With regard to the Ozark DC-9 accident at Sioux City, and the straight vs. swept wing argument, consider this accident summary:
Feb. 16, 1950 • Douglas DC-3 • Eastern Airlines • Lexington,
Kentucky, U.S. • Injuries: 18 minor or none
During letdown into Lexington, ice accreted on the leading
edges of the aircraft’s wings and on the propeller blades. To
offset the reduced effectiveness of the wings and propellers,
the pilot increased airspeed on his approach. After the aircraft
landed without incident, only the left engine was secured for
ramp loading operations. No action was taken to remove ice
from the aircraft.
When ramp loading was completed, the aircraft took off again.
It stalled shortly after it became airborne, and the pilot was
unable to regain control. The aircraft touched down, rolled
through a gully and came to rest in normal landing attitude.
Damage to the aircraft was substantial.
As I pointed out in another thread, the lift curve with a thin coating of roughness on the leading edge very often overlays the clean wing lift curve, up to a point. The stall will often occur abruptly at an angle of attack several degrees below that of the clean wing. When someone speaks of a wing "handling" any amount of ice, that simply means that they have not had occasion to attempt an angle of attack greater than the contaminated lift curve will allow. However, ANY contamination absolutely guarantees that the wing will not provide the same performance across its intended range of angles of attack. It doesn't matter whether it is straight, swept, slatted, fat or thin...you simply don't know where the lift curve is going to go off a cliff.