Baro VNAV 4 replies

31.12.2010

Submission:

READ all the Baro VNAV 4 entries first, start at entry 273 

Firdovsi Jalilovv - R.I.S.K. - Azerbaijan

The values 7nm and 5nm pointed by me are not significant in the discussion. These values were selected based on the assumption that LNAV/VNAV FAP is absolutely independent from LNAV FAF. And now Beat states that - “That means you will calculate the FAP based on the distance THR-FAF, the intermediate altitude and the nominal descend gradient of the NPA”. The quotation states that the FAP location is calculated based on the distance THR-FAF of the LNAV procedure. In other words, LNAV/VNAV FAP location depends on the location of LNAV FAF. Consequently, LNAV/VNAV FAP is not absolutely other history, it does depend on LNAV FAF location. Whereas Beat’s statement does not at all mean that FAF and FAP must be always located in one and the same position – as there can be differences in the values of the descend gradient of the NPA, and VNAV VPA. As for me LNAV FAF and LNAV/VNAV FAP should be always located at the same position for the following reasons. Let us address Beat’s quotation - “Furthermore the VNAV guidance will only be used when the VNAV mode is armed. In this case the FAP overrules the FAF”. I completely agree with this statement. Moreover, the onboard systems are designed in such a way when the VNAV mode is armed the onboard system does not at all know about the existence of familiar LNAV procedure. All the information for performing a VNAV procedure within the lateral boundaries of the RNP approach, the onboard system loads from a concrete record of one unique LNAV/VNAV procedure where only one FAP exists.

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