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2 Answers

Enroute gps mode

Asked by: 22907 views Instrument Rating, Private Pilot

how wide is the GPS eroute mode is and , terminal, approach on an ILS

2 Answers



  1. Wes Beard on Feb 23, 2012

    GPS enroute = 2NM
    GPS terminal = 1NM
    GPS approach = .3NM
     
    See my blog post on the subject including vertical scaling on FMSs
     
    http://allaboutairplanes.wordpress.com/2011/10/22/gps-approach-types-and-needle-sensitivity/
     
    To figure out what the sensitivity must be use the approach plaes and see RNAV1 for STARs and SIDs or 1NM scaling or RNAV2 for Q and T routes or 2NM scaling
     

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  2. John D. Collins on Feb 23, 2012

    GPS enroute CDI FSD (Full Scale Deflection) is +/- 5 NM for a non WAAS GPS and +/- 2 NM for a WAAS GPS. Terminal FSD is +/- 1 NM for both WAAS and non WAAS GPS.  On an ILS, FSD varies with the length of the runway and is angular..  The reason it varies is that the localizer antenna array is located off the departure end of the runway and is calibrated to produce a FSD of a fixed distance of +/- 350 feet at the threshold.  This means that a short runway will generate a wider angle and a longer runway a narrower one. Assuming the antenna array is located 1000 feet from the departure end of the runway, the FSD angle for a 5000 foot runway would be +/- 3.34 degrees and for a 10000 foot runway would be +/- 1.82 degrees.

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