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Instrument Flying Handbook
Navigation Systems
Required Navigation Performance

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Instrument Flying


Table of Contents

Chapter 1. Human Factors
Chapter 2. Aerodynamic Factors
Chapter 3. Flight Instruments
Chapter 4. Section I
Airplane Attitude Instrument
Using Analog Instrumentation
Chapter 4. Section II
Airplane Attitude Instrument
Using an Electronic Flight

Chapter 5. Section I
Airplane Basic
Flight Maneuvers
Using Analog Instrumentation
Chapter 5. Section II
Airplane Basic
Flight Maneuvers
Using an Electronic Flight

Chapter 6. Helicopter
Attitude Instrument Flying

Chapter 7. Navigation Systems
Chapter 8. The National
Airspace System

Chapter 9. The Air Traffic
Control System

Chapter 10. IFR Flight
Chapter 11. Emergency

MLS Coverage Volumes, 3-D Representation.
Figure 7-41. MLS Coverage Volumes, 3-D Representation.

Approach Azimuth Guidance
The azimuth station transmits MLS angle and data on one
of 200 channels within the frequency range of 5031 to 5091
MHz. The equipment is normally located about 1,000 feet
beyond the stop end of the runway, but there is considerable
flexibility in selecting sites. For example, for heliport
operations the azimuth transmitter can be collocated with
the elevation transmitter. The azimuth coverage extends
laterally at least. 40° on either side of (he runway centerline
in a standard configuration, in elevation up to an angle of 15°
and to at least 20,000 feet, and in range to at least 20 NM.

MLS requires separate airborne equipment to receive and
process the signals from what is normally installed in general
aviation aircraft today. It has data communications capability,
and can provide audible information about the condition
o the transmitting system and other pertinent data such as
weather, runway status, etc. The MLS transmits an audible
identifier consisting of four letters beginning with the letter
M, in Morse code at a rate of at least six per minute. The
MLS system monitors itself and transmits ground-to-air data
messages about the system's operational condition. During
periods of routine or emergency maintenance, the coded
identification is missing from the transmissions. At this time
there are only a few systems installed.

Required Navigation Performance

RNP is a navigation system that provides a specified level
of accuracy defined by a lateral area of confined airspace
in which an RNP-certified aircraft operates. The continuing
growth of aviation places increasing demands on airspace
capacity and emphasizes the need for the best use of the
available airspace. These factors, along with the accuracy of
modern aviation navigation systems and the requirement for
increased operational efficiency in terms of direct routing
and track-keeping accuracy, have resulted in the concept
of required navigation performance - a statement of the

navigation performance accuracy necessary for operation
with in a defined airspace. RNP can include both performance
and functional requirements and is indicated by the RNP type.
These standards arc intended for designers, manufacturers,
and installers of avionics equipment, as well as service
providers and users of these systems for global operations.
The minimum aviation system performance specification
(MASPS) provides guidance for the development of airspace
and operational procedures needed to obtain the benefits of
improved navigation capability. [Figure 7-42]

The RNP type defines the total system error (TSE) that
is allowed iii lateral and longitudinal dimensions within
a particular airspace. The TSE, which takes account of
navigation system errors (NSE), computation errors, display
errors and flight technical errors (FTE), must tint exceed the
specified RNP value for 95 percent of the flight time on any
part of any single flight. RNP combines the accuracy standards
laid out in the ICAO Manual (Doe 9613) with specific
accuracy requirements as well as functional and performance
standards, for the RNAV system to realize a system that
can meet future air traffic management requirements. The
functional criteria for RNP address the need for the flight paths
of participating aircraft to be both predictable and repeatable
to the declared levels of accuracy. More information on RNP
is contained in subsequent chapters.

The term RNP is also applied as a descriptor for airspace,
routes, and procedures (including departures, arrivals,
and IAPs). The descriptor can apply to a unique approach
procedure or to a large region of airspace. RNP applies to
navigation performance within a designated airspace, and
includes the capability of both the available infrastructure
(navigation aids) and the aircraft.

RNP type is used to specify navigation requirements for the
airspace. The following are ICAO RNP Types: RNP-l.0,
RNP-4.0, RNP-5.0, and RNP-10.0. The required performance
is obtained through a combination of aircraft capability and
the level of service provided by the corresponding navigation
infrastructure. From a broad perspective:

Aircraft Capability + Level of Service = Access

In this context, aircraft capability refers to the airworthiness
certification and operational approval elements (including
avionics, maintenance, database, human factors, pilot
procedures, training, and other issues). The level of service
element refers to the NAS infrastructure, including published
routes, signal-in-space performance and availability, and air
traffic management. When considered collectively, these
elements result in providing access. Access provides the
desired benefit (airspace, procedures, routes of flight, etc,)
RN? levels are actual distances from the centerline of the
flight path, which must be maintained for aircraft and obstacle
separation. Although additional PA A-recognized RN?
levels may be used for specific operations, the United States
currently supports three standard RNP levels:

RNP 0.3 Approach

RNP 1.0 — Departure, Terminal

RNP 2.0— En route