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-   -   Takeoff obstacle avoidance & runway analysis (https://www.airlinepilotforums.com/technical/49421-takeoff-obstacle-avoidance-runway-analysis.html)

IluvRNP 04-02-2010 06:38 AM


Originally Posted by tracer997 (Post 788136)
I appreciate the input(s). So if I had 135 (or even 121) Ops Specs that permit VMC departures, I could forget the computer generated or APG runway analysis which shows a lesser weight because of the obstacles. I still may be runway limited because of temp and PA. But is is probably going to be a better weight and thus eliminating a fuel stop.

No, the APG analysis pertains to the regulatory takeoff flight path, not the ODP or SID. AC 120-91 does permit visual avoidance of a takeoff flight path obstacle, but only if the procedure is approved and charted. That is entirely different than the ODP or SID issue.

Merkel 01-29-2011 06:54 AM

The question for me is if the weather is "hot and dusty", how do you know you can see and avoid terrain or obstacles? (Terrain is really not posted in a form you can quantify for your departure profile and not all the obstacles are listed on the ODP)

There is nothing anywhere I read that tells you where every obstacle is that you must see and avoid if you do not follow an ODP with a climb requirement greater than 200'/NM.

Look at MMU as an example. The SID requires a STD 200'/NM climb gradient but, RWY 23 requires 374'/NM to 700 feet with low visibility. With greater than 400' and a mile visibility, the climb gradient is standard 200’/NM.

In a conversation with APG, we ran the numbers for 23 for one of the types we operate and came up with a weight restriction off that runway with the APG contingency course. The contingency course provided in the runway analysis provides a turn to 220 at the runway end and goes out 30 miles. When I run the numbers for that weight restriction, I get 4.6% climb gradient.

I asked “if I see and avoid, will I be able to continue on one engine if I have an engine failure at V1 at a weight higher than that specified in the runway analysis”. In our discussion, APG sent me a picture of the survey they did for 23 and noted the obstacles. There were many and the resultant conclusion was if I departed heavier than the weight limit specified on their runway analysis, I would hit something if I experienced an engine failure at V1 because it was impossible to see and avoid all the obstacles.

So, my conclusion is, seeing and avoiding obstacles on departure as a contingency plan with an engine failure is not necessarily a good idea because you do not know where all the obstacles are to see and avoid. (You could hit them) Using a runway analysis gives you a contingency plan if needed and the applicable weight. They have identified all the obstacles and provided a course that will keep you away from those obstacles.

Your thoughts?

Likeabat 01-29-2011 05:45 PM


Originally Posted by Merkel (Post 938202)
Your thoughts?

My thought is that there is no other issue within part135 (or 91, for that matter) that is more convoluted and misunderstood than ODP's/when to fly them,etc. Give a scenario to a dozen charter pilots in the crew lounge and you'll get a dozen
different answers...that is, unless many of them stammer and bit...look at their watch...and say,"uhhhh...I gotta go".:D

I'm not saying this as an authority on the subject - far from it - I'm just amazed that there are so few clear, consise answers on a subject so important as clearing obstacles immediately after takeoff. All of the FAA's lawyer-speak, which invariably gets interpreted and misinterpreted differently by different FSDO's, POI's, and Pilots only serves to complicate the matter.

Maybe it is just me, but judging by the many different opinions and thoughts by various different posters that always arise when this subject comes up, I'd say that there is plenty of confusion on the subject.


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