The PBN concept
specifies aircraft RNAV system performance requirements in terms of
accuracy, integrity, availability, continuity and functionality needed
for the proposed operations in the context of a particular Airspace
Concept. The concept (PBN) relies on the use of both area navigation (RNAV)
and required navigation performance
(RNP) and revises the current RNP concept. It
represents a shift from sensor-based to performance-based navigation.
PBN offers a
number of advantages over the sensor-specific method of developing
airspace and obstacle clearance criteria:
a) Reduces need to
maintain sensor-specific routes and procedures, and their associated
costs.
b) Avoids need for
development of sensor-specific operations with each new evolution of
navigation systems, which would be cost-prohibitive.
c) Allows more
efficient use of airspace (route placement, fuel efficiency, noise
abatement).
d) Clarifies the
way in which RNAV systems are used.
e) Facilitates the
operational approval process for operators by providing a limited set of
navigation specifications intended for global use.
The concept of PBN
relies on the use of an Area Navigation (RNAV) system. The two core
components for the application of PBN are:
1.
Navaid Infrastructure
(both Ground and Space Based),
2.
Navigation Specification,
Applying these
components in the context of the Airspace Concept to ATS routes and
Instrument procedure s result in a third component
3.
Navigation application
A Navaid
Infrastructure is. Ground based Navaids, viz., VOR; DME (Not NDB) &
Space based Navaids, viz., GNSS/GPS, Glonass; future Galileo.
A Navigation
Specification is a set of aircraft and air crew requirements needed
to support a navigation application within a defined Airspace
Concept.
The Navigation
Specification defines the performance required of the RNAV system as
well as any functional requirements such as the ability to conduct
curved path procedures or to fly parallel offset routes.
Note:
RNAV and RNP systems are fundamentally similar. The key difference
between them is the requirement for on-board performance monitoring and
alerting.
The advantage of
this approach is that it enables harmonized and predictable flight paths
which result in more efficient use of existing aircraft capabilities, as
well as improved safety, greater airspace capacity, better fuel
efficiency, and resolution of noise issues.
Background
Under the
traditional approach, each new technology is associated with a range of
system-specific requirements for obstacle clearance, aircraft
separation, operational aspects (e.g. arrival and approach procedures),
aircrew operational training and training for air traffic controllers.
However, this system-specific approach imposes an unnecessary effort and
expense on ICAO as well as on States, airlines and air navigation
services (ANS) providers.
Performance based
navigation eliminates the need for redundant investment in developing
criteria and in operational modifications and training. Rather than
build an operation around a particular system, under PBN the operation
is defined according to the operational goals, and the available systems
are then evaluated to determine whether they are supportive.
It is increasingly seen as the
most practical solution for regulating the expanding domain of
navigation systems.
Performance
requirements are identified in navigation specifications, which also
identify the choice of navigation sensors and equipment that may be used
to meet the performance requirements. These navigation specifications
are defined at a sufficient level of detail to facilitate global
harmonization by providing specific implementation guidance for States
and operators.
The detail will continue in next
article.