Pilot's Guide to Avionics 2017-2018 - 34
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Installation and Flight Check Issues
FAA data shows that about 5,000 of the 32,000
ADS-B Out installations completed so far have
performance problems or transmit incorrect data.
Most of the aircraft with issues are single-engine
general aviation aircraft.
James Marks, with the FAA's Flight Standards
Service Aircraft Maintenance Division, is the ADS-B
Focus Team leader and is working hard to help cut
down on installation errors.
"The three most serious errors that we regularly
see are transmission of a wrong ICAO code, an
incorrect flight identification or call sign, and dual Out
boxes using different ICAO codes," Marks said.
ADS-B has an FAA-assigned 24-bit ICAO code.
call sign instead of an N-number. This issue does
not arise for the vast majority of general aviation
operators, but requires allowing call sign entry for
The third issue is a twist of technology. When the
ADS-B rule was first proposed, the idea was that
aircraft would have to equip with either a Mode S
transponder (operating on 1090 MHz) or a Universal
Access Transceiver or UAT (operating on 978 MHz).
Both meet the requirement for an ADS-B transmitter.
To ensure that an aircraft is seen in all airspace -
even outside of FAA ADS-B coverage - some aircraft
owners are equipping with both device types. This
approach can result in a "dual Out" problem.
"If the ICAO code in your Mode S transponder
- reporting to the ground on 1090 MHz - and your
UAT avionics - reporting on 978 MHz - are different,
your aircraft may appear on a controller's
display as two aircraft in close proximity,"
Marks explained. "Also, if your aircraft is
equipped with ADS-B In, you may see a
second aircraft displayed very close to your
own position, prompting you to try to avoid
an aircraft that isn't there."
The ADS-B Focus Team also is working
on a reporting issue called air/ground
determination. The FAA has detected ADSB-equipped aircraft reporting in airborne
mode while taxiing or stationary. This
problem stems from issues with the ADS-B
avionics that make the actual air/ground
determination and relay that information
to the FAA's ADS-B system. The FAA is
working with avionics manufacturers to
better understand the issue and determine
how to resolve it.
This graphic generally depicts the airspace where ADS-B Out will be required by
rule. For more information, visit www.faa.gov/nextgen/equipadsb/airspace.
This code is different from the flight identification,
which should match the aircraft's N-number. The
installation technician must enter this information
to comply with the rule, and glitches do occur. One
of the ADS-B Focus Team's highest priorities is to
promptly contact any aircraft owner with incorrect
ICAO codes or flight identification. The FAA handles
about 200 of these cases per month. Call sign
mismatch is a related issue for aircraft using a
"We emphasize making sure your
installation is compliant with the rule
before signing off on work, because many aircraft
equipped with ADS-B are operating with some type
of unresolved problem," Marks said.
One way to make sure everything is good is
to make certain your installer uses ground-based
testing equipment. This equipment will detect most
issues, but the ultimate test is to fly an aircraft in
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