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grid mora

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Active member
Aug 2, 2002
What type of altitude clearance does a grid mora provide? Is the the 1000agl and 2000agl in Mountains? Just like most other. Where do you find this information?
Jeppesen (Introduction)


I won't retype it or tell you what it is, you are on the right track. You can find the info on page 6 of the Chart Glossary in the intro section of your Jepps.
I have always wanted to know how much obstacle clearance is provided at MDA on a non-precision approach, assuming on course. How about at DH? Have to delve into TERPS to find this out?
Obstacle clearance at MDA on a non-precision approach is 300 feet ... and you would have to go to the TERPS, I believe, to find this out. Unless, of course, you did what I did ... I looked at the chart for the localizer approach at the airport where I used to teach ... there was a tower right on the final approach course about 2 miles out up to 1060 MSL ... so, the minimums for the approach were 1360 MSL ... pretty easy math.

I'm sure there's a standard for DH, but I don't know what it is. It is less important because, unlike an MDA, you won't be hanging out there. You get to DH, you either land or miss, whereas on a n-p approach you might be flying at MDA (or a stepdown fix, for that matter) for a mile or two to the MAP.

Fly safe ...

The 300' obstacle clearance only applies to circling minimums. Additionally a circling MDA will not be less than 350' HAA.

Obstruction clearance on final varies according to the type of approach and other criteria such as: length of the final, distance to the altimeter source, and alignment of the final to the landing runway.

Normally an MDA requires a 250' required obstacle clearance (ROC) predicated on a 7:1 descent gradient. (This is one of the reasons why the "dive and drive" method of flying a non-precision approach is giving way to the "constant angle" technique) The MDA DOES NOT necessarily provide a clear zone all the way from the FAF to the MAP. The straight-in landing MDA will not be less than 250 above TDZE.

The ILS GS normally provides obstacle clearance from 660' at the OM to 110' at DA (200 DH); but if required vis is at or above 1 mile an obstruction could penetrate the GS inside the DH.
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