VFR REGULATIONS 18 / LEARN · EXPLORE · CHECK
ADS-B Out and the transponder
Similar airspace, two separate requirements.
Your learning goals
- Apply compare the usual coverage.
- Recognize the limits and exceptions that affect this flight.
- Explain a decision using the scenario and supporting rule.
Compare the usual coverage
For a normally equipped trainer, both requirements cover B/C, the 30-NM veil, and above B/C within lateral limits to 10,000 MSL. The high-altitude comparison differs: transponder rules cover all airspace in the contiguous states/DC at/above 10,000 MSL with the 2,500-AGL exclusion; ADS-B’s corresponding rule specifies Class E. ADS-B also adds Class E at/above 3,000 MSL over the Gulf of Mexico, from the U.S. coastline out to 12 NM.
Out transmits; In receives
ADS-B Out broadcasts aircraft information using approved equipment. ADS-B In is reception of traffic/weather and does not meet an Out mandate. An approved combined installation may perform several functions, but a Mode C transponder alone is not ADS-B Out. Installed ADS-B Out normally transmits at all times, subject to the rule’s narrow FAA/ATC exceptions.
Plan exceptions before the boundary
No-engine-driven-electrical-system exceptions and ATC authorizations have specific limits; they are not blanket permission for B/C entry. Unequipped-aircraft requests must be made at least one hour beforehand. See the transponder lesson separately; approval under one rule does not automatically satisfy the other.
EXPLORE / APPLY THE RULE
Two equipment checks
| Where | Transponder / altitude reporting | ADS-B Out |
|---|---|---|
| B / C, 30-NM veil, above B/C within lateral boundaries to 10,000 MSL | Required | Required |
| Contiguous states/DC, ≥10,000 MSL, above 2,500 AGL | All airspace | Class E provision |
| Gulf Class E, ≥3,000 MSL, U.S. coast to 12 NM | No matching Gulf-only trigger; other requirements can apply | Required |
ADS-B In is neither column. Class A and special exceptions are outside this ordinary VFR comparison.
FLIGHT SCENARIO
What would change your plan?
Your airplane has Mode C and your tablet displays ADS-B traffic. Does this prove you meet ADS-B Out requirements?
- NoticeWhat does this situation require?
- VerifyWhat evidence is still missing?
- DecideWhat keeps an option open?
Compare your reasoning
No. Confirm the approved Out installation and its compliance. A receiving tablet and an altitude-reporting transponder do not establish Out capability.
SUMMARY
Similar airspace, two separate requirements.
No. Confirm the approved Out installation and its compliance. A receiving tablet and an altitude-reporting transponder do not establish Out capability.
Before moving on, explain the decision in your own words: what would you verify, and what would make you change the plan?
PRACTICE
Flashcards and knowledge check
Six flashcards, then five questions with explanations.
Enable JavaScript for flashcards and the knowledge check. The lesson and scenario remain available without it.
Sources & lesson notes
Sources & lesson notes
- 14 CFR §91.225Verified against eCFR text current through September 15, 2026.
- 14 CFR §91.215Verified against eCFR text current through September 15, 2026.
For U.S. private-pilot airplane study. Rules verified against eCFR text current through September 15, 2026, with linked FAA guidance. Scenarios isolate a rule; actual flight decisions require all applicable rules, aircraft limitations, and current information.