Radars include airborne early warning (AEW), anti-submarine warfare (ASW), and even weather radar (Arinc 708) and ground tracking/proximity radar. The military uses radar in fast jets to help pilots fly at low levels. While the civil market has had weather radar for a while, there are strict rules about using it to navigate the aircraft. Sonar Dipping sonar fitted to a range of military helicopters allows the helicopter to protect shipping assets from submarines or surface threats. Maritime support aircraft can drop active and passive sonar devices (sonobuoys) and these are also used to determine the location of enemy submarines. Electro-optics Electro-optic systems include devices such as the head-up display (HUD), forward looking infrared (FLIR), infrared search and track and other passive infrared devices (Passive infrared sensor). These are all used to provide imagery and information to the flight crew. This imagery is used for everything from search and rescue to navigational aids and target acquisition. ESM/DAS Electronic support measures and defensive aids systems are used extensively to gather information about threats or possible threats. They can be used to launch devices (in some cases automatically) to counter direct threats against the aircraft. They are also used to determine the state of a threat and identify it. Aircraft networks The avionics systems in military, commercial and advanced models of civilian aircraft are interconnected using an avionics databus. Common avionics databus protocols, with their primary application, include: Aircraft Data Network (ADN): Ethernet derivative for Commercial Aircraft Avionics Full-Duplex Switched Ethernet (AFDX): Specific implementation of ARINC 664 (ADN) for Commercial Aircraft ARINC 429: Generic Medium-Speed Data Sharing for Private and Commercial Aircraft ARINC 664: See ADN above ARINC 629: Commercial Aircraft (Boeing 777) ARINC 708: Weather Radar for Commercial Aircraft ARINC 717: Flight Data Recorder for Commercial Aircraft ARINC 825: CAN bus for commercial aircraft (for example Boeing 787 and Airbus A350) Commercial Standard Digital Bus IEEE 1394b: Military Aircraft MIL-STD-1553: Military Aircraft MIL-STD-1760: Military Aircraft TTP – Time-Triggered Protocol: Boeing 787, Airbus A380, Fly-By-Wire Actuation Platforms from Parker Aerospace See also Astrionics, similar, for spacecraft ACARS Acronyms and abbreviations in avionics ARINC Avionics software DO-178C Emergency locator beacon Emergency position-indicating radiobeacon station Flight recorder Integrated modular avionics Notes Further reading Avionics: Development and Implementation by Cary R. Spitzer (Hardcover – December 15, 2006) Principles of Avionics, 4th Edition by Albert Helfrick, Len Buckwalter, and Avionics Communications Inc. (Paperback – July 1,