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3D approach operations are very common nowadays. Which of the following options belongs to this type of approach?

1. RNP APCH (GNSS and baro VNAV)
2. GLS
3. RNP APCH (LNAV minima)
4. RNP 1
5. ILS
6. RNP APCH (SBAS)

  • A

    2, 3, 5 and 6.

  • B

    1, 2, 5 and 6.

  • C

    1, 3, 5 and 6.

  • D

    2, 4, 5 and 6.

Three-dimensional (3D) instrument approach operation’ means an instrument approach operation using both lateral and vertical navigation guidance.

1. RNP APCH (GNSS and baro VNAV) uses GNSS for lateral guidance and Baro VNAV for vertical guidance.

2. GLS stands for GBAS (Ground Based Augmentation System) Landing System. GBAS is used to improve GPS receiver position and intends to provide an alternative to ILS. The improved GPS position provides both lateral and vertical guidance and it is regarded as a precision approach.

3. RNP APCH (LNAV minima) is a non-precision approach, there is not vertical guidance.

4. RNP 1 is a navigation specification that requires aircraft to maintain lateral total system error within 1 NM for at least 95% of the flight time. It is not an approach at all. Not to be confused with RNP APRCH which includes GNSS for LNAV minimum, GNSS + Baro VNAV for LNAV/VNAV minimum and GNSS augmented by SBAS.

5. ILS stands for Instrument Landing System. It uses localiser for lateral guidance and glideslope and vertical guidance.

6. RNP APCH (SBAS) are approaches based on GNSS positioning augmented by SBAS (not to be confused with GBAS). If it is down to LP minima it is 2D approach. If it is down to LPV minima it is 3D approach. Since all choices include this option it should be referring to the LPV minima.

  • Combining all the information above, all the options available are 3D approaches, except RNP APCH (LNAV minima) and RNP 1. Therefore, the correct answer is 1, 2, 5 and 6.

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