"GPS Unreliable" NOTAM

"Richard Kaplan" wrote in message
...


If my plane had nothing but GPS-based avionics, what would my
options be?


Vectors.

In a previous article, "Richard Kaplan" said:
exists due to military testing or some atmospheric irregularity or whatever,
but the point is that the NOTAM really is out there and will be effective in
a few days. If my plane had nothing but GPS-based avionics, what would my
options be?

GPS 07/015 ZDC GPS UNRELIABLE WITHIN A 100 NM RADIUS OF PATUXENT
VORTAC (PXT) AT 10,000 MSL THROUGH FL400, AND DECREASING IN AREA
WITH DECREASE IN ALTITUDE TO 80 NM RADIUS AT 4000 FT AGL
1200-2000 DLY WEF 0307211200-0307252000

Stay away from Patuxent?


--
Paul Tomblin , not speaking for anybody
UNIX was half a billion (500000000) seconds old on
Tue Nov 5 00:53:20 1985 GMT (measuring since the time(2) epoch).
-- Andy Tannenbaum

Is this the groundhog day location? Maybe GPS don't like groundhogs rooting
around?



GPS 07/015 ZDC GPS UNRELIABLE WITHIN A 100 NM RADIUS OF PATUXENT
VORTAC (PXT) AT 10,000 MSL THROUGH FL400, AND DECREASING IN AREA
WITH DECREASE IN ALTITUDE TO 80 NM RADIUS AT 4000 FT AGL
1200-2000 DLY WEF 0307211200-0307252000


--
Richard Kaplan, CFII

www.flyimc.com

Doesn't leave you any out should comm go down. I've had that
happen due to P-static, ice on the antenna, and problems with the
radio in a rental.

Robert Henry wrote:

"Richard Kaplan" wrote in message
...


If my plane had nothing but GPS-based avionics, what would my
options be?


Vectors.

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759

Richard Kaplan wrote:

The recent thread regarding GPS as the sole navaid sometime in the future
has focused on terrorism as the "what if" scenario.

I am not focusing specifically on terrorism in my concern the need for
GPS redundancy; I am simply observing that there is no system or device I am
aware of anywhere in aviation which works 100% of the time, so certainly it
is always worh having a backup. Even if GPS has 12 satellites, it seems
clear by common sense that the best backup system would use a technology
different from GPS.

With that as background, look at the following NOTAM, which is currently
available on DUAT. We can theorize all we want about whether this NOTAM
exists due to military testing or some atmospheric irregularity or whatever,
but the point is that the NOTAM really is out there and will be effective in
a few days. If my plane had nothing but GPS-based avionics, what would my
options be?

GPS 07/015 ZDC GPS UNRELIABLE WITHIN A 100 NM RADIUS OF PATUXENT
VORTAC (PXT) AT 10,000 MSL THROUGH FL400, AND DECREASING IN AREA
WITH DECREASE IN ALTITUDE TO 80 NM RADIUS AT 4000 FT AGL
1200-2000 DLY WEF 0307211200-0307252000


Again, there are toy airplanes then there are real airplanes. All high-end jets
have triple IRUs feeding position to the FMS and LNAV. So, if the primary nav
sensor shoots craps around Podunk, Merrykanasa, you just coast along using
triple-mized inertial position until the GPS kicks back in.

wrote:


sensor shoots craps around Podunk, Merrykanasa, you just coast along using
triple-mized inertial position until the GPS kicks back in.

Make that triple-mixed.

If my plane had nothing but GPS-based avionics, what would my
options be?

Vectors.

Ray Andraka wrote:
Doesn't leave you any out should comm go down. I've had that
happen due to P-static, ice on the antenna, and problems with the
radio in a rental.

Now you're theorizing about a simultaneous double system failure -- GPS
and communications. It's impossible, just extremely unlikely.

You can keep adding redundency to get the probability of incapacitation
as low as you want, but eventually an event will happen which will take
out all of your backups at the same time. What's the odds of a DC-10
having all three hydraulic system fail at the same time? They said it
was impossible, yet it happened (Souix City, uncontained failure of a
turbine disk).

By far the most likely cause of simultaneous GPS and COMM failure is
loss of ship's electrical power. It would take out your VOR, ILS,
Loran, too. The way to protect against that is multiple electrical
busses (like in twins), or battery backup and/or handheld devices.

I wrote:
It's impossible, just extremely unlikely.

Obviously, that's a typo. It should read "It's NOT impossible".

"Ray Andraka" wrote in message
...
Doesn't leave you any out should comm go down. I've had that
happen due to P-static, ice on the antenna, and problems with the
radio in a rental.


Dial in last good frequency or 121.5 on the handheld.

"Roy Smith" wrote in message
...

You can keep adding redundency to get the probability of incapacitation
as low as you want, but eventually an event will happen which will take

Even assuming ATC has the manpower and frequency bandwidth to simultaneously
give vectors to all airplanes in an area of GPS outage, do we land nowhere
but runways with ASR approaches when it is IMC in that region until the GPS
service is resolved? And if we want to take off with a void clearance, do
we just consider airports without radar coverage down to the surface to be
unusable during IMC since there would be no navigation system available on
takeoff? Or maybe we just go by dead reckoning on takeoff? What happens if
there is a need for an emergency medical aircraft in a region where GPS is
out of service and no radar coverage is available? Central Pensylvania east
of Johnstown is just one excellent example --- there is a pretty
significantly sized area where there is no radar coverage available for
apporches, so I suppose if sole-nav GPS went out of service in the region
all the airports would just become VFR-only.

Clearly this situation is absurd, and for that reason we cannot and never
will switch to GPS-only navigation. Maybe there will be fewer but
strategically placed VORs and ILS systems but clearly there always must and
will remain some backup system besides just GPS.


--
Richard Kaplan, CFII

www.flyimc.com