What are the ADS-B Out requirements?
Updated · Wingman AeroCare, KFNL
Short answer: Since January 1, 2020, 14 CFR 91.225 requires ADS-B Out equipment meeting the performance standards of 14 CFR 91.227 to fly in Class A, B, and C airspace, within 30 nautical miles of the major airports listed in Part 91 Appendix D (the "Mode C veil"), and in Class E at and above 10,000 feet MSL (excluding the airspace at and below 2,500 feet AGL). Below 18,000 feet in the U.S., either a 1090ES or a 978 MHz UAT system is acceptable; in Class A, only 1090ES is allowed.
Where is ADS-B Out required?
Under 14 CFR 91.225, ADS-B Out is required:
| Airspace | Equipment allowed |
|---|---|
| Class A (FL180 and above) | 1090 MHz Extended Squitter only (91.225(a)) |
| Class B and Class C | 1090ES or UAT |
| Within 30 NM of airports listed in Part 91 Appendix D, Section 1, surface to 10,000 feet MSL | 1090ES or UAT |
| Above the ceiling and within the lateral boundaries of Class B or C, up to 10,000 feet MSL | 1090ES or UAT |
| Class E over the 48 contiguous states and DC, at and above 10,000 feet MSL, excluding the airspace at and below 2,500 feet AGL | 1090ES or UAT |
| Class E over the Gulf of Mexico, at and above 3,000 feet MSL within 12 NM of the U.S. coast | 1090ES or UAT |
These areas closely track where a Mode C transponder is already required under 14 CFR 91.215. Note the 2,500-foot AGL exclusion in the Class E rule: above 10,000 feet MSL, ADS-B Out is not required while you are within 2,500 feet of the ground. Over the Colorado Rockies, though, most mountain crossings put you more than 2,500 feet above some valley along the route, so the exclusion is hard to plan around and most mountain flyers simply equip.
What performance does the equipment need?
Under 14 CFR 91.227, the system must meet TSO-C166b (1090ES) or TSO-C154c (UAT) and broadcast position with specified accuracy and integrity, including:
- NACp (position accuracy) less than 0.05 NM
- NACv (velocity accuracy) less than 10 meters per second
- NIC (position integrity) less than 0.2 NM
- SDA (system design assurance) of 2
- SIL (source integrity level) of 3
In plain English: you need a position source good enough to meet these numbers, which in practice means a WAAS GPS, either built into the ADS-B unit or provided by a compatible panel navigator.
Does ADS-B replace my transponder?
No. ADS-B Out is required in addition to a transponder where 14 CFR 91.215 requires one. Some ADS-B products are combined transponder and ADS-B units, which is why many owners replace an old transponder and add ADS-B in one installation. The transponder still needs its 24-month check under 14 CFR 91.413.
Do I have to leave it on?
Yes. Under 14 CFR 91.225(f), an aircraft equipped with ADS-B Out must operate it in transmit mode at all times, unless otherwise authorized by the FAA or directed by ATC.
Is ADS-B In required?
No. ADS-B In (traffic and weather displays) is optional. Many owners choose it because it adds traffic awareness, especially in busy airspace like the Front Range.
1090ES or UAT: which should I choose?
- 1090ES works everywhere, including Class A and outside the U.S. Choose it if you fly in the flight levels, plan international trips, or want maximum flexibility.
- UAT (978 MHz) is U.S.-only and below FL180. Many UAT units also include a 978 MHz receiver for FIS-B weather and traffic, and UAT can be a cost-effective fit for piston owners who stay in the U.S. below the flight levels.
How do I confirm the installation is compliant?
After installation, fly the aircraft and request a Public ADS-B Performance Report (PAPR) from the FAA. It shows whether your system met the 91.227 performance requirements on that flight. Keep the passing report with your records, and request a new one after any significant avionics change. Installation itself is typically done under an STC or with a Form 337, and work that opens the static system or touches the transponder triggers retesting under 14 CFR 91.411 and 91.413.
How Wingman handles it
Wingman AeroCare handles avionics troubleshooting in-house at Northern Colorado Regional Airport (KFNL), coordinates transponder and pitot-static compliance, and manages major avionics installs through vetted partner shops, so you have one point of contact from planning through return to service. If your ADS-B system is failing PAPR checks or behaving oddly, call (970) 292-0719. See avionics upgrades.