Home' RTCA Documents for Review : DO-201B User Requirements for Navigation Data Contents ED-77A/DO-201BforOpenConsultation/FRAC
© EUROCAE, 2018
FAA AC 90-105A, RNP Scalability is a mandatory function in order for operators to be
The RNP system must be capable of manual or automatic entry and display of
navigation accuracy requirements in tenths of a nautical mile between 0.3 nm and 1.0
nm. The RNP system must provide lateral deviation displays and alerting appropriate to
the selected navigation accuracy and application.
A navigation database is required. The specific requirements on navigation database
are similar to those applicable to RNAV 1 and RNAV 2.
The RNP 0.3 navigation specification is primarily intended for helicopter operations. It
has a single accuracy of 0.3 nm for all phases of flight. A navigation database is
required. The specific requirements on navigation database are similar to those
applicable to RNAV 1 and RNAV 2.
No additional RNAV specifications are to be developed: ICAO foresees a transition to
RNP operations as the proportion of aircraft equipped with RNP systems increases and
the cost of transition reduces. Nevertheless, RNAV and RNP operations will co-exist for
RNP departure operations are being considered and when completed will be part of the
RNP AR navigation specifications.
Currently, PBN aims to harmonize longitudinal and lateral performance requirements
(i.e., 2D) for both RNAV and RNP specifications and in the future, it is expected to
include 4D Trajectory-based Operations (TBO).
PBN Transition to Final Approach (RNP to xLS)
The RNP transition to xLS operations consists of an instrument approach procedures
with initial and intermediate segment (or RNP SID/STAR) based on RNP transitioning
to a final precision approach segment based on ILS, MLS or alternatively GBAS. Similar
procedures with SBAS are covered in the RNP APCH navigation specification of PBN.
While these types of procedures are currently possible, the challenges remain when a
short final approach segment is desired (example 3 nm or 5 nm) connected to a sloping
and/or curved intermediate segment via an RF leg. It is desired that the navigation
database provide connection of an RF leg directly to FAF.
The use of GNSS and its augmentation systems such as GBAS or SBAS allows for the
development of multiple approach procedures to the same runway end with varying
glide paths and runway thresholds. Enhanced arrival procedures are being operationally
tested and validated via fast-time and real-time simulations for example:
Increased glide slopes: a glide path with a glide slope increased between 3.0° and 4.5°
compared to the standard 3°
Multiple runway aiming points: a glide path anchored to a shifted touch down points with
respect to the standard threshold
Double slope approaches: a final approach path split in two different segments, a first
steeper approach segment, followed by a standard one (3°)
From a navigation database perspective, several items will need further discussions
such as approach identification, coding of multiple thresholds, coding of multiple glide
paths, the possibility to code two glide paths in the same approach procedures, the size
of the navigation database etc.
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