Aerospace Systems Avionics subsystems

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  • Avionics subsystems

      • Communications 
      • Probably the first piece of avionics to exist, the ability to communicate from the aircraft to the ground has been crucial to aircraft design since its inception
      • Unmanned air vehicle (UAV) applications need to communicate with the ground without a pilot. This is currently a topic of major interest as efforts are made to integrate UAVs with manned tragic in controlled air space
          • Navigation
          • Navigation is the determination of position and direction (heading/altitude) on or above the surfaces of the earth
          • Accurate navigation is critical to air asafety and as such aircraft have multiple ways of determining position and heading e.g.:
            • Radio navigation system based on marker beacons
            • Inertial navigation system (INS)
            • Satellite navigation system (GPS)
                • Displays
                • Early cockpit display instruments were typically either mechanical e.g. Altitude gauge deflected by changes in atmospheric pressure, or electromechanical, e.g. Engine speed indicator
                • Cathode ray tube (CRT) displays were introduced towards the end of WWII initially driven by radar. Liquid crystal displays (LCDs) were introduced in the early 90s, however it is only recently, e.g. B777 and A380, that the reliability of electronic displays has reached such a level that backup mechanical instruments have been eliminated from the flight deck, leading to a true ‘glass cockpit’
                • Display software is often written in the same way as that for flight control software, as essentially the pilot will follow it. The display systems will take multiple different methods of determining altitude and heading that the aircraft use, and provide them in a safe and easy to use manner to aircrew
                • It is crucial that the pilot has the right information so he has control on the aircraft
                    • Collision-avoidance systems
                    • To supplement air traffic control, most large transport aircraft and many smaller ones, use a Traffic Collision Avoidance System (TCAS), which can detect the location of other nearby aircraft and provide instructions for avoiding a mid-air collision
                    • TCAS is a little box which communicates with other boxes on other planes. If two boxes recognise there may be a collision, a message is sent to the pilot. If the pilot does nothing, the TCAS will take control and make a manoeuvre to avoid the collision - pilots do not like these boxes as they do not have full control
                    • Smaller aircraft may use simpler traffic alerting systems such as TPAS, which are passive (they do not actively interrogate the transponders of other aircraft) and do not provide advisories for conflict resolution
                    • To help avoid collision with terrain, aircraft uses systems such as ground-proximity warning systems (GPWS), often combined with a radar altimeter.
                    • Newer systems use GPS  combined with terrain and obstacle databases to provide a similar alerting for light aircraft
                        • Weather systems
                        • Weather systems such as weather radar and lightning detectors are especially important for aircraft flying at night or in instrument meteorological conditions, where it is not possible for pilots to see the weather ahead. 
                        • Heavy precipitation or lightning activity are both indications of strong convective activity and


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