One of the most-often busted federal aviation regulations is VFR cloud clearances. That's because pilots often have a hard time judging how close they really are to clouds. We all know that in Class E airspace below 10,000 feet msl we need at least 3 statute miles of visibility and must remain 500 feet below, 1,000 feet above and 2,000 feet horizontally from clouds.
How can we know if we're really 2,000 feet from a cloud, or perhaps closer, say, 1,000 feet instead? The answer is you can't know for certain how close you are to a cloud because of the visual illusions cloud size can cause. But there are some tricks you can use to approximate your distance.
The first is to look at the area on the ground that the cloud is over. Find a prominent landmark and refer to your sectional chart to determine how far away you are. If you can't tell exactly what point the cloud is over, look for the shadow the cloud is casting on the ground to get an approximate location.
Another way to judge lateral cloud separation is to think not in terms of distance but time. In a typical light trainer traveling at 110 knots, for example, it will take you 10 seconds to travel 2,000 feet. If you believe you would penetrate a cloud if you continued flying for another 10 seconds, you're close enough.
Really, there's no way to tell exactly how far you are from clouds, and unless you're really close — or penetrate a cloud — you won't get a call from your friendly local FAA rep. But you shouldn't use the lame defense of "I didn't know" to purposely fly too close to clouds. There easily could be IFR traffic transitioning a cloud that won't see you until it's too late. To avoid any nasty surprises, give clouds a wider berth than necessary.
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