built up on the wings, and this had contributed largely to the accident. When attempting to find out why ice was present on the wings of the jet, the board determined that the airplane had been properly cleared of ice and snow during the two deicing procedures at the gate. However, about 35 minutes elapsed between the second time that the aircraft was deiced and the initiation of takeoff during which the airplane was exposed to continuing precipitation in below-freezing temperatures. The NTSB was unable to determine how much ice had built up on the wings following the second deicing, but considered it to be highly likely that "some contamination occurred in the 35 minutes following the second deicing and that this accumulation led to this accident." "The Safety Board views the evidence as conclusive that the primary factor in this accident was the reduced performance of the wing due to ice contamination. Therefore, the Safety Board evaluated the extent to which the decisions of, and procedures used by, the flight crew could have contributed to the accident," read the final report. Although, when the cockpit was examined, the engine anti-ice switch was found in the 'OFF' position, further investigations found that even slight pressure could move the switch, and the NTSB ruled this out as a contributing factor in the crash. Following the accident, USAir sent out a maintenance directive ordering engine anti-ice switches to be changed on F28s so they would lock into a selected position. Investigators found that a flaw in the design of the F28's wings made them extremely vulnerable to ice buildup. Because of the angle of the wings, even a very small amount of ice could have devastating effects. When the NTSB, in collaboration with Fokker, investigated the effect ice can have on an aircraft, they found that ice particles as small as of a density of one particle per square centimeter can cause a loss of lift over 20%. A document written by Fokker before the accident detailed the effect of ice on the wing of an F28 warned that an "uncontrollable roll" would begin even with a small amount of ice on the wings. Errors by the flight crew The report found that the flight crew was aware that the poor weather was likely to cause ice buildup, but neither of them took any action to check the condition of the wing