So what is the rule?It’s a handy trick that some CFI’s use. In many airplanes the person in the right seat can’t see the numbers on the right side of a conventional airspeed indicator. In most of the airplanes I have instructed in (mostly Cessnas, Cherokees, and Bonanzas), this trick works as a pretty good estimate of the recommended speed on short final. I’d never trust it without verifying it first, however. I have wondered if there is or was an FAA certification rule about it, but I’ve not researched it. The “trick” is rapidly becoming obsolete in this age of glass instruments.
On a conventional “steam gauge” airspeed indicator, when the needle is pointing to the 3 o’clock position, your IAS is approximately what the POH says it should be on short final. It’s handy to know because from the right seat, it’s often the case that the numbers on that area of the gauge can’t be seen because they are blocked by a “lip” around the gauge (or by some other obstruction), but the needle of the gauge — or at least its orientation — can be seen. But like I said, I don’t think it’s the case with every certified airplane. Verify it first!So what is the rule?