Many aviators know that the Garmin 650/750 equipment can be upgraded with a low or no cost software change to offer LNAV+V.
This would seem like a substantial safety improvement to me, however the people at CASA appear to make out that LNAV+V does not improve safety over the existing RNAV, and it is really required to be Baro-VNAV.
However the ATSB report on Lockhart River states:
“There were 49 respondents who reported that they had been involved in an incident involving RNAV (GNSS) approaches. The most common … was commencing the descent too early due to a misinterpretation of their position.”
If you have LNAV+V installed, the actual descent doesn’t start until the GPS position in the database complies with the start of the (normally) 3 degree approach path. That means, when following the glide slope indicator, either manually or coupled, it would not be possible to start the descent early.
In that case, isn’t it clear that LNAV+V provides a safety advantage over basic RNAV?
Yes, I accept that Baro-VNAV is even better and allows a lower minima, but there are only a limited number of approaches in Australia with Baro-VNAV and in some aircraft the cost would be quite expensive to upgrade. In the case of the Garmin 650/750 equipment the cost is either zero or very low to upgrade the software of existing units.