Select Approach, Enter, Activate.
Don’t ask too much :-)
Select Approach, Enter, Activate.
Don’t ask too much :-)
Hehe.. would be good to know though :)
Would that be in case of lost SBAS/integrity for example?
With SBAS, it provides the integrity data rather than using RAIM. Each approach type has an alarm limit. For SBAS vertical guidance, the limit is based on the maximum value of VPL (Vertical Protection Limit). VPL may not exceed 50 meters for an LPV with a DH>= 250 feet. The same value applies to LNAV/VNAV or advisory vertical guidance. A tighter VPL of 35 Meters is required for LPV with a DH <250 feet. There are similar limits for lateral navigation using HPL (Horizontal Protection Limit). For an LPV, this value must not exceed 40 meters. The LNAV and LNAV/VNAV use the same lateral criteria and it is quite large at 556 meters or 0.3 NM. These values are not generally displayed by the GPS, but one can use VFOM and HFOM to gain an expectation of the likelihood that the approach will be downgraded. The HPL/VPL figures are 99.99999% probability numbers whereas the HFOM/VFOM are 95% probability numbers. The latter are displayed in feet. A value of VFOM less than 60 will usually result in getting vertical guidance on most approaches, with a value of 40 feet covering LPV with a DH <250 feet. It is extremely rare for the lateral to be the cause of a downgrade, because the vertical always has poorer solution geometry. It would take an awful bad Carrington style event or jamming to not have LNAV, that is why it is a safe backup and downgrade.
To upgrade a non-WAAS G1000 to WAAS status is costly. I have seen quotes from EUR 35k to 50k. In comparison, for upgrade of a couple of G430 I have heard EUR 7k to 10k.
Garmin upgraded my 430 to a 430W last year for £2,200.
Part of the explanation is that new antennas are required, but still.
Why do you need a new antenna? Don’t the SBAS satellites transmit on the same frequency as the GPS satellites?
For WAAS you need new Antennas, and many times new cables too. The official price for the WAAS upgrade is $ 3350 plus VAT per unit.
The GNS430 to W upgrade is a whole new PCB inside.
Being transmitted on the same frequency does not mean that there are no signal differences. The navigation message for example is modulated with 250 BPS for WAAS versus 50 BPS for standard GPS. The navigation message contents are different, and so is obviously the WAAS satellite orbit.
So you need hardware capable of receiving the different speed navigation signal, and software capable of decoding the different navigation message, to handle the different orbits for using the geo ranging signal, and to apply wide area differentials as well as reliability info.
I don’t see a technical reason why a non-WAAS antenna should not work for WAAS, I think it’s mostly a certification issue.
The WAAS antenna issue is related to gain and mask angle. The non WAAS antenna and even some of the early WAAS antennas will work, but they don’t meet the TSO requirements and therefore the GPS is not certified in the US for sole source of IFR navigation.
There is also a GLS approach which I think is considered a precision approach. It is still pretty rare but RWY 14 in LSZH Zurich has it since Feb 6th 2015 (Jeppesen chart 12-40). It goes down to 200’ AGL just like an ILS approach.
