Mountanous Terrain and MEA?

[veneratio]

MEA / MOCA / 2000 foot obstacle clearance

- In the JEPS intro, it states that if there is an obstacle 5,001 AGL or higher, then there will be a 2000 foot obstacle clearance on the MEA.
- It also states, that there will be a 2000 obstacle clearance in mountainous terrain as defined by the state department

My questions are:

• How does the FAA determine if it’s mountainous terrain or not (I heard something of a 3000 ft elevation change in 5 nautical miles?)
• Does the 5,001 AGL or higher only for man-made structures?
• And after crossing an MCA to a new MEA, what minimum climb gradient is required until you get to MEA?

Tnx.

 

[BushwickBill]

Mountainous terrain is defined by the lack of fat people, dollar stores and IQ. Just check out that mountainous terrain map. See there you go!

 

[whaleroast]

• How does the FAA determine if it’s mountainous terrain or not (I heard something of a 3000 ft elevation change in 5 nautical miles?)
• Does the 5,001 AGL or higher only for man-made structures?
• And after crossing an MCA to a new MEA, what minimum climb gradient is required until you get to MEA?

Tnx.

If you start climbing at the fix where the MEA changes, I think 120 feet/nm is adequate to remain clear of obstacles.
And the 5001 AGL or higher is for both man-made and natural terrain

 

[minitour]

And the 5001 AGL or higher is for both man-made and natural terrain

if it's natural terrain that's 5001' above the ground...that's one helluva tree!

-mini

 

[desnapper]

FAA-H-8261-1
INSTRUMENT PROCEDURES HANDBOOK

Mountainous areas for the Eastern and Western U.S. are designated in Part 95, as shown in figure 3-9. Additional mountainous areas are designated for Alaska, Hawaii, and Puerto Rico. With some exceptions, the protected en route area minimum obstacle clearance over terrain and manmade obstacles in mountainous areas is 2,000 feet. Obstacle clearance is sometimes reduced to not less than 1,500 feet above terrain in the designated mountainous areas of the Eastern U.S., Puerto Rico, and Hawaii, and may be reduced to not less than 1,700 feet in mountainous areas of the Western U.S. and Alaska. Consideration is given to the following points before any altitudes providing less than 2,000 feet of terrain clearance are authorized:
• Areas characterized by precipitous terrain.
• Weather phenomena peculiar to the area.
• Phenomena conducive to marked pressure differentials.
• Type of and distance between navigational facilities.
• Availability of weather services throughout the area.
• Availability and reliability of altimeter resetting points along airways and routes in the area.
Figure 3-9. Designated Mountainous Areas.
[On page 3-8 in printed version.]
Altitudes providing at least 1,000 feet of obstacle clearance over towers and/or other manmade obstacles may be authorized within designated mountainous areas if the obstacles are not located on precipitous terrain where Bernoulli Effect is known or suspected to exist.
[Beginning of page 3-8]
Bernoulli Effect, atmospheric eddies, vortices, waves, and other phenomena that occur in conjunction with disturbed airflow associated with the passage of strong winds over mountains can result in pressure deficiencies manifested as very steep horizontal pressure gradients. Since downdrafts and turbulence are prevalent under these conditions, potential hazards may be multiplied.

the MCA is based upon the following climb gradients, and is computed from the flight altitude:
• Sea level through 5,000 feet MSL – 150 feet per NM
• 5000 feet through 10,000 feet MSL – 120 feet per NM
• 10,000 feet MSL and over – 100 feet per NM