Electronic flight instrument system
On the flight deck, the display units are the most obvious parts of an EFIS system, and are the features that lead to the term glass cockpit.
The PFD displays all information critical to flight, including calibrated airspeed, altitude, heading, attitude, vertical speed and yaw.
PFDs also increase situational awareness by alerting the aircrew to unusual or potentially hazardous conditions — for example, low airspeed, high rate of descent — by changing the color or shape of the display or by providing audio alerts.
LCD units generate less heat than CRTs; an advantage in a congested instrument panel.
MFDs are most frequently designed as "chart-centric", where the aircrew can overlay different information over a map or chart.
Examples of MFD overlay information include the aircraft's current route plan, weather information from either on-board radar or lightning detection sensors or ground-based sensors, e.g., NEXRAD, restricted airspace and aircraft traffic.
As with the PFD, the MFD can change the color or shape of the data to alert the aircrew to hazardous situations.
EICAS displays are often designed to mimic traditional round gauges while also supplying digital readouts of the parameters.
Proper care must be taken when designing EICAS to ensure that the aircrew are always provided with the most important information and not overloaded with warnings or alarms.
ECAM is a similar system used by Airbus, which in addition to providing EICAS functions also recommend remedial action.
Like personal computers, flight instrument systems need power-on-self-test facilities and continuous self-monitoring.
Even a fault as far downstream[3] as a jam in, say, the roll mechanism of an ADI triggers a comparator warning.
One channel, the internal, samples the output from its own symbol generator to the display unit and computes, for example, what roll attitude should produce that indication.
In similar fashion, EFIS is programmed to show the glideslope scale and pointer only during an ILS approach.
In the case of an input failure, an electromechanical instrument adds yet another indicator—typically, a bar drops across the erroneous data.
A de-clutter mode activates automatically when circumstances require the pilot's attention for a specific item.
The flexibility afforded by software modifications minimises the costs of responding to new aircraft regulations and equipment.
Should the PFD fail, transfer switching repositions its vital information to the screen normally occupied by the navigation display.
The low cost is possible because of steep drops in the price of sensors and displays, and equipment for experimental aircraft doesn't require expensive Federal Aviation Administration certification.
