V139 goes from southern NJ to eastern Long Island, cutting off the corner
of the coastline at New York, heading out about 40 miles over the ocean. I
just happened to notice that it's got MOCA's defined in addition to the
MEA's. The segment between MANTA and PLUME, for example, has a MOCA of
2000. This is 25 miles from the nearest bit of terrain higher than a
wavetop. Anybody have any idea why there's a MOCA defined?

There's some other strangeness with over-water airways in the area too.
PREPI is a waypoint 50 miles offshore (I assume it ties into the oceanic
route system). It's the intersection of V276 (RBV R122) and V312 (CYN
R100). What's strange is the MEA's along those airways.

V276 has an MEA of 1900 near RBV, then goes up to 3000 at D15, and 6000 at
D31. This is all perfectly reasonable, as it follows the floor of RBV's
service volume up with increasing distance from the station. What I don't
understand is why at D47, the MEA drops back down to 3000 (along with
another 2000 MOCA). How can reception get better lower down as you get
further from the VOR?

I'm sure this is all rather academic, since I don't imagine much flying is
done at those low altitudes that far out over the water.

On Sun, 15 May 2005 11:52:57 -0400, Roy Smith wrote:

> V139 goes from southern NJ to eastern Long Island, cutting off the corner
> of the coastline at New York, heading out about 40 miles over the ocean. I
> just happened to notice that it's got MOCA's defined in addition to the
> MEA's. The segment between MANTA and PLUME, for example, has a MOCA of
> 2000. This is 25 miles from the nearest bit of terrain higher than a
> wavetop. Anybody have any idea why there's a MOCA defined?

Tall ships or shipping lanes come to mind for me.

Allen

> Tall ships or shipping lanes come to mind for me.

That's a =very= tall ship!

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

I guess for MEA, if you fly lower, you might not get navigational
coverage or radio recacption with the center... It might be for other
things than Terrain...

On Sun, 15 May 2005 11:52:57 -0400, Roy Smith > wrote:

>V139 goes from southern NJ to eastern Long Island, cutting off the corner
>of the coastline at New York, heading out about 40 miles over the ocean. I
>just happened to notice that it's got MOCA's defined in addition to the
>MEA's. The segment between MANTA and PLUME, for example, has a MOCA of
>2000. This is 25 miles from the nearest bit of terrain higher than a
>wavetop. Anybody have any idea why there's a MOCA defined?
>
>There's some other strangeness with over-water airways in the area too.
>PREPI is a waypoint 50 miles offshore (I assume it ties into the oceanic
>route system). It's the intersection of V276 (RBV R122) and V312 (CYN
>R100). What's strange is the MEA's along those airways.
>
>V276 has an MEA of 1900 near RBV, then goes up to 3000 at D15, and 6000 at
>D31. This is all perfectly reasonable, as it follows the floor of RBV's
>service volume up with increasing distance from the station. What I don't
>understand is why at D47, the MEA drops back down to 3000 (along with
>another 2000 MOCA). How can reception get better lower down as you get
>further from the VOR?
>
>I'm sure this is all rather academic, since I don't imagine much flying is
>done at those low altitudes that far out over the water.

Farther away from land may mean less interference from other VOR stations.
Consequently that segment flight checked out to a lower usable altitude?

"Roy Smith" > wrote in message
...
> V139 goes from southern NJ to eastern Long Island, cutting off the corner
> of the coastline at New York, heading out about 40 miles over the ocean.
> I
> just happened to notice that it's got MOCA's defined in addition to the
> MEA's. The segment between MANTA and PLUME, for example, has a MOCA of
> 2000. This is 25 miles from the nearest bit of terrain higher than a
> wavetop. Anybody have any idea why there's a MOCA defined?
>
> There's some other strangeness with over-water airways in the area too.
> PREPI is a waypoint 50 miles offshore (I assume it ties into the oceanic
> route system). It's the intersection of V276 (RBV R122) and V312 (CYN
> R100). What's strange is the MEA's along those airways.
>
> V276 has an MEA of 1900 near RBV, then goes up to 3000 at D15, and 6000 at
> D31. This is all perfectly reasonable, as it follows the floor of RBV's
> service volume up with increasing distance from the station. What I don't
> understand is why at D47, the MEA drops back down to 3000 (along with
> another 2000 MOCA). How can reception get better lower down as you get
> further from the VOR?
>
> I'm sure this is all rather academic, since I don't imagine much flying is
> done at those low altitudes that far out over the water.

Roy Smith wrote:
> V139 goes from southern NJ to eastern Long Island, cutting off the corner
> of the coastline at New York, heading out about 40 miles over the ocean.
I
> just happened to notice that it's got MOCA's defined in addition to the
> MEA's. The segment between MANTA and PLUME, for example, has a MOCA of
> 2000. This is 25 miles from the nearest bit of terrain higher than a
> wavetop. Anybody have any idea why there's a MOCA defined?

To define an altitude that ensures navaid reception between those two fixes?

Hilton

In a previous article, "Hilton" > said:
>Roy Smith wrote:
>> 2000. This is 25 miles from the nearest bit of terrain higher than a
>> wavetop. Anybody have any idea why there's a MOCA defined?
>
>To define an altitude that ensures navaid reception between those two fixes?

MOCAs don't ensure navaid reception.


--
Paul Tomblin > http://xcski.com/blogs/pt/
"If you would like a transcript of this program, sit next to your radio with a
pencil and paper and write really fast." - The WRVO Playhouse.

Paul Tomblin wrote:
> Hilton wrote:
> >Roy Smith wrote:
> >> 2000. This is 25 miles from the nearest bit of terrain higher than a
> >> wavetop. Anybody have any idea why there's a MOCA defined?
> >
> >To define an altitude that ensures navaid reception between those two
fixes?
>
> MOCAs don't ensure navaid reception.

It does within 22 miles of a VOR, and since I don't have the charts in front
of me (I'm on the West Coast) I was just making a suggestion - I don't know
how far the relavent VORs are - that's why I phrased my answer as a
question. :)

Hilton

"Hilton" > wrote in message
nk.net...
>> >>
>> >> This is 25 miles from the nearest bit of terrain higher than a
>> >> wavetop. Anybody have any idea why there's a MOCA defined?
>> >>
>> >
>> > To define an altitude that ensures navaid reception between those two
>> > fixes?
>>
>> MOCAs don't ensure navaid reception.
>>
>
> It does within 22 miles of a VOR, and since I don't have the charts in
> front
> of me (I'm on the West Coast) I was just making a suggestion - I don't
> know
> how far the relavent VORs are - that's why I phrased my answer as a
> question. :)
>

Well, if it's "25 miles from the nearest bit of terrain higher than a
wavetop", it must be more than 22 miles from a VOR. VORs tend to be built
on land.

yupyupxav wrote:
> I guess for MEA, if you fly lower, you might not get navigational
> coverage or radio recacption with the center... It might be for other
> things than Terrain...

Wouldn't it be called out as a MRA rather than an MEA ?

Antonio

Steven P. McNicoll wrote:

VORs tend to be built
> on land.
>
>

Oh, then you haven't seen those new whale-mounted VOR's ? The problem
is they are NOTAM'd as "always intermittent".

Antonio ;-)

"Antoñio" > wrote in message
...
> yupyupxav wrote:
> > I guess for MEA, if you fly lower, you might not get navigational
> > coverage or radio recacption with the center... It might be for other
> > things than Terrain...
>
> Wouldn't it be called out as a MRA rather than an MEA ?

No.
MEA is defined for an airway segment, and at that altitude you are assured
to be able to get the VORs that define the airway. However, this altitude
may not be enough to get other VOR that defines an intersection. The
altitude at which you can define an intersection is called MRA, and it is
defined for the intersection. It has to be higher than MEA.


guillermo

MRA is an intersection reception altitude.



"Antoñio" > wrote in message
...
> yupyupxav wrote:
> > I guess for MEA, if you fly lower, you might not get navigational
> > coverage or radio recacption with the center... It might be for other
> > things than Terrain...
>
> Wouldn't it be called out as a MRA rather than an MEA ?
>
> Antonio

We seem to have wandered a bit (not that that's a bad thing), but I feel
the need to ask my original questions again.

1) Why is there a 2000 MOCA out over the ocean?

2) Why do the MEA's around PREPI get lower as you get further from the VOR?

> 1) Why is there a 2000 MOCA out over the ocean?

Are there perhaps offshore installations of some sort? Weather
stations? I know MOCA's are 1500 on the Q-routes over the Gulf, since
the oil platforms are sometimes 400+ ft tall at the tallest (antenna)
points.

> 2) Why do the MEA's around PREPI get lower as you get further from
the VOR?

I would like to know what MEA's mean offshore in the first place. The
MEA's on the Q-routes are 6000 ft. Why? They're not VOR based. You
can't get anything like consistent radio reception at 6000 (or 11000
for that matter) - you're always given lost comm instructions and relay
through airliners. There's no RADAR coverage. So why 6000 and not
2000? Haven't figured it out yet.

Michael

Michael > wrote:
>> 1) Why is there a 2000 MOCA out over the ocean?
>
>Are there perhaps offshore installations of some sort?

Not that I'm aware of. The tallest thing I can think of is something
like Ambrose Tower (http://www.njlhs.burlco.org/ambrose.htm), but it's
under 200 feet and in any case, these things are usually just a few
miles offshore; I've never heard of one being built 50 miles out in
the Atlantic.

"Roy Smith" > wrote in message
...
>
> Not that I'm aware of. The tallest thing I can think of is something
> like Ambrose Tower (http://www.njlhs.burlco.org/ambrose.htm), but it's
> under 200 feet and in any case, these things are usually just a few
> miles offshore; I've never heard of one being built 50 miles out in
> the Atlantic.
>

The Texas Towers radar sites were out further than that, but they weren't
that tall.