AOPA Pilot Magazine - December 2017 - 64

WHERE DO YOU NEED ADS-B?

For flights after January 1, 2020, ADS-B Out will be required in the airspace defined by
FAR 91.225-generally, where a transponder is required today. That is:
* In Class A, B, and C airspace.
* In Class E airspace at or above 10,000 feet msl, excluding airspace at and below 2,500 feet agl.
* Within 30 nautical miles of a Class B primary airport (in the Mode C veil).
* Above the ceiling and within the lateral boundaries of Class B or Class C airspace, up to 10,000 feet.
* In Class E airspace over the Gulf of Mexico, at and above 3,000 feet msl, within 12 nm of the U.S. coast.

Some owners are choosing not to
equip right now, and there's nothing
wrong with that. The ADS-B Out requirement is an airspace rule, and if you never
fly in the airspace defined by FAR 91.225
(see "Where Do You Need ADS-B?"),
equipage is not required. (Piper Cubs,
gliders, and other aircraft certificated
without an electrical system are exempt
from both the transponder and ADS-B
requirements.) Over time, however,
ADS-B Out hardware will be installed on

GARMIN USES traffic alert and collision

avoidance system (TCAS) symbology to
depict traffic information on this GNS
530W display. When a target's position
results in a traffic advisory, its symbol
becomes a solid yellow circle. A solid
white diamond denotes proximate traffic,
which is closer than six nautical miles
laterally and 1,200 feet vertically. All other
traffic is shown as a hollow white diamond.
Altitude trend is shown as an up arrow
or down arrow if the target's altitude is
changing at a rate of more than 500 feet
per minute.

64 | AOPA PILOT December 2017

many of these aircraft as owners move or
they're sold to pilots who need access to
airspace where it is required.
Other owners are seeking the leastexpensive options for compliance, and
there are a number of lower-priced
solutions available. Some are Mode S
Extended Squitter transponders operating on 1090 MHz (1090ES) that replace
the existing transponder with a new one
also incorporating ADS-B Out capabilities; others are universal access
transceivers (UATs), which generally are
remote boxes that operate on 978 MHz
(978UAT) and work in conjunction with
the aircraft's existing transponder. Think
of the hardware as a data transceiver that
sends information about your aircraft to
other ADS-B-equipped aircraft, as well as
to FAA ground stations.
The most enlightened owners are
embracing the plethora of information available from optional ADS-B In
services, using it to obtain a degree of
situational awareness that we have never

before seen in general aviation cockpits.
When the ADS-B system was designed,
the FAA opted for two datalink frequencies-1090 MHz and 978 MHz-in
large part because of concern that 1090,
the only transponder frequency, might
become too congested. Establishing the
978 MHz datalink allowed the transmission of weather information, including
bandwidth-intensive graphics such as
Nexrad weather radar images, into the
cockpit.
And let's face it, in-cockpit traffic and
weather information are the true incentives for general aviation to equip with
ADS-B. Simply being able to continue
accessing the same airspace we use today,
with our transponders, is a fairly hollow "benefit"-and certainly doesn't add
additional capability to the aircraft. (The
airlines will derive such benefits as more
efficient routing and reduced in-trail separation from ADS-B equipage, but those
capabilities are irrelevant to light general
aviation aircraft.)
It's easy to overlook the "other half "
of an aircraft's ADS-B system. Most of
the focus is on the datalink itself, and the
accompanying hardware-but equally
important is a Wide Area Augmentation
System (WAAS) GPS position source that
meets the accuracy requirements of FAR
91.227. Many of the less-expensive ADS-B
solutions include an integral WAAS GPS
receiver to provide position information
to the ADS-B transceiver. This often is
called a "blind" position source, because
nothing else in the cockpit can utilize that
information-that receiver will not let you
shoot any of the rapidly growing number of precision GPS approaches. WAAS
navigation allows localizer performance
with vertical guidance (LPV) instrument
approach procedures that are very similar to Category I ILS approaches. In
September 2017, there were 3,857 published LPV approaches in the United
States serving 1,881 airports-including
1,118 airports without an ILS.
If you fly under instrument flight
rules a lot and don't already have WAAS
GPS navigation capability, this may be
the time to consider an upgrade. Why
now? Because if you are planning to
equip with ADS-B, a WAAS GPS navigator that can serve as your required ADS-B

AOPA Pilot Magazine - December 2017

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