The cockpits of old – with a bewildering multiplicity of levers, buttons and analogue displays – are long gone, phased out beginning in the 1980s in favour of digitised systems known as EFIS, comprising a bewildering multiplicity of liquid-crystal displays along with and joysticks and soft keys to manipulate them.
The EFIS Revolution in Aerial Navigation
This revolution was essentially threefold. First was cockpit design, of course. Second, it changed the way pilots and co-pilots worked as well as interacted with each other. But above all, imagine the huge difference between, for example, an analogue counter and an electronic screen which offers more information and at the same time makes it much more visually intuitive, easy to interpret, and with a greatly reduced margin of error.
The transition from analogue to digital was gradual, incorporating different elements throughout the years. One of the first to be digitised was the attitude indicator (ADI), monitoring the aircraft’s orientation with respect to the horizon, then later replaced by a screen called the EADI ( ) which besides the attitude also the flight director, and can also sometimes present additional data: radio altimeter, flight mode annunciator, relative speed scale.
The Advent of the Horizontal Situation Indicator (HSI)
The second is a combination of flight instruments which provide information on the aircraft’s position with respect to different navigation points. Today the old HSI is called EHSI (tjust adding "electronic" to the name), and like the EADI, it can incorporate other functions (speed over ground, DME or distance measuring equipment, the graphical representation of the flight plan...).
The 'Glass Cockpit'
That’s what pilots and others dub this digitalised cockpit. Of course even the most sophisticated EFIS has a backup system completely isolated from it in case something goes wrong, and to ensure proper navigation. Its main components are screens providing data to the crew about the various elements and navigation systems. If above we talked about the EADI and the EHSI, in the glass cockpits the screens that appear are more complete (and complex), and are as follows:
- The PFD (Primary Flight Display) incorporates the main flight instruments on a single screen. It’s easy to imagine the difference in terms of information processing and comfort compared to the cockpits of, for example, the 1970s. In addition to the attitude indicator (ADI), here we’ll find speedometer, variometer, altimeter, heading indicator and indicator of drift, along with other readouts including radio altimeter and navigation frequencies.
- The MFD (Multi-function Flight Display) or ND (Navigation Display) is an evolution of the EHSI that can incorporate, in addition to the horizontal situation indicator, the GS (Ground Speed) or ground speed, DME, graphic representation flight plan, weather radar and other functions.
Beyond all this, some aircraft also have a screen called ECAM (Electronic Centralised Aircraft Monitor), which monitors the status of the aircraft systems as well as that of the engines.
The Control Panel
This essentially comprises the various controls and buttons which regulate the screens system, and also includes:
This device interprets the settings made on the control panel. It receives the information sent to it by the different systems and sensors of the aircraft, considers the adjustments made in the control panel (that is, how this information is going to be represented) and sends it to the screens.
Typically the smallest aircraft have only one but the largest can have up to three symbols generators in their EFIS. One sends information to the pilot's display system, another to the co-pilots, and the third is a backup generator, ready in case any of the other information systems fail.
There are three additional functions of the symbols generator: monitoring the screens to verify their operation; validating the data (that is, verifying that the information coming from the aircraft systems is correct); and comparing this with the data provided by the other symbols generators (so that if it finds data that do not match, it will inform the crew).