See and Avoid with NexAir

If you’re going to fly in today’s busy airspace, you’ll want a modern, automated Traffic Awareness system. Once you start flying with a good traffic awareness system, you’ll be surprised how much traffic there is that you never knew existed, or that ATC never told you about even when using flight following. You’ll also be surprised how much easier it is to spot traffic once it’s been pointed out to you by a traffic display that orients itself to your current heading.

How Much Traffic Data Do You Need?

Traffic Awareness systems leverage one of three basic technologies, Mode-S (good), ADS-B (better), and/or active transponder interrogation (best).

  • Mode-S uses the FAA’s  Traffic Information Services (TIS). TIS is an older, slower technology that’s only available around select FAA terminal radar installations, making coverage limited. You’ll see both transponder-equipped targets and primary returns. Mode-S is being replaced by NextGen ADS-B.
  • Automatic Dependent Surveillance-Broadcast (ADS-B), enables behind the scenes automated communications between your plane and ATC, as well as between your plane and other aircraft — including traffic data. Once you’re high enough to see at least one TIS-B capable ADS-B Ground Station, coverage is virtually contiguous throughout the continental U.S. You’ll see both transponder-equipped targets and primary returns.
  • Active Traffic Systems proactively interrogate all nearby transponders while you’re flying. They then filter and merge those transponder replies with Mode-S and ADS-B data to create the most complete traffic picture available.  Since your active traffic system is initiating the transponder interrogations, and since that system goes anywhere you do, you’ll see transponder-equipped targets anywhere you fly. You’ll also see primary returns when operating within Mode-S and/or ADS-B service areas.

Mode-S Transponder

We’re all used to Mode-C Altitude Encoding transponders which have been around for many decades. Well, Mode-S is a follow-on class of transponders that support something called Traffic Information Services (TIS). If you have a Mode-S transponder and compatible display such as a GNS 430, and you’re flying within the service volume for any of the 107 FAA Terminal radar installations equipped to support TIS, then you’ll see a display of traffic around your aircraft.

TIS Service VolumeLimited Volume — Mode-S traffic data is only supplied out to a distance of 7 NM and +/- 3,500′ around your aircraft, so it’s significantly smaller than the traffic volume for ADS-B which extends to a radius of 15 NM.

Avidyne’s AXP340 Mode-S Transponder (shown below) is a slide-in replacement for the venerable KT76A transponder, making it a great choice for upgrades, as well as for new installations. As with all new Mode-S Transponders being sold today, when used with an approved WAAS GPS position source, the AXP340 also supports ADS-B Out functionality.  

Now I See You, Now I Don’t — In aircraft that have both Mode-S and ADS-B, there are times when a specific nearby target will display on Mode-S, but not on ADS-B, and conversely times when a specific nearby target will display on ADS-B, but not on Mode-S.

Slower Updates — Mode-S traffic data is slower to update than ADS-B. When observing the flight of a glider circling clockwise in a thermal, with the glider at the 12-o’clock position, the ADS-B traffic display was perfectly synchronized with the position of the glider showing it at 12-o’clock, whereas the Mode-S traffic display showed the glider at 9-o’clock, a notable delay. Note that TIS is on it’s way out, being replaced by NexGen ADS-B solutions.

How’s It Work? — When TIS-capable radars receive an interrogation reply from a Mode-S transponder, on their next radar sweep they uplink a traffic information data packet to the Mode-S transponder. You can read more about TIS within the AIM, section 4-5-6.

What Do I Need? — You’ll need a TIS-capable Mode S transponder, such as the Avidyne AXP340, Garmin GTX 330, or BendixKing by Honeywell KT 73, and a display that can depict the traffic graphically — typically any modern panel-mount GPS with moving map will suffice.

Is It Worth It? — Given the rollout of NexGen ADS-B, you shouldn’t selectively invest in just a Mode-S solution unless you are also simultaneously equipping for ADS-B Out compliance. All new ADS-B Out transponders will also support Mode-S with TIS, so when you install an ADS-B Out capable transponder, you can benefit from Mode-S TIS, too.

ADS-B In — See the Traffic Around You

Garmin Pilot App ADS-B Traffic Display for an ADS-B Out Equipped Cessna 182Q.

Garmin Pilot App ADS-B Traffic Display for an ADS-B Out Equipped Cessna 182Q. Click to enlarge.

In exchange for spending the money on ADS-B Out compliance by 2020, you in turn can receive customized traffic data sent specifically to your aircraft. The data is uploaded to your ADS-B Receiver from the network of ADS-B ground stations via the 978 MHz Traffic Information Service–Broadcast (TIS-B) data link.

Shown to the right is the Garmin Pilot App running on an iPad displaying ADS-B traffic for an ADS-B Out equipped Cessna 182Q.

The FAA’s ATC system actually creates a TIS-B data packet just for you, and only you, that shows you all known traffic, detected via ADS-B or ground radar, within a 15 nm radius and 3,500 ft +/- your altitude. You’ll also receive ADS-B data from other ADS-B equipped aircraft. The traffic data can be displayed on your tablet and/or your panel mounted displays.

ADS-B Service Volume
Faster Updates — ADS-B traffic data is faster to update than Mode-S TIS. When observing the flight of a glider circling clockwise in a thermal, with the glider at the 12-o’clock position, the ADS-B traffic display was perfectly synchronized with position of the glider showing it at 12-o’clock, whereas the Mode-S traffic display showed the glider at 9-o’clock, a notable delay.

How’s It Work? — When you’re within radar coverage and within site of a TIS-B capable ADS-B Ground Station, the FAA’s ADS-B system continuously sends your aircraft Traffic Information Service – Broadcast (TIS-B) data packets. These TIS-B data packets are just for you, for your N-number, and they show you all the known traffic, detected via ADS-B or ground radar, within a 15 nm radius and 3,500 ft +/- your altitude. The traffic data can then be displayed on your tablet and/or your panel mounted displays.

More Useful Information and Warnings — Most companies that display ADS-B traffic data will analyze nearby targets and provide traffic alerts, either visually on your displays, and/or verbally through your audio panel. Some companies like Garmin, postprocess the data to show you the motion of the traffic relative to your aircraft, not just the traffic’s own flight path.

Shown below is ADS-B traffic being displayed on a Garmin GTN 650. Your aircraft is in the center (represented by the tip of the “own-ship” symbol). Two traffic targets are displayed. The low threat target is just inside of 2 NM distance at your 12-o’clock, level at 2,900 feet below your aircraft, and showing a green 30-second look ahead relative motion vector that will take it safely to the right of your flight path. The higher threat target is shown in yellow, 1 NM out at at your 8-o’clock, climbing from 1,200 feet above your aircraft, and moving slowly away to the left.

What Do I Need? — You’ll need an approved ADS-B Out solution (WAAS GPS position source and ADS-B Out transponder); an ADS-B In solution to receive the TIS-B data packet; and then a tablet, aviation portable, or panel mounted display that can depict the traffic graphically.

Don’t Fool Yourself — There are pilots flying today that are just using a portable ADS-B receiver with a tablet or aviation portable, without using any approved ADS-B Out solution. If you’re foolish enough to try to rely upon ADS-B traffic data without broadcasting your own ADS-B Out, you’ll only ever see somebody else’s TIS-B data, and as a result, coverage will be incomplete and intermittent. The only true way to get ADS-B traffic data that you can rely upon is to also equip with an approved ADS-B Out solution.

Is It Worth It? — Absolutely. ADS-B traffic data provides a very significant enhancement to safety for any pilot that operates in proximity to other aircraft. We’ve even seen ADS-B credited with preventing a midair collision when a pilot with ADS-B traffic data was able to warn two other aircraft 10 NM away that they were converging toward a midair in the traffic pattern.

NexAir can design the perfect ADS-B Out solution for your needs, with ideal GPS and ADS-B antenna placements that maximize your visibility to ATC and other aircraft. You’ll then receive the most complete N-number specific ADS-B traffic data possible from official FAA sources during every flight within ADS-B coverage areas. Get it right, get it done, and do it with NexAir.

Shown below is the new Lynx® MultiLink Surveillance System (MSS) NGT-9000, a single box transponder replacement that offers a full range of ADS-B benefits. In addition to providing all the functionality of a transponder, the color touch-screen NGT-9000 provides its own WAAS GPS position source and fully compliant ADS-B Out (1090ES Mode S Extended Squitter). It also provides both 1090Mhz and 978Mhz (UAT) ADS-B In for traffic (ADS-B, ADS-R and TIS-B), and weather/TFRs/NOTAMs (FIS-B). The NGT-9000+ version adds NextGen SkyWatch® Active Traffic (learn more about SkyWatch® and other active traffic systems below). WiFi is available for connectivity to iPad® and Android™ devices with applications such as WingX Pro and SkyRadar (other apps pending).

Active Traffic Systems — TAS and TCAS

If you need the best traffic solution available, you need an active traffic system. These systems proactively interrogate all nearby transponders while you’re flying, then they filter and merge those transponder replies with Mode-S and ADS-B data to create the most complete traffic picture available. Not only do they provide the most complete traffic data available, they also update faster than any other type of traffic solution.

Coverage That Moves With You — Since your active traffic system is initiating the transponder interrogations, and since that system goes anywhere you do, you’ll see all operational Mode-A, Mode-C, and Mode-S transponder-equipped targets anywhere you fly. You’ll also see FAA ATC primary returns when operating within Mode-S TIS and/or ADS-B TIS-B service areas.

There are two major classes of Active Traffic Systems, Traffic Advisory Systems (TAS), and Traffic Alert and Collision Avoidance System (TCAS I and TCAS II).

Traffic Advisory System (TAS)

These systems are popular among many owner-operators of high-performance aircraft that are not required by any regulatory mandate to have a TCAS II system. Examples of active Traffic Advisory Systems (TAS) are shown below.

Avidyne TAS-A Series ADS-B-capable Traffic Advisory System

Avidyne TAS-A Series ADS-B-capable Traffic Advisory System

Avidyne TAS-A Series ADS-B-capable Traffic Advisory Systems — Avidyne’s TAS-A Traffic Advisory Systems (TAS) combine ADS-B In traffic data with responses from actively-interrogated transponders of nearby aircraft that are within range. They then display the surrounding traffic on a host of compatible display systems, and provide audible and visual alerts in the event of a potential traffic conflict. All TAS-A Series systems provide real-time traffic monitoring and advisories, are not radar-coverage limited, and operate independent of ground-based systems.

Shown below is VeriTAS™, Avidyne’s ADS-B/TAS traffic detection & alerting technology that shows the true traffic picture. VeriTAS uses advanced algorithms designed under the FAA/MIT TSAA Program to automatically correlate Active (TAS) & Passive (ADS-B) targets with predictive collision avoidance logic.

Garmin GTS family of ADS-B enhanced Traffic Advisory Systems (TAS) — These innovative systems provide accurate, dynamic traffic surveillance — with ATC-like spoken audio alerts to help you quickly respond to potential flight path encroachments. Augmenting reports from radar-based air traffic control, the GTS 800 can combine both active and passive surveillance technologies when installed with a compatible ADS-B extended squitter Mode-S transponder such as the Garmin GTX 330 ES. Using this hybrid active/passive surveillance, the GTS 800 creates a 360° zone of detection around your aircraft, enabling you to see and identify other nearby transponder-equipped aircraft in time to take prompt corrective action.

GTS Systems feature exclusive CLEAR CAS™ (Correlated Location Enhanced ADS-B Receiver Collision Avoidance System) technology. Instead of the generic “Traffic, traffic” voice alerts, CLEAR CAS provides for expanded audio messaging in an ATC-like verbal format: “Traffic. One o’clock. High (or Low or Same Altitude). Two miles.” If surveillance bearing information is not available on the intruder, “Traffic, No Bearing” is called out. By vocalizing more specific traffic-spotting information, pilots know instantly where to look without going “eyes-down” to locate the intruder target on the cockpit display. This can save vital split-seconds in a fast-converging traffic situation.

As shown in this table, Garmin offers three levels of GTS Systems, including two that are TAS and one that is a TCAS I system (learn more about TCAS below).

L-3 SkyWatch® — For nearly 15 years, pilots have trusted SkyWatch Collision Avoidance Systems to enhance safety by helping them spot traffic. SkyWatch was the first Active Collision Avoidance System certified for general aviation. More than 15,000 systems are installed in aircraft ranging from single engine pistons to helicopters to light business jets. The SkyWatch System provides a 360° spherical envelope of monitored airspace around your aircraft. After receiving replies to its Mode C type interrogations, the SkyWatch system computes the responding aircraft’s range, bearing, relative altitude and closure rate, allowing up to 30 seconds warning time for the initiation of avoidance procedures. As shown below, the SkyWatch HP 497 provides an active surveillance range out to 11 NM, while the SkyWatch HP 899 provides an active surveillance range out to 35 NM.

SkyWatch Coverage

Traffic Alert and Collision Avoidance Systems (TCAS)

TCAS operates independently of ground-based radar or ADS-B systems to give aircrews proactive guidance on how to avoid a potential collision. The primary difference between TCAS I and TCAS II is that TCAS II systems will tell the flight crew how to maneuver (climb or descend) to escape an impending midair collision. This guidance is called a Resolution Advisory or RA.

TCAS Indicator

TCAS Indicator

TCAS I — Active interrogating system issuing real-time traffic alerts (TA), certified under TSO C118. TCAS I is the first generation of collision avoidance technology. It is cheaper but less capable than the more modern TCAS II system, and is mainly intended for general aviation use. TCAS I systems are able to monitor traffic out to a range of about 40 NM and offer information on the approximate bearing and altitude of other aircraft. It can also generate collision warnings in the form of a Traffic Advisory (TA). The TA warns the pilot that another aircraft is in the vicinity, announcing “Traffic, traffic“, but does not offer any suggested remedy; it is up to the pilot to decide what to do, usually with the assistance of Air Traffic Control. When a threat has passed, the system announces “Clear of conflict.”

TCAS II — Active interrogating system issuing traffic alerts (TA) and resolution advisories (RA), certified under TSO C119. TCAS II is the second and current generation of TCAS. It’s used in the majority of commercial aircraft. It offers all the benefits of TCAS I, but also offers the pilot direct, vocalized instructions to help avoid a collision. These instructions are known as a Resolution Advisories (RA). The action may be corrective, suggesting the pilot change vertical speed by announcing, “Descend, descend,” “Climb, climb,” or “Adjust vertical speed, Adjust.” By contrast a preventative RA may be issued which simply warns the pilots not to deviate from their present vertical speed, announcing, “Monitor vertical speed” or “Maintain vertical speed, Maintain.” When formulating an RA, the TCAS II system will take into consideration the performance characteristics of both aircraft using data encoded into the transponder replies, and also coordinate the two RAs so as to maximize the separation achieved (e.g., you’ll execute a climb while the other aircraft executes a descent).

Start the Conversation

If you’ve seen something here that sparks your imagination, get the conversation started. Email Dave Fetherston, call him at 877-318-0975, or submit an online Request for Quote or Request Repairs or Maintenance short form. We’re ready to collaborate with you so that you, too, can have a smarter plane and be a smarter pilot.