12-06-2012, 05:02 PM
Seminar on Autopilots and Avionics
Autopilots and Avionics.doc (Size: 56.5 KB / Downloads: 58)
Automatic pilots, or autopilots, are devices for controlling spacecraft,aircraft, watercraft, missiles and vehicles without constant human intervention. Most people associate autopilots with aircraft, so that's what we'll emphasize in this article. The same principles, however, apply to autopilots that control any kind of vessel.
Although there is great diversity in autopilot systems, most can be classified according to the number of parts, or surfaces, they control. To understand this discussion, it helps to be familiar with the three basic control surfaces that affect an airplane's attitude. The first are the elevators, which are devices on the tail of a plane that control pitch (the swaying of an aircraft around a horizontal axis perpendicular to the direction of motion). The rudder is also located on the tail of a plane. When the rudder is tilted to starboard (right), the aircraft yaws -- twists on a vertical axis -- in that direction. When the rudder is tilted to port (left), the craft yaws in the opposite direction. Finally, ailerons on the rear edge of each wing roll the plane from side to side.
Autopilot Parts
The heart of a modern automatic flight control system is a computerwith several high-speed processors. To gather the intelligence required to control theplane, the processors communicate with sensors located on the major control surfaces. They can also collect data from other airplane systems and equipment.
Autopilot Control Systems
An autopilot is an example of acontrol system. Control systems apply an action based on a measurement and almost always have an impact on the value they are measuring.
Autopilot Failure
Autopilots can and do fail. A common problem is some kind of servo failure, either because of a bad motor or a bad connection. A position sensor can also fail, resulting in a loss of input data to the autopilot computer. Fortunately, autopilots for manned aircraft are designed as a failsafe -- that is, no failure in the automatic pilot can prevent effective employment of manual override. To override the autopilot, a crew member simply has to disengage the system, either by flipping a power switch or, if that doesn't work, by pulling the autopilot circuit breaker.
Modern Autopilot Systems
Many modern autopilots can receive data from a Global Positioning System (GPS) receiver installed on the aircraft. A GPS receiver can determine aplane's position in space by calculating its distance from three or more satellites in the GPS network. Armed with such positioning information, an autopilot can do more than keep a plane straight and level -- it can execute a flight plan.