Why publish close-in obstacles

[MauleSkinner]

The truth is that you don't change any of your IFR departure procedures based on a tree 16ft AGL, 300ft off DER, 260 to the left of the DER. I was hoping maybe I was missing something but it looks like I am not. Those close in obstacles are a waste of time and ink.

How about this?...the airport is KACP.

trees, 1300 ft. from runway, on centerline, 50 feet AGL/159 MSL.

That's a line of trees, and the trees to the sides are taller...that's 233 ft/mile to lose your belly beacon. There's absolutely no way you can take off from this runway, be at your minimum of 35' over the DER, meet the minimum climb gradient of 200 ft/mile, and not hit trees.

Fortunately, it's a relatively short runway, so I was always limited by runway length, not climb gradient.

Fly safe!

David

 

[Checks]

For the plane I fly, a Sa-227, it is no problem clearing those trees. I did the calculations.

 

[JAFI]

For the plane I fly, a Sa-227, it is no problem clearing those trees. I did the calculations.

Single engine (new or very tired), at gross weight, on a 95 degree day? or under what conditions? The problem should not just be if everything is working in your favor - because the question should be what if nothing is working in your favor and what kind of risk are you looking at. If it is a 16 foot tree 90 degrees off runway heading or at the end of the runway, it may matter or it may not. That is why they publish the information - so you are informed enough to make a decision.

JAFI

 

[MauleSkinner]

For the plane I fly, a Sa-227, it is no problem clearing those trees. I did the calculations.

So did mine...but if the runway was long enough that I could carry enough fuel to go where I wanted to go without making a fuel stop, I wouldn't be able to.

Fly safe!

David

 

[Checks]

I am usually restricted by Acel-stop and/or climb gradient. In every case that I can find, if I meet acel-stop and my required 2.0 climb gradient(If weather above 1000/3) then these close in obstacles do not mean anything to me. I am would like to find a situation it does but I have been able to find one.
I imagine it is the same for most jets.

 

[HSDriver]

From the AIM

The reason they are published is to prevent having to impose steep climb gradients at every airport...

4. Obstacles that are located within 1 NM of the DER and penetrate the 40:1 OCS are referred to as “low, close-in obstacles.” The standard required obstacle clearance (ROC) of 48 feet per NM to clear these obstacles would require a climb gradient greater than 200 feet per NM for a very short distance, only until the aircraft was 200 feet above the DER. To eliminate publishing an excessive climb gradient, the obstacle AGL/MSL height and location relative to the DER is noted in the “Take-off Minimums and (OBSTACLE) Departure Procedures” section of a given Terminal Procedures Publication (TPP) booklet. The purpose of this note is to identify the obstacle(s) and alert the pilot to the height and location of the obstacle(s) so they can be avoided. This can be accomplished in a variety of ways, e.g., the pilot may be able to see the obstruction and maneuver around the obstacle(s) if necessary; early liftoff/climb performance may allow the aircraft to cross well above the obstacle(s); or if the obstacle(s) cannot be visually acquired during departure, preflight planning should take into account what turns or other maneuver may be necessary immediately after takeoff to avoid the obstruction(s).