Do RNAV LPV approaches use GPS or Baro Alt? (and temperature compensation on approaches)

As an anecdote, when EGNOS was first being tested but when it was transmitting with the “don’t use me for real” flag (which went on for quite a number of years because the Eurocrats had all sorts of bizzare plans e.g. tying EGNOS to Galileo (not the US Navstar system “which was at the mercy of the US president who was going to turn it off anytime he wanted”) and even sell decryption keys for Galileo for flight applications – according to the Galileo website this was claimed to create 100,000 jobs in €-land… with nobody realising that approximately 100% of the equipment is made in the USA where they have zero interest in this sort of crap ) the original LPV tests were done in Spain, with a CNX80 whose firmware was hacked to disregard that flag

PetitCessnaVoyageur wrote:

I mean, before the introduction of SBAS/WAAS (is it 2006 or 07 they were generalized ?)

Seems that it was earlier, with the Apollo CNX80 (later Garmin GNS480) first GPS navigator to be compliant with TSO-C146A, by 2002.

By MK206-34-08, you essentially need:

• 2 GIA63W PN 011-01105-00: $8000 each from Cessna Direct
• 2 CI2580-200 antennas, 1500$ each from Cessna direct
  I skip the Sirius/XM/FIS items, useless here. Wonder if it would be easy to get the installation approved without doing this “US-operators-use-only-part”
• Man-power: replacing two LRU, two antennas, bit of modification to cabling, updating SW… Don’t know how much, but clearly not terrible modification.

So today, clearly not cheap, and not something I’m willing to do.
But, let’s wait for good OH GIA63W to appear, and it may become more easily feasible.

PetitCessnaVoyageur wrote:

All in all, converting requires replacing the two GIA and two COM/GPS antennas. And upgrading the software. Not rocket science

NCYankee wrote:

and there was no reason in the first instance of not providing +V in a non WAAS environment. Although +V was included in the RTCA DO229, it was always optional. Remember, +V is only advisory, doesn’t have to be accurate

Got that.
So why the hell didn’t they implement it from the beginning in non WAAS box ?
I think this doesn’t need an answer

NCYankee wrote:

Remember, +V is only advisory, doesn’t have to be accurate

It is a not dissimilar decision to adding “Visual” approaches to 6.41. It is a passing of responsibility to the pilot not to be (too) stupid. It is up to us how we rise to that challenge.

tschnell wrote:

Except when you have an old G1000 which can only be updated to WAAS for big $$$

Old GIA63 can now be found dirt cheap.
Maybe some years from now, GIA63W will be the same ?
All in all, converting requires replacing the two GIA and two COM/GPS antennas. And upgrading the software. Not much mods involved, only hardware too expensive at the moment.

PetitCessnaVoyageur wrote:

If technically possible, i can always dream to see my non WAAS G1000 updated to provide +V to LNAV :-)

Although technically possible, it will never happen. The only way a non WAAS G1000 will get new function is if the system is upgraded to WAAS and the manufacturer adds the latest software.

PetitCessnaVoyageur wrote:

I wonder what are the conditions which made +V available outside SBAS, whereas it was not initially.

Competition, Avidyne added the capability, and there was no reason in the first instance of not providing +V in a non WAAS environment. Although +V was included in the RTCA DO229, it was always optional. Remember, +V is only advisory, doesn’t have to be accurate, if it is off the ideal descent path, who cares, it isn’t a case of a real vertical guidance where a sloped path must be surveyed for obstacles and integrity must be provided. The obstacle clearance is not an issue as once past the FAF, there are no obstacles involved until reaching the MDA. The +V is supposed to clear any step downs, but it is the pilot responsibility to comply with minimums based on the altimeter, so if the +V advises you go below a step down minimum, the pilot is required to level off until past the step down fix. +V is simply advisory to get from one altitude to a lower altitude where there are no obstacles involved.

JasonC wrote:

Because it isn’t really necessary in areas with SBAS

I mean, before the introduction of SBAS/WAAS (is it 2006 or 07 they were generalized ?)