TAS and ADS-B FAQs

This AvidyneLive topic addresses frequently asked questions (FAQs) about the ADS-B and Avidyne TAS600 and TAS600A series of traffic sensors. Please post any additional questions about the TAS600 traffic sensors or ADS-B here and I will be happy to answer them as best I can.

What is ADS-B?

ADS-B or Automatic Dependent Surveillance – Broadcast, is a system for air traffic surveillance.  With ADS-B, each aircraft broadcasts its own GPS position along with other information like heading, ground track, ground speed, altitude.  Receivers on the ground then receive this information and send it to air traffic control displays.  The ADS-B information can be used to augment existing primary and secondary (transponder-based) radar or used in lieu of those radar technologies.   Aircraft that broadcast this information are considered to be equipped with ADS-B Out.

The information broadcast by each aircraft can also be received by other nearby aircraft and that information can be displayed on a traffic display such as a multi-function display (MFD).  Aircraft that can receive ADS-B information have ADS-B In.

The ADS-B information used by air traffic controllers will allow improved separation services along with additional future applications such as continuous descent approaches.  ADS-B information in the cockpit will allow better situational awareness and traffic avoidance along with future applications such as self-separation.

Ground vehicles on airports will also be equipped with at least ADS-B Out to help prevent runway incursions.

What is the difference between ADS-B In and Out?

ADS-B Out systems automatically broadcast an aircraft’s (or ground vehicle’s) GPS position about every second.  ADS-B In systems receive those broadcasts from other air and ground vehicles along with from FAA ground stations.  The ground station data can include other traffic information along with weather and NOTAM information.  The data received with an ADS-B In system is dependent on the ADS-B link and the capabilities of the receiver.  Some ADS-B systems do both ADS-B In and Out.

What is the FAA mandate for ADS-B?

The FAA has mandated ADS-B Out by 2020 on all aircraft operating in current Mode-C airspace (Around class B and C airspace along with above 10,000 ft).  The mandate allows either 1090-ES or UAT ADS-B Out on aircraft.  The 1090-ES link is required for aircraft that fly above FL180. http://www.faa.gov/regulations_policies/rulemaking/recently_published/media/29305.pdf

The FAA and their contractor, ITT, are on track to have the entire ADS-B ground infrastructure in place by 2013, 7 years before the mandate.  This ground infrastructure is already available for most of the East coast and supports TIS-B, ADS-R, and FIS-B along with sending ADS-B information to ATC.  http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/enroute/surveillance_broadcast/coverage/

What ADS-B mandates are in Europe?

The European Commission issued a Notice of Proposed Rulemaking in 2009 that would mandate 1090-ES ADS-B Out after February 5, 2015 for aircraft over 12,500 lbs or cruise speed greater than 250 kts.  Europe chose 1090-ES since it works with their existing Mode-S Elementary Surveillance (ELS) and Enhanced Surveillance (EHS) mandates.  http://www.ainonline.com/news/single-news-page/article/europe-to-mandate-ads-b-five-years-ahead-of-faa-19715/

What is the difference between 1090-ES and UAT ADS-B?

The FAA mandate supports two technologies for ADS-B, 1090 MHz Extended Squitter (1090-ES) and Universal Access Transceiver (UAT).  1090-ES uses the same frequency used by Mode-S transponders and includes the ADS-B information as extra data on the Mode-S transponder transmissions, hence the ‘extended squitter’ name.  UAT uses the 978 MHz frequency that has been reserved for ADS-B.  Since there is a difference in frequencies between the two technologies, UAT receivers cannot receive 1090-ES ADS-B transmissions and 1090-ES receivers cannot receive UAT transmissions.

The ADS-B ground stations will re-transmit the information on the opposite link so that all aircraft can be seen on cockpit traffic displays.  This is known as ADS-R, R for rebroadcast.

The UAT technology also allows additional information to be uplinked to aircraft from ground stations through FIS-B (Flight Information System – Broadcast).  This information includes weather and TFR information similar to the information already provided by XM or Sirius/WSI.

What is FIS-B?

FIS-B stands for Flight Information System – Broadcast and is only available with UAT link ADS-B In.  When in range of a ground station, weather and NOTAM information can be received by a UAT receiver and displayed in the cockpit on a MFD or EFB.  The following data is currently available: AIRMETs, SIGMETs, METARs, NEXRAD, NOTAMs, TFRs, PIREPs, SUA Status, TAFs, and Winds/Temps Aloft.  This data is similar to information already provided by XM or Sirius/WSI, however the update rate is faster with FIS-B, but the geographical coverage area is much smaller.   For example at low altitudes, only 150nm of NEXRAD is available and 250nm of METAR, TAF, and AIRMET data.  Additionally at remote airports, no data may be available on the surface.

What is TIS-B?

TIS-B stands for Traffic Information System – Broadcast and involves ADS-B ground stations sending Secondary Surveillance Radar (SSR) targets to aircraft with ADS-B In.  TIS-B targets will be updated at least every 2 seconds on the surface, 6 seconds in the terminal area, and 12.1 seconds in the en-route airspace.

What is ADS-R?

ADS-R stands for Automatic Dependent Surveillance – Re-broadcast and involves ADS-B ground stations repeating ADS-B messages from one link (1090-ES or UAT) to the other link for aircraft with ADS-B In.  ADS-R targets will be updated at least every 2 seconds on the surface, 5 seconds in the terminal area, and 10 seconds in the en-route airspace.

How is ADS-B different from TAS?

TAS systems, which must meet TSO-C147, are on-board, active-surveillance Traffic Advisory Systems that independently interrogate nearby transponder-equipped aircraft and determine bearing and range from the replies.

ADS-B is dependent upon aircraft broadcasting their GPS positions to other aircraft.  To see other aircraft, they must be broadcasting ADS-B Out messages and you must be equipped with ADS-B In to receive those messages.  ADS-B is dependent on other aircraft having being equipped to support ADS-B Out.

How is TAS different from TCAS?

There are two types of TCAS (Traffic Collision Avoidance System), TCAS I and TCAS II.  TAS systems are almost identical to TSO-C118 TCAS I systems, in fact they use the same set of requirements or Minimum Operational Performance Standards (MOPS).  Both systems actively interrogate nearby Mode A, C, and S transponders and issue Traffic Alerts (TAs – “Traffic, Traffic”).  The difference is that TCAS I systems have a 1030 MHz receiver that can detect the number of nearby TCAS systems and thus send a more powerful interrogation when fewer aircraft are nearby.  TCAS II systems go beyond TCAS I systems in that they require dual Mode-S transponders, they can coordinate with other Mode-S transponders on other aircraft and they can issue Resolution Advisories (RAs – “Climb, Climb”).

Why is an Active Traffic System like the Avidyne TAS600 Series still important in an ADS-B environment?

Active Traffic Systems (including TAS and TCAS) use Mode-A, C, or S transponder interrogations to determine aircraft bearing and distance.  Altitude is determined by reported Mode-C altitude.  After the ADS-B mandate, aircraft will still be required to have a Mode-C or S transponder in airspace where it is currently required, thus Active Traffic Systems will continue to function.

Active Traffic Systems are valuable for three reasons in an ADS-B environment.   First, during the initial equipage period (through 2020) not all aircraft will have ADS-B.  Thus without an Active Traffic System, those unequipped aircraft would not be displayed on a cockpit traffic display even if you had ADS-B In.  Second, since the FAA mandate allows both 1090-ES and UAT ADS-B technologies, if the ADS-R system is not functional or you are out of range of a ground station, the ADS-B In will not display aircraft of the opposite type.  An Active Traffic System will display all aircraft independent of the type of ADS-B Out since all aircraft will still be required to have a Mode-C or Mode-S transponder.  Third, ADS-B is dependent on GPS signals, so during periods of poor satellite geometry or solar storms, GPS position and thus ADS-B will not be available.  The FAA is keeping ATC radars as a backup and an Active Traffic System can act as a backup to ADS-B in the cockpit.

Do Avidyne TAS600 series of traffic systems support ADS-B?

Avidyne is currently developing an ADS-B In upgrade to the TAS600 series of traffic systems.  Ryan 9900BX, TAS600, TAS610, and TAS620 owners can lock in a $2,000 upgrade price for ADS-B In simply by registering at http://www.avidyne.com/landing/tas600-adsb.asp.

What is the ADS-B upgrade plan for the TAS600 series of traffic systems?

Avidyne is planning on making an upgrade available to the TAS600 series of traffic systems to make them able to display traffic from 1090-ES equipped ADS-B Out aircraft.  This upgrade will turn the TAS600 series unit into a TAS600A series unit. Owners can lock in a $2,000 price for this ADS-B In upgrade by registering at http://www.avidyne.com/landing/tas600-adsb.asp.

How much will the ADS-B upgrade cost?

The upgrade is expected to cost at least $2,000.  However before the end of 2010, owners can lock in a $2,000 upgrade price by registering at http://www.avidyne.com/landing/tas600-adsb.asp.

Will I be able to buy an ADS-B equipped TAS600 series traffic system?

Yes.  Avidyne is going to offer TAS600A, TAS610A, and TAS620A traffic systems.  Availability and pricing has not been announced yet.  See http://www.avidyne.com/products/tas600a/index.asp for more information.

What will I get with ADS-B In support in my TAS?

ADS-B In support in the TAS will allow the TAS to receive ADS-B information from 1090-ES equipped ADS-B Out aircraft.  It will still also display traffic information from Mode-A, C, and S transponders.  The range for receiving ADS-B information is larger than can be used for active traffic interrogations, increasing the effective range of the TAS for ADS-B In.  The ADS-B position will also be used to enhance the accuracy of the bearing and range to a target.

The TAS also will receive the additional information provided by ADS-B (heading, track, on-ground status, etc) and provide this information to compatible traffic displays.  The MFD or other display must be updated to take advantage of this additional information.

Will the TAS600A allow me to comply with the FAA mandate?

No, you must equip with an ADS-B Out system to be compliant with the FAA ADS-B mandate.

What is Avidyne’s plan for ADS-B Out?

Avidyne has been watching the developments in ADS-B rule making very closely, and now that the rules are fully defined, we are able to continue forward with our plans for supporting ADS-B Out.  You can expect that Avidyne will bring innovative ADS-B technologies to the GA community at affordable prices in order to further our goal of aviation safety.

What should I do now about getting my airplane equipped for ADS-B?

First if you have an Avidyne TAS system, Avidyne recommends signing up for the TAS600A upgrade now to lock in the price and in order to get ADS-B In benefits as soon as possible.  With respect to ADS-B Out, there are two major reasons for waiting to equip.  First, as of this post, there are no products currently on the market which meet the FAA’s mandate for TSO-C166b (1090-ES) or TSO-C154c (UAT).  These TSOs are based on RTCA MOPS that were not published until late 2009, and thus no existing ADS-B manufacturers have created compliant systems.  Second, as more manufacturers enter the market, the prices of ADS-B systems are expected to drop significantly.  Just as panel mounted GPS systems evolved rapidly in the first 10 years of being on the market, with increasing features at reduced prices, similar trends are to be expected with ADS-B systems before 2020. 

Do you have more questions?   Please post them below.

Ted Lester, Product Manager

I currently have a Mode C transponder coupled to my TAS 600.  I assume that eventually I will need a Mode S transponder.  Will I need a Mode S transponder to upgrade to a TAS 600A?  If not, when will I need a Mode S transponder?  Also, would there be an advantage, costwise, to upgrading to a TAS615 when upgrading to a TAS 600A?  I would like to upgrade to a TAS 615, but only if it will give me the advantages of ADS-B in at the same time.

What physical avionics component will I have to install in my aircraft to transmit ADS-B OUT (UAT)? I was thinking that all ADS-B OUT would be transmitted by the Transponder (either Mode C or Mode S), but it sounds now like I will need an additional piece of equipment for UAT.

Ted,

Edited by tony - 09 Dec 2011 at 6:22am

Hi Ted,

Any update on the availability of the ADSB upgrade?
Will there be any way to determine if the target is received via ADSB or Legacy?

Avidyne expects to begin shipping upgrades early in Q1 2013, at which time, the $2K will be owed.  In addition to working hard to complete the development of the TAS ADS-B upgrade, Avidyne is also playing a key role in developing the standards for ADS-B traffic alerting systems.  Our active presence in the standards development community helps us to assure that the upgrades we offer our customers will meet their expectations for long-term compatibility with the next generation of surveillance technology.

Avidyne considers ADS-B an essential part of the next generation airspace and plans to support ADS-B technology in a major way, including the ability to display ADS-B traffic and weather data on the IFD540 and IFD440 products.

It had slowed down a little while we focused on IFD540 but the team is piling back on this project now that they are coming off of IFD540.

So, to be clear, the FAQ above says: "ADS-B In support in the TAS will allow the TAS to receive ADS-B information from 1090-ES equipped ADS-B Out aircraft."

Orest, thanks for that!  Perhaps somebody should update that FAQ entry to clarify it.

I'm not questioning whether having active traffic is a benefit compared to just ADS-B traffic, at least at this point.  It seems that the FAA has created a system that really has some big gaps, since it's possible to have two perfectly ADS-B In and Out compliant aircraft flying right next to each other that can't see each other on ADS-B without the assistance of a ground station.  (One may have a UAT while the other has a 1090-ES transponder and a TAS-605A!)  I've heard enough "TIS not available" warnings in rental G1000 airplanes that I'm skeptical of ground infrastructure for stuff like this.

Edited by MikeK - 04 Jun 2014 at 3:10am

Thanks, Dean.  Of course, in those rural areas, the airplanes may not have Mode C either!

It seems like a silly technology.

Go figure .. Allmost all aircraft are equipped with a transponder. How hard can it be to just have that transponder transmit who he is, call sign & aircraft type, flightlevel, speed and heading.

Nowadays boats have this technology as well. It is called ais and it has made radar completely obsolete. A receiver will cost something like 400 usd while a transponder will cost 700 to 800 usd. You caneven view everything on a ipad

dryan wrote: Traffic displays will only permit you to view one source of traffic at a time

Edited by MikeK - 05 Jun 2014 at 8:10pm

Stiletto1 wrote: Is that really how long it takes to relay traffic information via ADSB-In?  Seems to me the traffic has already moved a significant distance by the time ADSB shows it to you...

It might be helpful to think about what the system/network does as separate from what your display does.

While the target data might only be updated every five or ten seconds, the target display can be coasting or averaging the data.  Such that what you see is probably a current and accurate depiction unless the target is maneuvering.

I have certainly seen cases where I have flown in trail of a buddy by a mile or so, and his ADS-B still showed me in a climb when I had actually leveled off.  It takes a few sweeps for the system to recognize a rate change.  It fixed itself after a minute or two.

I think it has always been this way for ATC.  We're just getting our first look at what a controller deals with in terms of equipment limitations.

For what it's worth, the "real" equipment on the airliners (TCAS) is very good at determining target distance (as good as a DME) but quite poor at determining azimuth.  This is a physical limitation of having an antenna array that is only an inch tall versus the 30-foot tall dish at ATC.  But it turns out that distance and closure rate (combined with altitude data) is more than enough for the job of collision avoidance.  The position/location is only meant to be good enough for the pilot to look out the proper segment of the window area.

As posted elsewhere, none of these systems work well with a primary target.  They also won't detect skydivers, balloons, flocks of birds, gliders, and so on.

The most likely (80%+) place to have a mid-air collision is on final approach for a runway.

The next-most likely (80%+ of what's left) location is in the traffic pattern.

The next-most likely (80%+ of what's left) is over a VOR or other commonly used navigation waypoint.

Your chances of having a collision away from one of those three places is astonishingly small, despite the "he was right there" stories.  You don't have to miss by a mile.  You just have to miss.

David Bunin


Edited by DavidBunin - 10 Sep 2017 at 11:15am

Might have missed this technicality in the above discussions, but I haven't found a well referenced answer to this one:

Edited by n7ifr - 25 Oct 2018 at 7:16pm

Good news: Clarification from FAA email on ADSB Transponder settings.

I am sorry, I am behind the curve on this.