AOPA Pilot Magazine - June 2023 - 87

RNP value is 2; that is, 2 nm either side of
the centerline of an airway or route 4 nm
wide. The terminal phase encompasses
the initial stages of an approach and the
legs of a missed approach, and is defined
by the RNP 1 standard; that is 1 nm each
side of the centerline of a lane 2 nm wide.
The approach phase is a path from the
final approach fix to the missed approach
point, and the basic RNP value is 0.3; that
is, 0.3 nm from the centerline to the edge,
or 0.6 nm wide in total-except when you
are flying to LPV or LP minimums that
are based on an angular course that narrows
like a localizer as you descend
toward the threshold.
INSTRUMENT TIP /
PBN bingo
Making sense of new acronyms
BY BRUCE WILLIAMS
AV I AT ION DOESN'T NEED more abbreviations,
acronyms, and initialisms, but the
adoption of performance based navigation
(PBN), with all its advantages, has
added squares to the aviation lingo bingo
card. And to make matters worse, some of
the most important new terms have different
meanings, depending on when and
how they're used.
To make sense of these new and repurposed
terms, let's begin with the main
concept: PBN. Essentially, PBN is a set of
standards for navigating during each key
phase of flight.
That core idea has been around for
a long time. For example, VOR-based
airways are typically 8 nautical miles
wide, 4 nm each side of the centerline.
Ground-based navaids are spaced along
the airway to ensure that the angular
courses they transmit can accurately
define each segment of a route. Minimum
en route altitudes guarantee that aircraft
can reliably receive the line-of-sight
signals and stay in a lane that keeps them
above obstacles.
That idea of roads-some relatively
wide and straight, others narrower and
sometimes curved-has a new name
under PBN-navigation specifications, or
Nav Specs. Each Nav Spec is associated
with a key phase of flight.
The basic IFR Nav Specs are described
in Aeronautical Information Manual 1−2−1
and other publications. Each Nav Spec is
associated with a Required Navigation
Performance (RNP) value. En route, the
PBN is also based on another fundamental
concept. Under PBN, you can use
any approved system to fly the routes and
procedures associated with a particular
Nav Spec. The procedures themselves
don't need to be renamed or changed if
new navigation hardware meeting the
Nav Specs is adopted. Today, for those
of us flying typical general aviation aircraft,
a suitable RNAV system (described
in AIM 1−2−3) that meets the basic PBN
Nav Specs is an IFR-approved, panelmount
GPS or GPS enhanced with WAAS.
Now let's clarify more of the jargon
presented in AIM Section 2,
Performance-Based Navigation (PBN) and
Area Navigation (RNAV). It's here that
we encounter another problem: The
FAA sometimes uses the same term in
different ways.
For example, according to the AIM,
RNAV (area navigation) is " a method of
navigation that permits aircraft operation
on any desired flight path within the coverage
of ground. " Familiar enough.
RNP, as we've seen, is " a statement
of navigation performance necessary
for operation within a defined airspace. "
PBN
RNP APCH
LNAV
RNAV
ENR
LPV
PBN Bingo Card
NAV SPECS
TERM
AR
RNP
RNAV (GPS)
LP
APPROACH
RF
AOPA PILOT / June 2023
87
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AOPA Pilot Magazine - June 2023

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