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The captain's and the first officer's static selectors were found in normal positions; both were guarded and operable. All connections to the static manifold and from the manifold to the static selectors were proper. The flex-hose assemblies from the static selector valves were properly connected with the aircraft piping.
Simulated icing tests were arranged by the Board and run subsequent to the accident using a B-29 Air Force icing tanker, a test Electra, and a chase Electra for photographic purposes. Flight tests duplicated airplane speeds, configurations, and outside air temperatures, which existed during the final approach of Flight 320 to La Guardia. The tests showed that ice buildup on the fuselage was confined to the forward section and did not approach the area of the static ports, even when the test airplane was yawed drastically. Ground tests on an Electra fuselage section which included the static ports were run to simulate careless washing, splashing of a fluid solvent on a cold fuselage, and a leak in the nose wheel well. These tests did not induce any significant instrument errors. Under the most drastic test, that of a suction induced by twin hemispheres in the vicinity of both static ports on opposite sides of the aircraft, the altimeter error was approximately 175 feet at an airspeed of 135 knots. It is important to note that this venturi effect was man-made and, so far as is known, is not reproducible naturally.
Maintenance
The maintenance records for American Airlines, N 6101A, were reviewed and it was found that they were complete and showed that the required maintenance had been performed, that the complaint entries of an airworthiness nature were corrected, and that they were properly signed off. THe aircraft had been flown a total of approximately 302 hours.
Training
Captain DeWitt's Electra ground school training was completed on December 4, 1958, at Fort Worth, Texas. The course consisted of 84:30 hours of instruction, of which 68:30 hours were devoted to aircraft systems and 16 hours to operations and performance.
An Electra simulator was not available but Captain DeWitt did receive training in a Link trainer equipped with the flight director system similar to that installed in the Electra but not having drum-type altimeters or instantaneous vertical speed indicators. According to American Airlines' records, Captain DeWitt, during December 1958, completed five hours of Link training utilizing the flight director system.
Captain DeWitt's flight training in Electras commenced December 11, 1958. This consisted of day and night takeoffs and landings, airwork, autopilot operation, emergency procedures, and systems operation. On December 15, 1958, Captain DeWitt took his first type rating flight check with an FAA inspector after 8:07 hours of Electra training. This check consisted of required maneuvers and navigational problems, holding at a fix, 2-engine out ILS approaches, crosswind takeoffs and landings, and circling approaches simulating 400 feet and one mile visibility. Captain DeWitt failed the portion of the check which required him to perform an ILS approach simulating a 200-foot ceiling and one-half mile visibility with engines Nos. 1 and 2 reduced to zero thrust. After additional practice, Captain DeWitt on December 16, 1958, with a total of 11:59 hours of Electra training, successfully passed his type rating check and an instrument check.
