NextGen GPS backup?

[drizzt76]

Reading the thread about GPS outage made me think of a concern I have with NextGen. It sounds like they are shutting down all NDB's and many VOR's after NG is implemented. What will be a backup if the GPS system fails?. The signal can be blocked by 30 dollar GPS scrambler from China... I just don't like the idea of putting all your eggs in one basket.

 

[bflynn]

Nor do a lot of us.

So tune up that Mark-1 eyeball....

 

[Piloto]

I doubt there would be a wide area GPS outage but a localized one created by some interference or intentional jamming. Airliners and the military can easily overcome this by resorting to inertial navigation like it was before the GPS days. Airliners are equipped with triple IRS that can provide navigation with some degree of degradation (0.5nm/hour drift). Most affected would be GA were piston planes which are not IRS equipped. For this you would have to rely on dead reckoning until GPS comes back on line.

José

 

[kkoran]

If you can see the ground: pilotage.

If you can't see the ground: dead reckoning

 

[Brad Z]

There will still be a network of high volume VOR DMEs in place to serve as a ground based backup. Nowhere near the number we have today, but enough to find you way back to the ground.

 

[SCCutler]

I suggest a simple system, robust, effective and already built.

Loran.

 

[kkoran]

There will still be a network of high volume VOR DMEs in place to serve as a ground based backup. Nowhere near the number we have today, but enough to find you way back to the ground.

Unfortunately, in some circumstances (such as going missed on a GPS approach using a network of VORs that ensures coverage above 5000 agl), the issue might be avoiding the ground.

 

[Ted]

I suggest a simple system, robust, effective and already built.

Loran.

Since they shut it down, what has become of the equipment? Curious whether it's been taken down or is just sitting there... waiting.

For this to make the most sense, GPSs would need to be GPS/LORAN units that have both functions in one. Although I do happen to have a LORAN sitting in the basement for just such an occasion.

 

[L.Adamson]

I suggest a simple system, robust, effective and already built.

Loran.

And................only a small percentage of aircraft would still have one of these units available. Just keep a few VORs in place, as is planned.

 

[Bob Noel]

And................only a small percentage of aircraft would still have one of these units available. Just keep a few VORs in place, as is planned.

In my airplane:

LORAN: 1
GPS: 0

Yes, I can be stubborn.

 

[aterpster]

Unfortunately, in some circumstances (such as going missed on a GPS approach using a network of VORs that ensures coverage above 5000 agl), the issue might be avoiding the ground.

Most missed approach procedures can be flown using dead reckoning quite safely to 5,000 feet. And, what is the probably that the GPS system is lost at DA or MDA?

 

[gismo]

Most missed approach procedures can be flown using dead reckoning quite safely to 5,000 feet. And, what is the probably that the GPS system is lost at DA or MDA?

While I agree with you, I've never encountered any training scenarios that practiced this. Seems like a good idea though.

 

[KSCessnaDriver]

Since they shut it down, what has become of the equipment? Curious whether it's been taken down or is just sitting there... waiting.

IIRC, a couple of the stations still function, because of our contractual obligations with international treaties. eLoran would have been exactly what we needed. A combo GPS/eLoran receiver would have been the ticket. But alas, when DC is left to make decisions, they aren't always the best.

 

[SCCutler]

The eLoran group estimated the cost to add Loran to future GPS navigators would be under a grand (for certified stuff); not exactly rocket surgery, since the navigator function would be all shared with the GPS.

My Loran always worked, never, ever lost position. It's still ready... waiting...

 

[somorris]

The eLoran is (as I understand) ground based. That would be reassuring under some circumstances. I used to have a Loran unit and it always worked great. Does anyone know how vulnerable eLoran is to interference/jamming?

 

[Piloto]

The eLoran is (as I understand) ground based. That would be reassuring under some circumstances. I used to have a Loran unit and it always worked great. Does anyone know how vulnerable eLoran is to interference/jamming?

Unlike GPS, LORAN is more subject to interference by lightning and aircraft static buildup than by a jammer. Later improvements in LORAN using only H fields antennas and static wicks has reduced substantially this vulnerability. Similar to GPS WAAS, eLoran uses monitor stations to compute timing corrections that are broadcast to users to achieve similar accuracy to GPS. Unlike GPS LORAN range from a chain is about 1000nm with no altitude data provided. But unlike GPS a couple of old trucks is all that is required to deploy a chain.

José

 

[olasek]

The signal can be blocked by 30 dollar GPS scrambler from China...

There is plenty of hyperbole in this statement.
Even if it can be blocked - it will do it over a small area. For $30 maybe you can jam GPS on area size of a football field, you have to spend like $500 to be effective over a few miles.

 

[aterpster]

Unlike GPS, LORAN is more subject to interference by lightning and aircraft static buildup than by a jammer. Later improvements in LORAN using only H fields antennas and static wicks has reduced substantially this vulnerability. Similar to GPS WAAS, eLoran uses monitor stations to compute timing corrections that are broadcast to users to achieve similar accuracy to GPS. Unlike GPS LORAN range from a chain is about 1000nm with no altitude data provided. But unlike GPS a couple of old trucks is all that is required to deploy a chain.

José

I remember attending an event at KELP when the feds celebrated closing the mid-continent gap in 1991. A couple of days later my wife and visited the then-new Loran station in southeastern New Mexico. It was huge with a giant antenna.

 

[Ted]

There is plenty of hyperbole in this statement.
Even if it can be blocked - it will do it over a small area. For $30 maybe you can jam GPS on area size of a football field, you have to spend like $500 to be effective over a few miles.

Even then, let's think about how long that means for an aircraft.

At 120 kts GS you're covering 2 miles per minute. So that means that within 2 minutes or so (less in a faster plane), your GPS is back online.

That's probably long enough for you to start fiddling with it, push a few buttons, and then wonder WTF you did to fix it.