Safety Board Rules Out Terrorism, Looks To Wing Icing
OTTAWA (AP) _ The Canadian Aviation Safety Board has ruled out terrorism in December’s crash of an U.S. military charter and is looking more closely at icing on the wings as a possible cause, the panel’s head said.
″There are many pieces of the puzzle in place now - some pieces missing,″ Chairman Bernard Deschenes told reporters Wednesday after seven days of public hearings came to an end.
Deschenes said it was important to ″clear the air″ by noting that intensive investigation found no evidence that an explosion - whether terrorist or accidental - caused the Dec. 12 crash of the Arrow Air DC-8.
There were eight crew members and 248 U.S. soldiers on the plane, which crashed just after takeoff from a refueling stop in Gander, Newfoundland. All aboard were killed.
The safety board could take another 12 months before issuing its final report, which is likely to identify a series of likely contributing causes, Deschenes said.
Among the possibilities, besides icing, are pilot error, engine malfunction and structural failure.
One of the final witnesses on Wednesday was a DC-8 expert who said ice on the wings is the only reasonable explanation for the crash.
Ralph Brumby, who works for McDonnell Douglas Corp., the plane’s manufacturer, said any contamination on a wing’s forward edge greatly decreases lift and increases drag.
″A very small amount of roughness, as little as medium-coarse sandpaper, will increase the stall speed by as much as 20 to 30 percent,″ he said.
Freezing drizzle was falling when the plane bringing U.S. servicemen home from the Middle East landed in Gander, but no witnesses saw ice on the DC-8′s wings.
Brumby said he and other McDonnell Douglas specialists looked into many other suggested causes for the crash.
″I haven’t found (another) reasonable explanation that will develop the flight path″ actually recorded in the plane that crashed, Brumby said.
The flight data recorder recovered from the Arrow Air wreckage showed a takeoff remarkably similar to other occasions in which ice or snow on the wings were blamed for crashes on takeoff, he said.
The plane apparently reached an adequate takeoff speed, but had trouble lifting off and stalled at a speed of about 160 knots, Brumby said.
Under the conditions that morning, the normal stall speed for the plane would be 138 knots, he said.
The important factor in determining ice’s effects is the roughness created on the plane’s leading edge, not the weight of the ice, Brumby said.
″The kind of roughness that we think would cause this kind of stall is four-hundredths of an inch,″ he said.
The plane began its flight in Cairo, Egypt, with fuel stops in Cologne, West Germany, and Gander on the way to Fort Campbell, Ky., where the troops from the 101st Airborne Division were based.
After takeoff from Gander, the plane banked to the right and veered in that direction, losing altitude until it smashed into a rocky hillside at the side of Gander Lake.