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illegal signals knocking out gps



 
 
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Old January 22nd 11, 03:04 AM posted to sci.geo.satellite-nav,rec.aviation.ifr
macpacheco
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Posts: 29
Default illegal signals knocking out gps

On Jan 21, 5:06*pm, HIPAR wrote:
On Jan 20, 9:56*pm, mac wrote:

Have anyone heard about illegal signals
*knocking out GPS systems at the Newark Liberty International
Airport?


The reference station for GPS aided landing system at Newark is
installed directly adjacent to the New Jersey Turnpike, a very busy
highway that's a major artery of the illegal drug distribution
network. *So, it's shouldn't be surprising that jammers are appearing
there to thwart GPS tracking by law enforcement. *Of course, there are
many other motives for jamming, mostly not intended to purposely
disrupt aviation.

By all accounts, these ground based augmentations normally work
extremely well. *Interference incidents highlight the dangers of over
reliance on GPS.

--- *CHAS


You see, I'm a glass half empty guy, while CHAS is a glass half full.
Nothing personal.
LAAS schedule has been delayed and delayed and delayed for a while.
FAA cut all funding to install LAAS stations, all stations operating
were installed with airport authority or airline money. If even the
FAA don't think it's time to deploy LAAS, something is fishy about it.

Using LAAS for CAT I operations add very little value versus WAAS
LPV200. It just allows the aircraft to autoland, while LPV200 requires
the autopilot to be disconnected below DH. And that's the only
authorized use for LAAS today that WAAS can't do. Someone will come
out and talk about curved approaches, constant descent approaches. All
of those features aren't an LAAS feature, those are features of
advanced FMS systems. Since airlines hate any system that's useful for
aviation in general, they did everything they could to kill/delay
WAAS, but eventually common sense prevailed, but that did delayed WAAS
support on Boeing and Airbus aircraft. But that's changing. Any
aircraft with advanced dual FMS and dual GPS/WAAS sensors can do
everything LAAS can except for full CAT I/II/III approaches. Oh and
there's the ground surface monitoring as well, but that's one more
thing that WAAS might be good enough for, but FAA politics (fully
killing LAAS wouldn't be good press) prevent that re analysis. Even
CAT I/II approaches might be doable if a dual FMS/INS/SBAS sensor is
required and the INSs are used to monitor GBAS calculated positioning.

LAAS landing for CAT III approaches is still not a sure thing before
L5 GPS at least reaches IOC. Or Galileo comes along. As much as I hate
GLONASS, it would be possible to use it as well to enhance precision,
but like me, the FAA have no lust love for Russian systems.
But on my first message I was not criticizing LAAS behavior, I was
just making a very unobjective analysis of its algorithms.
Its quite possible that airborne WAAS receivers on approach to EWR
would have faulted just like LAAS receivers on the ground did. Jamming
is a very serious issue indeed.

Finally, it's entirely possible that triple constellation, dual
frequency WAAS receivers with onboard redundant 2nd generation atomic
clocks will eventually be used for CAT IIIb approaches without LAAS,
CAT III approaches require triple FMS, sensors, autopilot, electrical
bus, power generation. Before GPS, 747s and other large aircraft had
triple inertial systems, today the vast majority of those aircraft
replaced one such INS with a GPS receiver, eventually each individual
sensor might use GNSS+SBAS for positioning with an INS and atomic
clock for automated integrity monitoring / jamming / spoofing
detection.

Yeah, I'm guessing a lot in the previous paragraph. But no one can
deny that there's always heavy politics behind billion dollar programs
like WAAS and LAAS. And while WAAS has already achieved everything it
can without L5 and Galileo, LAAS is still where WAAS was 8 years ago,
in a very limited production usage. 15 years ago when I got my
private, LAAS was supposed to come online more or less simultaneously
with WAAS.

Like the American founding fathers reminded us 200 yrs ago, oversight
is essential for an honest democracy, do not hope that your
congressman really cares about your taxpayers dollars ! The hidden
hands of the defense/aerospace industry reach everywhere, without the
people showing they're looking at everything with a critical eye,
billions and billions of US public money go to the toilet every year.
If it was up to me, LAAS would have been cancelled about 5 yrs ago,
and the money reverted to reaching L5 FOC capability as soon as
possible and an independent study of why the FAA has decided to throw
L2C in the trash bin in it's semi codeless transition plan. WAAS and
LAAS would be impossible today without the L2 band. Sure L2C isn't as
great as L1 or L5, but it should be a third frequency both in the
ground segment and on the user part of the system. Triple frequency
GNSS/GBAS can reach sub inch actual accuracy, with VPL/HPL around one
meter (enough for CAT IIIb landing), while dual frequency GNSS/GBAS
will stay in the 5-10 meter VPL/HPL range. The issue around L2C is
just the typical irrational paranoia from the FAA safety people. John
Deakin article on using handheld GPSs for IFR is very enlightening on
the overall FAA certification to perfection paranoia attitude. The
WAAS semi codeless transition plan will reduce availability in the
first years, a WAAS will switch from being able to use 32 GPS
satellites to only being able to use IIF and better satellites (at FOC
there will only be 24 such satellites, so 8 less satellites). If at
least the ground segment were allowed to fully use L2C, both L1CA+L2C
for IIR-M satellites and L1CA+L5+L2C for IIF and IIIx birds. WAAS
can't generate an UDRE for a satellite with a single frequency input
from the reference stations, so all IIR-M will be wasted once the
migration for L5 is implemented.

AOPA and NBAA should have been all over this. Why aren't they ?

Marcelo Pacheco
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