"MEA Gap" on Lo-Enroute Chart

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dougwells

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Doug Wells
I've been a long-time reader of On-Approach here at POA. These forums are an incredible resource. I am an active CFII and always find something new and useful reading this forum. However, I've never posted a question .... until now. Here it is:

On Low-Enroute chart L-9, between FFU and PUC, Victor Airway V134 states "MEA GAP". Any idea what that means?

Looking at the associated sectional chart, I see that obstacle clearance is still OK at 13,000 MSL. Can I assume the "Gap" is for communications and/or Navigation? Has anyone seen this before?

Thanks,

Doug Wells
U42, Salt Lake City #2
CFII, MEI, ATP
 
dougwells said:
I've been a long-time reader of On-Approach here at POA. These forums are an incredible resource. I am an active CFII and always find something new and useful reading this forum. However, I've never posted a question .... until now. Here it is:

On Low-Enroute chart L-9, between FFU and PUC, Victor Airway V134 states "MEA GAP". Any idea what that means?

Looking at the associated sectional chart, I see that obstacle clearance is still OK at 13,000 MSL. Can I assume the "Gap" is for communications and/or Navigation? Has anyone seen this before?
Click to expand...

There's a gap in course guidance.
 
Thanks to both of you. Very helpful (and quick too!!)

Doug
 
One point -- MEA never guarantees comm coverage. You may have comm coverage where there's an "MEA gap," and you may be out of comm range where there's good nav signal coverage. There's no way for the pilot to know in advance where those comm gaps are, especially out in the wide-open spaces in the western US, and most especially in the Rockies. You'll find out only when ATC says, "Cessna 123, you'll be out of communication range for the next 50 miles, report 35 east of Whatever VOR."
 
Ron Levy said:
One point -- MEA never guarantees comm coverage. You may have comm coverage where there's an "MEA gap," and you may be out of comm range where there's good nav signal coverage. There's no way for the pilot to know in advance where those comm gaps are, especially out in the wide-open spaces in the western US, and most especially in the Rockies. You'll find out only when ATC says, "Cessna 123, you'll be out of communication range for the next 50 miles, report 35 east of Whatever VOR."
Click to expand...

Terrain, obstacles, navigation and communications coverage are all considered when MEAs are established. The MEA does not guarantee direct pilot-controller communications, that's true, but there was a time when pilots and airways traffic controllers had no direct communications at all. All communications was relayed through INSACS/ATCS/FSS. That still works, and if you're receiving the NAVAID you should be able to reach FSS through the RCO.
 
roncachamp said:
Terrain, obstacles, navigation and communications coverage are all considered when MEAs are established.
Click to expand...
One more time -- only obstructions (terrain or man-made) and nav signal coverage are considered for MEA's. There is no guarantee of ATC comm coverage at the MEA, and there are VOR's with no comm outlets.
 
Ron Levy said:
One more time -- only obstructions (terrain or man-made) and nav signal coverage are considered for MEA's.
Click to expand...

Saying it one more time won't make it any more correct:

Order 8260.3B United States Standard for Terminal Instrument Procedures (TERPS)


1718. MINIMUM ENROUTE INSTRUMENT ALTITUDES (MEA).

An MEA will be established for each segment of an airway/route
from radio fix to radio fix. The MEA will be established based
upon obstacle clearance over the terrain or over manmade
objects, adequacy of navigation facility performance, and
communications requirements. Segments are designated
West to East and South to North. Altitudes will be
established to the nearest 100 foot increment; i.e., 2049
feet becomes 2000, and 2050feet becomes 2100.


Order 8260.19D Flight Procedures and Airspace

250. COMMUNICATIONS REQUIREMENTS.

Order 8200.1, U.S. Standard Flight Inspection
Manual, chapter 8, defines communication
tolerances and flight inspection procedures.
Even though gaps in navigation course guidance
may be approved, reliable communications
coverage over the entire airway or route segment
at minimum en route IFR altitudes must be
available.​

a. MEAs or MAAs are predicated upon
continuous approved communications capability
for the entire designated segment. All available
resources must be explored before restricting the
use of altitudes of an airway or route due to a lack
of acceptable communications coverage. Coordination
must be effected with ATC for determination of the
acceptability of communications coverage in a
particular area. ​

b. Mandatory communications with the appropriate
ARTCC are not required; communications with other
ATC facilities are allowable. Where necessary, in order
to provide direct communications with a center,
appropriate recommendations for a peripheral site should be made.

There is no guarantee of ATC comm coverage at the MEA, and there are VOR's with no comm outlets.
Click to expand...
Yes, there are, but are there VORs without comm outlets on airways without direct pilot-controller communications at the MEA?
 
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Ron Levy said:
I stand corrected. Thank you for the reference.
Click to expand...

AFaIK, comm issues are one reason that IFR GPS doesn't automatically allow flight at the MOCA when the MEA is higher. Comm access has to be checked.
 
gismo said:
AFaIK, comm issues are one reason that IFR GPS doesn't automatically allow flight at the MOCA when the MEA is higher. Comm access has to be checked.
Click to expand...
IIRC, flight is allowed, but lost-comm instructions must be issued. No doubt roncachamp will quote the correct page from 7110.65 on that.
 
Make sure if you send any students with Lynn then they know this cold, he will bring it up and quiz them on it. At least he did me.

BTW how's it going down there, wish I had finished my ME before leaving, twins up here are horably expensive to rent, 300+.
 
OK answer this:
Why an MEA gap?
Why not just raise the MEA like the rest of the airways, til you can receive the VOR signal?

(I will hold back my proposed answer.)
 
Let'sgoflying! said:
OK answer this:
Why an MEA gap?
Why not just raise the MEA like the rest of the airways, til you can receive the VOR signal?
Click to expand...

That may leave too few cardinal altitudes or put it up in Class A airspace, which means no Victor airway at all.

The A/FD indicates PUC VOR/DME has several restrictions, one of them applies to V134:

VOR unusable:
275°–300° byd 25 NM blo 12,000'

Note too that this segment of V134 uses the PUC R-293 out to 48 miles, 8 miles beyond the Standard Service Volume. The PUC datasheet shows an Expanded Service Volume to 48 miles, but it must be rather flaky or there'd be no MEA GAP shown on the chart.

Looking at the other end of this airway segment, the A/FD shows several restrictions on FFU, but none of them affect the FFU R-110 which is V134. However, the FFU datasheet does indicate the R-110 is unusable beyond 20 miles below 15,000 MSL, the restriction is dated 6/19/09. Methinks the MEA GAP and 20/48 COP are fairly recent additions to the charts, and they were judged preferable to an MEA of 15,000.

Mealsothinks if these are recent additions to the charts, the FFU restriction should also have been a recent addition to the A/FD.
 
Let'sgoflying! said:
Why not just raise the MEA like the rest of the airways, til you can receive the VOR signal?
Click to expand...
Presumably because some aircraft have trouble climbing to those higher MEAs, so raising the MEA would effectively shut down that airway to those aircraft.
-harry
 
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