Dick,
Baro VNAV is very onerous for both the pilot and owner of the aircraft. Here is an extract from a recent CASA Flight Safety article:
Crew training
As well as having a suitably equipped aircraft, each member of the flight crew must have a current instrument approach procedure endorsement. This includes approved training in how to safely conduct a baro-VNAV operation, including:
use of baro-VNAV instrument approach charts, including LNAV/VNAV minimums, temperature limitations, and vertical flight path angle
principles of baro-VNAV vertical guidance, including path display and depiction and the effect of temperature
use of MDA and DA for LNAV and LNAV/VNAV minimums respectively
approach procedure selection from the relevant onboard navigation database
barometric pressure (QNH) selection (altimeter subscale setting), and cross checking and verification procedures, including effect of incorrect setting
VNAV mode selection and monitoring
VNAV failure modes and mode reversions
VNAV flight tolerances.
Other requirements
the GNSS navigation database must be valid, and the entire approach procedure capable of being loaded into the system
the pilot must verify that the approach in the system is in accordance with the approach chart
for two-pilot operations, the same barometric altitude from two independent sources must be displayed, and one must be in each pilot’s primary field of view
the aerodrome must have a promulgated ICAO PANS-OPS design-compliant baro-VNAV approach procedure
the aerodrome needs to have accurate aerodrome QNH and temperature available through either an aerodrome air traffic service, an aerodrome weather information services (AWIS) or automatic terminal information services (ATIS).
Approved approaches:
The Airservices Australia website lists aerodromes at which baro-VNAV approaches have been approved, validated or are planned. It also shows locations at which baro-VNAV approaches cannot be made, because the aerodrome has an unsuitable approach alignment, has been deregistered or has no local QNH or temperature available.
Where a baro-VNAV approach is available, the RNAV GNSS chart will specify that the aerodrome QNH and temperature are required, and the temperature range under which the procedure can be flown. For the RNAV GNSS RWY 32L approach at Launceston, for example, the temperature range is minus 5 to plus 61 degrees Celsius.
The actual path flown by the aircraft will depend on the ambient air density. A temperature higher than ISA will result in a steeper approach path; conversely temperatures lower than ISA will result in a lower descent profile. Where temperature and aerodrome QNH are temporarily unavailable, the LNAV-only approach must be used.
So when it comes to GNSS approaches—don’t ‘push your own baro’. If you want vertical guidance, make sure you are properly equipped, trained and that the approach is approved for where you’re going.
Airservices will also have a vested interest in this:
The implementation of Baro-VNAV approaches is to be funded through normal industry cost recovery arrangements administered by Airservices using the same mechanism as that used to fund procedures maintenance.
Baro VNAV will not be permitted at aerodromes without an AWIS and those that do will not necessarily have much lower minimums than LNAV. The aircraft barometric system will also have to be compliant.
SBAS will not require any of this b******t. Modern navigators have this capability already, most if not all minima are 200' and all the pilot needs is a 3D endorsement.
WAAS is the US version of SBAS and is far superior to Baro VNAV. It is possibly an option over there, but I do not read of anyone using it.
As I type the Government is requesting submissions from aviation interests for the 2019 budget. GeoScience wants it and if we are blasé about this then SBAS will be available for other industries, but not for aviation due to further certification requirements. Just because the airlines have their collective heads up their a**e over this does not make it right.
If you would like the appropriate person to contact regarding this then please PM me. You probably know him already.
Please put your efforts toward SBAS.
Last edited by Jenna Talia; 14th Apr 2018 at 12:10.