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Global Positioning System


The GPS equipment must be approved in accordance with TSO C-129. ... Phase 1 You can use GPS only if ground-based nav equipment is monitored and operational. ... – PowerPoint PPT presentation

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Title: Global Positioning System

Global Positioning System
  • What pilot/students need to know!

GPS Generally
  • The GPS is a U.S. satellite based radio
    navigational , positioning, and time transfer
    system operated by the DoD.
  • The system provides highly accurate position and
    velocity information and precise time on a
    continuous global basis to properly equipped

There are two levels of service
  • Standard Positioning Service (SPS)
  • Precise Positioning Service (PPS)

(SPS) and (PPS)
  • 100 meters-95
  • 300 meters-99.99
  • PPS Is more accurate than SPS however it is
    limited to authorized U.S. and users who can
    satisfy specific U.S. requirements

Each satellite transmits specific code
  • It is called a CA or Course/Acquisition code.
  • It contains information on the satellites
    position,GPS system time, clock error and the
    health and accuracy of the data.

Your Receiver...
  • matches each satellites CA Code with an identical
    copy of the code contained in the receivers
  • By shifting the receivers code its matching the
    satellite and by comparing this shift with the
    satellite internal clock...wala!..magic!

Measuring distance
  • The distance derived from this computing is
    called pseudo-range because it is not a direct
    measurement but rather, measurement based on
  • Your receiver needs to know the satellites exact
    position in space
  • The receiver does the math to tell you where you

There are 24 satellites
  • A minimum of five satellites are always
    observable by a user anywhere on earth.
  • On December 8, 1993 the FAA granted approval to
    use GPS to conduct oceanic, domestic enroute,
    terminal IFR operations, and certain instrument
    approach procedures, under specified conditions

General Requirements
  • The GPS equipment must be approved in accordance
    with TSO C-129.
  • Aircraft using GPS under IFR must be equipped
    with an alternate means of navigation.
  • Procedures must be established if satellite
    reception is impaired, i.e.. delay or cancel

...more conditions
  • The GPS flight must must be conducted in
    accordance with FAA-approved flight manual or
    flight manual supplement.
  • Aircraft navigating by GPS are considered (by
    ATC) to be RNAV aircraft. The /R on the flight
    plan tells them that.(GPS goes in remarks)
  • Prior to flight GPS NOTAMS

There are/were three Phases of operations...
  • Phase 1 You can use GPS only if ground-based nav
    equipment is monitored and operational.
  • Phase II GPS without actively monitoring
    ground-based nav equipment..avionics must be
    installed an working..but not turned on.
  • Phase III is where approach plates are titled
    GPS and you do not need other nav gear.

  • Aeronautical Information Manual (Navigation Aids
    Chapter 1 Page 1-36)
  • FAA Advisory Circular AC 90-94 Guidelines for
    using GPS for IFR...

Lets talk about the 3 Phases!
  • Phase 1 ended February 1994 when the FAA declared
    GPS operational for civil operations.
  • Phase II began February 1994 when the FAA
    declared the system useable.
  • (Dont need to actively monitor ground-based as
    long as something tells you GPS is working.

Phase III
  • Phase III requires modification of the instrument
    approach procedure name to include GPS on the
    chart. You need neither the traditional avionics
    nor the ground station navaid(s) to be
    operational or monitored to fly non precision
    approach...if RAIM is monitoring the integrity of
    your GPS System.

What is RAIM
  • Receiver Autonomous Integrity Monitoring.
  • Your receiver tells you if you are receiving
    adequate signal to fly the GPS...if not, delay
    the flight or cancel as appropriate.
  • The reason being that Phase I,II, III have
    additional criteria

To repeat...
  • GPS must be TSOd
  • Receiver should have database with airport of
    choice...and no LOC, LDA or SDF approach.
  • If approach not in is probably
    unsafe that is why it is not there.
  • GPS should store all waypoints depicted on the
    approach chart.

  • Approach must be flown in accordance with FAA
    Aircraft Flight Manual or flight manual
  • Any required alternate airport should have an
    approved instrument approach other than
    GPS...NOTAMS is a pilot responsibility.
  • The GPS overlay approaches are limited to the
    U.S. national airspace.

and last but not least...!
  • Procedures should be established by the pilot in
    the event of GPS outages..meaning rely on other
    equipment, delay departure or discontinue IFR

Pilot Operations
  • To quote AC 90-94, ...All pilots must be
    thoroughly familiar with GPS equipment installed
    in the aircraft and its limitations.
  • The pilot should follow the specific start-up and
    self-test procedures for the GPS receiver as
    outlined in the FAA AFM or Flight Manual

  • Request from Briefer
  • Use identifier GPS, through the Direct User
    Access Terminal System (DUATS)
  • ..remember, if the NOTAMS indicate GPS is not
    working...the approach is not authorized.

Appropriate Approach
  • The pilot must select appropriate approach from
    GPS receiver to determine RAIM integrity for that
  • If GPS is out amend /R flight plan.

How about the alternate?
  • If the GPS aint working...the alternate must
    have an approved approach...other than GPS
    or..Loran-C!...which is anticipated to be
    operational at the estimated time of arrival!
  • What do you use?
  • ILS, NDB...?

Thats all Folks!
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