Terrain clearance on ODPs

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pstan

Pre-takeoff checklist
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Lets say a runways's Obstacle departure procedure lists a climb of 500 feet per nm to 9500 feet (example, runway 6 at Gunnison CO, KGUC), field elevation about 7700 feet. If I was to pass the departure end of the runway at 35 feelt agl, and climb at the stated gradient, what obstacle clearance am I assured?

AIM 5-2-8 doesn't seem to specify it.

I'm guessing 48 feet per nm, would this be correct?

Pstan
 
This might help....

ClimbDescent-Table.jpeg
 
pstan said:
Lets say a runways's Obstacle departure procedure lists a climb of 500 feet per nm to 9500 feet (example, runway 6 at Gunnison CO, KGUC), field elevation about 7700 feet. If I was to pass the departure end of the runway at 35 feelt agl, and climb at the stated gradient, what obstacle clearance am I assured?

AIM 5-2-8 doesn't seem to specify it.

I'm guessing 48 feet per nm, would this be correct?

Pstan
Click to expand...
yes, 48 feet per mile.
 
Last edited:
Thanks Aggie and Maule, that's what I was looking for. Pstan
 
It's 48 feet per NM only at the standard climb gradient of 200 ft per nm. At increased climb gradients, the clearance increases as well. The obstacle clearance surface climbs at 76% of the airplane climb gradient, so for a 500 '/nm climb gradient, the OCS climbs at 380'/nm, for a clearance of 120'/nm.

Reference: FAAO 8260.3C. The 76% is kind of baked into formula 14-1-4. it's not worded expressly as "76% of the climb gradient", but that's what it amounts to.
 
that's interesting, thanks Russ. I will certainly look at your link. Pstan
 
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