4
$\begingroup$

KGRF has a SID requiring a climb gradient of 469 FPNM for obstacles. In the takeoff minimums section, there are takeoff minimums listed for a VOCA (Visual Climb Over Airport) but nothing else. My understanding was that a VCOA was an alternative if you did not want to fly an ODP (Obstacle Departure Procedure). But this airport only has a SID (and no ODP?)Which would lead me to believe that you could fly a diverse departure out of this airport. However if you could fly a diverse departure, what would be the point of even having a VCOA since the required climb gradient for both would still be 200 FPNM?enter image description here enter image description here

$\endgroup$
5
  • 1
    $\begingroup$ @757toga, isn’t that the purpose of a VCOA? It enables one to depart without having to meet the climb requirements of an ODP. It’s technically not a procedure (nor is DVA), but it is a way of departing IFR. $\endgroup$
    – Timbo
    Commented Jun 27, 2023 at 2:18
  • $\begingroup$ @Anthony Schrayer, this is probably an error on the Army’s part. If I had to guess, there should be a “Diverse departure not authorized” under the section DEPARTURE PROCEDURE (not shown). The clues are that there is no mention of takeoff mins other than for VCOA and the SID departure for Rwy 33 is supposed to be for military only (apparently). There is a lot wrong with this situation. $\endgroup$
    – Timbo
    Commented Jun 27, 2023 at 2:22
  • $\begingroup$ @757toga, I think you’re slightly mistaken regarding the climb. An ODP can definitely have greater than a 200 ft/NM requirement. Typically the takeoff mins would say something like “Std with min climb of XXX ft/NM to <altitude>.” What you would not expect to see is a VCOA without also having a non-standard takeoff and/or climb requirement minimums. $\endgroup$
    – Timbo
    Commented Jun 27, 2023 at 22:41
  • $\begingroup$ @757toga, yep I interpreted your “may not” as not permissive rather than optional. We’re on the same page, thanks. $\endgroup$
    – Timbo
    Commented Jun 28, 2023 at 1:13
  • $\begingroup$ "RADAR REQUIRED" and Diverse "Vector", VCOA is non-radar. There are times when an aircraft cannot achieve initial climb gradient or, more likely, will not be able to climb to some required minimum crossing altitude near the start of the route due to the short distance to join the airway. This is especially likely in mountainous areas. 200ft/NM slope is not strictly required of all IFR aircraft, it is only the assumed climb for airway design, aircraft that cannot meet this(maybe a tailwind or near service ceiling or both) must calculate an earlier start of climb. VCOA provides this head start. $\endgroup$
    – Max Power
    Commented Jun 28, 2023 at 8:46

2 Answers 2

6
$\begingroup$

Edited based on new information… I communicated with both the procedure designer for Gray AAF and with the FAA’s Flight Standards office. There are 2 answers for this question:

First, the VCOA at Gray was created for ATC purposes rather than obstacle clearance, so this is not a good example for the question asked. The procedure designer says that you can fly a diverse departure at this location.

Second, per the 8260.46J (and has been the case for several of the previous iterations), “When the Flight Procedures and Airspace Group will not approve a CG in excess of 500 ft/NM (600 ft/NM for helicopters) and any of the obstacles forcing such a CG are located outside the ICA (extended) greater than three SM from DER; a stand-alone VCOA procedure may be used as the only option available for obstacle avoidance.”

Therefore, in general the VCOA may be the only option. This, however, is the only time a stand-alone VCOA would occur. Otherwise, one should expect to see a climb gradient higher than standard, takeoff mins higher than standard, or an ODP in addition to the VCOA.

$\endgroup$
2
  • 1
    $\begingroup$ VCOA is as it says "visual" and does not provide any obstacle clearance surfaces, therefore it is not an instrument procedure despite its primary usefulness being the start of an IFR flight. It is better classified as a maneuver. It also doesn't require radar services. $\endgroup$
    – Max Power
    Commented Jun 28, 2023 at 8:58
  • 1
    $\begingroup$ @Timbo How is it that that obstacle doesn't require an ODP on every runway? If you takeoff any runway and then turn immediately out of the ICA towards that peak with a standard climb gradient you won't make it anywhere near the altitude required to clear it. $\endgroup$
    – Chris
    Commented Jun 29, 2023 at 21:48
0
$\begingroup$

I believe you can not fly a diverse departure if a VCOA is published. (Unless you're part 91, in which case takeoff minimums and ODPs aren't mandatory to begin with). The takeoff minimums say "9900-5 for VCOA," not "9900-5 for VCOA or standard otherwise."

There is some support for this in TERPS standards. From Volume 4, 1.4.6:

b. Where obstacles more than 3 statute miles from the DER penetrate the OCS:

b. (1) Publish standard takeoff minimums with a required CG to a specified altitude, and

b. (2) Develop a VCOA procedure to an altitude that will provide obstacle clearance without a CG, and/or

b. (3) Develop a specific textual or graphic departure route to avoid the obstacle(s).

From the wording it's clear that (3) is not mandatory if (1) and (2) are published. That is, a VCOA (2) may be mandatorily published without an ODP (3).

An example of an airport where some runways have only VCOA published where a diverse departure is clearly not possible is KBIH. At KBIH, there is an obstacle only 17 nautical miles from the airport that is over 10000 feet above airport elevation. No matter what runway you take off from, if you turn toward that obstacle out of the initial climb area, you won't get anywhere close to clearing it with a 200 fpnm climb gradient. Such an obstacle is high enough that it can't exist anywhere within 46 nautical miles of the airport and still allow for a diverse departure.

KBIH does have ODPs published for other runways. But since each runway is analyzed separately under TERPS criteria, I don't see how this is really any different from an airport with only a VCOA published.

$\endgroup$
6
  • $\begingroup$ The trick is that a VCOA is in addition to #1. For KBIH, there is not a greater than standard climb mentioned for 3 of the runways. VCOAs are not standalone. $\endgroup$
    – Timbo
    Commented Jun 29, 2023 at 22:51
  • $\begingroup$ @Timbo #1 appears to be mandatory either way? #1 and (#2 and/or #3). Well, the English isn't super clear. The fact that they didn't publish #1 is odd, but it doesn't seem to me that it authorizes a diverse departure. In any case, objects definitely penetrate the OCS here. $\endgroup$
    – Chris
    Commented Jun 29, 2023 at 23:12
  • 1
    $\begingroup$ I have sent an inquiry into the FAA. I’ll post what I find out. The problem, in my mind, is that a pilot could reasonably believe that a diverse departure was allowable since it is not explicitly stated otherwise. Per the AIM 5-2-9D, a pilot would expect a diverse departure unless one of those items (D1-4) appeared. A VCOA is not one of those and is only mentioned later as an “option” to fly. $\endgroup$
    – Timbo
    Commented Jun 29, 2023 at 23:58
  • $\begingroup$ General comment — DoD does not develop procedures in strict accordance with FAA Orders. In other words, you cannot infer specific applicability of these orders into a DoD procedure. For Gray AAF, the VCOA has nothing to do with obstacle clearance as it would per the .46. $\endgroup$
    – Timbo
    Commented Jun 30, 2023 at 0:04
  • $\begingroup$ @Timbo That's why I used KBIH as an example. $\endgroup$
    – Chris
    Commented Jun 30, 2023 at 0:35

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .