ADS-R Rebroadcast

AIM ¶ 4-5-10 — ADS-R Rebroadcast

AIM 4-5-10 explains ADS-R: how the ADS-B ground system translates traffic between 978 MHz and 1090 ES so all ADS-B In users see nearby traffic.

In Plain English

ADS-R (Automatic Dependent Surveillance-Rebroadcast) is a translation service built into the ADS-B ground network. Because U.S. ADS-B uses two different datalink frequencies — 978 MHz UAT (typically GA below 18,000 ft) and 1090 MHz Extended Squitter (airliners and international ops) — aircraft on one link cannot directly hear traffic on the other. ADS-R fixes this by receiving messages on one frequency, reformatting them, and rebroadcasting them on the opposite frequency.

Why it matters:

ADS-B In equipped aircraft see nearby ADS-B Out traffic regardless of which link the other aircraft uses.
Aircraft on the same frequency exchange data directly air-to-air and don't need ADS-R.
ADS-R is a ground-based service — out of range of a ground station, you lose the cross-link translation.

Reporting malfunctions: ADS-R is monitored by maintenance personnel, not ATC. Report poor performance to the nearest Flight Service Station by radio or phone, or email [email protected]. Include condition observed, date/time, altitude and location, aircraft type and call sign, and avionics type and software version.

AIM Source Text

FAA AIM ¶ 4-5-10

4-5-10. 4-5-10. Automatic Dependent Surveillance-Rebroadcast (ADS-R) Introduction. ADS-R is a datalink translation function of the ADS-B ground system required to accommodate the two separate operating frequencies (978 MHz and 1090 ES). The ADS-B system receives the ADS-B messages transmitted on one frequency and ADS-R translates and reformats the information for rebroadcast and use on the other frequency. This allows ADS-B In equipped aircraft to see nearby ADS-B Out traffic regardless of the operating link of the other aircraft. Aircraft operating on the same ADS-B frequency exchange information directly and do not require the ADS-R translation function. (See FIG 4-5-7 and FIG 4-5-8 .) Reports of ADS-R Malfunctions. Users of ADS–R can provide valuable assistance in the correction of malfunctions by reporting instances of undesirable system performance. Since ADS–R performance is monitored by maintenance personnel rather than ATC, report malfunctions to the nearest Flight Service Station (FSS) facility by radio or telephone, or by sending an email to the ADS-B help desk at [email protected] . Reports should include: Condition observed; Date and time of observation; Altitude and location of observation; Type and call sign of the aircraft and; Type and software version of avionics system. Previous | Top | Next AIM | ATPUBS | FAA | Send your comments regarding this website.

Oral Exam Questions a DPE Might Ask

Q1What is ADS-R and what problem does it solve?

Per AIM 4-5-10, ADS-R is a datalink translation function of the ADS-B ground system that bridges the two ADS-B frequencies (978 MHz and 1090 ES). It receives messages on one frequency and rebroadcasts them on the other so ADS-B In aircraft can see nearby ADS-B Out traffic regardless of which link the other aircraft is using.

Q2If two aircraft are operating on the same ADS-B frequency, do they need ADS-R to see each other?

No. Per AIM 4-5-10, aircraft operating on the same ADS-B frequency exchange information directly and do not require the ADS-R translation function.

Q3How and to whom do you report an ADS-R malfunction?

Per AIM 4-5-10, because ADS-R is monitored by maintenance personnel rather than ATC, malfunctions should be reported to the nearest Flight Service Station by radio or telephone, or by emailing the ADS-B help desk at [email protected]. The report should include the condition observed, date and time, altitude and location, aircraft type and call sign, and the avionics type and software version.

Related Paragraphs in AIM Chapter 4

¶ 4-5-1

Radar Capabilities and Limitations

¶ 4-5-2

ATCRBS Secondary Surveillance Radar

¶ 4-5-3

Surveillance Radar

¶ 4-5-4

Precision Approach Radar

¶ 4-5-5

ASDE-X/ASSC Surface Surveillance

¶ 4-5-6