Ftrplt and
alphacentauri, I agree that CASA has not said you can’t use LNAV+V, however every letter I get back is relatively negative. Here are a couple of quotes from letters I have received from Mr Carmody.
Firstly, on 3 April 2018:
“I am advised that the type of LNAV+V equipment that you highlight presents an average descent profile based on the length of the approach and the altitude to be lost. It does not consider any obstacles or terrain at the location, nor does it consider whether the average profile displayed will cause a descent below the approach steps. For this reason, CASA guidance … specifically warns pilots not to rely solely on LNAV+V information for their descent … ”
In a letter from Mr Carmody dated 24 January 2018:
“…some aircraft systems provide advisory vertical guidance (e.g. LNAV+V) which is not certified and based on a GPS derived vertical position … the slope from which the advisory vertical guidance is derived is not subject to certification of the vertical path and may not be within prescribed vertical limits.”
For some reason Mr Carmody is clearly getting advice from others (as Mr Carmody does not have an aviation background) which show no enthusiasm for LNAV+V. Never in any of the letters that have come back to me do they mention that at a minimum, the LNAV+V has a starting point for the descent incorporated in the database. This makes it a lot more difficult to start descending early if the vertical guidance is going to be used.
In all of the replies, CASA just keeps going on about Baro-VNAV, when the cost is far higher for fitment in most cases, and there are not that many Baro-VNAV approved approaches so far.