Man and Machine — Page 278, Lesson 454

I want to walk you through the start of the "Man and Machine" chapter, which is all about how we design the cockpit around the pilot. Let's begin with the cockpit seat itself. The main considerations in designing a cockpit seat are: lumbar support, vibration absorption, long-term comfort, anthropometric data, G-force protection, prevention of what's called 'submarining', and securing the pilot. Let me explain each one. Lumbar support means supporting the lower curve of your spine so you don't get back pain on long flights. Vibration absorption is about damping out the engine and airframe vibrations that would otherwise fatigue you. Long-term comfort is exactly what it sounds like — you might sit in that seat for eight or ten hours. Anthropometric data refers to the measurements of the human body; the seat has to fit a range of pilot sizes from the 5th percentile female to the 95th percentile male. G-force protection means the seat helps you tolerate positive and negative accelerations without blacking out or losing control. Prevention of 'submarining' is a specific term — it means stopping the pilot from sliding forward under the lap belt during a crash or hard landing, which can cause serious injury. And securing the pilot means the harness and seat locks keep you firmly in place during all phases of flight and in turbulence. Now let's move to the hardware side — specifically, displays. When we decide how to present information to you, the basic choice is between a digital display or an analogue display. Even if we're using a cathode ray tube — that's the old-style glass screen — we still have the choice of showing the information digitally or in analogue form. Experiments have shown something very practical. For purely quantitative information — that means numbers you need to read precisely, like the amount of fuel in a tank in kilograms or litres — digital displays give better results. You can read the exact number quickly. But for qualitative or comparison information — for example, is the engine temperature rising or falling, or is my heading changing left or right — an analogue display provides more easily assessed information. Your eye can see the position of a needle and the trend at a glance. There's also a specific warning: if the end point of a display is important, such as on an altimeter where you need to know you're approaching your assigned altitude, then moving tape displays should not be used. A moving tape display is a vertical strip that scrolls numbers past a fixed pointer, and it can make it harder to judge the end point compared to a conventional round dial. The most important requirement in display and control design is standardization. Standardization should allow you, the pilot, to make an easy transfer from one aircraft type to another with minimum training time and expense. It can also prevent accidents caused by transferring procedures between aircraft types — if the fuel shutoff is always in the same place, you don't reach for it and grab the wrong switch. However, total standardization is not possible, and it would inhibit new design technology. But it should certainly be the goal for all similar types within an operating fleet. Now let's look at the conventional analogue standard "T" display. An aircraft using conventional displays will usually have a standard 'T' layout. The most important instrument — the artificial horizon or attitude indicator — is at the centre. The other primary flight instruments — the altimeter, the airspeed indicator, and the direction indicator — are grouped around it. The altimeter is typically to the left of the attitude indicator, the airspeed indicator to the right, and the direction indicator below. That forms the shape of a capital T. That figure shows you the standard 'T' arrangement. So when you step into any conventional cockpit, you know exactly where to look for your primary instruments, and that's the whole point of standardization.