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Which of the following PBN procedures is not classified as a 3D approach procedure? RNP APCH to..
  • A
    GLS minima.
  • B
    LNAV minima.
  • C
    LPV minima.
  • D
    LNAV/VNAV minima.

Refer to figure.
Prior to PBN (performance based navigation) and the excellent accuracy and integrity of GNSS systems that we have today, there were 2 types of approach, those with vertical guidance (precision approaches) and those without (non-precision approaches).

When PBN approaches initially were certified, they were simply LNAV (lateral navigation), and were a non-precision, 2-dimensional (2D) approach. LNAV approaches still exist and are widely used, however, now the technology is now good enough to give vertical guidance also, and now exist 2 more categories of approach, LNAV/VNAV (lateral and vertical navigation) and LPV (localiser performance with vertical guidance). These are known as APV approaches (Approaches with vertical guidance), and are 3D approaches that sit in between non-precision and precision approaches.

LNAV/VNAV uses a barometric VNAV system to give vertical guidance on the approach, and is a 3-dimensional (3D) approach with lower minimums than LNAV only.

LPV minimums are even lower, as low as 200ft (ILS CAT I) due to the narrowing effect of the allowed track (like a localiser), and the incredibly accurate position data - and integrity - gained by using SBAS augmentation.

LNAV, LNAV/VNAV and LPV approaches are all the same type, RNP APCH. They just operate to different minima, depending on which system is being used.

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