Air Navigation Institute

Flight Procedure Design Discussion Forum
It is currently Wed Aug 15, 2018 3:18 am

All times are UTC




Post new topic Reply to topic  [ 4 posts ] 
Author Message
 Post subject: SDF 15% plane
PostPosted: Tue May 01, 2018 11:31 am 
Offline

Joined: Tue May 01, 2018 10:42 am
Posts: 3
I am looking for opinions on discounting obstacles underneath the 15% plane following the FAF or SDF. PANS-OPS states that Obstacles that are within the fix tolerance area and are no more than 9.3 km (5.0 NM) past the earliest point of the fix tolerance area need not be considered. This implies that the obstacles have to be both inside the fix tolerance area and not more than 5.0NM from early fix.

However this statement does not match figure Figure I-2-2-11 which shows that after nominal fix obstacles within the whole width of the protection area may be discounted as long as they are not more than 5.0NM from early fix.

My reasoning about the intention of the plane and the protection it affords thinks that the Figure is correct and that the full width may be considered and I think the figure uses the same principle as para 2.7.2 and figure I-2-2-9.


Top
 Profile  
 
 Post subject: Re: SDF 15% plane
PostPosted: Tue Jul 10, 2018 9:03 am 
Offline

Joined: Tue May 01, 2018 10:42 am
Posts: 3
Seriously?! 88 views and no one has anything to say about this?? If you are a designer you must have had to deal with this at some point!


Top
 Profile  
 
 Post subject: Re: SDF 15% plane
PostPosted: Fri Jul 27, 2018 2:37 am 
Offline

Joined: Wed Oct 20, 2010 6:35 pm
Posts: 28
Location: New Zealand
Hi,
It is interesting that you've had so many views and no comments. If you look at the PBN section I think that supports the argument of considering the full area not just the fix tolerance area.
2.5.3 Obstacles that are close-in, located at a distance do ≤9.3 km (5.0 NM), need not be considered in the
determination of the minimum altitude/height (MA/H) of the segment after the fly-by waypoint when the elevation of
the obstacle is less than or equal to:
Max. ElevObst ≤ OCA – MOC − do × 0.15


Top
 Profile  
 
 Post subject: Re: SDF 15% plane
PostPosted: Thu Aug 09, 2018 4:19 pm 
Offline
User avatar

Joined: Mon Feb 22, 2010 2:35 pm
Posts: 83
Location: Honduras, Central America (FIR MHTG)
Usually when text mismatches figures in PANS OPS, text is the correct interpretation.

In the conventional case its very specific that to comply "Obstacles that are within the fix tolerance area and are no more than 9.3 km (5.0 NM) past the earliest point of the fix tolerance" so this means only obstacles that satisfy both conditions may be considered for applying this criteria.

For the PBN case the restriction to be within the fix tolerance is withdrawn. (Don't know if this is the actual intention, as you can now evaluate all obstacles within 5NM from your fix which could be the whole segment)

So going back to the conventional case, the issue is that the figure seems to be more logical an it probably is. Let's do a case scenario.

You have an obstacle that is outside of the fix tolerance (left or right) which you want to disregard, if you translate that obstacle to the centerline it will now be within the fix tolerance and you could disregard, if after demonstrating that this obstacle can be disregarded in the centerline position, why would it not be possible to disregard it outside of the fix tolerance area? So basically I would disregard the obstacle as its below the 15% plane

_________________
Civ. Eng. Antonio Locandro
AIM COCESNA GIS Specialist
http://www.cocesna.org/ais.php
email: antonio.locandro@cocesna.org
Tegucigalpa, Honduras (FIR MHTG)


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group