Anybody know what the future holds for NBD approaches?
—
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Jason Simpkins
UNIX support
N8852A B-35
#include <std.disclaimer>
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30
Nov
NDB support in the future
In article <jsimpkin.115.000CC…@gulfaero.com> jsimp…@gulfaero.com (Jason Simpkins) writes:
>Anybody know what the future holds for NBD approaches?
NDB? Shoot, they are all doomed along with almost
every other electronic aid. The FAA last I heard wants
to do away with NDBs, VORs, ILSs, Loran (well, Coast Guard),
MLSs, and even enroute radar
within 15 years. GPS and terminal area radar will be it.
—
-Rob Strand
r…@ucscvm.ucsc.edu
Are they serious? FAA _really_ wants us to be stuck with GPS and terminal
radar with _no_ other navaids available?
Just for comparison:
1. How much does an ADF and panel unit cost?
2. How much does a single or dual VOR receiver and OBS for each cost?
3. When will they let us use GPS for *everything* ADF, VOR, ILS, DME, XYZ,
PDQ will do? (including precision IFR approaches to 200 AGL or lower!
not to mention Cat IIIb…)
geez … just when I thought I might be able to someday afford a plane —
now there’s another $5-6K I have to spend for a _TSO’d_ GPS receiver (and
a Mode S transponder that the radar won’t talk to yet … >:-( …)
<BGB> li…@ccwf.cc.utexas.edu
In article <199407212030.PAA04…@news.cs.utexas.edu> ll…@utxdp.dp.utexas.edu (Bruce G Bostwick) writes:
>Are they serious? FAA _really_ wants us to be stuck with GPS and terminal
>radar with _no_ other navaids available?
>Just for comparison:
>1. How much does an ADF and panel unit cost?
>2. How much does a single or dual VOR receiver and OBS for each cost?
>3. When will they let us use GPS for *everything* ADF, VOR, ILS, DME, XYZ,
> PDQ will do? (including precision IFR approaches to 200 AGL or lower!
> not to mention Cat IIIb…)
In the long run, I’ll bet that 2 GPS units will cost less
than the alternative pile of ’30s to ’50s technology.
Differential GPS can do precision approaches.
Heck, Trimble has even developed a 4 antenna differential
GPS system that does away with all the gyro instruments!
—
-Rob Strand
r…@ucscvm.ucsc.edu
In article <199407212030.PAA04…@news.cs.utexas.edu>,
ll…@utxdp.dp.utexas.edu (Bruce G Bostwick) wrote:
> Are they serious? FAA _really_ wants us to be stuck with GPS and terminal
> radar with _no_ other navaids available?
> Just for comparison:
> 1. How much does an ADF and panel unit cost?
too much
TAP has several listings in the $2500+ range
> 2. How much does a single or dual VOR receiver and OBS for each cost?
TAP has several listings in the $1600 (KX-125) to $2800 (inc gs)
> 3. When will they let us use GPS for *everything* ADF, VOR, ILS, DME, XYZ,
> PDQ will do? (including precision IFR approaches to 200 AGL or lower!
> not to mention Cat IIIb…)
Yeah, that’s something I’m interested in… when can I nuke my
ADF and LORAN and put in a TSO’d non-precision approach GPS
receiver and not have to worry about "ADF required"?
–
Bob Noel aka Kobyashi Maru
My views are my own, not MITRE’s
(why use a disclaimer when people are
too ———- to understand it?)
In article <jsimpkin.115.000CC…@gulfaero.com>, jsimp…@gulfaero.com (Jason Simpkins) writes:
>Anybody know what the future holds for NBD approaches?
My Guess is that NDB approaches will be around long after
VORs are a thing of the past. The NDB is very inexpensive
to set up and maintain. Witness the fact that the NDB
has survived the VOR which by all measures is a better
system. The VOR on the other hand is not inexpensive
to set up or maintain. I think it will be the first
to go. But it will take 20 years + in my opinion. GPS
will take over if we start building new GA aircraft
that come equiped with GPS recivers as the default.
Otherwise its a big investment to buy a New GPS for
an old aircraft.
- Hide quoted text — Show quoted text -
>–
>*********************************************************
>Jason Simpkins
>UNIX support
>N8852A B-35
>#include <std.disclaimer>
>*********************************************************
In article <30mi94$…@darkstar.UCSC.EDU>, r…@scilibx.ucsc.edu (Rob Strand) writes:
>In article <jsimpkin.115.000CC…@gulfaero.com> jsimp…@gulfaero.com (Jason Simpkins) writes:
>>Anybody know what the future holds for NBD approaches?
>NDB? Shoot, they are all doomed along with almost
>every other electronic aid. The FAA last I heard wants
>to do away with NDBs, VORs, ILSs, Loran (well, Coast Guard),
>MLSs, and even enroute radar
>within 15 years. GPS and terminal area radar will be it.
The FAA said the same thing about the NDB when the VOR
was first introduced. The NDB will last because it is
cheap. The VOR will be the first thing to go. Already
the TACAN is going the VOR will be next.
- Hide quoted text — Show quoted text -
>–
>-Rob Strand
> r…@ucscvm.ucsc.edu
In article <rwn-2207940825170…@bnoel.mitre.org> r…@mitre.org (Bob
Noel) writes:
> When will they let us use GPS for *everything* ADF, VOR, ILS, DME, XYZ,
> PDQ will do? (including precision IFR approaches to 200 AGL or lower!
> not to mention Cat IIIb…)
>
Yeah, that’s something I’m interested in… when can I nuke my
ADF and LORAN and put in a TSO’d non-precision approach GPS
receiver and not have to worry about "ADF required"?
Nobody worries about the lack of redundancy of such a future system?
Pierre
In article <PJ.94Jul22160…@linz.ensmp.fr>, p…@linz.ensmp.fr (Pierre
JOUVELOT) wrote:
> Yeah, that’s something I’m interested in… when can I nuke my
> ADF and LORAN and put in a TSO’d non-precision approach GPS
> receiver and not have to worry about "ADF required"?
> Nobody worries about the lack of redundancy of such a future system?
I do. I also worry about the integrity, reliability, and accuracy.
I can’t really voice my concerns too much because (1) I don’t have all
of the gory details and (2) some people worry about anything said on
internet being perceived as coming from my company. I realize that
sounds weasally (is that a word?), sorry.
–
Bob Noel aka Kobyashi Maru
My views are my own, not MITRE’s
(why use a disclaimer when people are
too ———- to understand it?)
In article <PJ.94Jul22160…@linz.ensmp.fr> p…@linz.ensmp.fr (Pierre JOUVELOT) writes:
> Yeah, that’s something I’m interested in… when can I nuke my
> ADF and LORAN and put in a TSO’d non-precision approach GPS
> receiver and not have to worry about "ADF required"?
>Nobody worries about the lack of redundancy of such a future system?
>Pierre
What lack of redundancy?
There are twenty something satellites, and as few as 4 are
enough at once.
It’s not hard to imagine that planes will be routinely equipped
with 2 or even 3 GPSs with prices dropping as they are.
An aside–Av Week just reported that someone has developed
a GPS receiver that is smaller than 1 cubic inch and runs
on 1.5 watts.
–
-Rob Strand
r…@ucscvm.ucsc.edu
In article <PJ.94Jul22160…@linz.ensmp.fr>,
Pierre JOUVELOT <p…@linz.ensmp.fr> wrote:
>In article <rwn-2207940825170…@bnoel.mitre.org> r…@mitre.org (Bob
>Noel) writes:
> Yeah, that’s something I’m interested in… when can I nuke my
> ADF and LORAN and put in a TSO’d non-precision approach GPS
> receiver and not have to worry about "ADF required"?
>Nobody worries about the lack of redundancy of such a future system?
*** PRECISELY MY POINT!!!!! ***
if, God forbid, the GPS constellation should go south right when I’m
shooting a tricky ILS (or, almost as bad, someone should happen to get
in the way of that fourth satellite or the pseduolite happens to get
run over by a fuel truck or something!), I’d really like something
else to fall back on when I come back for another shot.
it IS nice to have some different set of technology to turn to …
–
<BGB>
li…@ccwf.cc.utexas.edu / Sometimes a cigar
(really Bruce Bostwick) / is just a cigar.
from the great state of TEXAS / – Sigmund Freud
In discussing the relative expense of maintaining navigation
systems, don’t forget that GPS is _very_ expensive to maintain.
The satellites must be accurately tracked, new orbital elements
calculated, and new satellites must be launched on a regular
schedule as the old ones wear out.
—
Jim Wolper CFII
Department of Mathematics <email: wolp…@pequod.isu.edu>
Idaho State University
Pocatello, ID 83209-8085 USA
Bruce G. Bostwick (li…@bashful.cc.utexas.edu) wrote:
: In article <PJ.94Jul22160…@linz.ensmp.fr>,
: Pierre JOUVELOT <p…@linz.ensmp.fr> wrote:
: >
: >In article <rwn-2207940825170…@bnoel.mitre.org> r…@mitre.org (Bob
: >Noel) writes:
: > Yeah, that’s something I’m interested in… when can I nuke my
: > ADF and LORAN and put in a TSO’d non-precision approach GPS
: > receiver and not have to worry about "ADF required"?
: >
: >Nobody worries about the lack of redundancy of such a future system?
: *** PRECISELY MY POINT!!!!! ***
: if, God forbid, the GPS constellation should go south right when I’m
: shooting a tricky ILS (or, almost as bad, someone should happen to get
: in the way of that fourth satellite or the pseduolite happens to get
: run over by a fuel truck or something!), I’d really like something
: else to fall back on when I come back for another shot.
: it IS nice to have some different set of technology to turn to …
You wouldn’t be shooting an ILS unless you were using standard ILS
equipment, but assuming that you meant you’d be shooting a Differential
GPS Precision approach:
The whole constellation going out? Really. Be real.
Pseudolite gets run over by the fuel truck: When was the last time the
fuel truck ran over the ILS shack? :-) Plus, many of the current plans
would give differential GPS signals for an entire metro area, not just
one airport. Obviously these approaches would not be able to come down
to Cat II/III standards, but the corrections for GPS in side of a metro
area should be good enough for a standard ILS-type Precision GPS approach.
On the reliability issue, I would be more worried about the equipment
aboard the aircraft than the groud-based or space-based equipment. The
repair and cost of maintaining a typical GPS could get so expensive that
we would have to throw away a bad one and buy a new one rather than fix
the old one, as we can with current instrument systems. This is almost
moot though, since you would probably never see a failure of a GPS system
in your aircraft for quite some time.
As far as "someone getting in the way" goes… um, they are probably
flying an aircraft and as such won’t be in the way for long. Even if they
are, supposedly there are going to be enough satellites in orbit to handle
this (I.e. the Xth satellite jumps in where the 4th left off by manuvering
it into the 4th’s orbit and deorbiting the 4th into the atmosphere or into
a rescue orbit for the shuttle to pick up..?) and the certified GPS’s are
usually programmed to be this smart anyway, using other satellites in
view.
Anyway, I don’t see how flakey old systems that are ground-based are any
more safe than brand new equipment that the PILOT can monitor.
Regards,
—
Nathan N. Duehr – ndu…@netcom.com
Pvt. Pilot, N0NTZ (ham), Pikes Peak 120 (CAP), AOPA 01119032-9 (Joined 1992)
Colorado Wing CAP Net Control Station, 76 Senior Sqdn. Comm. Officer.
Member: Natl. Weather Service "SkyWarn" Severe Weather Spotting Team,
Amateur Radio Emergency Services, and the Rocky Mountain Radio League.
I’m only an IFR student with about 40 approaches under my belt. Even
with my limited experience I’ve been in a situation where all 5 ground
based approaches were unusable at my home field at the same time.
My home airport (CVO, Corvallis Muni) has an ILS, two VOR/DME, a VOR A
and an NDB approach. My instructor decided to go up to Salem and do an
ILS and a Back course approach there, then back to CVO for the ILS.
When we finished at Salem we found out the CVO VOR was out of service,
leaving the ILS and the NDB approachs available. For most of the summer
the FAA has insisted that the NDB was working, but the three 172s *I*
have access to can’t recieve it unless they are within about five miles.
Also, the NDB is the IAF for the ILS.
We tell Eugene (they do approach control for Corvallis) that we want the
ILS. They respond with "Radar contact lost, Cessna 80337 cleared direct
Lewisburg NDB," etc. We had to respond "Unable" since the NDB needle
was pointing in the wrong direction and all we could ID was static.
Eugene approach told us that they quite often loose radar contact on
single engine GA aircraft in that area since their transponders don’t
usually put out a very strong signal.
We canceled IFR and flew the approach VFR with instructor vectors.
This was a real eye opener to me, an airport with five IFR approaches
based on three independent navigation systems (VOR, ILS/NDB/Radar, NDB)
was inaccessable.
The more I hear about GPS the more I agree that it is the system of the
future. The FAA has already published non-percision overlay GPS
approaches at CVO (and a few other airports). They have anounced plans
for a diferential system that will give enough accuracy to support
precision approaches. In my mind there are only a small handful of
minor problems to be overcome.
* GPS boxes used for IFR require current data. Update subscriptions are
too expensive.
* The user interface for GPS IFR procedures is cruely primitive.
* IFR GPS boxes are new, only a few shops have installed and certified a
complete system. A month or so ago I listened to a presentation by a
salesman from II morrow. He told us about the one installation he
knew about that had achieved certification. It cost more (in labor)
to get the certification than the hardware cost.
–
Randy Stockberger
ran…@cv.hp.com
Corvallis, OR
503-750-3589
—
Are they serious? FAA _really_ wants us to be stuck with GPS and terminal
radar with _no_ other navaids available?
Just for comparison:
1. How much does an ADF and panel unit cost?
2. How much does a single or dual VOR receiver and OBS for each cost?
3. When will they let us use GPS for *everything* ADF, VOR, ILS, DME, XYZ,
PDQ will do? (including precision IFR approaches to 200 AGL or lower!
not to mention Cat IIIb…)
Actually the price for a GPS unit is rapidly declining to less than the
cost of the other units. Certainly you can get non-TSO GPS new for less
money than it would cost to replace any one of the units you mentioned.
The TSO unit costs more, but seriously, it’s very new (there’s only one
on the market) so you can probably expect the price to come down with a
little competition (if nothing else).
The major bugaboo is still precision approaches, but even today I’d toss
my DME, my cranky old rho-theta R-NAV and the second VOR unit in favor of
a GPS and never know the difference.
geez … just when I thought I might be able to someday afford a plane —
now there’s another $5-6K I have to spend for a _TSO’d_ GPS receiver (and
a Mode S transponder that the radar won’t talk to yet … >:-( …)
I’d don’t understand. If you didn’t blow 10K on the rest of an IFR
nav stack, why would you sweat $5K for a GPS unit? Frankly, I’ve heard
all this crying before when everybody had to put encoding transponders
and now everybody is going to have to put 760 channel radios in.
-Ron
Yeah, that’s something I’m interested in… when can I nuke my
ADF and LORAN and put in a TSO’d non-precision approach GPS
receiver and not have to worry about "ADF required"?
Nobody worries about the lack of redundancy of such a future system?
Which redundancy are you referring to? Actually, you’re not requird
to have all that crap (ADF’s and LORANS). I think a single VOR/GS
and GPS will do just as much for redundant systems.
-Ron
In article <30mmhhINN…@topaz.sensor.com>, r…@topaz.sensor.com (Ron Natalie) writes:
> Are they serious? FAA _really_ wants us to be stuck with GPS and terminal
> radar with _no_ other navaids available?
> Just for comparison:
> 1. How much does an ADF and panel unit cost?
> 2. How much does a single or dual VOR receiver and OBS for each cost?
> 3. When will they let us use GPS for *everything* ADF, VOR, ILS, DME, XYZ,
> PDQ will do? (including precision IFR approaches to 200 AGL or lower!
> not to mention Cat IIIb…)
> Actually the price for a GPS unit is rapidly declining to less than the
> cost of the other units. Certainly you can get non-TSO GPS new for less
> money than it would cost to replace any one of the units you mentioned.
Only for non approved models, the few certified uinits are more than a VOR.
Throughout this thread I get the feeling that some of us would actually like
to see less options for navigation than more. This is the strangest thing I’ve
ever heard. First, I think there is currently alot of hype around GPS. I do
not have one simply because I can’t see forking out $6 K for a device to
support three approaches. If and when things change I would like to have one
especially when a moving map, certified panel unit is availible. Next, I
have flown with friends who do have a GPS unit and I’ve noticed that they do
loose the signal or something on occassion, not a nice thing when flying an
approach. Finally, the engineer in me keeps telling me that a GPS precission
approach would require a level of accuracy beyond that of the ILS, there is
just something about a radio transmitter tied to the end of the runway that is
reassuring. I guess what I’m trying to say is why all this pie in then sky
talk over GPS when we ought to ask for as much as we can get, there are still
a great number of airports supporting towns with populations over 50,000 that
don’t even have one ILS approach. I think the promise of the as yet tested
(in a real sense) deferrential GPS approach provdes the powers that be a
good excuse to not maintain what facilities that exist let alone add to
them.
Tim Kramer
N30450 C-177A
r…@mitre.org (Bob Noel @ The MITRE Corporation) once wrote….
>…
>Yeah, that’s something I’m interested in… when can I nuke my
>ADF and LORAN and put in a TSO’d non-precision approach GPS
>receiver and not have to worry about "ADF required"?
A fellow from Allied Signal Aerospace (nee Bendix/King) stated that
GPS would never be useable for nonprecision approaches! I assume
this is due to the fact that the GPS receiver must get its altitude
information from the (mode C) encoder rather than directly from the
satellites.
Q: Do GPS receivers the use the altitude encoder output have a way to
enter local barometric pressure?
Q2: Suppose we add put a little transmitter near each field that simply
broadcasts the local pressure in digital format. Could we forget about
DGPS to get accurate 3D position information?
–Bill
—-
William W. Plummer C, MASM, dBASE to your spec.
7 Country Club Dr. plum…@altamira.theme.com
Chelmsford, MA 01824 PP-ASEL, N1NGK, MA RE Broker
Home: 508-256-9570 (leave msg.) @TALL FASHIONS: 508-251-8844
A fellow from Allied Signal Aerospace (nee Bendix/King) stated that
GPS would never be useable for nonprecision approaches! I assume
this is due to the fact that the GPS receiver must get its altitude
information from the (mode C) encoder rather than directly from the
satellites.
Is there a smily missing here? First off GPS is usable for non-precision
approaches today. Did you mean precision approach? Nobody in their
right mind would use Mode C for that. It’s only got 100′ resolution and
it’s pressure altitude. An baro altimeter will never be useful vertical
guidance in a precision approach (it isn’t now).
Q: Do GPS receivers the use the altitude encoder output have a way to
enter local barometric pressure?
I don’t know of any GPS that hooks to an altimeter.
Q2: Suppose we add put a little transmitter near each field that simply
broadcasts the local pressure in digital format. Could we forget about
DGPS to get accurate 3D position information?
Why is this going to be a better solution. First off a standard baro
encoder doesn’t have enough resolution, even if you had a correction
card and local pressure somehow. Why do you think that the CAT II and
III guys use radar altimeters. Second, why is this transmitter any
easier than DGPS?
-Ron
In article <30p7si$…@cwis.isu.edu> wolpj…@cwis.isu.edu (Jim Wolper) writes:
>In discussing the relative expense of maintaining navigation
>systems, don’t forget that GPS is _very_ expensive to maintain.
>The satellites must be accurately tracked, new orbital elements
>calculated, and new satellites must be launched on a regular
>schedule as the old ones wear out.
>–
Yep, all true….but…..
This cost is going to be paid regardless of whether GA/Commercial avaition jumps
on board. The military wants is regardless, the automotive industry wants it (
already starting to see moving maps in cars!), the maritime industry wants it,
the ground survey industry (or whatever you call it) wants it, etc, etc. Thus,
the question of cost here is how the cost is going to be distributed and amortized.
The original comment about the "low" cost on NDB is partially correct and partially
incorrect. Certainly, the hardware cost of an NDB installation is much lower than
a VOR, Localizer, or ILS. On the otherhand, now that the GPS constellation is up
and functioning, the "hardware" cost for installing a non-precision GPS approach
at a new airport is essentially ZERO…no new transmiters to install, maintain,
etc. Just the satelite constellation thats already up there and already being
maintained. An the cost of running the GPS constellation is INDEPENDANT of the
number or location of approaches that are formulated using the system.
Now lets consider other issues related to NDB vs GPS approaches.
If the NDB approach already exists, an overlay approach can be defined that
mirrors the NDB approach "exactly". Thus, no new information relative to
the TERPS needs determined, and I’m not even sure if it is required that
separate "survey" flights by the FAA be conducted.
If an NDB approach does not exist, why would you want to create an NDB
approach as opposed to a GPS approach? Both would require an appropriate
survey and TERPS analysis by the FAA but the NDB approach requires new
ground based hardware to be installed ($$$), AND has limited range, AND
has possible ground interference, AND is limited to "straight" line of
flight paths with their associated terrain clearance limitations. The
only factors against GPS that I can see is that at least at present,
the "majority" of aircraft don’t have approach capable IFR GPS’s installed
(This will probably change significantly in the next 3-5 years), and
creating a GPS approach "incur" a tangential cost in that data for the
approach has to be added to the "installed" databases at some point in
time. But since routine database updates are required for IFR GPS
receivers anyway, this is essentially a non-issue.
As to the concerns about redundancy, I see too issues here. The first
is the concern about redundancy in the cockpit. This is addressable
by having "dual" GPS receivers with independant antennas, just like
many/most IFR aircraft have dual VOR receivers and two separate VOR
antennas. This done, the main reliability concern falls back to that
of loss of electrical power (alterator failure, electrical short, etc)
and this effects GPS, VOR, ADF, etc all equally. Another interesting
plus for GPS is that at least one manufacturer (Garmin?) puts battery
back-up INSIDE the GPS receiver itself so that in the event of a power
loss, the receiver can keep functioning for an extended period of
time (hours?). I doubt that you’ll see this added as a feature on
ADF receivers.
The second reliability/redundancy issue concerns the GPS constellation
itself. In this case, it has been pointed out by another poster that
the loss of one satelite is unlikely to cause any problems with the
receiver since the constellation has "redundancy" in that there are
several (2-3?) more satelites than the minimum required to provide
coverage. You’ll recall that one of the "interim" stages of operation
of the system was the period when they did not have the full constellation
in place. The loss of more more than one satelite at the same time seems
very unlikely, probably (I’ll admit that I’m speculating here) much less
than having a ground based navaid go down while you’re on an approach.
I guess that I can conceive of human events that could interfere with
the constellation as a whole. Certainly there’s the possibily of war
(someone shooting down the satelites). Probably of more realistic
concern would be some sort of error in the "software maintenance" of
the constellation. I’m a little fuzzy here, but I assume this would
consist of some sort of mass error being included in software that is
uploaded to all the satelites simultaneously and also activated
simulateously. Now to me this would seem like an idiotic way to
run/maintain the system. Granted, it may be physically possible,
but I don’t think I’d lay awake at night worring about it.
Well enough rambling for now.
Bruce Bateman
In <211-PCNews-125b…@altamira.theme.com> plum…@altamira.theme.com (William W. Plummer) writes:
- Hide quoted text — Show quoted text -
>r…@mitre.org (Bob Noel @ The MITRE Corporation) once wrote….
>>…
>>Yeah, that’s something I’m interested in… when can I nuke my
>>ADF and LORAN and put in a TSO’d non-precision approach GPS
>>receiver and not have to worry about "ADF required"?
>A fellow from Allied Signal Aerospace (nee Bendix/King) stated that
>GPS would never be useable for nonprecision approaches! I assume
>this is due to the fact that the GPS receiver must get its altitude
>information from the (mode C) encoder rather than directly from the
>satellites.
>Q: Do GPS receivers the use the altitude encoder output have a way to
>enter local barometric pressure?
>Q2: Suppose we add put a little transmitter near each field that simply
>broadcasts the local pressure in digital format. Could we forget about
>DGPS to get accurate 3D position information?
>–Bill
Now, I’m not a terribly big fan of GPS (for the same reason that I’m
not a big fan of modern computers. Too small, efficient, and clean.
I like ‘em big and with motorgenerators!), but I gotta tell you this
is bullshit.
There is no reason that a GPS receiver can’t be used for a nonprecision
approach. Where does the altitude data come from? The pilot,
looking at his or her altimeter!
greg
>>A fellow from Allied Signal Aerospace (nee Bendix/King) stated that
>>GPS would never be useable for nonprecision approaches! I assume
>>this is due to the fact that the GPS receiver must get its altitude
>>information from the (mode C) encoder rather than directly from the
>>satellites.
GPS provides location in three dimensions not just two.
Now whether or not your GPS gives you a read-out of the
third dimension may be at issue. But the system itself
can and does provide information on altitude as well as
latitude and longitude.
Incidently why would you use mode-C for anything. It is
the aircraft that needs to know its altitude. That information
is provided by the altimeter. Mode-C only transmits your
altitude to an Air Traffic Controller. It has no other function.
It gets its information from either an encoding altimeter or
a blind encoder. Either way its sends you altitude only to
the nearest 100ft to ATC.
There are at least three non-precision GPS only approaches
available in the US with many more to follow.
—Bill
In article <211-PCNews-125b…@altamira.theme.com>,
plum…@altamira.theme.com (William W. Plummer) wrote:
> A fellow from Allied Signal Aerospace (nee Bendix/King) stated that
> GPS would never be useable for nonprecision approaches! I assume
> this is due to the fact that the GPS receiver must get its altitude
> information from the (mode C) encoder rather than directly from the
> satellites.
no, your assumption is incorrect. Any problems with GPS use for
approaches have nothing to do with baro pressure. Your VOR, ILS,
MLS, and NDB don’t have any baro input either.
> Q: Do GPS receivers the use the altitude encoder output have a way to
> enter local barometric pressure?
don’t need it
–
Bob Noel aka Kobyashi Maru
My views are my own, not MITRE’s
(why use a disclaimer when people are
too ———- to understand it?)
Bob Noel (r…@mitre.org) wrote:
: when can I nuke my
: ADF and LORAN and put in a TSO’d non-precision approach GPS
: receiver and not have to worry about "ADF required"?
Right now. The Garmin 155 is TSO’d C129 A1 for non-precision approaches.
(Since Apr) Mine is finally in, and hope to get it certified sometime soon.
Actually, many units for some time have been able to eliminate your worry
about "ADF required". For some time they have been approved for "enroute"
and "terminal". Terminal means you can use them to find places that are
part of an approach, iaf, missed, etc.
My ADF has been dead for a couple years, so that’s the main reason I’ve been
so quick into the GPS thing for approaches. Probably will cost me more in
money and frustration, but I’m buying a GPS and a very good ADF, at least
in theory.
dave allen – Fly because you love it.
William W. Plummer (plum…@altamira.theme.com) wrote:
: A fellow from Allied Signal Aerospace (nee Bendix/King) stated that
: GPS would never be useable for nonprecision approaches! I assume
: this is due to the fact that the GPS receiver must get its altitude
: information from the (mode C) encoder rather than directly from the
: satellites.
Not so. GPS receivers (can) get altitude info directly from the satellites.
My Garmin 155 does. The first time I fired it up, it told me my altitude
within 30 feet. However, this is not consistently the case. At least not
for precision approaches (did you mean precision or non?) GPS has already
been demonstrated even for precision approaches (well, DGPS).
: Q: Do GPS receivers the use the altitude encoder output have a way to
: enter local barometric pressure?
Yes. The Garmin 155 requires the local altimeter setting for approaches. It
also is wired to the altitude encoder, and uses the altimeter setting to
correct the "mode-C" altitude. It then compares this with the altitude it
computes from the satellites, as an indication of how well it’s doing and
whether it is confident enough of the position it’s calculating from the
satellites to let you do the approach.
(I don’t speak for Garmin. Just a customer, and so far happy.)
dave allen – Fly because you love it.