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TCAS Display

Collision Avoidance Systems, ADS-B

Modern aircraft have a number of systems to their disposal to enhance flight safety. The common term you will hear is aircraft collision avoidance systems. These systems range from radar, TCAS, portable CAS, terrain awareness system (TAWS), ground proximity warning system (GPWS), synthetic vision in EFIS and the obstacle collision avoidance system.

TCAS or Traffic Collision Avoidance System interrogate other transponders and process these replies from other aircraft enabling them to show these on the PFD, MFD displays or a special iVSI indicator.
Some even issue aural warnings to the pilot helping him to avoid a potential midair collision or even flight into terrain.

For the experimental homebuilt aircraft pilot these are usually quite expensive systems, except for the portable CAS and the good old see and be seen system (which has obvious flaws). New ADS-B In solutions nowadays offers a receiver with connection to a mobile device as weather/ traffic display.

Automatic Dependent Surveillance-Broadcast

There are two components to this system: an OUT and an IN. With ADS-B Out an aircraft is equipped with a suitable transponder at 1090 MHz and certified GPS receiver and the aircraft can transmit its GPS position, altitude and more. This OUT system can use also another frequency at 978 MHz to relieve congestion. The FAA would like to see 1090 MHz exclusively used above 18000 ft. It requires no input from you, but needs integration with other aircraft systems like a GPS receiver for its position and a transponder for transmissions.

ADS-B In receives traffic information at two frequencies from nearby ADS-B Out aircraft, when triggered from ground station transmission, or your own ADS-B transponder. When in proximity to a ground station, some ADS-B devices will also receive FIS-B weather, NOTAMs, and TFR information when the app you use supports it.


Weather information (FIS-B) is broadcast from ground towers on 978 MHz with service distances up to 250 NM, should you want to know that. Be aware that in Europe this service is still not implemented. ADS-B weather transmits the following information: radar imagery, lightning, METARs, TAFs, PIREPs, NOTAMs, AIRMETs/SIGMETs, cloud tops, turbulence and winds aloft, freezing level and special use airspace status. Satellite imagery is currently not displayed.

ADS-B Traffic Overview with ADS-B In solution in the aircraft
Equipment Onboard:Visible Traffic:
No ADS-B OutOnly the ADS-B Out equipped traffic
No ADS-B Out, but nearby ADS-Out equipped aircraftAll traffic visible within 30 nm from the ADS-B Out equipped aircraft
With ADS-B Out transponder on-boardAll traffic visible within 30 nm from your aircraft

As more and more aircraft will be outfitted with ADS-B Out, in the end your traffic view should be well over 99%.


The received data also encompasses of weather reports and radar through FIS-B, but at the moment for the US only. As said, FIS-B can also contain information like temporary flight restrictions (TFR) and NOTAMs to aircraft with UAT (USA only). With an external display (either standalone, Wifi connected EFB device or an EFIS) traffic can be shown to the pilot.

Flying with ADS-B increases the pilots situational awareness of traffic if they have an EFB device paired with an ADS-B In solution. This way its possible to see any conflicting traffic around them. For air traffic control one of the advantages are a more efficient traffic flow, reducing delays and wait time in holdings for airliners.

Satellite ADS-B

By using low Earth orbit (LEO) satellites (Iridium) is it possible to track aircraft over areas where previously radar coverage or ADS-B towers are unable to provide service. As such, ADS-B is expected to replace worldwide radar as time goes by and aircraft suddenly disappearing forever will be a thing of the past. Aircraft will probably need a top and bottom antenna to receive ground stations and satellites at the same time.

ADS-B 2020

ADS-B NextGen

Automatic Dependent Surveillance-Broadcast (or ADS-B) is an essential part of the US Next Generation Air Transportation System (NextGen) and mandatory in the USA as of 2020. The FAA has published rules (§91.225 and §91.227) requiring ADS-B out in class A, B, and C for all aircraft (also not above the shelves of those air spaces and within the 30 nm mode C veil) and in class E above 10000 ft but not below 2500 ft AGL.

Detailed information by Paul Bertorelli of Avweb in their "So You Blew Off ADS B Now What?" video. The Federal Aviation Administration also has a web page on their site explaining it all: ADS-B Airspace.

Remember that it will be up to you to check that your ADS-B solution is operating properly as part of the pre-flight action, general aviation operators are exempt from this rule. You can use the FAA ADS-B Service Availability Prediction Tool (SAPT) for that.


Well, then you are limited to under 10000 ft, no entry into class A, B or C, not within the Mode C veil and you do not fly above class B or C airspaces. Basically you are an anonymous blip on the radar screen with altitude reporting. With ADS-B your aircraft ID and flight track (GPS precision) are recorded for the public to see.

No Electrical System?

If you are flying with a non-electrical system airplane then you are exempt from an ADS-B Out solution.


The situation in Europe is somewhat difficult as you can imagine, most have ADS-B as a requirement now. So many countries so many opinions and EASA is hard at work with their SERA, Standardized European Rules of the Air. Meanwhile AOPA France held a presentation about ADS-B and if it was important to GA. In a nutshell: it does not matter, we need to equip our aircraft sooner or later. Read more in the next link: AOPA France ADS-B

New Zealand 2022

NZ requires aircraft to carry ADS-B operating in transponder mandatory airspace above flight level 245 from December 31, 2018. NZ CAA is proposing to mandate ADS-B OUT in all transponder mandatory controlled airspace from December 31, 2021. Note that rules for the performance standards for all existing and new ADS-B OUT systems apply from 20 July 2018. For more information about the ADS-B implementation details, go to the website ADS-B, check your visibility.

Other countries are implementing ADS-B too, so do check for any regulations we might have missed.

Flight Plans

For the ICAO flight plan you need to indicate which type of ADS-B you have. There are four possibilities: B1, B2, U1 and U2.

  • B1 - ADS-B on 1090 MHz out
  • B2 - ADS-B on 1090 MHz out / in
  • U1 - ADS-B on 978 MHz UAT out
  • U2 - ADS-B on 978 MHz UAT out / in

Check your aircraft manuals to verify which type you have. ATC is only interested in the fact that you can transmit ADS-B, so the B1 or the U1 should suffice. Within ForeFlight you will find these codes under the Aircraft tab then scroll down to 'Filing -> ICAO surveillance'.

Written by EAI.

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