Avionics Systems

Today’s avionics include sensors, radio communications equipment, computers, and control and naviga­tion systems. They also include the displays in the cockpit.

The job of sensors is to collect information. Sensors on the outside of an aircraft collect information about its speed and height. Other sensors in the engines monitor temperature, pressure, and speed. Yet others measure tire pressure. Sensors inside the plane monitor the air pressure and temperature. Radar in an airplane’s nose searches the sky ahead for storms.

Radio equipment lets the crew talk to air traffic controllers on the ground. Radios are also able to receive signals from navigation beacons on the ground and some­times from satellites in space. Devices called transponders send out radio signals that identify each plane to air traffic controllers. Military aircraft have even more avionics for their weapons and defense systems.

Computers and other electronic sys­tems process all the information arriving from the sensors. A huge amount of information floods into an aircraft’s
cockpit. The plane’s avionics help cut it down to a level that pilots can manage. Displays show the information pilots need on screens and other instruments.

It is possible that an airliner will be struck by lightning one or more times in a year. A lightning bolt produces millions of volts, and avionics can be put out of action by just a few volts too many. When lightning strikes an airplane, however, it flows around the plane’s metal body. It does not get inside the plane, and so the avionics are safe. The crew and passengers are protected from lightning in the same way.

Some parts of a plane’s body are now being built from light materials, such as carbon fiber, instead of metal. The new materials are used because they are lighter and stronger than most metals, but they do not keep lightning out in the way that metal does. One way to protect the delicate avionics in these aircraft is to cover the plastic or carbon fiber parts of the body with a thin metal mesh. If lightning hits the airplane, the metal layer stops it from reaching the computers and electronics inside.

Control systems enable the crew to control the aircraft. Some control systems, such as the autopilot, are auto­matic: They work by themselves. Others are manual and are operated by the crew. Actuators, for example, are an air­craft’s mechanical muscles. They move parts of the plane, such as the rudder in the tail, the moving parts of the wings, and the landing gear.