On Board Navigation System Architecture

Air navigation

It is a set of methods, systems, and facilities used to determine and control and aircraft’s position, track and guidance so it reaches its destination safely

Air navigation

It is a set of procedures, navigation aids and systems used for position determination, route, guidance and approach/landing guidance

Air navigation

It is a set of techniques used to determine the position of an aircraft, allowing it to move along a predetermined trajectory.

Navigation in aviation

It is the combined use of methods, systems and facilities to determine position, control track, and provide guidance so an aircraft reaches its destination safely

Heading

Track

Two key elements in air navigation

Above FL 200 or 20,000 ft or 6100 m

At transonic and supersonic speeds

Unless authorized by the appropriate ATS authority, VFR flights shall not be operated: (2)

Instrument flight rule

The pilot operates the aircraft in IMC (Instrument meteorological conditions)

IMC

weather conditions below the VMC standards but still safe for the aircraft to operate with the proper navigation and flight instruments

14.5 Instrument Flight rules

IFR are detailed in CAR-ANS part ______

Ground-based

Space-based

Onboard

Classification of navigation systems (3)

Pilotage

Dead reckoning

Early navigation methods (2)

Pilotage

simplest and oldest form of navigation
based on the observation of visual references to navigate
limited to visibility conditions (VMC)

Dead reckoning

Position estimated from speed, heading and elapsed time, corrected for wind; errors accumulate over time and distance, making it unreliable for long overwater or low-visibility flights

Previous preparation of route is required to calculate headings distance and times

NDB

VOR

DME

ILS

Radio navigation (ground based radio navAids) (4)

NDB

ground beacons that provide a bearing to the station; simple but susceptible to coastal/refraction errors and limited accuracy

VOR

provide reliable radials for course guidance and formed the backbone of airway networks

radar

ILS, DME and _____ enabled structured terminal procedures and safe instrument approaches long before satellites

GNSS –Global Navigation Satellite System

provide continuous global position and time enabling RNAV and point-to-point navigation; dramatically reduced dependednce on local ground infrastructure ; uses Aeronautical Information Regulation and Control (for trilateration)

SBAS (WAAS, EGNOS) and GBAS

____ and _____ improve accuracy, integrity and availability to support precision approaches comparable to ILS

Inertial navigation

self contained navigation system, since It does not require any information or signals from external systems or ground-based navaids to operate
based on the use of gyroscopes and accelerometers to navigate

LORAN-C (Long Range Navigation System)

based on the use of radio signals emmited from antennas on the ground to navigate
oceanic long range navigation, but tends to disappear (GNSS is more accurate)

RNAV (Area Navigation)

integrates several systems to improve its accuracy and reliability
based on receiving and processing information from various navigation systems to determine the current position and navigate

RNP (Required Navigation Performance)

same operating principles as the RNAV
includes navigation performance monitoring and alerting system
allows to know current accuracy of the system

widely used in the design of complex approach and departure procedures due to its excellent performance and accuracy requirements

PBN (Performance Based Navigation)

navigation specified by required performance (Accuracy, integrity, continuity, availability) rather than by sensor type; enables RNAV and RNP procedures with onboard monitoring and alerting

Modern aircraft use sensor function

Cross-checking between GNSS, INS, radio aids.
Redundancy ensures reliability.

Modern trends in navigation system integration. (3)

Safety

Importance of Onboard Navigation Systems:

Accurate positioning reduces the risk of CFIT and mid-air conflicts by providing continuous lateral and vertical awareness in IMC
Redundancy and integrity monitoring detect and mitigate faulty inputs before they lead to unsafe guidance

Efficiency

Importance of Onboard Navigation systems:

Optimized routing (RNAV/RNP) and continuous descent approaches reduce fuel burn and flight time;

point‑to‑point navigation eliminates circuitous ground‑based airway constraints

Compliance

Importance of Onboard Navigation systems:

Navigation systems must meet ICAO/FAA/EASA performance and certification standards to be used for IFR, RNP, and precision approach operations; operators require approvals tied to demonstrated performance.

Operational capability

Importance of Onboard Navigation systems:

Precision approaches using GNSS+SBAS/GBAS and RNP AR procedures enable access to airports lacking ILS and support curved or noise‑abating approach paths.
Integration with autopilot and FMS allows automated flight segments, reducing crew workload for routine navigation while requiring vigilance for system anomalies.

Integration

Importance of Onboard Navigation systems:

Multiple navigation sources (GNSS, INS/IRU, VOR/DME, radar, vision systems) are fused onboard to provide continuous, resilient solutions; this fusion plus procedural redundancy is central to safe operations

Safety

Efficiency

Compliance

Operational capability

Integration

Importance of Onboard Navigation systems (5)

ICAO (International Civil Aviation Organization)

Sets global standards for air navigation and safety
Defines requirements for performance-Based Navigation
Publishes Annexes (Annex 10 on Aeronautical Telecommunications) covering navigation systems
Promotes harmonization across member states to ensure inter-operability

It determines an aircraft’s location in three dimensions: latitude, longitude, and altitude. In aviation this is essential for navigation, separation, approach procedures, and flight planning.

Coordinate pair

Latitude and longitude together give a unique horizontal position on the Earth’s reference surface (ellipsoid). In aviation coordinates are usually expressed in decimal degrees or in degrees and minutes for charts and flight management systems.

True altitude

vertical distance above mean sea level (MSL)

Indicated altitude

what the barometric altimeter displays after setting the local pressure (QNH/QFE)

Pressure altitude

altitude relative to the standard pressure datum (1013.25 hPa); used for flight levels.

Geodetic (GNSS)

altitude height above the ellipsoid; differs from MSL by the geoid separation

Barometric altitude

measures ambient pressure and converts to altitude using the International Standard Atmosphere; requires correct pressure setting and is affected by temperature and pressure variations.

GNSS (GPS) altitude

computed from satellite ranges; gives geodetic height which must be converted to MSL using geoid models for operational use. GNSS can provide high vertical accuracy but may differ from barometric readings by tens to hundreds of meters unless harmonized

Heading

Compass (magnetic or true)

____ is the Direction the aircraft’s nose points

Affected by Pilot control, wind does not change heading itself

Reference frame: ____

Track

Ground-referenced bearing

____ is the Actual path over the ground; Determined by combining heading with wind effect

Affected by Wind drift, ground speed
Reference frame: ____

Course

Planned bearing on charts or FMS

____ is the Intended path over the ground during flight preparation

Affected by Pilot planning; must be maintained by adjusting heading

Reference frame:

Cardinal

Quadrantal

____ and ____ points were initially used to express the relative direction to a point

Sexagesimal system

-numerical direction system consisting of 360 starting from north
-derived from the cardinal point system
-particular direction can be precisely expressed using angles

Geographic North Pole (True North)

real north pole of the earth, where the meridians converge and through which the plant’s axis of rotation passes

Magnetic compass

used to determine the direction in relation to magnetic north
compass needles aligns with earth’s magnetic field lines

Magnetic north pole

point through which the magnetic field lines re-enter the planet
point which all compasses point

Magnetic course

angle between magnetic north and course

Magnetic variation

magnetic declination
angle between true north and magnetic north

Smalller

Greater

East variation: MC will be ____ than TC

West variation: MC will be ____ than TC

Isogonic lines

agonic line

Lines that join points of equal magnetic Variation

the line that joins points of zero variation is called ___

Drift

Error in navigation that is:

Caused by wind pushing the aircraft off its intended course
Measured as the angle between heading and track
Corrected by adjusting heading into the wind (wind correction angle)

Deviation

Error in navigation that is:

Errors in compass reading caused by magnetic interference
Each aircraft has a deviation card showing correction values for different headings

Correction

Error in navigation that is:

Pilots apply corrections to heading to compensate for drift and deviation
Modern systems (GPS, FMS) automatically calculate and adjust for these errors

Drift

Deviation

Correction

Errors in navigation (3)

onboard navigation system

An _____ provides continuous, accurate position, velocity, and attitude information to the vehicle and crew.

Engine instruments

Flight instruments

Navigation instruments

types of instruments in an aircraft (3)

Engine

Instruments that measure operating parameters of the aircraft

Flight instruments

The instruments used in controlling the aircraft’s flight

Airspeed indicator (ASI)

Shows the aircraft’s speed relative to the surrounding air.

Altitude Indicator (AI)

Displays the aircraft’s orientation relative to the horizon (pitch and bank).

Critical for instrument flight when outside visual references are limited.

Turn coordinator

Shows rate of turn and coordination (whether the aircraft is slipping or skidding).

Helps maintain balanced turns.

Heading indicator (directional gyro)

Displays the aircraft’s heading relative to magnetic north.

More stable than a magnetic compass but requires periodic adjustment.

Vertical speed indicator (VSI)

Shows the rate of climb or descent in feet per minute.

Useful for maintaining smooth altitude changes.

Instruments that are used by the pilot to guide the aircraft along a

Sensor

Display (HMI)

Parts of instrument systems (2)

Direct-sensing instrument System

Remote-sensing instrument system

Types of instrument system (sensors) (2)

Gyroscopic sensors

Pitot-static sensors

Classification of sensors (2)

Gyroscopic sensors

Attitude indicator, heading indicator & turn coordinator are examples of ____ sensors

Pitot-static sensors

Altimeter, airspeed indicator, & vertical speed indicator are examples of ____ sensors

Mechanical gyro

Solid State gyro

Types of gyro (2)

Mechanical gyroscope or gyro

Comprised of a wheel or rotor with its mass concentrated around its perimeter.

The shaft about which the rotor spins is called the axis. Gyros are defined in their orientation as either horizontal or vertical by reference to the spin axis, not the rotor.

Rigidity

____ is the gyro’s property of maintaining its axis in a fixed direction in space unless subjected to an external force. It is caused by the inertia of the spinning mass

Gimbals

Suspension devices which allows aircrafts freedom to maneuver without disturbing the orientation of the gyro

Precession

____ is what happens when you push on a spinning gyroscope:The effect doesn’t show up exactly where you pushed.Instead, the movement appears 90° later in the direction of spin

greater

The faster the rotor spins, the _____ the gyro’s rigidity

larger

A gyro with a greater mass will have a ____ moment of inertia

directly proportional

inversely proportional

The rate of precession is ______ to the applied torque but _____ to the moment of inertia and the rotor rpm rate.

Gyroscopic sensors

Provide the pilot with critical attitude and directional information and are particularly important while flying under IFR

Pressure driven

Vacuum driven

Electrically driven

Gyroscopic sensors can be classified to type of drive (3)

venturi

The velocity of the air rushing through a ____ can create
sufficient suction to spin instrument gyros.

vane-type engine-driven pump

_____ operates without external lubrication and installation requires no connection to the engine oil supply.

Solid-State gyroscope

Modern aircraft make use of highly accurate solid state devices with little to none moving parts

Ring-laser gyros

Microelectromechanical systems (MEMS)

Examples of solid State gyroscope

Attitude indicator

Gyroscopic sensors that depicts the position of the airplane in relation to the Earth's horizon on terms of pitch and bank (roll)

Artificial horizon

Bank angle

angle between horizon and lateral axis

Pitch angle

angle between horizon and longitudinal axis

The ____ in the attitude indicator iOS visible when gyro is not functional; indicates instrument should not be used

gyroscopic effect of rigidity

Attitude indicator uses _____ in space to measure attitude

Heading indicator

Gyroscopic sensors that:

Used to inform the pilot of the aircraft's heading in relation to a directional reference
Known also as the directional gyro or heading gyro.
It must be set according to the magnetic compass indication before takeoff, and
Occasionally adjusted to the magnetic compass while the aircraft is in steady, level flight.

shaft

lubber

The heading indicator dial (compass card) is directly driven by the _____ from the gyro. The compass card rotates as heading changes and the heading is read against the index line in the 12 o’clock position (the ____ line).

Turn coordinator

Gyroscopic sensors that:

Gives information about the direction and rate of a turn.
Works on the principle of precession.
Additionally, it indicates if the turn is being flown in coordinated flight.

Rate of turn indicator

The measuring device in turn coordinator that uses a rate gyro to measure rate of turn about a vertical axis.

Slip indicator

The measuring device in turn coordinator which is a very simple pendulous device which is used mainly to show whether or not a turn is balanced and if not, to indicate the extent of slip or skid

Pitot tube

Static vents

Pitot-static sensors use ____ to measure the dynamic pressure due to the forward motion is the airplane through the air, and

____ to measure the static, outside barometric pressure as the airplane gains or loses altitude.

straightens

Recoils

The free end of the coiled tube in pitot-static sensors _____ when Pressure is higher.

When Pressure is reduced, the tube _____.

Aneroid

Bellows

Differential pressure

Evacuated sealed diaphragm is called an ____.

When a number of diaphragm chambers are connected together, the device is called ____.

This accordion like assembly of diaphragms can be very useful when measuring ____

Air speed indicator

The ____ is a differential pressure gauge that compares team air pressure with static pressure.

It measures the difference in pressure from the pitot tube and static vent

VSI (Vertical speed indicator)

The ____ is a differential pressure gauge that compares free-flowing static air pressure in the diaphragm with restricted static air pressure around the diaphragm in the instrument case.