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The GPS

The GPS. Kent State University Flight Instructor Refresher Clinic Feb 2008. Objectives. Learn the basic operational theory behind GPS How to use this wonderful piece of equipment Look up and find the GPS options in the AIM. GPS operations.

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The GPS

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  1. The GPS Kent State University Flight Instructor Refresher Clinic Feb 2008

  2. Objectives • Learn the basic operational theory behind GPS • How to use this wonderful piece of equipment • Look up and find the GPS options in the AIM

  3. GPS operations • A Global Positioning System will utilize timing and information from satellites in orbit around the Earth. • Each satellite emits a signal, that signal has a time stamp and any additional coding (military). The satellites utilize an atomic clock to detect time.

  4. Your receiver • Your receiver receives the signal and takes the time stamp and using the speed of light with known errors, derives the distance. • This forms a sphere around the satellite. With the one sphere there is no way for the receiver to calculate your position.

  5. Position • So it uses several satellites at once to find the position. • Spherical Trigonometry states that when two spheres intersect, that intersection will be a circle. • When three are present, they intersect at a point. This point is off in are aircraft because the receivers we use only have a quartz clock, so the GPS is programmed to adjust the spheres until it forms a point.

  6. More • With three satellites we can derive a fairly accurate 2D position, but with four satellites a fairly accurate 3D position could be found. • How accurate is a standard GPS? • 100m • What about in the altitude given? • Would you trust it as a primary altimeter, or even a back up?

  7. WAAS What if we could get the accuracy of a GPS to 10m or better? WAAS is a Wide Area Augmentation System. This system is to enhance capable GPS units to provide better accuracy and vertical guidance.

  8. LAAS

  9. Website • http://www.trimble.com/gps/howgps-error.shtml • http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/ • http://www.how-gps-works.com/faq/q0110.shtml

  10. So are you legal • You have a Garmin 430 equipped Arrow • You are flying to DVL • The DVL VOR is out of service So Can you fly this route with using only the GPS? If so why, if not why?

  11. First question • Is your GPS IFR approved? • What TSO is it approved under • C-129 • GPS enroute only if you have navaid back-up • So if a VOR is out of service for one segment of your flight you must change that segment so a navaid is available even with a GPS • Garmin 430/530 fall under this category

  12. TSO • C-146a • New TSO • Allow GPS users to fly routes without navaid back-up • Requires WAAS! • Examples are: 430/530W, G1000W, 480/580(no longer supported)

  13. TSO • As more GPS receivers gain the reliability and public trust more will be qualified under the new TSO • This knowledge is important as it can force adjustments for flying routes and Trans-oceanic flight • Also it is required to be installed in a certain fashion as outlined in AC 20-138A

  14. AIM Requirments • VFR • VFR pilots should never solely rely on one system for Nav. AIM 1-1-20b1 • Many VFR and Handheld GPS lack RAIM alerting capability and as such lack guaranteed navigational accuracy • No requirement in VFR GPS for up to date Databases AIM 1-1-20b3b1 • So what is RAIM

  15. RAIM • Receiver autonomous integrity monitoring • Required for instrument approaches • Basically it monitors the number of satellites the receiver currently has a lock on • AIM 1-1-20J for procedures for lose of satellites • ERAIM will pick the best of 6 sats

  16. IFR Requirements • Must Fall Under TSO C-129 or C146a • Must have alternative means of navigation unless under 146a. AIM 1-1-20e1b • Operations must be done as per the FAA approved Aircraft Flight Manual

  17. IFR Long Range and Oceanic • 1-1-20F1 • GPS may be used to replace one of the other required approved means of long range (Dual INS)

  18. Approaches • RAIM – For non-WAAS and as a back up in case of WAAS Failure • 3 types in most GPS • 1 Stand alone • 2 Overlay • 3 Non-gps

  19. Approaches • Stand Alone • GPS only Duh! • RAIM and IFR approved GPS required • Almost always Preloaded in GPS

  20. Approaches • Overlay • Follows path of existing navaid approach • Must specify which approach you are doing (navaid or GPS) • Utilize what ever navigational system you choose primarily • RAIM still required

  21. Approaches • Three types of vertically guided approaches • LNAV/VNAV, LPV, and Precision (Cat I,II, and all III) • The first two are specifically for WAAS GPS

  22. LNAV/VNAV • Provides both lateral and vertical guidance • Formed to use FMS systems to provide approaches with vertical guidance to more place. • GPS with WAAS is expected to be able to utilize these approaches in place of a FMS. • Opens new approaches to the GA area. • Minimums are higher than the other vertically guided approaches

  23. LPV • LPV= Localizer Precision With Vertical Guidance • Near precision approaches • 250 ft. and one mile vis. • Eventually will be added as an option to all GPS approaches for all those who are equipped properly • Uses GAMMA 3 or GAMMA plus a Delta add on

  24. Note • Traditionally the GPS would use a typical indicator (CDI, HIS) • WAAS will indicate the error in angle measurements just like a localizer and vertical guidance for LPV • However, for LNAV/VNAV it can show either distance off glide path or angle off glide path

  25. Approaches • All other approaches may be in the database of the GPS • GPS may not be Used for navigation on those, only as an additional aid for situational awareness.

  26. RNP Note • The newer RNP approaches are coming about through airline research and FAA sideline support. • GPS and WAAS when combined with other systems typically equipped on transport category Aircraft provide extreme accuracy and reliability. • This is required for RNP to be successful

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