An accumulation of ice on the wings of the Arrow Air DC8 may have contributed to the crash that killed 256 people Thursday, according to air-safety experts, who stressed that too little information is available to draw firm conclusions.
Speculation that ice might have been a factor is based on the knowledge that it was drizzling or snowing in sub-freezing temperatures during a refueling stop at Gander, Newfoundland, and that the plane was not de-iced before it attempted to take off.
The plane was on the ground for more than an hour. "It would have been cold when it came in for refueling , and precipitation would freeze almost immediately," an expert said. At takeoff from Gander, the temperature was about 26 degrees Fahrenheit.
It is known that the flight engineer -- third in command in the cockpit -- walked around the aircraft before takeoff for the customary visual inspection to ascertain that everything was in order. Gander, a cold-weather airport, has full de-icing facilities, but their use is at the pilot's option.
Canadian investigators said in Gander yesterday that some crews taking off about the time of the Arrow flight asked for de-icing and that some did not.
Ice can have a dramatic effect on aircraft performance because it disturbs the flow of air over the wing top. Smooth flow is essential to impart "lift" to an airplane so it can fly. A coating of ice would render inaccurate pre-flight calculations about the airspeed necessary to lift off or to fly.
Adding credence to the icing theory is the fact that the plane crashed on its belly, with the rear striking first, and that the wreckage was strewn over a considerable distance, about three-fourths of a mile. That suggests that it never gained much altitude. Had it stalled after beginning to fly, it probably would have nosed into the ground.
Other possible explanations for the plane's behavior are inoperative or "frozen" flight controls, a poorly set control, failure to turn on engine anti-ice equipment or some kind of multiple engine failure on the four-engine McDonnell Douglas DC8. The importance of de-icing was driven home for the airline industry in January 1982 when an Air Florida plane taking off in a heavy snowstorm from National Airport struck the 14th Street Bridge and plunged into the Potomac River, killing 78 people.
Although the plane received de-icing treatment, the National Transportation Safety Board called it "deficient." After being treated, the plane sat in a line awaiting takeoff for 49 minutes, by which time a buildup of ice and snow had recurred.
The Air Florida crew did not use engine anti-ice procedures during ground operations or on takeoff, and investigators discovered that ice had blocked inlets for important engine-monitoring instruments. Although the plane left the ground, it stalled and clipped the bridge because the engines were not developing sufficient power.
In a related matter The San Diego Tribune reported that a mechanic who worked in July on the Arrow Air jet that crashed said it had a history of engine trouble. He said mechanics warned the company not to fly the plane and initially refused to affirm its airworthiness after a repair.
The Federal Aviation Administration checked that report yesterday and found that Arrow had replaced the engine in question in August because of compressor stall problems. That is the jet-engine equivalent of a backfire.