IFR MEAs

[Greg R]

Greetings. I've got a peculiar question. There is a lot to explain before I can actually ask the question. Please be patient when reading the following.

Victor Airways are VOR based and Tango Routes are GPS based. On the US Government low altitude charts, Victor Airways are black and Tango Routes are blue. It is common now to see two MEAs on a victor airway. (I am not talking about MOCA.) One is based on using the VOR and the other is written in blue and is based on using GPS. The GPS MEA has a "G" after the altitude. Logically, the GPS-based MEA can be lower than the VOR-based MEA as there is little trouble receiving satellite information. I am only talking about Victor Airway MEAs at this point. A good example of this is seen on V348 between BELAY intersection and the Modena VOR (MXE) on low altitude Enroute chart L-34. The Modena VOR sits on the 30 mile Mode C line West of Philadelphia International Airport. The part of V348 I am referring to extends Southwest from the Modena VOR. One can easily see that V348 has an MEA in black (the traditional MEA that we learned about years ago) and the new MEA (in blue) that is allowed to be used if you are using GPS to verify that you are on the correct course.

Tango routes are written in blue and have their MEAs listed in blue with the letter "G" after the altitude. This is to remind us that we are using GPS and to get us used to seeing GPS MEAs. The first Tango routes seen were published in 2005 around Charlotte. These can be seen on L-25 and L-36.

Sometimes Victor Airways and Tango Routes are co-located.

Now look at Enroute A1-L (the low altitude chart for Southeast Alaska). West of Juneau is the co-located routes of T278 and V317. Look at that part between CSPER intersection and Elephant VOR (EEF). The MEA for V317 is 7000 but if you use GPS your MEA is lowered to 5000. Yet if you fly T278 (the exact same route) and use your GPS to fly T278, your MEA is only 6100.

This makes no sense to me. I cannot understand that if you fly the same ground track over the ground and use your GPS to verify your position, your MEA is lower if you arbitrarily say you are flying the victor airway as compared to if you say you are flying the Tango route. It must be some quirk in the way Tango MEAs are derived as compared to Victor MEAs. Can anybody explain this peculiar finding?

I look forward to hearing from you.
Thanks, Greg.

 

[poadeleted20]

Can't help with the MEA issues, but if you look closer, you'll see that V317 is defined by Sisters Island VOR (SSR), not Elephant NDB (EEF). EEF defines the Blue 37 NDB airway which runs near but not coincident with V317. And somewhere in that noncoincidentness may lie the answer to your original question.

 

[roncachamp]

Greetings. I've got a peculiar question. There is a lot to explain before I can actually ask the question. Please be patient when reading the following.

Victor Airways are VOR based and Tango Routes are GPS based. On the US Government low altitude charts, Victor Airways are black and Tango Routes are blue. It is common now to see two MEAs on a victor airway. (I am not talking about MOCA.) One is based on using the VOR and the other is written in blue and is based on using GPS. The GPS MEA has a "G" after the altitude. Logically, the GPS-based MEA can be lower than the VOR-based MEA as there is little trouble receiving satellite information. I am only talking about Victor Airway MEAs at this point. A good example of this is seen on V348 between BELAY intersection and the Modena VOR (MXE) on low altitude Enroute chart L-34. The Modena VOR sits on the 30 mile Mode C line West of Philadelphia International Airport. The part of V348 I am referring to extends Southwest from the Modena VOR. One can easily see that V348 has an MEA in black (the traditional MEA that we learned about years ago) and the new MEA (in blue) that is allowed to be used if you are using GPS to verify that you are on the correct course.

MXE VORTAC has a few restrictions that affect MEAs on V378:

10/29/99 VOR unusable 170° - 248° byd 8 NM blo 6000'
10/29/99 VOR unusable 170° - 248° byd 27 NM blo 7500'
10/29/99 VOR unusable 170° - 248° byd 30 NM blo 9500'

If navigating by GPS, VORTAC signal coverage is not an issue so there's also a lower GNSS RNAV MEA.

Tango routes are written in blue and have their MEAs listed in blue with the letter "G" after the altitude. This is to remind us that we are using GPS and to get us used to seeing GPS MEAs. The first Tango routes seen were published in 2005 around Charlotte. These can be seen on L-25 and L-36.

Not always, see T265 between KRFD and KDPA on L-28. The "G" on the MEA is superfluous when the route requires GNSS anyway.

Sometimes Victor Airways and Tango Routes are co-located.

Now look at Enroute A1-L (the low altitude chart for Southeast Alaska). West of Juneau is the co-located routes of T278 and V317. Look at that part between CSPER intersection and Elephant VOR (EEF). The MEA for V317 is 7000 but if you use GPS your MEA is lowered to 5000. Yet if you fly T278 (the exact same route) and use your GPS to fly T278, your MEA is only 6100.

Elephant is not a VOR, it's an NDB. T278/V317 is between HAPIT and Sisters Island VORTAC. Slightly north there's a LF/MF airway, B-37, between SPARL and Elephant NDB.

This makes no sense to me. I cannot understand that if you fly the same ground track over the ground and use your GPS to verify your position, your MEA is lower if you arbitrarily say you are flying the victor airway as compared to if you say you are flying the Tango route. It must be some quirk in the way Tango MEAs are derived as compared to Victor MEAs. Can anybody explain this peculiar finding?

MEAs are based on terrain and obstacle clearance, adequacy of navigation facility performance, and communications requirements. GPS does not have the nav signal limitations that VOR has, that's why there can be lower MEAs with GPS nav.

What's odd is the 5000G and 6100G on T278/V317.

 

[poadeleted20]

What's odd is the 5000G and 6100G on T278/V317.

And that's the question he was asking. Guess neither of us has the answer to why it's 5000 for GPS on V317 and 6100 for T278.

 

[roncachamp]

And that's the question he was asking. Guess neither of us has the answer to why it's 5000 for GPS on V317 and 6100 for T278.

I don't think so.

This makes no sense to me. I cannot understand that if you fly the same ground track over the ground and use your GPS to verify your position, your MEA is lower if you arbitrarily say you are flying the victor airway as compared to if you say you are flying the Tango route. It must be some quirk in the way Tango MEAs are derived as compared to Victor MEAs. Can anybody explain this peculiar finding?

I think he's asking why MEAs can differ when navigating by GPS versus VOR.

 

[EdFred]

Ron, where does it define T278 as being defined by the NDB and not the VOR? Green book?


The other interesting thing is that B37 which is defined from the NDB also has the lower -G MEA.

 

[Ted]

I don't think so.

I agree with Ron.

Now look at Enroute A1-L (the low altitude chart for Southeast Alaska). West of Juneau is the co-located routes of T278 and V317. Look at that part between CSPER intersection and Elephant VOR (EEF). The MEA for V317 is 7000 but if you use GPS your MEA is lowered to 5000. Yet if you fly T278 (the exact same route) and use your GPS to fly T278, your MEA is only 6100.

 

[roncachamp]

I agree with Ron.

Well, if you, like Ron, think he was asking why T278/V317, which is in Alaska, has 5000G and 6100G MEAs, why do you think he mentioned V378, which is in Pennsylvania and Maryland, and has only 4000G?

 

[chucky]

Tango airways are RNAV routes, I think, not specifically GPS routes. I've been looking at the TERPS manual, and while I'm not sure I understand it, it seems to me that the obstacle clearance areas for an RNAV route can actually be wider than the Victor 8nm/10nm area, when near a TACAN or VOR facility. The GPS MEA for the route, though, would probably use the Victor airway area, which might explain why the 'Victor+G' MEA is lower than the 'T' MEA.

I think you can find examples where the 'T' MEA is lower than the equivalent Victor GPS MEA - look over at T269/V440. Here, I would guess that the Victor obstacle clearance area has expanded to much wider than the 'T' area, since we are so far (~100nm) for the VORs.

I'm out of my depth, though. I might be completely missing the point.

 

[Ted]

Well, if you, like Ron, think he was asking why T278/V317, which is in Alaska, has 5000G and 6100G MEAs, why do you think he mentioned V378, which is in Pennsylvania and Maryland, and has only 4000G?

V378 was an example of an airway where the GPS MEA was lower than the standard MEA. This would be logical since the restrictions of normal VORs don't apply from a navigational standpoint.

His question, as I see it, is why do you have T278 colocated with V317, where V317 is 5000G and T278 is 6100G. It's a good question, I have no idea. A link to the chart he's looking at can be found here:

http://www.runwayfinder.com/?x=-135.98602294921875&y=58.11706682078877&z=9&view=ifr

 

[roncachamp]

Tango airways are RNAV routes, I think, not specifically GPS routes.

From AIM 5-3-4.a.3.(a):

"Published RNAV routes, including Q−Routes and T−Routes, can be flight planned for use by aircraft with RNAV capability, subject to any limitations or requirements noted on en route charts, in applicable Advisory Circulars, or by NOTAM."

From IFR Enroute Low Altitude chart legend:

(T-route) - "Low Altitude RNAV Route GNSS required"

From AIM Appendix 4. Abbreviations/Acronyms:

"GNSS . . . . . . Global Navigation Satellite System"

 

[roncachamp]

V378 was an example of an airway where the GPS MEA was lower than the standard MEA. This would be logical since the restrictions of normal VORs don't apply from a navigational standpoint.

Yes, I already explained that.

His question, as I see it, is why do you have T278 colocated with V317, where V317 is 5000G and T278 is 6100G. It's a good question, I have no idea.

He wrote:

"This makes no sense to me. I cannot understand that if you fly the same ground track over the ground and use your GPS to verify your position, your MEA is lower if you arbitrarily say you are flying the victor airway as compared to if you say you are flying the Tango route. It must be some quirk in the way Tango MEAs are derived as compared to Victor MEAs. Can anybody explain this peculiar finding?"

It's very clear to me that he was asking why MEAs differ on the same track dependent on whether navigation is by GPS or VOR. He didn't even mention that T278 has two GPS MEAs.

The very existence of T278 is an oddity, as it exists only between HAPIT and SSR, which is also V-317. Establishing a GPS MEA on V317 between those points was all that was needed and wouldn't have cluttered the chart.

 

[poadeleted20]

Ron, where does it define T278 as being defined by the NDB and not the VOR? Green book?

I don't think it is defined by the NDB rather than the VOR, nor do I think I said it was, just that EEF is an NDB defining B37 while V317 is defined by SSR. It isn't entirely clear what defines the east end of T278, but based on the way the T278 and V317 blocks are put together on the black airway line, I'd say SSR is the defining fix for the east end of T278.

The other interesting thing is that B37 which is defined from the NDB also has the lower -G MEA.

Yes, it is.

 

[roncachamp]

It isn't entirely clear what defines the east end of T278, but based on the way the T278 and V317 blocks are put together on the black airway line, I'd say SSR is the defining fix for the east end of T278.

Order JO 7400.9T Airspace Designations and Reporting Points


T-278 HAPIT to SSR

HAPIT Fix (lat. 58°11'58"N., long. 137°31'12"W.)
SSR VORTAC (lat. 58°10'40"N., long. 135°15'32"W.)

AMENDMENTS 8/27/2009 74 FR 31845 (Added)

 

[poadeleted20]

Order JO 7400.9T Airspace Designations and Reporting Points


T-278 HAPIT to SSR

HAPIT Fix (lat. 58°11'58"N., long. 137°31'12"W.)
SSR VORTAC (lat. 58°10'40"N., long. 135°15'32"W.)

AMENDMENTS 8/27/2009 74 FR 31845 (Added)

Goody! I read it right!

 

[EdFred]

I don't think it is defined by the NDB rather than the VOR, nor do I think I said it was, just that EEF is an NDB defining B37 while V317 is defined by SSR. It isn't entirely clear what defines the east end of T278, but based on the way the T278 and V317 blocks are put together on the black airway line, I'd say SSR is the defining fix for the east end of T278.

Yes, it is.

I read your first post wrong.

 

[Greg R]

Thank you all for your discussion. I appreciate all of the above.

I guess I was not clear. I think my question is real simple. Before I get to my question, I first want to clarify a few things.

Victor airways are VOR based. Victor airways are NOT based on NDBs. I did not mention B37 because I did not want to add more to the discussion. Since it was brought up, I will say that there are 4 types or low altitude airways based on LF/MF (low frequency/medium frequency) navaids (NDBs). These are designated by the letters A for amber, B for blue, G for green and R for red. Amber and Blue airways are north-south airways and Green and Red airways are east-west airways. All of these airways are charted in brown on low altitude charts. (As stated previously, Victor airways (VOR based) are charted in black and Tango Routes (GPS based) are charted in blue on low altitude charts.) [For those who really like minutia, there is only one LF/MF route left in the lower 48. It is G13 that extends southeast from KMQI as seen on L-35. All others in the lower 48 states have been eliminated.]

I love all of the above stuff. Minutia is fun for me. Before I pose my question again, I want to emphasize that victor airways, Tango routes and even LF/MF airways can be co-located. That means they are in the exact same place for part or all of their route.

I joined Pilots of America with the hopes that one of the Pilots of America members might be able to bring reason to what I have found to be unreasonable. I am hopeful that somebody will be able to explain why when using your IFR approved GPS to identify your location over Tango 278 your MEA is 6100 feet and if you use your same IFR approved GPS to verify your position on Victor 317 or your position on B37 your MEA is 5000. That makes no sense to me. It is important to note that these airways are co-located on the part I was asking about. That means they are in the exact same place.

It does not make sense to me that if you are using the same GPS, to verify your position at the same location, your MEA is different by 1100 feet just because you chose to call the route you are flying a tango route, a victor airway or a LF/MF airway. Logic dictates that the MEA should be the same if based on the same form of navigation over the same course.

Again, thanks to all for your discussion. I hope I did a better job trying to explain my dilemma.

Greg.

 

[Greg R]

I see that I made a mistake in my original note. V317 is defined by the Sisters Island VOR. I originally said Elephant VOR. I did not have the name of Sisters Island VOR on the part of the low altitude chart I was looking at and I incorrectly called the NDB EEF a VOR. Sorry for the error. That error, however, does not change my dilemma. Thanks.
GR.

 

[twdeckard]

Awesome post. Question was clear to me when you posed it. Answer is not yet. Here is the angle I am taking in my research:

Is it becuase you need a TSO 146a IFR WAAS GPS? In order to plot the T-route they need to guarantee adequate satellite visibility for something close to 100% of the time. 146a buys them a tighter requirement and in this case they have to raise you up a bit to get the right geometry against the horizon.

Since you can fly the victor with your poor cousin C129 certified unit and I suspect its TSO is less stringent, becuase it doesn't deliver WAAS accuracy or simply becuase the standard was contrived earlier.

What do you think?

 

[poadeleted20]

Is it becuase you need a TSO 146a IFR WAAS GPS?

No. A c129 non-WAAS GPS is sufficient to fly T-routes as long as you have a working VOR for backup to fly an alternate route in case the non-sole-source GPS stops working properly.

 

[roncachamp]

Thank you all for your discussion. I appreciate all of the above.

I guess I was not clear. I think my question is real simple. Before I get to my question, I first want to clarify a few things.

Victor airways are VOR based. Victor airways are NOT based on NDBs. I did not mention B37 because I did not want to add more to the discussion. Since it was brought up, I will say that there are 4 types or low altitude airways based on LF/MF (low frequency/medium frequency) navaids (NDBs). These are designated by the letters A for amber, B for blue, G for green and R for red. Amber and Blue airways are north-south airways and Green and Red airways are east-west airways. All of these airways are charted in brown on low altitude charts. (As stated previously, Victor airways (VOR based) are charted in black and Tango Routes (GPS based) are charted in blue on low altitude charts.) [For those who really like minutia, there is only one LF/MF route left in the lower 48. It is G13 that extends southeast from KMQI as seen on L-35. All others in the lower 48 states have been eliminated.]

Well, it was actually you that brought B37 into the discussion when you wrote, "West of Juneau is the co-located routes of T278 and V317. Look at that part between CSPER intersection and Elephant VOR (EEF)." Elephant is not a VOR, it's an NDB and it defines the LF/MF airway B37 between EEF SPARL. It's Sisters Island VORTAC that defines T278/V317 between SSR and HAPIT.

I love all of the above stuff. Minutia is fun for me. Before I pose my question again, I want to emphasize that victor airways, Tango routes and even LF/MF airways can be co-located. That means they are in the exact same place for part or all of their route.

I joined Pilots of America with the hopes that one of the Pilots of America members might be able to bring reason to what I have found to be unreasonable. I am hopeful that somebody will be able to explain why when using your IFR approved GPS to identify your location over Tango 278 your MEA is 6100 feet and if you use your same IFR approved GPS to verify your position on Victor 317 or your position on B37 your MEA is 5000. That makes no sense to me. It is important to note that these airways are co-located on the part I was asking about. That means they are in the exact same place.

It does not make sense to me that if you are using the same GPS, to verify your position at the same location, your MEA is different by 1100 feet just because you chose to call the route you are flying a tango route, a victor airway or a LF/MF airway. Logic dictates that the MEA should be the same if based on the same form of navigation over the same course.

My best guess is it's a chart error, multiple GPS MEAs on the same track just don't make any sense. Establishing T278 between HAPIT and SSR doesn't make any sense either because that track was already defined as V317, simply adding a GPS MEA to V317 would have accomplished the same thing without cluttering the chart.

 

[twdeckard]

No. A c129 non-WAAS GPS is sufficient to fly T-routes as long as you have a working VOR for backup to fly an alternate route in case the non-sole-source GPS stops working properly.

Yes, I stand corrected. An operator can fly the t-routes with their poor cousin GPS assuming they also have a VOR receiver. But someone using GPS as their sole source of navigation must have WAAS.

So the airway author has to buy the more stringent 146. He/She cannot assume you are also using VORs.

I don't agree with Steve, I don't think its a charting error. I believe the MEAs are determined by two different technical standards orders and the integrity prediction costs them the higher MEA. Now the fact that its not an error doesn't make it sensible and its simply an artifact of the time/technology shift across the two points in regulatory history.

This is a guess and I'll dig into it later in the weekend unless one of the sea-lawyers beats me to it.

 

[chucky]

The width used to determine obstacle clearances on T-routes and V-routes can be different. As roncachamp pointed out above, though, the T-route in question requires GPS, whereas the section of the TERPS I read dealt with VOR/DME RNAV systems. Maybe someone more familiar with the TERPS document can actually find the relevant criteria.

 

[Greg R]

Well, I hit another dead end. I thought I found the answer to my question but I did not.

In the July 1, 2005 issue of the Federal Register (found at: http://www.federalregister.gov/arti...t-rules-terminal-transition-routes-rittr#p-18) it says: “RITTRs would be depicted in blue on the appropriate IFR en route low altitude chart(s). Each route depiction would include a GNSS Minimum En route Altitude (MEA) to ensure obstacle clearance and communications reception.”

So the MEAs for Tango Routes require radio communication ability as well as terrain clearance. The MEAs for Victor and LF/MF airways require terrain clearance and navigation reception (not communication). So I thought that the regs allowed a lower MEA for the Victor and LF/MF Airways because radio communication was not required. Not so when it comes to defining a GPS MEA. The AIM 5-3-4 (c) says: “The use of TSO−C145a or TSO−C146a GPS/WAAS navigation systems is allowed in Alaska as the only means of navigation on published air traffic routes including those Victor and colored airway segments designated with a second minimum en route altitude (MEA) depicted in blue and followed by the letter G at those lower altitudes. The altitudes so depicted are below the minimum reception altitude (MRA) of the land−based navigation facility defining the route segment, and guarantee standard en route obstacle clearance and two−way communications.”

For those who may not know, “RITTERs” means ‘Area IFR Terminal Transition Routes.’ Also known as “Tango Routes.” Colored airways are the LF/MF airways we’ve discussed previously (Green, Red, Blue, and Amber).

So terrain clearance, radio navigation and communication do not explain the difference in MEAs.

Maybe the person who wrote the MEA for T278 made a mistake. I doubt it but these things do occur. (I mistakenly called an NDB a VOR - and I do know the difference).

Greg.

 

[TangoWhiskey]

Always check your NOTAMS:

!FDC 0/1957 (PAZA A0135/10) ZAN AK.. ROUTE ADVISORY: THE FOLLOWING RNAV "T" ROUTES PUBLISHED ON THE ALASKA IFR ENROUTE ALTITUDE CHARTS ARE UNUSABLE: T222 T223 T225 T226 T227 T228 T229 T230 T232 T234 T236 T238 T240 T246 T252 T260 T269 T275 T278 T280.

https://pilotweb.nas.faa.gov/PilotWeb/

Under ARTCC notices for Anchorage. I don't know why they're unusable--could it be the suspected charting error on GPS MEA?

 

[Greg R]

Wow. Thanks.
GR

 

[roncachamp]

Well, I hit another dead end. I thought I found the answer to my question but I did not.

In the July 1, 2005 issue of the Federal Register (found at: http://www.federalregister.gov/arti...t-rules-terminal-transition-routes-rittr#p-18) it says: “RITTRs would be depicted in blue on the appropriate IFR en route low altitude chart(s). Each route depiction would include a GNSS Minimum En route Altitude (MEA) to ensure obstacle clearance and communications reception.”

So the MEAs for Tango Routes require radio communication ability as well as terrain clearance. The MEAs for Victor and LF/MF airways require terrain clearance and navigation reception (not communication). So I thought that the regs allowed a lower MEA for the Victor and LF/MF Airways because radio communication was not required. Not so when it comes to defining a GPS MEA. The AIM 5-3-4 (c) says: “The use of TSO−C145a or TSO−C146a GPS/WAAS navigation systems is allowed in Alaska as the only means of navigation on published air traffic routes including those Victor and colored airway segments designated with a second minimum en route altitude (MEA) depicted in blue and followed by the letter G at those lower altitudes. The altitudes so depicted are below the minimum reception altitude (MRA) of the land−based navigation facility defining the route segment, and guarantee standard en route obstacle clearance and two−way communications.”

So two-way radio communications is guaranteed at the second MEA depicted in blue and followed by the letter G but not at the higher MEA?

 

[Greg R]

I wrote the FAA and here is the answer I got today:

Dear Gregory :

Thank you for reporting the problem

Control Number 10943 has been assigned to this issue for tracking purposes.
This concern has been closed with the following Response:

It appears that the 1,100 ft difference in the GNSS altitudes between T278 and V317 come from criteria changes. T278 was developed in 2009. According to the notes on the -16, T278 crosses over a Wildlife refuge. Due to criteria, the MEA's would have been higher than originally as on V317 and an additional 1000 feet was added due to the wildlife refuge to result in the alitutde of 6100. A review and update of T278 and V317 will be completed as soon as practical to get the airway altitudes as closse as possilbe.

 

[flyingcheesehead]

It appears that the 1,100 ft difference in the GNSS altitudes between T278 and V317 come from criteria changes. T278 was developed in 2009. According to the notes on the -16, T278 crosses over a Wildlife refuge. Due to criteria, the MEA's would have been higher than originally as on V317 and an additional 1000 feet was added due to the wildlife refuge to result in the alitutde of 6100. A review and update of T278 and V317 will be completed as soon as practical to get the airway altitudes as closse as possilbe.

Well jeez, way to kill a good discussion with facts.

My original guess was going to be that it was due to some of the terrain that's fairly close in to the VOR, and since the VOR needle is more sensitive the closer you are to the VOR but the GPS always has the same sensitivity, that full deflection on the VOR would be narrower than full deflection on the GPS when close to the VOR. However, since airway widths aren't defined as a certain deflection on the VOR but instead are defined as 4nm each side of the centerline, so I figured there was more to it than that.

Well, if you, like Ron, think he was asking why T278/V317, which is in Alaska, has 5000G and 6100G MEAs, why do you think he mentioned V378, which is in Pennsylvania and Maryland, and has only 4000G?

Steven, you were the first person to mention V378. The OP used V348 in an example of a GPS MEA on a Victor airway, and his question was about T278 and V317. I think Ron got the intent of the question correct here

Can't help with the MEA issues, but if you look closer, you'll see that V317 is defined by Sisters Island VOR (SSR), not Elephant NDB (EEF). EEF defines the Blue 37 NDB airway which runs near but not coincident with V317. And somewhere in that noncoincidentness may lie the answer to your original question.

but missed the fact that the OP was not asking about Blue 37, he was asking about T278/V317 and mistakenly called EEF a VOR when the VOR is actually SSR (it's identified on the opposite side on the chart).

Okay, enough with reading comprehension and on to more fun stuff:

[For those who really like minutia, there is only one LF/MF route left in the lower 48. It is G13 that extends southeast from KMQI as seen on L-35. All others in the lower 48 states have been eliminated.]

I am a fan of minutia as well - And I'm guessing you got the above from reading the note in the AIM about the NDB airway system only existing in Alaska and coastal NC, looked at the chart and saw the Green 13 airway in coastal NC.

However, in this case, the AIM is just flat-out wrong. The only NDB airway I've ever flown (via GPS in a G1000-equipped airplane - how's that for technical irony) is not in NC and *is* still in existence: Blue 9 from DEEDS to MTH NDB (Marathon Key) in Florida.

Yes, I stand corrected. An operator can fly the t-routes with their poor cousin GPS assuming they also have a VOR receiver. But someone using GPS as their sole source of navigation must have WAAS.

So the airway author has to buy the more stringent 146. He/She cannot assume you are also using VORs.

Sure they can. It's up to the *pilot* to be legal.

The very existence of T278 is an oddity, as it exists only between HAPIT and SSR, which is also V-317. Establishing a GPS MEA on V317 between those points was all that was needed and wouldn't have cluttered the chart.

Very true - And I noticed some other oddities in the area as well:

* T269, which is colocated with V440 that passes through HAPIT, has a 6200 MEA, while the GPS MEA for the colocated V440 is 8000.

* T269 on the other side of Sitka (to the southeast on the airway) has a 7100 MEA, while the colocated V311 shows only a 6000 MEA (with no GPS MEA) until FLIPS, and then shows both *6000 and 6000G with a 9000 MEA.

* T280 from FLIPS is colocated with V473 and shows 7100G while V473 shows 7000, 6000G, and *6000.

So this appears to happen in numerous locations nearby.

I'm also not sure I buy the wildlife refuge explanation, since the charted exclusions are supposed to mean you stay 2000 AGL and the highest point within the refuge anywhere near the airway is 2362 MSL. That means that the 5000G MEA on the Victor airway would easily keep you more than 2000 AGL. It also doesn't explain the lower GPS MEA on T269 vs. V440 (which also passes over a refuge, though by a large altitude margin), unless they've changed the altitudes they want us flying over a refuge when IFR for some reason.

 

[roncachamp]

Steven, you were the first person to mention V378. The OP used V348 in an example of a GPS MEA on a Victor airway, and his question was about T278 and V317.

The OP wrote:

I am only talking about Victor Airway MEAs at this point. A good example of this is seen on V348 between BELAY intersection and the Modena VOR (MXE) on low altitude Enroute chart L-34.

He made a typo, V348 is over Lake Superior. It's V378 that runs between MXE and BELAY.