Clarification about the term "GPS Shutdown"

I have found that in practice this is not as great a problem as you
might think.

 

How do you know it's noon without a clock?

Compared to the movement of a typical vehicle, or even a person walking.

How will you find out where you are?

I watch my GPS, and I do not get lost.

It depends on which datum one has in mind, and how much accuracy one
requires.

 

Why a Christian in particular?

How does that tell you which hemisphere you are in?

Ocean currents won't stop while you calculate a fix.

No. Typically I can't see any stars at all in the sky above where I
live.

I carry extra batteries.

Drifting with the current.

Of course it is, in some situations. That doesn't mean that it is
practical or a good idea, or cost-free.

In some situations, yes. In others, no.

Perhaps, but it works well here. Watching the stars or looking for
trees is a bad idea in some parts of the world as well.

 

For twelve hours at a time?

I usually don't see any stars at all in the sky. And watching them
rotate is difficult when they when they move at 0.00069 rpm.

Where did I ask that?

You look at the scenery around you.

 

Apparently it has been a problem for the military.

The advantages they provide when one has the batteries outweigh that
disadvantage.

 

One must not look directly at the sun.

It was a major motivation for GPS.

 

The movement of a typical vehicle or walking person, or a typical water
or air current.

No, it's quite relevant, as it reveals a human tendency to resist change
(or, conversely and more rarely, to seek it out in extremes).

Not if you're holding a telephone.

 

Not very much for a country the size of the United States.

A compass doesn't tell you where you are, or where you are going.

 

The human being can push a button.

 

.

If you consider the equipment required to maintain RNP 10 across
the Pacific a luxury, then you must not run an airline.[/QUOTE]

The RNP 10 requirement for the Pacific are only possible due to GPS, that is
certain. For the North Atlantic, RNP 10 is easilly met without GPS. MD-11's in
service with KLM are a good example. No GPS at all. (This is not excl. to KLM
MD-11's it is just a case with which I'm famillar).

Almost all aircraft in oceanic airline service employ triple INS. In most cases
they are integrated via FMS, in which a filter can increase the accuracy by
combining all three INS'.

A fairly common airline INS such as the LTN-92 will deliver 2 NM/hr per spec, a
triple installation reduces that to about 1.2 NM/hr error. After an 8 hour (out
of range of DME) flight, the cumulative error would be just less than 10 NM,
meeting RNP 10. Of course upon arrival over land at the other side, the error
will converge to less than 0.2 NM as soon as a few DME's are tuned and the
postion fixed.

So for Pacific Oceanic, I agree that GPS is required to meet RNP 10 even if
triple INS equipped.

However this funny thread is about what happens if GPS goes down for some brief
period, say 24 - 72 hours. Will airliners stop crossing the Pacific? Of course
not. ATC will quickly agree that the thing to do is increase spacing and keep
on going. At worst flights will be delayed or routed differently. Ho hum. No
different than North Atlantic operations where route congestion causes delays
and re-routings... mostly in the summer months.

I would add that if airlines INS' could reach the performance of some military
INS at 1 NM/hr, that GPS would simply not be needed for RNP 10 in the Pacific.
The cost of doing so might be prohibitive, and of course a GPS makes it much easier.

I wasn't addressing airliners. I was stating requirments for 'basic VFR'. And
I know of at least one Airline in the US that has no choice but to complete
certain approaches VFR with MD-80 and B737's. If they can't, then those few
airports are not served. Of course those aircraft are well equipped for IFR.

True, not even NDB. But most where sched airlines operate have at least an NDB
approach, then VOR, then LOC then ILS. RNAV non-prec. approaches exit too, but
I'm not sure how many airlines use such. I've talked with a lot of airline
pilots in Canada and the US who have not shot an NDB approach in over 10 years.
I've met others who have not shot a VOR approach in recent memory ... their
ops tend to take them to large airports where even a lowly LOC approach is
considered as a last resort. Back course? C'mon are you serious?

I would hope so. But there is nothing like the sweat of a non standard hold at
an NDB on a windy day. (Not sure if such holds even exist anymore).

A triple 2 NM/hr INS (LTN-92) should have a cumulative error of 1.2 NM/hr, so
should be good for 10/1.2 = 8.3 hours.

In any case, we're talking about an emergency. GPS is not available. INS does
quite well alone and ATC will accomodate to keep the flow going in an emergency.
The Class I NOTAM would take 5 minutes to write for each control area.

Of course the dest. has to have a CAT III ILS and its monitors have to show it
in spec before the approach can be made (and a bunch of other specific details
as well). Further, the aircrew have to be trained and certified for the
operation as well. I was answering the other posters seeming belief that all
aircraft have suddenly and totally switched to GPS for precision approach and
all other manner of flying. Very few use GPS for even CAT I approaches to date
and that requires a local differential installation.

It surprises me that RNP 10 is required on the longer/thinner routes such as
LAX-Sydney. In fact it would be belligerent to insist on it if it is.

Where does this "6 hour fix" come from? As I state above, the LTN-92 (and
equivalent class INS from H'well and Sextant, etc.) would singly do it for 5
hours and combined, for over 8 hours.

To do such a fix at Hawaii would require flying very close to get a geometry
that would pull the INS error to less than, say, 1 NM. If there are enough
DME's on the islands and you flew right up the middle, you could probably pull
it down to better than 0.2 NM.

I'm not sure if a theta/rho solution (VOR/DME) is an available update in the
systems, that would do it too w/i about 0.5 NM at a range of about 28 NM from
the station. (Assuming a 1° radial error which is probably generous).

This all flies in the face of best fuel economy and service. Great circle or
even flying routes to take best advantage (or least penalty) from wind at cruise
altitude (one of the CNS/ATM goals).

Cheers,
Alan

 

There are usually 1 or 2 ADF's, 2 VOR's and 2 LOC receivers (VOR Rx really) at
least on GS (and two in most transport cat.).

There are HUNDREDS of ground stations of each sort in the US alone. Europe has
a higher density of transmitters than most parts of the US.

So a single or dual failure on the aircraft leaves the pilot with a variety of
alternatives. Many ground stations could be out (and at a given time, many are
down for calibration in any case).

Magnetic compass failure? Never heard of it! Oh, I suppose if the liquid
leaked out it would be useless.

Mx, you just don't know enough about aircraft nav to even touch the subject.

Cheers,
Alan

 

You need CAT IIIc which does not use GPS at all.

LAAS (DGPS) will get there eventually... but it will still require INS and will
remain the domain of big budgets.

 

I think it's time to stop feeding the troll.

 

Yes I have.

Sure. IFR Aircraft generally have two receivers (VFR usually have two as well),
and the number of gorund stations is in the many hundreds.

Yes I have. And the fact that the US Gov't is warning about it mean that the
contingency planners have seen it as a defense.

Very randomly. The V-1's were pointed at London and hit London. But no
specific targets (eg: a specific V-1 coulnd not be programmed to relaiably hit
parliament). V-2's even less so.

Hitting the containment dome of a nuke station would require reliable guidance
of 10m or less.

Navigation computers can't do anything without information from sensors.

 

Reread the reply:
"They click on, giving you more than enough time to start the generators. Many
of them will signal a generator to start automatically and manage the transition
more than smoothly enough to protect the power supplies of the equipment."

How it works.

1-UPS takes over generating AC from its batteries using a static inverter.
2-UPS signal to the generator starts the generator up.
3-UPS detects stable and usable power from the generator, and switches over and
helps during transition to keep spikes and noise in check.
4-UPS monitors the gen power, recharges its batteries and intervenes when there
is a problem using its batteries.
5-UPS returns to mains power after mains return to service for a reasonable
interval (programmable).

The generator can be diesel, gasoline, nat-gas, stirling engine, turbine...
whatever.

Cheers,
Alan.

 

Mx is usenet champion in evasive manoeuvering. He won the 2003 most evasive
snipper award in three different NG's.

 

He has to do it within 10 nm of his assigned track to avoid
hitting other aircraft.

There's more than one aircraft over the oceans these days.

 

Yes, because they still have to have young officers

Of course. But they still train people to navigate without GPS, because
they might run into situations when GPS isn't available, and their
lifes might depend on finding the way back to friendly lines with the
aid of a map and a compass, or maybe even ONLY a map (one of the silk
escape maps hidden in uniforms).


Juergen Nieveler

 

Unless GPS stops working - if only for the simple reason that you run
out of batteries, or your receiver gets sat on by an elephant, or
something else that Murphy's law will make happen.

It's always a good idea to be able to find your way without GPS, it's
only a tool.


Juergen Nieveler

 

A compass might not tell you where you are, but it DOES tell you where
you are going. And the INS should have stored your last position before
GPS went down.

Besides, over the Atlantic there really are only two directions if you
want to reach radar coverage again - due east or due west.

Juergen Nieveler