A flight director is a tool a pilot can use to compute a trajectory and stay on path during a flight. It tells the pilot how to adjust pitch and bank to keep an aircraft in position to complete a planned itinerary. Flight directors can work with an autopilot or provide feedback to a pilot handling her own aircraft, and come in a variety of styles, depending on the manufacturer. Many flight simulators also have a flight director available for people who want to use it.
This device works with the attitude indicator, which measures the pitch and bank of the aircraft, projecting it against an artificial horizon so pilots know where they are in relation to the earth. The flight director takes planned information about the route and tells the pilot when to bank the plane right or left, and when to raise the nose up or down, to keep the plane on track. It provides visual cues on the attitude indicator to help the pilot adjust the path of the plane's flight.
When the plane is on course, the cross hairs of the flight director will be centered on the attitude indicator. If the plane needs to bank, the vertical bar will move, telling the pilot he needs to adjust the course, and the device will also provide information about how many degrees to bank. Once the plane is settled, the bar will move back to the center. Likewise, the horizontal bar, indicating pitch, can also move to tell the pilot to move the nose of the aircraft up or down.
The flight director is one among a large number of tools pilots can use to navigate more safely and reliably. People receive training in how to use these tools when they learn to fly, and can get in-depth training on how to use instruments if they want to receive an instrument flight rating, allowing them to fly in more places and in a wider variety of conditions. Like other components of the navigation system, technicians need to periodically inspect it to make sure it is computing and displaying data correctly, to prevent accidents.
If a plane does not have a flight director, people can install one. The length of time required for installation varies, depending on the aircraft, and may be part of a cockpit overhaul, where people replace multiple instruments and controls to bring the cockpit up to date.