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Proper Approach Airspeed

The concept of proper airspeed control for the approach to a mountain airstrip cannot be over emphasized.

The landing distance will increase by the square of the ratio of the touchdown speed to the normal touchdown speed.


In this example, we use 55 for the actual touchdown speed divided by the normal touchdown speed. This ratio is 1.1 or a 10-percent increase in speed. The landing distance increased by the square of the ratio or 21 percent increase in landing distance.

You might think, that's not too bad. I only need 1,200 feet to land, so what's another 252 feet (1,200 x 1.21 = 1,452)?


Once you start believing, "What's another 252 feet," it displays the beginning of complacency. Or, maybe you decide to add an extra 5 knots for the wife, another 5 knots for the kids and another 5 knots for the dog. In this example, we change the approach speed to 70. The ratio become 1.4, and squaring the ratio means there is a 96-percent increase in landing distance.

Ask yourself, do I want to nearly double my landing distance on a short mountain airstrip? If not, use exact airspeed control.


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