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Asked by: Jason
AFD, clearance, slope, VFR Airspace, General Aviation
What is clearance slope and how can I use that information as a VFR pilot?
on Feb 08, 2012
Please give more context, since there are a number of concepts which could reasonably be described as “clearance slope”. These terms generally mean that there is an inclined plane starting from some location to another through which no obstacles can penetrate. These typically apply to instrument flight and don’t affect VFR pilots.
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on Feb 08, 2012
Here are examples of what I’m asking about:
“Tree, 550 ft Left of center, 59 ft high, 1,900 ft from end, 29:1 clearance slope.””Pole, 400 ft Left of center, 30 ft high, 975 ft from end, 26:1 clearance slope”
What does 29:1 or 26:1 translate to? What are other ways to say the same thing?
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For every 29 feet of horizontal distance, you need to climb 1 foot to clear those obstacles. And that assumes that you start at the departure end of the runway. If you’re climbing out at 75 knots, you need a climb rate of about 160 ft/min.
Still, VFR, you can visually avoid the obstacles even if you can’t outclimb them. It’s more relevant when you’re taking off IFR and can’t see anything.
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on Feb 10, 2012
Yeah you know by the performance charts whether or not you can clear the trees/obstacle. As far as other things like mountains, antennas, and the like you can simply maneuver around them if you don’t wait till the last second. It’s when you cannot see these things that you have to check the old chart on the inside back cover of the instrument approach plates. Remember, if its moving down in the windscreen you will pass over it hopefully with a good margin (assuming you maintain the current situation), if not then you better bank the airplane away from it!
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