Poets perceive a feline quality in fog. Carl Sandburg wrote that it “comes on little cat feet.” Pilots have reason to view fog with considerably less affection, so those who happen not to be cat people may well agree with all that feline imagery. The stuff is silent, opportunistic, and treacherous.
The essential problem with fog is one of perspective—literally. When you look down from above (or up from below), light only has to penetrate a few hundred feet of obscuration. In a more nearly horizontal plane, the murk goes on indefinitely. This is why you might be able to see the moon but not the other side of the field, and why the runway lights that are so clear while you’re above the deck blur to a milky glow on short final.
The resulting complications are exactly what you’d expect: Deprived of visual references, pilots either lose control entirely or risk running into something they can’t see. Neither outcome is good. In airplanes, accidents resulting from fog penetration are fatal nearly three-quarters of the time. Helicopters benefit—somewhat—from their slower approach speeds; in them, the figure is 60 percent. It’s worth remembering that even the airlines with all their automation aren’t allowed to attempt an approach if surface visibility is below the prescribed minimum.
As with other types of VFR into IMC—and in GA, even IFR flights land visually—the best remedy is avoidance. Pay close attention to temperature/dew-point spreads before taking off on those beautiful autumn evenings. If they start closing in, land where the visibility is still good. Change your plans if necessary. In a pinch, even landing off the airport beats crashing onto it. On foggy mornings, don’t assume you can hold things together long enough to climb out on top. Plenty of others paid for that mistake with their lives and those of their passengers. Unless you’re a sharp instrument pilot with an active clearance—and aren’t fazed by the prospect of being unable to get back in if something goes wrong—resign yourself to staying put until it lifts, and the cat pulls back its claws.
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