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4 Answers

KLN 94 VOR Substitution

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Aircraft Systems, Instrument Rating

I came across the AC 90-100 compliance table on the FAA website and had a couple questions about using a KLN 94 under IFR:

1. The table says that the KLN 94 cannot be used for VOR substitution (although others such as the G430 can). Is this true and why? Or is the table just dated?

2. If the KLN 94 cannot be used for VOR substitution, can it still be used as an alternate means when the underlying VOR is functioning based on AC 90-100a?

Thanks.

4 Answers



  1. John D Collins on May 31, 2014

    The reason that the KLN94 and most of the early GPS units can’t be used to substitute for VOR is because they do not support the “course to fix” leg type in the database. Support for this is a requirement for being able to fly some SIDs and STARs.

    AC 91-100A deals with approval to use GPS units on RNAV SIDs and STARs which are considered as RNAV 1 procedures. The KLN94 and most of the early GPS units are not approved to fly these procedures, as indicated in the compliance table spreadsheet. You will never see an RNAV SID, STAR, or ODP in the KLN94 database for this reason.

    Your guidance for the use of a GPS on conventional routes (those routes or procedures based on ground Navaids) is spelled out in AC 90-108.

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  2. Mark Kolber on Jun 01, 2014

    Solid answer by John as usual.

    Point is that AC 90-100A “applies to operation on U.S. Area Navigation (RNAV) routes (Q-routes and T-routes), Departure Procedures (Obstacle Departure Procedures and Standard Instrument Departures), and Standard Terminal Arrivals (STARs).”

    Could be clearer but the “RNAV” modifies all the other terms: RNAV routes, RNAV DPs and RNAV STARs

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  3. Lee Elson on May 20, 2015

    I’m an occasional user of the KLN94 and rely heavily on the POH. In chapter 5.5, it says that the KLN94 has an “OBS” mode and one characteristic is:
    “The course is defined by the active waypoint and the selected magnetic
    course. A course “to” or “from” the active waypoint may be
    selected.”

    How is this different from “course to fix” leg type that John mentions? Why does this not allow one to fly RNAV SID’s/STAR’s?

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  4. John D Collins on May 20, 2015

    Lee,

    Functionally they are similar and one could use it to navigate the leg. However, it may not be coded into a database on the KLN94 and may only be activated manually with the pilot selecting the mode, the correct value for the course, assigning a CDI full scale deflection value and establishing the integrity needed to fly the leg type. What the RNAV specification requires is that it be able to be defined in the database and retrieved from the database without the pilot being able to change it. Since it is a manual operation using the KLN94, it is not permitted to be used for this purpose. It is similar to the pilot not being authorized to enter the waypoints for an approach as an alternate way of flying an approach that is not in the database.

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