Precise control of an airplane’s power is not that big a deal, that is, unless you want to fly precisely. In that case, it’s an absolutely critical part of the equation. Unless you control your ship’s power very accurately, you can’t nail the numbers, and nailing the numbers is the key to nailing the performance. And that matters a lot on everything from check rides to short field arrivals. If you’re 15 knots fast on base going into a short field, you’re in trouble already.
Unfortunately, it can be hard to accurately control the power in many airplanes simply because of the way the throttle control is implemented in the cockpit. Ask for a little throttle in many, and you get a lot of throttle instead. Ask for even less and you often wind up getting none at all. Part of it is in the design of many throttle systems (lever, linkage and cabling), as there’s simply too much slop built into the controls. Part of it is in the whole need for mechanical advantage. Put a long lever on anything and you get great power and limited control.
