Outline:

INTRODUCTION

Automatic Dependent Surveillance-Broadcast, or ADS-B, represents one of the most significant shifts in aviation surveillance technology in decades, and every pilot and CFI operating in today’s airspace must understand not only what it does but precisely what it does not do. This outline draws from a CFI Bootcamp ground lesson covering the full ADS-B picture — how the system works, where 14 CFR 91.225 and 91.227 require ADS-B Out, what ground-based services like TIS-B, ADS-R, and FIS-B actually deliver, where the system’s blind spots lie, and how to integrate the technology responsibly in the cockpit — giving instructors and pilots the depth of knowledge needed to use this equipment with accurate situational awareness rather than false confidence.

1. The Meaning Behind ADS-B

Summary

ADS-B stands for Automatic Dependent Surveillance-Broadcast, and each letter describes a fundamental characteristic of how the system operates. Understanding what each letter means gives pilots a precise mental model of the system’s capabilities and its inherent dependencies.

Supporting Points

• Automatic: the system transmits approximately once per second with no radar interrogation and no pilot action required

• Dependent: position data comes entirely from the aircraft’s own GPS source, so any GPS degradation directly degrades ADS-B output

• Surveillance: ATC and other aircraft use the broadcast to track equipped aircraft, including in areas where radar is weak or absent

• Broadcast: the transmission is openly received by anyone with a compatible receiver, including ground stations, other aircraft, and public flight-tracking services

Conclusion

Grasping what each letter means forms the foundational knowledge a pilot needs before learning the regulatory and operational layers built on top of it.

2. ADS-B Out and ADS-B In Two Separate Functions

Summary

ADS-B Out is the transmit side of the system, required by regulation in specific airspace, while ADS-B

In is the receive side, which is entirely optional but provides significant traffic and weather situational awareness benefits. Pilots and CFIs must understand that these two functions are operationally and legally independent of one another.

Supporting Points

• ADS-B Out transmits GPS position, velocity, pressure and GPS altitude, ICAO address, Flight ID, squawk, IDENT, emergency status, and accuracy and integrity values

• ADS-B Out is required in the rule airspace and is what keeps the aircraft legal and visible to ATC

• ADS-B In receives direct air-to-air traffic from same-link aircraft, TIS-B radar targets, ADS-R cross-link traffic, and FIS-B weather and NOTAMs on 978 UAT only

• ADS-B In is never required by regulation and may exist as a separate box or as a separate function within an integrated avionics unit

Conclusion

The distinction between Out and In is one of the most important concepts a CFI can teach, because pilots who conflate the two often misunderstand what their display is actually showing them.

3. The Two Data Links 1090ES and 978 UAT

Summary

ADS-B operates on two separate radio frequencies — 1090 MHz Extended Squitter and 978 MHz Universal Access Transceiver — each with distinct capabilities, restrictions, and equipment configurations. Choosing the correct link for the intended operation is both a regulatory and a practical decision.

Supporting Points

• 1090ES uses the same frequency as Mode S transponders with extended squitter and is the only link permitted in Class A airspace at FL180 and above

• 978 UAT operates on a dedicated frequency, requires a separate unit installed alongside a transponder, and is allowed only below FL180

• FIS-B weather uplink is available exclusively on 978 UAT; a 1090ES-only receiver receives no FIS-B products

• 978 UAT supports an anonymous mode in which a random 24-bit ICAO address is broadcast instead of the aircraft’s registered address, available only when squawking 1200 with no ATC services and no IFR flight plan

Conclusion

Understanding the capabilities and restrictions of each link allows pilots and CFIs to make informed equipment decisions and to recognize exactly what information their avionics are capable of providing on any given flight.

4. The ADS-B Out Rule 14 CFR 91.225 and 91.227

Summary

Under 14 CFR 91.225, ADS-B Out is required in Class A, Class B, and Class C airspace, within the 30 NM Mode C veil around listed Class B airports, and in Class E airspace at and above 10,000 feet MSL, with specific Gulf Coast provisions. Section 91.227 establishes the performance standards the equipment must meet, including position accuracy, integrity, update rate, and latency.

Supporting Points

• Class A airspace requires 1090ES specifically; Class B and Class C require ADS-B Out from the surface to the top of those airspaces; Class D, Class G, and Class E below 10,000 MSL outside the veil are not on the required list

• The 30 NM Mode C veil surrounding listed Class B airports requires ADS-B Out from the surface to 10,000 MSL

• 14 CFR 91.227 mandates position accuracy better than 0.05 NM, integrity containment better than 0.2 NM, updates at least once per second while airborne, and total position latency no greater than 2.0 seconds — in practice requiring a WAAS GPS source

• If ADS-B Out is installed, it must remain in transmit mode at all times, on the ground and in the air, unless ATC directs otherwise; deviations for unequipped aircraft require ATC authorization at least one hour before flight

Conclusion

A thorough command of where the rule applies and what performance it demands is essential for any CFI advising students on aircraft airworthiness and legal operation in today’s airspace.

5. Broadcast Services TIS-B, ADS-R, and FIS-B

Summary

Ground stations in the FAA’s ADS-B network uplink three categories of information to equipped aircraft: TIS-B radar traffic, ADS-R cross-link traffic rebroadcast, and FIS-B flight information services. Each service has specific conditions that must be met before it is available to the pilot.

Supporting Points

• TIS-B takes radar and multilateration targets of non-ADS-B aircraft and broadcasts them to nearby ADS-B users at or below FL240; the receiving aircraft must be a qualified client, within range of a ground station that provides TIS-B, and detectable by at least one ATC radar serving that station

• ADS-R bridges the two data links by having a ground station receive 1090ES and rebroadcast on 978, and vice versa, so that a single-link receiver can see traffic on the opposite link; a 978-only receiver hears a 1090ES airliner only when a ground station relays it

• FIS-B delivers weather and aeronautical information including Aviation Routine Weather Reports, AIRMETs, SIGMETs, PIREPs, TAFs, NEXRAD, winds aloft, lightning, icing forecasts, and NOTAMs exclusively on the 978 UAT link and is received only within radio line of sight of a transmitting ground station

• TIS-B and ADS-R are delivered within a cylinder called the hockey puck — 15 NM radius and plus or minus 3,500 feet centered on the aircraft — and are provided only to qualified clients whose ADS-B Out meets the NACp, NIC, and related accuracy thresholds required by 91.227

Conclusion

Understanding how each uplink service works, and when each depends on a ground station being in range, is what separates a pilot who uses the system intelligently from one who assumes the display reflects complete traffic and weather information.

6. ADS-B Blind Spots Traffic You Will Not See

Summary

Several categories of aircraft and operational conditions result in no target appearing on an ADS-B In display, and pilots must understand each gap to avoid the dangerous assumption that an empty traffic screen means an empty sky. These blind spots are predictable and systematic, not random failures.

Supporting Points

• Aircraft with no transponder — including many gliders, balloons, ultralights, and some antique airplanes — produce no ADS-B Out and no TIS-B target, and will not appear on any traffic display under any circumstances

• Aircraft equipped with only a transponder but located outside radar coverage will not generate a TIS-B target because TIS-B requires radar to first detect the aircraft before the ground station can uplink it

• Traffic on the opposite data link that has no ground station relay within range is entirely invisible to a single-band receiver; a 978-only box cannot directly receive a 1090ES transmission from another aircraft without ADS-R assistance

• Traffic outside the 15 NM radius or beyond plus or minus 3,500 feet of a qualified client’s hockey puck is not sent, and aircraft operating as receive-only without qualifying ADS-B Out are not clients and receive only partial puck coverage from other clients nearby

Conclusion

Teaching student pilots to treat a clear traffic display as an aid to visual scanning rather than a guarantee of no traffic is one of the most safety-critical lessons a CFI can reinforce each time ADS-B In is used in training.

7. FIS-B Weather Blind Spots NEXRAD Latency and Product Age

Summary

FIS-B weather products carry significant inherent latency between when a weather event occurs, when the radar observes it, when the mosaic is assembled, and when the transmission cycle delivers it to the cockpit — making FIS-B NEXRAD appropriate only for strategic routing decisions, never for tactical maneuvering near convective weather. Every product on the display has its own age, and that age must be actively managed.

Supporting Points

• The CONUS NEXRAD mosaic is assembled every 2 minutes at the source but transmitted on a 15-minute cycle, meaning the picture displayed can routinely be 5 to 15 or more minutes older than the timestamp shown on the display

• FIS-B NEXRAD is appropriate for strategic decisions made 20 or more minutes ahead — choosing a route that avoids a convective area entirely — and is not appropriate for picking a path between or through active cells

• Every FIS-B product carries its own update and transmission interval: METARs update every minute and transmit every 5 minutes; TAFs update every 6 hours; winds aloft update every 12 hours; AIRMETs and SIGMETs transmit every 5 minutes as available

• When the uplink is lost, stale products can remain on the display; pilots must actively read product age labels and know the update cycle for each product type before acting on any displayed information

Conclusion

Building the habit of checking product age every time weather data is consulted is a discipline that CFIs should model and explicitly teach from the first flight on which FIS-B weather is used.

8. Ground Station Line of Sight and Coverage Gaps

Summary

FIS-B, TIS-B, and ADS-R all depend on radio line of sight between the aircraft and a ground station, which means low-altitude flight in valleys, hilly terrain, and even the traffic pattern at some airports can result in complete loss of uplink services without any warning to the pilot. Losing uplink produces a display that looks exactly like a display with no nearby traffic or weather events.

Supporting Points

• Ground stations transmit like any VHF or UHF radio source and are blocked by terrain, buildings, and the Earth’s curvature at low altitudes, making coverage unreliable in the pattern and at low cruise altitudes near mountainous terrain

• TIS-B also requires radar line of sight to the target aircraft, and radar siting near some airports leaves low-altitude gaps where transponder-equipped aircraft are not detected and therefore generate no uplink target

• No warning is given to the pilot when the aircraft exits the TIS-B service volume; an empty screen in that situation looks identical to an empty screen in an area with full coverage and no traffic

• Pilots should check how many ground stations their receiver is hearing before relying on the traffic or weather picture, and should brief known low-altitude coverage gaps for any planned route

Conclusion

Teaching pilots to verify uplink reception before interpreting the display — rather than assuming coverage — is a fundamental element of responsible ADS-B In use that directly supports sound aeronautical decision-making.

9. Configuration Errors and Cockpit Discipline

Summary

Incorrect Flight ID, a wrong or duplicate ICAO address, and an improperly configured UAT anonymous mode are setup errors that degrade ADS-B services for the affected aircraft and for ATC without triggering any obvious cockpit warning. Cockpit discipline with the display — keeping eyes outside rather than head-down on the EFB — is the behavioral counterpart to proper configuration.

Supporting Points

• Flight ID must match the aircraft identifier on the flight plan exactly; a mismatch causes ATC to receive a call sign conflict, which can delay traffic services and creates tracking ambiguity in areas without radar coverage

• The ICAO 24-bit address is programmed at installation and should be verified using the FAA’s free Public ADS-B Performance Report after any avionics work, re-registration, or aircraft change to confirm that what the aircraft transmits matches what the FAA expects to receive

• UAT anonymous mode must be disabled before requesting any ATC service or filing an IFR flight plan; operating anonymously while receiving ATC services results in a call sign mismatch and forfeits the search-and-rescue identification benefit of ADS-B

• ADS-B traffic information is a situational awareness aid, not a collision avoidance system; no avoidance maneuver is authorized from a displayed target alone, and see-and-avoid responsibility under 14 CFR 91.113 remains with the pilot at all times regardless of what the display shows

Conclusion

Combining correct equipment configuration with disciplined scan habits — glancing at the display to orient the eyes, then looking outside to find the aircraft visually — completes the loop between technology and airmanship that every CFI must model and teach.

10. The Preflight ADS-B Check and Key Takeaways

Summary

A structured preflight ADS-B check ensures the system is legally configured, properly connected, and understood before every flight, closing the gap between having equipment installed and using it correctly. The six key takeaways from this lesson form a mental checklist that applies every time ADS-B In data is consulted in flight.

Supporting Points

• Before flight, confirm: official briefing and TFR check completed independently of FIS-B; Flight ID matches the flight plan; anonymous mode off if requesting ATC services; squawk set and altitude reporting on; receiver connected with correct GPS source; ownship filtered and altitude filter settings known; ground stations heard and weather products updating with age labels visible

• Treat FIS-B NEXRAD as 5 to 15 or more minutes old and use it only for strategic routing, never for threading between active convective cells

• An empty traffic screen is not an empty sky; aircraft without transponders, aircraft outside radar coverage, traffic beyond the hockey puck boundary, and aircraft on the opposite link without an ADS-R relay can all be present and invisible

• Low-altitude coverage gaps should be anticipated and briefed before flight, and the absence of uplink services should be recognized as a possibility whenever operating in the pattern, in terrain, or at low cruise altitudes

Conclusion

Pilots and CFIs who internalize the full operating picture of ADS-B — what it sends, what it receives, and what it never shows — are better equipped to make sound aeronautical decisions and to teach the next generation of pilots to use modern avionics with both confidence and appropriate skepticism.