VOR impact study

Jim Logajan said:
To get a better idea of their policy and plans, I searched and found the following DoD/DHS/DoT published PDF formatted document on the BTS web site (TLAs are us):

2008 Federal Radionavigation Plan
http://ntl.bts.gov/lib/31000/31300/31340/02_2008_FEDERAL_RADIONAVIGATION_PLAN.pdf

Sections I skimmed through that seemed interesting: 3.2.4 GPS Backup, 3.3.1 Mitigating Disruptions to Sat Nav Svs, 3.4 Aeronautical Transition Policy, and 5.1.5 on VOR and DME.

Quote from 3.4.1:

"The pace and extent of the transition to SATNAV will depend upon a number of factors, including:
• NAS performance;
• achievement of GPS and GPS augmentation systems program milestones; and
• user acceptance."

I believe the last bullet point translates to "if they ***** a lot we'll keep the old stuff running longer."
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For amusement sometime, look at past RNPs. In general the timeframes for the grand plans in the RNPs are almost never met.

A let's not forget that the DoD operates a very large fleet of aircraft and modifying the navigation equipment is not cheap, especially in today's environment.
 
Ted DuPuis said:
But my question: How many aircraft had LORAN compared to the number of aircraft that have VORs and GPSs installed? Remember to factor in flight hours, as that is important in determining the impact.
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There was a reason that LORAN was superseded by GPS. GPS is a lot better, more accurate and more stable, at least in my experience. You also can't do LORAN approaches. There is no question that I would have chosen GPS over LORAN when both were operational. I flew some airplanes which had LORAN installed. One of them was pretty early on in the LORAN era. It seemed like you had to manually switch LORAN chains, and the accuracy was pretty bad in some places. That situation improved when they filled in the mid-continent gap and receivers became more sophisticated. It was also better than having no point-to-point navigation at all. One of my bosses took out LORAN and installed GPS in one of the mapping airplanes sometime in the early 1990s. Even though it was a primitive GPS with no moving map, it was better than the LORAN that was installed previously, and much better than the other airplane which only had a pair of VORs. Later on I flew some airplanes which had both LORAN and GPS installed and the only time I turned on the LORAN was out of curiosity.

I don't know how much it would have cost to support the LORAN chains, but I don't know if the number of users would have justified it although it seems that others liked their LORAN.
 
Everskyward said:
There was a reason that LORAN was superseded by GPS. GPS is a lot better, more accurate and more stable, at least in my experience. You also can't do LORAN approaches.
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Nobody ever said that Loran was better than GPS. Far from it. The point was that if you wanted a backup to GPS then Loran would have been a far better, more accurate, and more reliable backup than VOR.

You evidently were not around in the infancy of GPS when it was pretty widely accepted FAA philosophy that there would NEVER be a precision GPS approach. If you augmented Loran accuracy with the same methods we now use to augment GPS you could certainly have nonprecision Loran approaches. GPS does give you that vertical component that Loran could never give you, but eLoran and glideslope WOULD give you a precision approach capability.

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weirdjim said:
Nobody ever said that Loran was better than GPS. Far from it. The point was that if you wanted a backup to GPS then Loran would have been a far better, more accurate, and more reliable backup than VOR.
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But there were far more airplanes with VORs installed than LORAN. I don't think I ever saw an airplane with just LORAN and no VOR. LORAN seemed like it was in vogue for less than 10 years.

weirdjim said:
You evidently were not around in the infancy of GPS when it was pretty widely accepted FAA philosophy that there would NEVER be a precision GPS approach.
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I'm not just talking about precision approaches. The FAA never got very far along in developing non-precision LORAN approaches either. It seems that this would have cost a lot of money for both the government and the aircraft owner for something that was just going to be a backup.
 
I have lost signal on 430's several times, usually for about 1 minute and then it comes back. Sort of baffling.

I've also had original mid 70's Cessna Nav radios decide to take a vacation, twice I think.

Stuff Breaks.
 
Bob Noel said:
Three.
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You can count me in that group as well. Better yet would be fully implementing eLORAN which offers better accuracy, less issues with p-static, and is compatible with LORAN-C (what we used before it was shut down completely in the US).
 
Jeanie said:
So, here's my question... why do they want to decommision them anyway? They don't use that much electricity do they? Do they really require expensive and difficult maintenance?
Frankly, they should leave them in place as there are a lot of folks who use them and they are a good back up to GPS not working ....
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VORs are expensive to operate and maintain, partly because they're locations are widely scattered, often in fairly remote regions and partly because many of them are really old technology and need to be updated or replaced if they're going to be used in the not too distant future.
 
Everskyward said:
But there were far more airplanes with VORs installed than LORAN. I don't think I ever saw an airplane with just LORAN and no VOR. LORAN seemed like it was in vogue for less than 10 years.

I'm not just talking about precision approaches. The FAA never got very far along in developing non-precision LORAN approaches either. It seems that this would have cost a lot of money for both the government and the aircraft owner for something that was just going to be a backup.
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I don't have my AOPA magazines from the 80's or 90's. IIRC AOPA was hot for LORAN approaches but, like a fickle child, dropped any interest in LORAN and became hot for GPS when the GPS constellation was better populated. GPS became the new shiny thing.

One of the technical challenges for LORAN was the seasonal variation in position....something like 1700' foot delta in one long term stability demonstration. Seems variations in local moisture is part of the error budget. Not a concern for a marine navigation system.
 
gismo said:
VORs are expensive to operate and maintain, partly because they're locations are widely scattered, often in fairly remote regions and partly because many of them are really old technology and need to be updated or replaced if they're going to be used in the not too distant future.
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I wouldn't be surprised if the value of the land has increased. The VOR doesn't have a huge footprint, but land isn't cheap in some parts of the country.
 
IMHO, better antennas would do a lot to help guard against interference in GPS. These days of healthy constellation mean that you do not need to chase the birds low on the horizon.
 
zaitcev said:
IMHO, better antennas would do a lot to help guard against interference in GPS. These days of healthy constellation mean that you do not need to chase the birds low on the horizon.
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Due to the geometry involved, one get's significantly better position accuracy from SVs that aren't overhead so even with a "healthy constellation" there's value in chasing the low birds. In addition you need to be able to track SVs at low angles relative to the aircraft when turning so a narrow cone of reception would cause some loss of signal and or accuracy then. I could see some advantage to an antenna with variable or at least multiple acceptance angles. With that the GPS receiver could "narrow the field" in response to terrestrial interference and continue to operate in a slightly degraded mode instead of failing completely. The technology for this exists today albeit with a price, size, and weight penalty but I suspect those issues could be overcome within a few years if someone was pushing in that direction.
 
Bob Noel said:
I don't have my AOPA magazines from the 80's or 90's. IIRC AOPA was hot for LORAN approaches but, like a fickle child, dropped any interest in LORAN and became hot for GPS when the GPS constellation was better populated. GPS became the new shiny thing.

One of the technical challenges for LORAN was the seasonal variation in position....something like 1700' foot delta in one long term stability demonstration. Seems variations in local moisture is part of the error budget. Not a concern for a marine navigation system.
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There are several cyclic (and somewhat predictable) variations in LORAN accuracy including a diurnal (daily) one and this is inherent in any system using ground waves (half the LORAN signal effectively propagates through the ground) so the only plausible "fix" is some form of localized differential corrections ala WAAS. During LORANs heyday there were a few such systems but AFaIK there never was a wide area version like WAAS but I see no technological reason why this couldn't be done. Perhaps the ground reference stations could even be piggybacked on the WAAS network. It's not obvious to me how the correction data would be broadcast though. Using geosync SVs for that would limit the redundancy that LORAN could offer.
 
Bob Noel said:
I wouldn't be surprised if the value of the land has increased. The VOR doesn't have a huge footprint, but land isn't cheap in some parts of the country.
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You're probably correct WRT the value of the land in urban areas but I think that represents a fairly small portion of the existing VOR installations. Plus the land is likely already paid for so this cost isn't really an operating expense, just an untapped short term revenue source.
 
gismo said:
You're probably correct WRT the value of the land in urban areas but I think that represents a fairly small portion of the existing VOR installations. Plus the land is likely already paid for so this cost isn't really an operating expense, just an untapped short term revenue source.
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just to beat the horse a little more. There is the consideration of other potential uses of the property... especially if it can provide local tax revenues as opposed to be taken out of use by the Feds.
 
Everskyward said:
There was a reason that LORAN was superseded by GPS. GPS is a lot better, more accurate and more stable, at least in my experience. You also can't do LORAN approaches. There is no question that I would have chosen GPS over LORAN when both were operational. I flew some airplanes which had LORAN installed. One of them was pretty early on in the LORAN era. It seemed like you had to manually switch LORAN chains, and the accuracy was pretty bad in some places. That situation improved when they filled in the mid-continent gap and receivers became more sophisticated. It was also better than having no point-to-point navigation at all. One of my bosses took out LORAN and installed GPS in one of the mapping airplanes sometime in the early 1990s. Even though it was a primitive GPS with no moving map, it was better than the LORAN that was installed previously, and much better than the other airplane which only had a pair of VORs. Later on I flew some airplanes which had both LORAN and GPS installed and the only time I turned on the LORAN was out of curiosity.
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Thank you for the education, Mari. I never had the opportunity to use LORAN while it was functional, so this is good to know.

I don't know how much it would have cost to support the LORAN chains, but I don't know if the number of users would have justified it although it seems that others liked their LORAN.
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My question is if the people who were upset about the LORAN leaving ever actually used it, or just liked having it... same as the VORs. I'm sure if it was all your plane had you used it, but the 310 I fly has a LORAN and a GPS. The LORAN was never used once the 530 was installed.
 
Ted DuPuis said:
My question is if the people who were upset about the LORAN leaving ever actually used it, or just liked having it... same as the VORs.
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I did some work for the II Morrow company back in the day when Loran was purely for marine work. I've flown with everything from A-N range (don't know what that is, do you kiddies?) through ADF, VOR, Loran, and GPS.

Most of my flying in the early days was with Loran plus VOR for the plain and simple reason that the mossbacks in the FAA distrusted a NIH Loran system. I used Loran as my primary navaid (after the MK-I Mod A eyeball) and the VORs were turned on because the FAA said I had to. Then GPS came along and GPS became the primary with Loran as the backup and the VORs ... well I GUESS the on-off switch still works.

GPS primary, Loran backup is my choice. GPS primary, VOR backup is a poor second. GPS primary, ADF secondary if I want to listen to the ballgame on my way home.
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weirdjim said:
I did some work for the II Morrow company back in the day when Loran was purely for marine work. I've flown with everything from A-N range (don't know what that is, do you kiddies?) through ADF, VOR, Loran, and GPS.
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You bet I know what the A-N range is. Wish I could've gotten to fly with them.

I actually use ADFs when up in Canada when I'm bored. They're fun. I think VORs are fun as well.

Doesn't mean I don't understand why they want to decommission them...
 
gismo said:
Due to the geometry involved, one get's significantly better position accuracy from SVs that aren't overhead so even with a "healthy constellation" there's value in chasing the low birds. In addition you need to be able to track SVs at low angles relative to the aircraft when turning so a narrow cone of reception would cause some loss of signal and or accuracy then. I could see some advantage to an antenna with variable or at least multiple acceptance angles. With that the GPS receiver could "narrow the field" in response to terrestrial interference and continue to operate in a slightly degraded mode instead of failing completely. The technology for this exists today albeit with a price, size, and weight penalty but I suspect those issues could be overcome within a few years if someone was pushing in that direction.
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I would guess that the Garmin Antennas aren't isotropic, since you are going to mount it on top of an aircraft. They likely have a gain pattern that points mostly up.

You also referred to the relative geometry of the satellites. This is usually referred to as dilution of precision (DOP). The best position can be calculated if the SVs have nearly a 90 angle between the line of sight vectors.

Raytheon makes a military antenna called CRPA, which allows the receiver to point "beams" at SVs that it wants to receive and "nulls" at jammers. Here's a description of the device:

Anti-jam GPS Receiver (AGR)
Raytheon’s Anti-jam GPS Receiver (AGR) supports the Tactical Tomahawk missile program. The AGR is a PPS (i.e., Y-code) GPS receiver that operates on both the L1 and L2 frequencies. When configured with a multi-element Controlled Reception Pattern Antenna (CRPA), the AGR’s post-correlation nulling techniques allow continued satellite track in the presence of high levels of hostile jamming.
 
zaitcev said:
I was returning on Tuesday from FTG and PUB VOR was out. That left a considerable gap at non-oxigen altitudes. There never was an opportunity to get lost, due to easily referenced terrain features, but I almost busted Delta around KPUB by drifting right, and had to make a left turn when I realized what I am looking at.

I have AV8OR, but its battery life is pathetic and one of airplanes I rent has no cigar lighter outlet (well actually its VOR receiver is broken too...).
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BRK has also been up and down lately. Perhaps the maintenance guy is on vacation around here? ;)
 
Laura_D said:
Hi all, I'm currently involved in a research project and am hoping the community here can help me out. I'm sure most of you are aware that the FAA is planning to significantly reduce the number of operational VOR's by 2020, in conjunction with NextGen implementation. I'm interested in the impact this may have.

It is my understanding that many pilots are already using GPS as their main method of navigation but rely on VORs as a back up. I am aware of the concerns regarding the reliability of GPS, including the recent LightSquared interference issues. I know another major concern, expecially for GA pilots, is the cost of the avionics that will be required for NextGen.

Besides these concerns, what other issues might be involved with this proposed loss of VOR service? Any input would be appreciated! :)
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I was wondering if anyone has done anymore research into this, or if this post is still active. I'm currently getting ready to begin my Dissertation for my Doctorates, and my thesis will be on the reduction of VOR systems and the impact it will have as we continue to transition more towards GPS.
 
Robert Price said:
I was wondering if anyone has done anymore research into this, or if this post is still active. I'm currently getting ready to begin my Dissertation for my Doctorates, and my thesis will be on the reduction of VOR systems and the impact it will have as we continue to transition more towards GPS.
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Don’t you think enough has already been written on the subject and that it’s pretty much old news? Especially since you revived an 11-year-old thread? What new contribution do you think you can bring?
 
Robert Price said:
I was wondering if anyone has done anymore research into this, or if this post is still active. I'm currently getting ready to begin my Dissertation for my Doctorates, and my thesis will be on the reduction of VOR systems and the impact it will have as we continue to transition more towards GPS.
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I would suggest a focus that isn't primarily on the impact on general aviation users. They are an important group of users of the national airspace system but they are not the group that the system is primarily designed around.

Larger G.A. airplanes, and transports, use flight management systems that use multiple inputs to update their internal position(s) estimates. The DME/DME and RHO/DME inputs rely on the VOR and DME networks. Most of those airplanes now also have GPS input(s) which provide the most accurate position updating under normal circumstances. The larger airplanes will typically also have inertial reference systems.

When GPS fails, or becomes unavailable, the FMS units fall back to the next most accurate source for position updating which is usually DME/DME/IRU. Those systems can navigate quite accurately in that mode but you lose the ability to fly many RNAV procedures. The VOR reductions are likely looking more toward the needs of these aircraft when establishing the minimum necessary VOR/DME network and not primarily the needs of GA aircraft with only VOR as a backup to GPS.
 
Robert Price said:
I was wondering if anyone has done anymore research into this, or if this post is still active.
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That red box you clicked on that said this is an 11 year old thread, are you sure you want to continue? That didn't answer your question?
 
Funny to read this retro thread.

I hatred GPS and it will never be popular....

Even further back, I hatred cars, they will never be popular and also smell worse then the horses..... :lol::lol:
 
Robert Price said:
I was wondering if anyone has done anymore research into this, or if this post is still active. I'm currently getting ready to begin my Dissertation for my Doctorates, and my thesis will be on the reduction of VOR systems and the impact it will have as we continue to transition more towards GPS.
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Yes. And you just made it active again after 11 years. It's been happening and pretty much is done now. Just curious, what's your field, what are you going to become Doctor of?
 
Seems a more fitting topic for a freshman term paper than for a doctoral thesis, but then colleges ain't what they used to be.
 
Can't say it better than others have already:

Racerx said:
That red box you clicked on that said this is an 11 year old thread, are you sure you want to continue? That didn't answer your question?
luvflyin said:
Yes. And you just made it active again after 11 years. It's been happening and pretty much is done now. Just curious, what's your field, what are you going to become Doctor of?
MauleSkinner said:
Doctor of Dead Threads
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Piperonca said:
  1. New
  2. Troll
  3. Old
  4. News
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There was an FAA flight check King Air that did a VOR impact study at the Linden (Virginia) VOR.
 
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