Using a calculator, an E-6B computer or even a ruler on a performance chart can simplify some of our number crunching. But when they aren’t available, a few simple rules of thumb can make the difference.

By Joseph E. (Jeb) Burnside

Playing the numbers game—striving to nail airspeeds, fuel consumption, ETAs, and takeoff and landing distances, can be one of the more satisfying parts of flying. For example, it’s gratifying to know we can hold 120 KIAS and the glideslope all the way to decision height and then slide the mains onto the runway. But sometimes, we just want to go fly without all the hassle. Sure, there must be sufficient fuel in the tanks and we still have to have something in the way of a plan before firewalling the throttle, but sometimes we can get by without a full-blown written flight plan by using some…