transportation.

Investigators recovered over 90 percent of the primary structural components of the aircraft and most of the system's components. They found that at the moment of impact, the flaps were correctly set for the approach and that the landing gear was extended. The propeller blade angles were relatively uniform and consistent with the power readings displayed on the instruments recovered from the aircraft, and matched the power levels that the pilots said they were using during the approach. Neither of the two vertical speed indicator mechanisms were recovered. Both altimeters were recovered, but since the diaphragms of both had been overstressed due to submersion, it was impossible to determine if either of the altimeters had been displaying accurate information before the crash.

Investigators obtained all of the maintenance and pilot complaint records of all operators, civil and military, of the type of altimeter used in the flight. They did not find any incident that involved the failure of more than one of the altimeters at a time, and after reviewing the possibility of a simultaneous failure of both altimeters, the CAB concluded that it would involve such an extreme mathematical improbability that it chose to reject the theory of a simultaneous failure, and it rejected parts of the testimony of the surviving crew members. It concluded that after consideration of all possible scenarios, a failure of just one of the altimeters was also unlikely to have occurred. Based on eyewitness testimony and the analysis of the impact, the CAB concluded that it was likely that one or more of the pilots had misread the altimeter due to their unfamiliarity with the new style. It also said there was a possibility that in addition, the pilots had misread the vertical speed indicators, which used a different scale than what had been used in older aircraft and well as in the training that the captain had received.

The CAB concluded that all of the required airport, boundary, and runway lights were on and functioning at the time of the accident. However, because the lights were slanted upward at between three and five degrees, and because of a dike located between the end of runway 22 and the water, the CAB concluded that they would not have been visible to the crew because of the aircraft's premature descent below the cloud level.

The CAB's conclusions were criticized by the president of the Air Line Pilots Association, who called the report "grossly inaccurate in a number of respects". He said the report failed to reasonably explain the cause of the accident, and it assumed factors that had not been established by fact. He said that all of the pilots at American Airlines were united in their criticism of the report, saying it "slandered and wrongfully accused" crew members of the plane, and was aimed at "conveniently writing the accident off the books" rather than accurately determining a cause. He said that in the association's judgement, the crash was the result of marginal weather conditions and inadequate approach and lighting aids at the airport. First officer Frank Hlavacek said he was "furious" over the CAB report, saying the board tried to take the easy way out by blaming a dead captain. He said he hoped that American Airlines would protest the report.