This document provides an overview of global positioning systems and flight management systems used in aircraft. It defines key terms and describes the components and functions of GPS, WAAS, INS, barometric altimeters, and how they integrate with an aircraft's flight management system. It explains how GPS and WAAS provide lateral and vertical navigation guidance for different types of instrument approaches, including LNAV, LNAV+V, LNAV/VNAV, LP, and LPV approaches. It also covers requirements, limitations, and safety aspects of using GPS and WAAS for navigation.

1. Global Positioning Systems
(GPS/WAAS)

2. Terminal Learning Objective
Action: Identify capabilities and functions of a Flight
Management System (FMS) with the Global
Positioning System (GPS/WAAS).
Condition: In a classroom or in the aircraft and
without reference for the written exam.
Standard: IAW the Guardrail student evaluation plan.

3. Administrative Data
SAFETY REQUIREMENTS: NONE
RISK ASSESSMENT LEVEL: IV/E – Low
ENVIRONMENTAL CONSIDERATIONS: No
Impact.
Evaluation: This material may be evaluated in
the Phase II/III Flight Evaluation.
Classification: Unclassified.

4. Agenda
•
•
•
•
•
•
FMS Terms
FMS Inputs
Global positioning System (GPS)
Wide Area Augmentation System (WAAS)
GPS Instrument Approaches
AR 95-1 Compliance

5. REFERENCES
•
FM 2-04.240 (FM 1-240), Chapter 7
•
AIM, Section 1-1-19
•
FAA-H-8261-1A, Instrument Procedures Handbook, Chapter 5 and
6
•
AR-95-1, Chapter 5
•
SEMA Hand - Out, GPS RNAV And Approach Charts
•
SEMA Hand – Out, RC-12X Flight Management System Universal
SCN 1100 Operator’s Manual

6. Flight Management System
(FMS)
Automates a wide variety of in-flight tasks:
• Aircraft performance and flight plan
management.
• Computes aircraft position using multiple aircraft
sensors (VOR,GPS, INS).
• Contains navigation database.
• Provides performance and flight path guidance
information to pilot navigation displays and
automatic flight control systems

7. FMS INPUTS
Navigation Inputs from each "active" sensor are
blended or deselected then summed up to provide
the best possible position data.

8. FMS Sensor Inputs
•
•
•
•
•
•
•
ADC (Air Data Computer)
DME/DME
VOR
GPS / WAAS
IRU / INS (Inertial Reference System)
Fuel Flow
Barometric Altitude

9. Common GPS/FMS Terms
ADC – Air Data Computer
GPS - Global Positioning System
IRU – Inertial reference Unit
INS – Inertial Navigation System
EGI - LN-100 Inertial Navigation System with embedded Global Positioning System (GPS)
RNAV - Area Navigation
GNSS - Global Navigation Satellite System
SBAS - Satellite Based Augmentation System. A general term for WASS navigation
GLS - GNSS Landing System ( LPV and LAAS Approaches)
WAAS - Wide Area Augmentation System
LNAV - Lateral Navigation (GPS/WAAS)
LNAV+V - LNAV approach where an advisory only descent angle is provided
APV - Approach with Vertical Guidance
LNAV / VNAV– GPS/WAAS Lateral Navigation with WAAS or Barometric Vertical Guidance
LPV - GPS/WAAS Localizer Performance with GPS Vertical Guidance
GLS - GNSS Landing System ( LPV and LAAS Approaches)
RAIM - Receiver Autonomous Integrity Monitoring
ANP – Actual navigation Performance
RNP – Required Navigation Performance

10. Inertial Navigation System
(INS)
• INS uses a computer and motion sensors
(accelerometers) mounted on
gyro-stabilized, gimbaled platforms to
continuously calculate velocity and dead
reckoning position without the need for
external references.
• INS gyros can also provide aircraft attitude
(pitch, roll, and heading).
• Once aligned with a known position, INS
continuously calculate position and velocity.
• INS position accuracy decays with time.

11. Air Data Computer (ADC)
The Air Data Computer (ADC) provides the FMS with:
• True Air Speed (TAS)
• Barometric Altitude
• Pressure Altitude (PA)
• Indicated Airspeed (IAS)
• MACH Airspeed
• Static and Total Air Temperature
All this is translated into useful information and
displayed to the pilot as basic flight instruments and
used by the FMS.

12. Student Check
Q: An Inertial Navigation System (INS) requires
external navigational aids to operate.
True or False?
• A: FALSE, INS uses a computer and motion
sensors (accelerometers) mounted on gyrostabilized, gimbaled platforms to continuously
calculate velocity and dead reckoning position
without the need for external references.

13. Embedded Global positioning
system / Inertial Navigation System
(EGI)
• LN 100 is an INS system incorporating an imbedded GPS that
is a component of the RC-12X’s mission equipment.
• INS alone without up-dating, errors are cumulative and
increase with time (about .6NM per hour error).
• GPS greatly enhances the performance of an INS by providing
an in-flight position up-date capability for the INS.
• When GPS is not available because of mountain shadowing of
satellites or jamming, INS provides accurate position
information until the GPS satellites are in view or the jamming
is over.

14. Area Navigation (RNAV)
• Permits point to point navigation.
• We will see an increased dependence on RNAV
with the FAA’s NextGen evolution.

15. ADS-B
• Automatic Dependent Surveillance Broadcast (ADS-B
– Evolving system that utilizes aircraft
transponders and GPS signals to display an
aircraft’s precise position combined with other
data and broadcast to other aircraft and air
traffic controllers without ground based radar.
• ADS-B may eventually replace ground based
ACT radar.

16. Global Positioning System
(GPS)
• GPS is a space-based radio-navigation system
consisting of a constellation of satellites and a
network of ground stations used for monitoring
and control.
• Minimum of 24 GPS satellites orbit the earth of
which at least 5 are observable by a user
anywhere on earth.
• Minimum of 4 satellites is necessary to establish
an accurate three-dimensional position.

17. 24 Satellites, a minimum of 4 is required.

18. GPS Coverage
Accurate three-dimensional navigation is
available to an infinite number of GPS receivers
anywhere on or near the Earth within Line of
Sight to GPS satellites.

19. How GPS Works

21. Global Navigation Satellite Systems
GNSS
The generic term for air navigation utilizing GPS
for RNAV operations for all phases of flight from
departure, enroute, terminal, approach, and
surface.

22. Receiver Autonomous Integrity Monitoring
(RAIM)
• The RAIM system monitors the status of GPS
satellites and broadcasts the GPS status as part
of data message transmitted by GPS satellites.
• GPS status information is available by the Notice
to Airmen (NOTAM) system.
• RAIM Prediction

23. In-Flight (RAIM)
• Continuous fault detection
• Excludes a failed satellites from the FMS position
solution.
• RAIM Prediction in flight provides early indications
of unscheduled satellite outage that has occurred
since takeoff.
• WAAS availability precludes In-Flight RAIM.

24. RAIM FAILURE
• If a RAIM failure occurs after the Final Approach
Way Point (FAWP), the receiver will continue
operating without an annunciation for up to 5
minutes allowing completion of the approach
(See AR-95-1).
• If a RAIM failure/status annunciation occurs
prior to the Final Approach Waypoint (FAWP),
the approach should not be completed since
GPS may no longer provide the required
accuracy.

25. Standard GPS Accuracy
Basic GPS signal (worst case scenario) –
• Approximately 100 meters (328 ft) lateral
FAA-H-8083-15A
• Approximately 140 meters (460 ft) vertical
Pg 7-27
www.faa.gov
460 ft
328 ft

26. FMS Navigation Databases
•
Navigation databases certified for en route and terminal operations
are loaded into the FMS.
•
Contain airports, VORs, VORTACs, NDBs, airways and named
waypoints (WPs), intersections shown on en route charts,
instrument approach charts, SIDs, and STARs.
•
There is no specific requirement to check the latitude and longitude
of each published database waypoint, type of waypoint and/or
altitude constraint. Verify only the general relationship of waypoints
in the procedure, or the logic of an individual waypoint's location.

27. Use of GPS for IFR Oceanic,
Domestic En Route, and Terminal
Area Operations
•
GPS procedures may be restricted outside the United States. Check
for restrictions in FLIP GP and area planning (AP) documents.
•
GPS procedures for IFR navigation in the terminal area, equipment
must include an updatable navigation database.
•
GPS airborne navigation databases may come from the National
Geospatial Agency (NGA) or from an approved commercial source
such a Jeppessen.

28. GPS Satellite Jamming and
Interference
•
GPS as with all navigation aids, interference,
whether intentional or unintentional, is a
concern. A number of methods for minimizing
interference have been identified and tested and
others are being investigated.
•
The Wide Area Augmentation System
(WAAS) helps to detect and mitigate these
effects.

29. ANTI-SPOOFING
• SELECTIVE AVAILABILITY (SA) - Used to
deny hostile use of precise GPS positioning
data.
• SA is implemented by DoD to intentionally
degrade a non DoD user’s navigation solution
resulting in a five-fold increase in positioning
error.
• Selective Availability was discontinued in
May 2000 but could be re-activated.

30. Levels of Accuracy Available
• Standard Positioning Service (SPS) – Accuracy
is 100 meters lateral and 140 meters vertical
and can be received by anyone with a GPS
receiver.
• Precise Positioning Service (PPS) - Accuracy
better than 7 meters horizontal. Available to PPS
users in possession of proper cryptography.

31. Actual Navigation Performance
(ANP)
• ANP is a measure of the system’s best estimate
of error, calculated to allow for flight technical
error.
• ANP = 1.00 nm, means a 95% chance that the
FMS position is within 1.00 nm of the actual
position.

32. Required Navigation Performance
(RNP)
•
RNP is a statement of navigation performance necessary for operation
within a defined airspace.
•
RNP navigation requires inputs from GPS and/or WAAS to calculate the
precision "corridor" or "highway" of an RNP procedure.
•
Maintaining a narrow "RNP" corridor of flight space in both vertical and
lateral planes allows for increased aircraft operations for any given period of
time.
•
Flight Management Systems are used to navigate RNP procedures with
RNP procedures in their databases.
•
Standard GPS approaches require at least .3 nautical mile RNP
accuracy on final approach, however, some RNP approaches require
greater than .3NM accuracy on final approach.
•
FAA requires specialized aircrew training requirements for RNP GPS
instrument approaches.

33. Standard RNP

34. Radius -TO-Fix leg
“RF”
RNP
0.11

35. GPS Course Deviation Indicator (CDI)
Scaling
• Enroute – Greater that 30 miles from destination airport, GPS
full scale CDI sensitivity equals +/- 5NM, or each GPS CDI dot
equals 1.0NM linear deviation off course.
• Terminal – Within 30 miles from the airport, GPS CDI full
scale sensitivity automatically changes to +/- 1NM, or each dot
equals .2NM linear deviation mile off course.
• Approach - At two miles from the final approach waypoint
(FAWP), GPS CDI full scale sensitivity automatically changes to
+/- .3 NM, or each dot represents approximately 365 feet off
course.

36. RNP Navigation

37. Student Check
Q: Standard GPS Final approaches require
accuracy of at least
a. .1 nautical mile accuracy.
b .5 nautical mile accuracy.
c. .3 nautical mile accuracy.
A: c. .3 nautical mile accuracy.

38. Satellite Based Augmentation Systems
(SBAS)
SBAS systems correct and improves the accuracy
of GPS receivers.
• North America – WAAS
• Asia - Multi-Functional Satellite Augmentation
System (MSAS)
• Europe - Euro Geostationary Navigation Overlay
Service (EGNOS)
Eventually, GPS users around the world will have
access to precise position data using an SBAS
or other compatible system.

39. Wide Area Augmentation System
(WAAS)
•
North America’s Satellite Based Augmentation System (SBSA) utilizes an
additional two geostationary satellites that work in conjunction with 25
ground stations, providing improved position accuracy and integrity to the
base GNSS System.
•
WAAS ground stations interpret existing GPS satellite constellation signals
and make corrections to any errors that may exist.
•
WAAS satellites repeat correction signals down to WAAS capable receivers.
•
An additional sensor added to the FMS based on geostationary satellites.
•
There are now more published LPV approaches than ILS approaches in the
United States.

40. How WAAS Works

41. WAAS STATIONS

42. Benefits of SBAS/WAAS
• ILS-like approach procedures (LPV).
•Higher level of service and accuracy.
•An electronic glide path can be generated independent of
ground equipment or barometric aiding.
•Key benefit - Vertically-Guided Instrument Approach
minimums as low as 200 feet AGL.

43. WAAS ACCURACY
WAAS improves GPS signal accuracy from 100
meters (328 ft) to approximately 7 meters (23ft).
www.faa.gov

44. WAAS - Safeguards
• WAAS system is designed to strictest of safety
standards.
• Users are notified within six seconds of any of
hazardous or misleading information that would
cause an error in the GPS position estimate.
• Provides indications where system is unusable.
• Precludes In-Flight RAIM Monitoring

45. LNAV Instrument Approaches
• LNAV is a Non-Precision Approach when Lateral
Navigation only is provided by GPS and/or WAAS.
• The pilot flies the final approach with Lateral Navigation
provided by GPS, however, the pilot is responsible for
vertical navigation.
• The pilot descends to step-down altitudes and to the
Minimum Descent Altitude (MDA) referencing the pilot’s
barometric altimeter.
• LNAV+V - When an Advisory Only Descent Angle is
provided.

46. GPS Approaches With Vertical
Guidance
• LNAV/VNAV - When Lateral along with Vertical Navigation is
provided. The LNAV is provided by GPS and the VNAV is
provided by either WAAS or an FMS Barometric Aided VNAV
computation (Baro-Aiding).
• Localizer Performance with Vertical Guidance (LPV) When WAAS is required for both Lateral and Vertical navigation.
LPV minimums will usually be lower than LNAV/VNAV or LNAV
minimums.

47. Baro-Aiding VNAV
• Without WAAS or Baro-Aiding, the GPS derived vertical
navigation cannot be relied upon since the vertical error
can be quite large (± 460 feet) and no integrity is
provided.
• Baro-Aiding is a method of augmenting GPS lateral
navigation with a vertical navigation solution computed
by the FMS using a non satellite input source (Altimeter
In-Put).
• To ensure that Baro-Biding is accurate, the current
altimeter setting must be entered.
• Pilots must correct the descent path and DA/MDA for
colder than standard temperatures.

48. Baro-Aiding
Temperature Compensation

49. LPV Approach - Localizer
Performance with Vertical Guidance
• Localizer performance with GPS vertical
guidance.
• LPV approaches can only be accomplished with
WAAS GPS receivers.
• LPV minimums may be as low as 200 feet AGL
with required approach and runway lights.
• Has the potential to provide precision approach
accuracy to almost all runways.

50. Localizer Performance Approaches
(LP)
• LP procedures require WAAS for later guidance
only.
• Used at locations where the terrain or
obstructions do not allow publication of vertically
guided LPV procedures.
• LP approaches take advantage of the angular
lateral guidance and smaller position errors.
provided by WAAS to provide a lateral only
procedure similar to an ILS Localizer.
• LP procedures may provide lower minima than a
LNAV procedure due to the narrower obstacle
clearance surface.

51. Level of Service Lights (FMS LOS)
•
LOS is based on predicted GPS horizontal and vertical accuracy against
required horizontal and vertical approach limits.
•
LPV - Highest LOS provided by the FMS, equated with LPV approach
minimums. When the FMS determines that LPV LOS is available, the
LPV LOS light will be illuminated.
•
LNAV + VNAV - Second highest LOS . When the FMS determines
LNAV + VNAV level of service is available, the LNAV + VNAV Level of
Service light will be illuminated.
•
LNAV - Lowest LOS. When the FMS determines that only LNAV level
of service is available, the LNAV Level of Service light will be
illuminated.
NOTE: LPV approach operations require two operational FMS.

52. WAAS LPV Approaches Identified by a “W”

53. Level Of Service

54. Standard Format for RNAV/GPS Minimums
Approach minima (LPV, LNAV/VNAV, LNAV) is predicated on
Level Of Service (LOS) annunciated.

55. GPS Approach Procedures
•
•
Stand-Alone - Procedures are designed for use only by GPS
systems.
GPS overlay – GPS procedure overlaid on conventional VOR,
VOR/DME, etc. procedures. Are titled with the type of Navigational
Aid (NAVAID), including "or GPS" (e.g., VOR or GPS RWY 24).
•
Approaches that may be flown in the GPS mode will contain “RNAV”
or "GPS" in the title (e.g., "VOR or GPS RWY 24," "GPS RWY 24,"
or "RNAV (GPS) RWY 24").
•
When flying overlay GPS approaches, the underlying ground-based
NAVAIDs are not required to be operational and associated aircraft
avionics need not be installed and/or operational.
•
ILS Approaches – The ILS approach transition and published
missed approach segments may be flown in the FMS mode,
however, the ILS final approach segment must be flown with the
LOC navigation source selected.

56. Flying GPS Approaches
•
•
•
•
•
Fly the full approach from an Initial Approach Waypoint (IAWP) or
feeder fix unless specifically cleared otherwise.
When receiving vectors to final, place the FMS in the no-sequencing
mode (Activate Approach) and use Command Heading.
An "arm" annunciation should occur 30 NM straight line distance
from the end of the runway reference point and then it should arm
automatically.
Without arming, the receiver will not change from en route CDI and
RAIM sensitivity of ±2 NM either side of centerline to ±1 NM terminal
sensitivity.
Within 2 NM of the FAP with the approach mode armed, the
approach mode will switch to active, which results in changing to
approach CDI sensitivity of ±0.3 NM at the FAWP.

57. GPS Approach Formats
Standard “I”
Standard “T”

58. Terminal Arrival Area (TAA)

59. Terminal
Arrival
Area (TAA)
Right Base
Left Base
Straight-In

60. Terminal
Arrival
Area (TAA)
Right Base
Left Base
Straight-In

61. Fly-By Waypoint
Fly-Over Waypoint

62. GPS Missed Approach
• Pressing the Go-Around button will automatically
sequence the FMS to the missed approach
segment of the procedure past the Missed
Approach Way Point (MAWP).
• Turns should not begin prior to the MAWP.

63. Local Area Augmentation System
(LAAS)
• LAAS provides a GPS corrected navigation
signal that is broadcast from a LAAS VHF data
broadcast transmitter at or near some airports.
• LAAS avionics must be installed on aircraft.
• LAAS covers approximately a 30-mile radius and
provides up to Category III precision approach
minimums (DA 50 feet) with accuracy within 1
Meter.

64. Local Area Augmentation System
(LAAS)
LAAS improves GPS signal accuracy from 100 meters
(328ft.) to approximately 1 meter (3ft.).

65. How LAAS Works

66. JPALS
Joint Precision Approach and Landing
System
• Mobile, LAAS-like DoD system
• All-weather, all-mission, all-user
landing system based on local area
Differential Global Positioning System
(DGPS).
• Provides accurate and reliable landing
guidance for fixed and rotary wing
aircraft during all weather conditions.

67. JPALS
• Features a high GPS
anti-jam protection to
assure mission continuity
in a hostile environment
• Compatible with civil and
military GPS signals

68. AR 95-1 Chapter 5
Flight Procedures and Rules
GPS is authorized for IFR flight if—
• IFR GPS is authorized in the applicable
sovereign airspace- check DOD FLIP Area
Planning (AP).
• Installed GPS equipment is certified for IFR
operation.
• Precise Positioning Service (PPS) will be
operated in the PPS mode.
• Current DOD/US Government FLIP products
will be carried and accessible at all times.

69. AR 95-1
User Defined Waypoints • IFR RNAV/GPS departure, arrival, en route and
terminal procedures will only be flown using
waypoints retrieved from an approved
non-corruptible database.
• Manual entry or update of the navigation
database other than storing “user defined data”
is not authorized (except for approved EMER
GPS procedures).

70. AR 95-1
Approved Databases –
• Use of commercial IFR databases (for example,
Jeppessen) in Army aircraft is only authorized in
the United States and US territories.
• Use of commercial databases elsewhere in the
world is restricted to en route navigation or to US
military facilities overseas unless approved by
USAASA/USAASD–E.

71. AR 95-1
IFR Alternate Selection –
An airfield will not be selected as an alternate If
the global positioning system (GPS) is required
for the approach and descent from en route
minimum altitude for IFR operation, approach,
and landing cannot be made in VFR conditions..

72. AR 95-1
Prior to IFR GPS Flight Check—
• All required navigation performance (RNP) levels must
be met when operating in designated RNP airspace.
• IFR GPS flight will not be conducted with an expired
navigational database.
• Appropriate suffix for GPS/RNAV equipment will be
entered on the flight plan, e.g.: “G” for DD 175
or “S / ITG /S” for DD 1801.
NOTE:
Flight Plans Requesting “Q” or “T” Routes”, RNAV SIDs
and STARs require filing in the ICAO Flight plan format.

73. AR 95-1
GPS Substitution of Navigation aids–
When operating IFR in the US National Airspace
System (NAS), GPS waypoints may be used as
substitutes for ADF and/or DME receivers.
Consult DOD FLIP/host nation for authorized
substitutions.

74. AR 95-1
RNAV/GPS Departure Procedures (DP)• (DP) must have terminal RAIM availability prior
to departure.
• The CDI sensitivity will be set to + or - 1nm
sensitivity or as published.

75. AR 95-1
GPS approach Requirements :
•
•
•
•
•
When using a Digital Aeronautical Flight Information File (DAFIF) database,
terminal procedures authorized to be flown are RNAV/GPS procedures and
GPS overlay approaches if the title contains “or GPS” and the procedure
has a Final Approach Fix (FAF) and the procedure can be retrieved from the
database.
Underlying NAVAIDS on overlay approaches should be tuned and
monitored during the approach.
DAFIF will not be used in Flight Management Systems (FMS) to
drive/sequence other conventional NAVAID terminal procedures, for
example, NDB, VOR, TACAN.
Same approach must be reviewed and displayed to the crew from the
current DOD FLIP procedure.
Compare the database retrieved procedure loaded in the GPS to the
published procedure to ensure accuracy, If differences are detected, the
published product, supplemented by NOTAMs, will take precedence over
the database procedure.

76. AR 95-1
GPS Approach Procedures
• Verify the GPS system begins to sequence when
entering the terminal area, that the approach is armed
prior to the Initial Approach Fix (IAF) and that course
sensitivity on the CDI changes appropriately.
• If a RAIM failure/status annunciation occurs or the GPS
does not sequence to the “active approach” mode, the
pilot will request an alternate procedure or if already
passed the Final Approach Waypoint (FAWP), the pilot
will climb to the missed approach altitude and execute
the missed approach.

77. AR 95-1
GPS Approach Minimums
• Approach minimums listed as GLS (or LPV), and
LNAV/VNAV, categories will only be flown if the aircraft
is appropriately equipped.
• Barometric Vertical Navigation (baro-VNAV) decision
altitude (DA) is not authorized with a remote altimeter
setting. If local altimeter setting is not available, the MDA
becomes the published LNAV MDA, cold temperature
restrictions apply.
• Circling from RNAV/GPS approaches may be
accomplished if circling minimums are published.

78. AR 95-1
GPS Missed Approach
Upon missed approach, pilots will ensure the
missed approach function has been
appropriately activated on the GPS.

79. Student Check
Q: An IFR alternate airfield may be selected if the
global positioning system (GPS) is required for
an IFR approach to that airfield and descent
from en route minimum altitude for IFR
operation, approach, and landing cannot be
made in VFR conditions..
True or False?
A: FALSE

80. Summary
•
•
•
•
•
•
FMS Terms
FMS Inputs
Global positioning System (GPS)
Wide Area Augmentation System (WAAS)
GPS Approaches
AR 95-1 Compliance

81. Questions ?