Ergonomy — Page 9, Lesson 13

Let's start with the word "ergonomy" itself. Ergonomy, also known as human engineering, is the science of the relationships between people and machines. In plain terms, it's about designing equipment so it interacts smoothly with the human body and human actions. In aviation, this means shaping and positioning controls, levers, and knobs so they're easy to operate and unlikely to cause an incorrect selection. For instruments, it means designing them so they're unlikely to be misread, and placing them in a layout that makes the information easy and correct to interpret. Over time, standard layouts came to be adopted for exactly this reason. Now, let's look at how instruments were historically arranged. The "flying" instruments—the ones that covered the handling of the aircraft—were arranged in what's called the "basic six" layout. These six instruments are the airspeed indicator, the gyro horizon, the vertical speed indicator, the altimeter, the course indicator, and the turn and slip indicator. Other instruments, though, tended to be scattered around the cockpit in whatever positions were most convenient for the designer and manufacturer—seldom to suit the needs of the pilot. That's a key point: the basic six was for flying, but everything else was placed for the builder's convenience, not the pilot's. Since the introduction of the basic six, developments in aircraft instruments and operations led to the introduction of the "basic T." That's the next standard layout, and it's shown in Figure 1.8. The basic T arranges the primary flight instruments in a T-shaped pattern, which became the modern standard. Now let's talk about how instruments present information. Presentations can be in analogue or digital form. Analogue is typically a pointer on a dial, whereas digital is a row of numbers. Look at the two types of altimeter display: Figure 1.10 shows an analogue altimeter, and Figure 1.11 shows a combined digital-analogue altimeter. With the three-pointer analogue system, the altitude information—say, 24,020 feet—is harder to absorb at a single glance than with the digital display. The digital numbers are much easier to read. However, note that one pointer still remains in the design of the mainly-digital presentation. Why? Because the human eye and brain cannot easily interpret rate information from moving numbers. While the altimeter is primarily designed to show altitude, with a separate instrument—the vertical speed indicator—to show rate of change of altitude, pilots pick up a lot of secondary information about vertical rate from the angular rate of the altimeter pointer. That's why the pointer is kept: it gives that rate cue that numbers can't. Finally, let's consider electronic displays. Historically, instruments have been located on instrument panels, though this is now changing with modern electronic displays. Compare the traditional layout in Figure 1.12 with the modern electronic, or "glass," layout in Figures 1.13 and 1.14. That's the shift from analogue dials to integrated electronic screens.