Traffic limitations with ADS-B Receivers: Clarity is an ADS-B receiver and is subject to the limitations of ADS-B receivers, especially with respect to traffic. ADS-B receivers can receive traffic information under some, but not all circumstances. ADS-B receivers may show some traffic, but remember that other traffic targets are out there that are invisible to ADS-B receivers. Just because an ADS-B receiver shows an aircraft does not mean it shows all aircraft. Do not rely on Clarity or any other non-certified ADS-B receiver to provide traffic information for separation, spacing, or collision avoidance. Always be diligent about your responsibility to see and avoid other aircraft, and never use Clarity or any other ADS-B receiver information as a primary flight display, or as the principal means of aircraft avoidance. Clarity is not certified, and users assume all risk of use.
General Traffic Information
Clarity receives traffic reports of nearby airplanes either directly from the aircraft (Air-to-Air), or by way of FAA Ground Stations transmitting TIS-B and ADS-R. The manner in which the FAA implemented the ADS-B system has subtleties that give rise to broad confusion about when traffic is available to a pilot.
Traffic is transmitted from two sources:
• Directly from ADS-B Out equipped aircraft (Air-to-Air)
This should be considered the primary benefit to Clarity users. Note that at present most aircraft don’t have ADS-B Out, so most aircraft aren’t visible with Air-to-Air. But more are equipped every day and in time Air-to-Air messaging will grow in value.
• Ground Stations (TIS-B, ADS-R)
TIS-B and ADS-R traffic reports from Ground Stations shouldn’t be considered valuable to Clarity users unless you are certain your aircraft has ADS-B Out, which is required to trigger TIS-B/ADS-R. Most aircraft are not yet equipped with ADS-B Out Transponders.
Clarity, with its internal omnidirectional antenna, principally receives traffic information via Air-to-Air transmissions from nearby ADS-B OUT-equipped “target” aircraft. Essentially, the target aircraft is broadcasting its position to everyone, including Air Traffic Control. These Air-to-Air location reports represent the primary value of the Clarity traffic function because it isn't subject to the complicated subtleties associated with TIS-B from ground stations.
• Air-to-Air messages are broadcast only by ADS-B Out equipped aircraft. They are transmitted on either 1090MHz or 978MHz, depending on how the transmitting aircraft is equipped
o Aircraft that fly above 18,000 feet transmit on 1090 MHz
- (generally turbine powered aircraft, and turbo-charged piston aircraft)
o Aircraft that fly below 18,000 feet can transmit on either 978 MHz, or 1090 MHz
- (generally non-turbocharged piston aircraft)
• For your airplane to receive Air-to-Air traffic requires no expensive avionics equipment; all you need is a Clarity and an iPad/ tablet.
What do I need to receive Air-to-Air Traffic from ADS-B Out equipped target aircraft?
• Traffic not equipped with ADS-B Out are not visible to Clarity via Air-to-Air messaging.
If you want to make use of Air-to-Air Traffic, buy a Clarity unit, and combine it with a suitable EFB App that takes advantage of Clarity’s traffic messages. Both Clarity units receive all Air-to-Air Traffic messages on both 978 and 1090 MHz.
TIS-B and ADS-R: Ground Station Sourced Traffic
The NextGen ADS-B system provides lots of data, including the Air Traffic Control traffic picture. But traffic targets are not broadcast to everyone, only to those aircraft with the latest ADS-B Out equipment installed.
Clarity is not an ADS-B Out device, and using Clarity will not trigger traffic messages from ground stations.
Ground Stations transmit traffic in two forms which are fundamentally different.
• TIS-B (Traffic Information Service-Broadcast) is essentially ATC’s traffic picture obtained from ground-based radar surveillance. TIS-B is available in terminal areas, and wherever RADAR services are available. TIS-B traffic usually does not include ADS-B Out aircraft, but only legacy transponder-equipped aircraft which have been located by ATC secondary surveillance RADAR.
The ADS-B Out limitation applies. Only aircraft with the right kind of ADS-B Out equipment will receive nearby traffic targets over TIS-B.
• ADS-R (Automatic Dependent Surveillance-Rebroadcast) is a simple repeater. Messages received on 1090 MHz are re-broadcast on 978 MHz, and messages received on 978 MHz are re-broadcast on 1090 MHz. This makes a data-connection between the two ADS-B channels.
Again, the ADS-B Out limitation applies equally here. Only aircraft with the right kind of ADS-B Out equipment willreceive traffic targets over ADS-R.
Q and A on TIS-B and ADS-R
Q: If my airplane has ADS-B Out, will I receive TIS-B/ADS-R Traffic near my aircraft?
A: Maybe. If ALL of the following are true, you’ll get TIS-B/ADS-R Traffic:
- Your ADS-B transmitter has to comply with the most recent version of ADS-B out (currently version 3). Note that the present version of the Garmin 330 is not of the latest standard, so it is our understanding that users of Garmin 330ES with ADS-B Out will NOT receive TIS-B/ADS-R
- Your transmitter must also have the appropriate configuration to indicate receive capability on either 1090 MHz, 978 MHz, or both. Then you‘ll receive TIS-B on the indicated receive channel. If your equipment states receive capability on both 978 MHz and 1090 MHz, you’ll receive TIS-B on only 978 MHz. You’ll also receive ADS-R on the indicated receive channel. Clarity receives on both 978 MHz and 1090 MHz.
Q: Can I see traffic when in the vicinity of other aircraft receiving TIS-B/ADS-R?
A: Yes. You’ll receive TIS-B/ADS-R messages when within reception range and around any aircraft triggering TIS-B/ADS-R.
Q: So what good is TIS-B and ADS-R to me?
A: Exactly. We recommend users not consider TIS-B and ADS-R as having relevant value unless the aircraft they are flying is properly equipped with ADS-B Out to trigger TIS-B and ADS-R messages. But the Air-to-Air receive capability of Clarity is unhampered by these restrictions, and its coverage is doesn’t depend on having line-of-sight with a ground station. It should be remembered, though, that only ADS-B Out aircraft are visible with Air-to-Air reception.