Marc adler 2008-02-19 12:27:29
Does anyone know if FSX will simulate WAAS?
Oh, wait a second. Does FS9 simulate it?
Beech45whiskey 2008-02-19 20:38:29
I haven’t recently searched the usual download sites for a WAAS-enabled,
IFR-certified GPS unit, but most certainly the default FS2004 GPS and the
RealityXP Garmin GNS430/530 add-ons do NOT simulate WAAS functionality for
As far as FSX, I suspect that out of the box it does not, but I would hope
that someone might make an add-on that does. Since I have not actually
played with FSX, this is only speculation.
As of this writing, there is only one IFR-certified GPS available for WAAS
approaches in the US and that unit is the Garmin GNS480. Garmin bought
this unit when they bought out the company that originally manufactured
this GPS. That company was, believe it or not, a division of UPS (the
As you may have seen in another thread, Garmin had also promised to release
an upgrade for owners of the Garmin GNS430/530 series, but this upgrade
continues to slip, even beyond their latest promised date of sometime
Marc adler 2008-02-21 00:51:09
So is WAAS going to be the wave of the future then? (Total speculation
Actually makes a lot of sense.
Yeah, I noticed that. Also mentioned was something about glass cockpits
with WAAS built in. Does that mean I’ll have to forget all the VOR/ILS
stuff I’m learning now? (Again, speculation welcome.) How does WAAS
work for landings, anyway? Is there a glidescope and all that?
Jay beckman 2008-02-21 00:51:35
As far as how things work in the USofA, if there is a GPS or GPS Overlay
approach that has been mapped out by the FAA, a WAAS-enabled GPS will be
able to fly a precision approach (with lateral and vertical guidence) to any
runway, at any airport, anwywhere, anytime better than if there was an
I attended an AOPA open house about a year ago and they had a video showing
a traditional coupled ILS approach on the left side of the screen and a
WASS-enabled, GPS-coupled approach on the right side. Relativly speaking,
the “analog” ILS approach looked like it was being flown by a drunken sailor
while the GPS RNAV/VNAV needles never moved even the least little bit.
PS…I find it really interesting that I can take my terestrial GPS (a
Garmin V Plus) up flying with me and because it’s WAAS enabled, it can
actually find a point in space more closely (to within 3′ when it’s running
really tight…) than the KLN94B GPS that is mounted in the panel of our
Beech45whiskey 2008-02-21 17:22:51
Jay, a couple of minor corrections. At this point in the US many of the
existing GPS approaches are not certified as WAAS approaches. That is,
many GPS approaches do not offer the lowest minimums (ceilings and vis) to
those with WAAS-enabled, IFR-certified GPS’s.
Below is an example of such an approach. WAAS enabled or not, you only get
to fly to the non-precision GPS minimums (LNAV minimums row of the minimums
table at the bottom of the chart) on this GPS approach into Lake Placid,
What I will admit to not knowing, however, is that whether a WAAS-enabled
GPS will provide the pilot a glideslope-like descent to the MDA on
approaches such as this one, rather than approach-course guidance only that
requires the pilot to “dive and drive” each step of the approach.
There *may be* a feature of WAAS-enabled GPS’s that present a glideslope
descent to the MDA of approaches like this, which would be pretty cool.
I’ll let you know in a few months when my aircraft’s GPS is upgraded to
WAAS. 🙂 The theory here is being that a stabilized, 3 degree descent,
like those flown on an ILS, is safer than a step-down pattern used on
Continuing, a GPS approach has to be certified as a WAAS-approach before
the FAA will let those with the WAAS GPS’s fly a glideslope-like approach
to low minimums using their GPS.
Additionally, if an approach is a GPS overlay approach (which means that
the FAA took the approach course, minimums, and fixes of an existing VOR or
NDB approach and authorized the approach to be flown using an IFR-certified
GPS using the same approach details), then most likely it cannot be a
candidate for a WAAS approach as well, since most likely the final approach
course of the approach is not aligned with the runway to a point where the
FAA could grant the lowest minimums possible. Call this an educated
And finally, when compared side-by-side with WAAS-enabled GPS approaches,
ILS approaches offer lower minimums and it will be this way for the known
future. From the rumors that I have heard, the FAA still has some inherent
concern about GPS being 100% accurate for 100% of the time, so the proven
technology of the ILS system reigns supreme.
Check this out. Here is a GPS with LPV (WAAS-enabled) minimums to rwy 28
at my home airport:
And here is the ILS to the same runway:
Notice that the ILS has a decision height of 613 and a visibility of 1800
RVR (1,800 feet), whereas the LPV minimums of the GPS approach only go as
low as 740 feet and 4000 RVR (4,000 feet).
Given the choice, I would pick an ILS over the LPV approach to this runway
for the simple reason that the minimums are lower.
Beech45whiskey 2008-02-21 17:22:55
It is the next step for those who fly IFR with an IFR-certified GPS, yes.
However, VFR pilots most likely will not make the leap, since the increased
accuracy of a WAAS-enabled GPS would not be used in VFR flight.
Furthermore, as Jay eluded in his post, WAAS-enabled GPS’s will open the
door for the FAA to be able to provide precision approaches, similar to an
ILS approach, at smaller airports that would never have had the money to
install ILS equipment. This, in turn, will theoretically improve safety of flight.
ILS won’t go away in the next twenty years, if I had to speculate.
Additionally, you probably won’t see VORs go completely away either as
there are many aircraft that only have VOR receivers for navigation.
The GPS calculates, then presents a glideslope to the pilot.
Dallas 2008-02-22 02:24:03
How does one pronounce WAAS?
Beech45whiskey 2008-02-22 02:24:10
After all those words this is the question you come up with??? 🙂
I have heard it pronounced as “waasss” and that is what I have adopted but
like SCSI, which people pronounce as either SEXY or SCUZZY (my preference),
I am sure that there will be multiple, correct pronunciations.
Frank stutzman 2008-02-22 02:24:16
As I understand from talking to pilots who have done these approaches, you
do indeed get a stabilized, 3 degree descent.
I forsee a problem in the future for us bug-smashers, though. I’m
guessing that when WAAS is in full use, the “dive and drive” non-precision
approaches will not be certified and every new approach will be LPV. Why
is that a bad thing? Because there are many, many airports that will end
up having very high minimums because of terrain in the approach path.
This isn’t a problem for the commercial carriers because they don’t
typically go to airports that have these problems.
I have a local company (www.anpc.com) that has something better, IMO.
Its called a Transponder Landing System. It interogates the planes
transponder, geometrically calculates the planes position, and then
broadcasts left/right, up/down guidance on a ILS frequency. Lots of
advantages: ILS like minimums, non-straight approach paths, minimal
equipment in the plane, no database, cheaper ground equipment.
They had an experimental set up done at one of my local airports and I
played with it. From the pilots perspective, its pretty much like flying
an ILS. Does require a person on the ground, but any line boy could do it.
Alas, ANPC has to deal with the FAA. In the past few years I think they
have given up on doing this for the civilian world and are focusing on
Bonanza N494B “Hula Girl”
Hood River, OR
Beech45whiskey 2008-02-22 02:24:33
Interesting. This will be interesting to see first-hand.
Beech45whiskey 2008-02-22 12:03:25
This is what I get for posting while on the phone. I normally use
adjectives in a paragraph once per post.
Jay beckman 2008-02-22 12:03:27
This is exactly how Phil Boyer described it/showed it when I went to the
AOPA Town Hall Meeting.
(Terrain issues excepted…) WAAS will yield accuracy equal to or better
than an ILS (latterally and vertically)
Can’t wait to go to Palm Springs in November (AOPA Convention) and see all
the new goodies.
Dallas 2008-02-22 12:03:40
I was trying to avoid the same problem I had with “METAR”.
After only seeing the word in print on the internet and newsgroups, when the
time came to discuss it orally in the real world I didn’t know whether it
was ME-TAR or MET-AR.
I just wisely asked, before I used the word… glad I did, I would have
Will 2008-02-22 20:18:34
One would have to assume it is a true glideslope, but until you just printed
some approaches below I had not seen *one* WAAS approach chart, and I just
kept hearing lots of promises.
One would have to also assume that the technology would enable in theory a
pilot to create very precise approaches for any runway that has a safe
instrument escape in a missed approach. But as most of these devices are
under strict scrutiny by FAA, most of the user interface to enable such
broad capability will be forbidden under the theory that if the FAA doesn’t
approve it and publish it it must not exist.
This is one of those areas where PC-based software and handheld GPS for
experimental aircraft (i.e., software not for certified IFR use) may end up
eclipsing the official FAA approved instruments. The problem in such
experimental use is how do you guarantee the accuracy of the signal, given
poorly placed antennas and jury-rigged non-realtime instruments in a
makeshift cockpit? I’ve had handheld GPS units in an airplane that were
two miles off the target because of an obscured signal and no way for the
software to get that information from the antenna. Very very dangerous if
you don’t understand such issues.
Very interesting thought, but I guess here is where WAAS shines and shows
true functional superiority over ILS. Is there any reason why one could
not design a WAAS approach that curves to a straight in course to the runway
before you get to short final? You take a VOR type approach to a point
close in and then the approach would arc in and come into the run straight
on, down to minimums.
Sounds smart to me.
Sure would be nice if airplanes did a better job of allowing the one system
to cross check the other simultaneously, instead of always making the pilot
choose one or the other and locking out instruments from indicating the
not-selected technology. I personally would get a lot of comfort in
having two course indications one from ILS and one from GPS, and if one
deviates from the other I need to get my head into it and figure out why
before I get too far into the approach.
Chris thomas 2008-02-23 04:40:15
In article <1jsoh57zemylv.dlg@ID-259643.user.individual.net>,
I would say “Definately Yes”.
BTW, what WAAS adds to GPS is a correction. Using a GPS receiver in a
known location, a special GPS unit continuously monitors the reported
location, and then calculates a correction. The monitor location for
Southern Calif is the ATC complex in Palmdale. The correction is
actually a set of corrections, based on which GPS sats are being used.
For example “Using sats 1, 3, 17, the reading is 20′ bearing 123
degrees from correct” or some such.
The WAAS corrections from Palmdale are uplinked to a leased transponder
on a geosync comm satellite; transmission frequency is the same as the
normal GPS sats. Your GPS receives receives this signal just like the
other GPS sats (which aren’t geosync, but that’s irrelevant). It has a
funny satellite number on the GPS display, and the messages from this
sat have a prefix number which indicates they are corrections rather
positions. Because the GPS doesn’t have to do anything special to
receive the WAAS transmission, it adds next to nothing to the cost of
the GPS. I have an inexpensive Garmin handheld GPS and it is WAAS
The problem with WAAS is the correction for Palmdale may not be exactly
the same as that for Santa Monica, where I am. One of the factors
causing reading errors is the ionospheric density between you and the
satellite, and this depends (slightly) on where you are. The “fix” for
this is LAAS, (Local rather than Wide Area Augmentation System). If
each airport had a GPS receiver at the runway threshold, then the GPS
position error can be reduced to virtually zero for a/c using that
runway. The only problem is designing a common system for transmitting
LAAS to the a/c — the WAAS method doesn’t work. The LAAS can be
updated over very short intervals, compared to WAAS, where there are
significant delays in the sat uplinking process. Also, LAAS can quickly
begin transmitting “Do not use GPS here – readings are distorted” in
time for an a/c to execute a missed approach. FCC has specs on how long
navaids can transmit incorrect info before they must be shut down, and
this is one of the issues in gualifing GPS and GPS/WAAS for precision
approaches. There’s currently no way to way that a GPS sat has gone
bonkers in anything like real time.
Caution — I’ve been out of the LAAS implementation loop for a while, so
I’m not current on what’s going on.
Dallas 2008-02-23 11:35:24
Still a nice piece.