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SID vs. ODP

Asked by: 1439 views Airspace, FAA Regulations

Reference KAVL.

Asheville Four SID does not allow for use if departing runway 16 (NA-ATC). But the ODP does allow for IFR departures using runway 16.

Why would the Ashville Four SID not allow for use on runway 16 but the ODP does allow runway 16 departures?

What is the limiting factor to publish NA-ATC?

Thank you for the feedback and all comments appreciated.

5 Answers



  1. Mark Kolber on Dec 06, 2013

    I bet if you thought about it you’d find you know the answer since we’ve discussed ODPs before. Here’s some prompting questions:

    1. What is an ODP for?
    2. Does a SID guarantee terrain clearance?
    3. What type of SID is the Asheville Four – self-nav or vectored?
    4. What is the difference between self-nav and vectored departures (or arrivals or any clearance)?

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  2. Dan Chitty on Dec 06, 2013

    Mark,

    Thank you for the prompt. See below according to the AIM….

    1. ODP is the default procedure if a SID is not available.
    2. ODP and SID both provide obstacle/terrain clearance
    3. Asheville Four is a vectored SID
    4. Pilot is responsible navigating on self-nav DPs and ATC will provide navigation to a fix for vectored DPs.

    Based upon this above, I still do not understand why runway 16 is excluded from the Asheville Four.

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  3. John D Collins on Dec 06, 2013

    Dan,

    A SID is both a departure procedure that provides for terrain and obstacle clearance and meets the needs of ATC. An ODP is a departure procedure that provides terrain and obstacle clearance and provides the pilot a means of getting to the enroute structure.

    Ask the rhetorical question “I wonder what NA-ATC stands for in the SID”? A SID is a creature of ATC and apparently ATC doesn’t have a need or want departures using the SID to be from runway 16. That does not mean that an aircraft can’t use runway 16 for an IFR departure, it just means that the SID can’t be used. It could be that traffic departing runway 34 which has higher terrain to the north and requires a higher climb gradient, and in addition the main noise sensitive and populated area areas of Asheville lie to the north. Regardless of the reason, there would not be a SID in the first place if ATC, in this case Asheville departure control didn’t want it for some operational reason. Regardless of the reason, NA-ATC means Not Authorized by ATC and that ATC, for what ever its reason is, does not want the SID to be used when departing from runway 16, however, it is not a TERPS reason. BTW, many piston aircraft might not be able to comply with the SID because of its climb gradient requirement.

    From 8260.46D DP Design

    “c. Standard Instrument Departures (SIDs). SIDs are developed to assist in meeting environmental, capacity, and air traffic control requirements. SIDs may be requested by specific ATC facilities, the military services, or other proponents to enhance operations. A SID also provides protection from obstacles and is depicted graphically; however, it will not contain the “(OBSTACLE)” designation following the procedure title on the chart, and may not be flown unless approved by ATC.”

    If Order 8260.46D was not in your assigned list of reading material, add it.

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  4. Dan Chitty on Dec 06, 2013

    Thank you John for the additional information.

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  5. Mark Kolber on Dec 07, 2013

    It is still kind if interesting to see a note like this on this type of DP. SIDs are only flown as assigned by ATC to begin with. Add to that, it’s a pure vectored DP. A pilot can’t fly any of it without direct ATC involvement. So if the note is intended for pilots, is it just to say, “don’t expect vectors when departing on 16.”

    While understanding the notation I’m trying to figure out it’s operational significance. I can see where, for planning purposes, a NA on a self-NAV SID can make sense, informing a pilot not to consider it, but not for a vectored one like this.

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