MOCA/MEA question

P&H

P&H

Well-Known Member
I'm having trouble finding the answer to this question. I've looked through the AIM, IFH, and Instrument Proc. Handbook.

How much separation from the terrain does the MOCA or MEA guarantee?

Also, to those that have the answer, where can I find it?

Thanks,
P&H
 
2000 in mountainous terrain area(mountainous is considered 4000 feet i think) and non mountainous is 1000.

For as to where...let me look
 
bLizZuE said:
2000 in mountainous terrain area(mountainous is considered 4000 feel i think) and non mountainous is 1000.

For as to where...let me look
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I went looking out for where it actually spells out the answer. I pratically read everything in Title 14 and the best I could find was FAR 91.177
FAR 91.177 said:
(a) Operation of aircraft at minimum altitudes. Except when necessary for takeoff or landing, no person may operate an aircraft under IFR below—
(1) The applicable minimum altitudes prescribed in parts 95 and 97 of this chapter; or
(2) If no applicable minimum altitude is prescribed in those parts—
(i) In the case of operations over an area designated as a mountainous area in part 95, an altitude of 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or
(ii) In any other case, an altitude of 1,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown.
However, if both a MEA and a MOCA are prescribed for a particular route or route segment, a person may operate an aircraft below the MEA down to, but not below, the MOCA, when within 22 nautical miles of the VOR concerned (based on the pilot's reasonable estimate of that distance).
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AIM 5-4-5

Note: OROCA is an offroute altitude which provides obstruction clearance with a 1000 foot buffer in nonmountainous terrain areas and a 2000 foot buffer in designated mountainous areas within the US. This altitude may not provide signal coverage from ground-based navigational aids, air traffic control radar, or communications coverage.
 
I think yours is more specific than mine. I knew it was in the AIM regarding approaches, but your reference is much better.
 
P&H said:
I'm having trouble finding the answer to this question. I've looked through the AIM, IFH, and Instrument Proc. Handbook.

How much separation from the terrain does the MOCA or MEA guarantee?

Also, to those that have the answer, where can I find it?

Thanks,
P&H
Click to expand...


Probably TERPS is the ultimate source:

1720. OBSTACLE CLEARANCE, PRIMARY AREA.
a. Nonmountainous Areas. The minimum obstacle clearance over areas NOT designated as mountainous under FAR 95 will be 1000 feet over the highest obstacle.

b. Mountainous Areas. Owing to the action of Bernoulli Effect and of atmospheric eddies, vortices, waves, and other phenomena which occur in conjunction with the disturbed airflow attending the passage of strong winds over mountains, pressure deficiencies manifested as very steep horizontal pressure gradients develop over such regions. Since downdrafts and turbulence are prevalent under these conditions, the hazards to air navigation are multiplied. Except as set forth in (1) and (2) below, the minimum obstacle clearance over terrain and manmade obstacles, within areas designated in FAR 95 as "mountainous" will be 2000 feet.
(1) Obstacle clearance may be reduced to not less than 1500 feet above terrain in the designated mountainous areas of the Eastern United Sates, Commonwealth of Puerto Rico, and the land areas of the State of Hawaii; and may be reduced to not less than 1700 feet above terrain in the designated mountainous areas of the Western United States and the State of Alaska. Consideration must be given to the following points before any altitudes providing less than 2000 feet of terrain clearance are authorized.
(a) Areas characterized by precipitous terrain.
(b) Weather phenomena peculiar to the area.
(c) Phenomena conducive to marked pressure differentials.
(d) Type of and distance between navigation facilities.
(e) Availability of weather services throughout the area.
(f) Availability and reliability of altimeter resetting points along airways/routes in the area.
(2) Altitudes providing at least 1000 feet of obstacle clearance over towers and/or other manmade obstacles may be authorized within designated mountainous areas provided such obstacles are NOT located on precipitous terrain where Bernoulli Effect is know or suspected to exist.
NOTE: When approving MEAs with less than 2000 feet of obstacle clearance in designated mountainous areas, a record of such approval will be maintained by the Flight Inspection Field Office.
 
I appreciate the responses. I know the 1,000ft separation and 2,000ft mountainous rules, I just couldn't find anywhere that, as said above, "spelled it out" in terms of a MOCA.

I would think the FAA would be clearer on this. Under the actual definition of "MOCA," it makes no reference to the guaranteed separation. An oddity, I'd think.

Very helpful site, thanks.
 
P&H said:
I appreciate the responses. I know the 1,000ft separation and 2,000ft mountainous rules, I just couldn't find anywhere that, as said above, "spelled it out" in terms of a MOCA.

I would think the FAA would be clearer on this. Under the actual definition of "MOCA," it makes no reference to the guaranteed separation. An oddity, I'd think.

Very helpful site, thanks.
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You are confusing two separate issues. The 1000/2000 rule that you already knew about is for *unpublished* routes, and are mentioned in 91.177.

What I quoted you are the criteria from TERPS which are used to determine *published* routes, such as airways. The clearances just happen to be the same. :) But MEA's, *can* be lower than what is required, as indicated in the material that I posted.
 
Maybe I know what you're talking about, maybe I don't. What's TERPS?
 
bLizZuE said:
Maybe I know what you're talking about, maybe I don't. What's TERPS?
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TERPS is the set of criteria used to design instrument approaches, airways, etc. TERminal Instrument Procedures, it stands for. The primary publication is FAAO 8260.3. It's available on the internet.

(You will see the word TERPS on Jepp instrument approach plates. On international plates, you will see Pan-Ops, their equivalent to TERPS. Canada uses TERPS, I believe.)
 
P&H said:
I appreciate the responses. I know the 1,000ft separation and 2,000ft mountainous rules, I just couldn't find anywhere that, as said above, "spelled it out" in terms of a MOCA.

I would think the FAA would be clearer on this. Under the actual definition of "MOCA," it makes no reference to the guaranteed separation. An oddity, I'd think.

Very helpful site, thanks.
Click to expand...

I'm not entirely sure, but I think perhaps what you're looking for is the fact that the MOCA guarantees the same as any published airway, which is the 1000/2000 ft. PLUS the fact that it guarantees navaid reception for up to 22 miles. Perhaps I'm not understanding completely what your asking though.
 
PanJet said:
I'm not entirely sure, but I think perhaps what you're looking for is the fact that the MOCA guarantees the same as any published airway, which is the 1000/2000 ft. PLUS the fact that it guarantees navaid reception for up to 22 miles. Perhaps I'm not understanding completely what your asking though.
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:yeahthat:

Both give you 1000/2000 obstacle clearance along the entire route, but the MOCA only gives you navaid reception within 22nm of the navaid while the MEA gives you navaid reception along the entire route.
 
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