WAAS GPS approach question.

[Dico]

Hello,

I read on the Garmin page that their 480 is Waas certified...so that
you can fly precision approaches without an ILS... what does this
mean exactly? If I'm coming into an airport with only an NDB
approach, can I use the 480's capabilites to fly a precision approach
and get down to a lower MDA/DH?

-dr

[Mark]

> Hello,
>
> I read on the Garmin page that their 480 is Waas certified...so that
> you can fly precision approaches without an ILS... what does this
> mean exactly? If I'm coming into an airport with only an NDB
> approach, can I use the 480's capabilites to fly a precision approach
> and get down to a lower MDA/DH?
>

It means you can use the LPV minima line on a RNAV(GPS) approach chart, and
that assuming your 480 was properly installed you can follow localizer-like
and glideslope-like needle guidance on that approach.

[Matt Barrow]

"Dico" > wrote in message
oups.com...
> Hello,
>
> I read on the Garmin page that their 480 is Waas certified...so that
> you can fly precision approaches without an ILS... what does this
> mean exactly? If I'm coming into an airport with only an NDB
> approach, can I use the 480's capabilites to fly a precision approach
> and get down to a lower MDA/DH?


If the airport has only an NDB approach, how are you going to fly a GPS
approach of any sort?

[Doug]

Can you use the 480's glideslope to guide you into a VOR approach that
is NOT GPS, but using a descent gradient that will hit the altitude at
the waypoints as charted? Same approach as flying it by hand, just a
stabilized, even descent. Hope that makes sense.

[Michael Ware]

"Matt Barrow" > wrote in message
...
>
> "Dico" > wrote in message
> oups.com...
> > Hello,
> >
> > I read on the Garmin page that their 480 is Waas certified...so that
> > you can fly precision approaches without an ILS... what does this
> > mean exactly? If I'm coming into an airport with only an NDB
> > approach, can I use the 480's capabilites to fly a precision approach
> > and get down to a lower MDA/DH?
>
>
> If the airport has only an NDB approach, how are you going to fly a GPS
> approach of any sort?
>
>
>
In other words, if there isn't a published approach, you can't invent one
for your own use. It's not legal and not safe.

[Mike Adams]

"Doug" > wrote:

> Can you use the 480's glideslope to guide you into a VOR approach that
> is NOT GPS, but using a descent gradient that will hit the altitude at
> the waypoints as charted? Same approach as flying it by hand, just a
> stabilized, even descent. Hope that makes sense.
>

Assuming it's a VOR(GPS) approach, and not a circle to land only, Yes. The 480 provides VNAV
guidance suitable for LNAV/VNAV or if not charted, then referred to as "advisory VNAV", but basically it
works the same - you get vertical guidance to the runway.

Mike

[Dave S]

Dico wrote:
If I'm coming into an airport with only an NDB
> approach, can I use the 480's capabilites to fly a precision approach
> and get down to a lower MDA/DH?
>
> -dr
>

No.

But if you have an RNAV approach with precision/vertical guidance
component, (and I am presuming the approach lighting is up to snuff
before that type of approach chart is issued).. then you could use the
480 box to execute that approach without any ground based navaid guidance.

Dave

[[email protected]]

WAAS Approaches have vertical guidance but they
are not classified as "Precision"

Bill Hale

[Mark Hansen]

On 04/20/06 15:24, wrote:
> WAAS Approaches have vertical guidance but they
> are not classified as "Precision"
>
> Bill Hale
>

Are you sure about that? I thought the P in LPV stood for Precision?
Also, the LPV approaches have a DA rather than an MDA, which also
implies a precision approach, doesn't it?


--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

[Brad]

Officially, LPV refers to "Localizer Performance with Vertical
Guidance". Officially it's not precision, perhaps
not-so-non-precision. With horizontal and vertical accuracies in the
1-2m range, its arguably more accurate than a Cat III ILS. It does not
however,have the integrity of a Cat III. The LPV approach does indeed
have a decision altitude which currently is as low as 250ft HAT, and
the recent approval of 200' DA's will likely start showing up on
procedures next year.

Brad

[soxinbox]

I thought the FAA approved the use of GPS for any NDB waypoint. A plane
without ADF can fly any ADF approach with a IFR approach certified GPS. GPS
waypoints can also be used in lue of ADF for missed approach holds, so you
can fly any approach that has "ADF required" without an ADF if you have an
IFR certified GPS.

"Matt Barrow" > wrote in message
...
>
> "Dico" > wrote in message
> oups.com...
>> Hello,
>>
>> I read on the Garmin page that their 480 is Waas certified...so that
>> you can fly precision approaches without an ILS... what does this
>> mean exactly? If I'm coming into an airport with only an NDB
>> approach, can I use the 480's capabilites to fly a precision approach
>> and get down to a lower MDA/DH?
>
>
> If the airport has only an NDB approach, how are you going to fly a GPS
> approach of any sort?
>
>
>

[Ron Rosenfeld]

On Fri, 21 Apr 2006 01:53:42 GMT, "soxinbox" > wrote:

>I thought the FAA approved the use of GPS for any NDB waypoint.

They did. But note the word "waypoint"


>A plane
>without ADF can fly any ADF approach with a IFR approach certified GPS. GPS
>waypoints can also be used in lue of ADF for missed approach holds, so you
>can fly any approach that has "ADF required" without an ADF if you have an
>IFR certified GPS.

Note this from the AIM: (emphasis mine)

"(6) Charted requirements for ADF and/or DME can be met using the GPS
system, **EXCEPT** for use as the principal instrument approach navigation
source."

This would be true for a stand alone NDB approach (i.e. with no GPS
overlay); and for the primary DME approach at Martin State (near BWI).

If there is a published GPS overlay, that would be different. But not all
NDB approaches have GPS overlays.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[Ron Rosenfeld]

On 20 Apr 2006 15:24:09 -0700, "
> wrote:

>WAAS Approaches have vertical guidance but they
>are not classified as "Precision"
>
>Bill Hale

What makes you say that. The only definition I'm aware of (in the P/CG)
only requires that the approach provide electronic vertical guidance:

"PRECISION APPROACH PROCEDURE- A standard instrument approach procedure in
which an electronic glideslope/glidepath is provided"

I might argue that an LNAV approach with "advisory" vertical guidance does
not really meet that definition, but surely an LPV approach provides
"electronic vertical guidance".
Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)