Man and Machine — Page 283, Lesson 459

I want to walk you through a new topic now: how information is presented to pilots in the cockpit, and then specifically how engine instruments are laid out. Let's start with an impressive example of information presentation: the ILS, or Instrument Landing System, displayed on the windscreen. Here, information from the ILS equipment is processed by a computer to show a constantly changing picture of runway data as the procedure is flown. The key advantage is that there is no requirement for a change of eye focus for the pilot — you don't have to look down at an instrument and then back up at the outside world. However, even though your eyes don't need to refocus, there is still the need for the transfer of attention. You have to consciously shift your mental focus between the windscreen display and other tasks. Now, another method of presenting information is voice presentation — using a recorded voice message. This technique has been developed in some experimental aircraft, but it has not been adopted for normal commercial aircraft. Why? Because the voice has been found distracting, and after a time it tends to be ignored — pilots tune it out. Voice information has only found a major use in two specific safety systems: the Ground Proximity Warning System, or GPWS, and the Traffic Collision Avoidance System, or TCAS. Those are the exceptions where a voice warning is standard. Let's move on to hardware — specifically, engine instruments. The information from engine instruments is just as relevant to the pilot as that from flight instruments, so it's important to ensure these instruments are not only easy to read but, as far as possible, unambiguous. The layout principle is this: the instruments in each column should all relate to only one engine, and the instruments in each row should show the same information — for example, RPM, TIT (Turbine Inlet Temperature), and torque. This is shown in Figure 14.5. This arrangement enables the operator to spot immediately any discrepancy on any instrument and identify the engine concerned in the minimum time. In an ideal layout, the columns of instruments will be aligned with the appropriate power lever — so all No 1 engine instruments are above No 1 power lever, and so on. Another aid to rapid identification of a problem is to rotate the instruments so that all needles are aligned, either vertically or horizontally, in normal cruise flight. That way, if one needle is out of alignment, it stands out instantly. Now, beyond the primary engine instruments, a number of instruments are required to display secondary information. There are a number of different possible configurations, two of which are shown in Figure 14.6. There are advantages and disadvantages to each layout. The ideal layout could have a bank of instruments below the primary instruments, but cockpit space may not allow this. In Figure 14.6, the layout at A might be preferable, but this type of layout could only be used with an even-engined aircraft — it could not be used with a three-engined aeroplane. Since the purpose of these secondary instruments is to warn of possible problems and guide the pilot to the correct identification of the engine concerned, there is a great deal of research needed to identify the best layout for each aircraft type.