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18 Answers

IFR Altitudes

Asked by: 10096 views Airspace, FAA Regulations

The KCLT HUGO TWO SID has a segment off the CLT 093 radial eastbound (V54-409) with MOCA 3,100 and MEA 11,000 to SDZ VOR. Looking at the low enroute chart on Skyvector shows a MEA 3100 to 2500 along the route to SDZ VOR (V54).

Question: Why such a high MEA 11,000 on the SID yet the MEA on V54 low enroute chart to SDZ VOR Is much lower (3100-2500)?

Thank you for the feedback.

18 Answers



  1. Mark Kolber on Jan 25, 2014

    Perhaps obviously, 2500′ and 11,000′ can’t both be the “minimum” altitude that assures terrain separation and signal reception.

    I don’t recall whether it was this forum or not but I’ve seen this question raised before. There are others like it — both SIDs and STARs. For a STAR example, see the DRONE1 arrival into KORF. Compare the FL190 “MEA” on the RDU-TYI-CVI segment with the 2500-1800′ MEA on the en route chart for the exact same route.

    Best “consensus” answer I’ve been able to find (that makes sense to me) is that the “MEA” on the SID and STAR takes factors other than terrain and signal reception into account. For example, a STAR with a FL190 minimum segment altitude is pretty much designe primarily for high flying aircraft

    IOW, despite being described and shown as an “MEA,” it’s just minimum altitude for a segment of a procedure, more like the minimum altitudes on an approach chart than an “MEA” referring only to terrain separation and signal reception. IOW, it’s a “course MEA” tied to a specific procedure rather than an en route MEA that represents the minimum altitude assuring terrain separation and signal reception.

    BTW, the KORF STAR procedure? I’ve been assigned and flown it – at the lower altitudes, which is what originally led me to the same question as you have.

    .

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  2. John D Collins on Jan 25, 2014

    In the case of Hugo 2, it is a good question. Since this is a radar SID, the only time the transition routes and possibly the altitudes could come into effect would be if the aircraft was NORDO. I fly this SID all the time from Rock Hill, SC KUZA and in 20 years have never flown the charted route or at the charted altitudes. Prior to departure, my clearance has always included something like: “Bonanza 1234 is cleared to Raleigh Durham Airport via Hugo 2 radar vectors to GIPPR then as filed, maintain 3000 expect 7000 10 minutes after departure, departure frequency 120.05, squawk 1234, hold for release.”

    After read back and when I am ready for departure, I contact Charlotte on the RCO, and they say something like, Bonanza 1234 enter controlled airspace on heading 090. Verify this clearance will allow compliance with terrain or obstruction avoidance. Then they give me the normal release time and void time information.

    If you lose radio contact or are not able to establish it once you are airborne, you need to comply with 91.185.

    With the above clearance, my altitude would be the last assigned one of 3000 and then after 10 minutes I would climb to 7000. I would not climb to 11,000 feet. My route would initially be a heading of 090, but once I had determined I had lost radio contact and it was not possible to reestablish it, squawk 7700/7600 according to the AIM and take a direct course to GIPPR, and after GIPPR follow the flight plan route.

    So, I don’t see the point of the 11,000 on the chart. I may give a call to Charlotte approach on Monday and see what they say.

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  3. Dan Chitty on Jan 25, 2014

    Thank you John and Mark for the feedback.

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  4. Mark Kolber on Jan 25, 2014

    So, I don’t see the point of the 11,000 on the chart. I may give a call to Charlotte approach on Monday and see what they say.

    It will be interesting to hear the response. The only thing I can think of offhand (other than an error) is that, in general, SID and STAR segment altitudes are completely susceptible to ATC modification (since they aren’t really MEAs ;)). It’s only in the “Climb via” and “Descend via” clearance situations that one would actually use the published altitudes on a SID or STAR. AFAIK, it’s far more common for these altitudes to be ignored than honored.

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  5. Dan Chitty on Jan 25, 2014

    My understanding is that “Climb Via” and Descend Via” are only applicable to published crossing restrictions not segment altitudes. According to the chart legend, the segment altitudes on the Hugo Two (or any SID/STAR) are MOCAs and MEAs of which ATC cannot issue “Climb Via” for segment altitudes. Is this correct?

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  6. Mark Kolber on Jan 26, 2014

    Isn’t that the question you asked, Dan? How can the 11,000 altitude on the Hugo Two truly be a “MEA” when the en route chart shows the MEA to be about 8,000′ lower?

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  7. Dan Chitty on Jan 26, 2014

    Mark,

    My last post above pertains to the specifics of ” Climb Via” and if “Climb Via” is applicable to segment altitudes.

    My understanding is that “Climb Via” and Descend Via” are only applicable to published crossing restrictions not segment altitudes. According to the chart legend, the segment altitudes on the Hugo Two (or any SID/STAR) are MOCAs and MEAs of which ATC cannot issue “Climb Via” for segment altitudes.

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  8. Mark Kolber on Jan 26, 2014

    Dan, how would you fly the example STAR shown in Figure 4-24 on Page 4-25 of the Instrument Procedures Handbook if north of the chart at 12,000′ in a piston and instructed to “Proceed direct DRAKE. Descend via the MAHEM TWO Arrival.”

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  9. Mark Kolber on Jan 26, 2014

    Sorry.. that’s figure 4-23

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  10. Dan Chitty on Jan 26, 2014

    According to the AIM, the altitudes listed on the segments of MAHEM TWO arrival are
    MEAs and MEAs are not considered restrictions. Only crossing restrictions apply to “Descend Via” clearances. With this type of STAR, I wonder if ATC cannot issue Descend Via based upon how the AIM defines restrictions regarding a STAR ?

    Anyhow, I could not be reading the AIM correctly and I also do not have any practical experience with Descend Via.

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  11. Mark Kolber on Jan 28, 2014

    I’ve been giving this one a bit of thought, Dan. I’m not convinced I’m right so, John and others, please fee free to join the conversation, even if it’s just to say I’m all wet.

    Truth is, “descend via” is a bit confusing when you look at it in the AIM and the IPH. For example, the IPH clearly says, “Pilots might also be given direct routing to intercept a STAR and then use it for vertical navigation. For example, ‘proceed direct Mahem, descend via the Mahem Two arrival.'” (my emphasis) Problem is, if you look at the Mahem Two chart in the IPH, there are no published altitudes at all to “vertically navigate” after MAHEM.

    There are actually two things the AIM and IPH (as well as the ATC handbook) say is authorized by “descend via” clearances
    • Vertically and laterally navigate the procedure
    • descend from a previously assigned altitude at pilot’s discretion to the altitude depicted, and once established on the depicted arrival, to navigate laterally and vertically to meet all published restrictions.

    So, to me, the question becomes, is that vertically navigate the published restrictions or vertically navigate using the procedure’s published altitudes subject to published restrictions. I go with the latter if only because it makes far more sense to me. I don’t see where only crossing restrictions apply to a STAR.

    A clearance to “descend via” a STAR authorizes a pilot’s discretion descent to the altitudes published for each segment. But, while generally authorized to descend to those altitudes, the pilot must abide by any published restrictions along the way.

    Using the IPH’s MAHEM TWO arrival as an example, a piston clearance to “Proceed direct DRAKE. Descend via the MAHEM TWO Arrival” authorizes the pilot to “descend from a previously assigned altitude at pilot’s discretion to the altitude depicted for that waypoint” (10,000′) and continue to remain at or above the published altitudes for the segments after that – at or above 10,000 to WEBAD; as assigned thereafter since there are no published altitudes after WEBAD.

    A turboprop, however, would not descend all the way down to 10,000 upon reaching DRAKE since it would be subject to the 11,000′ crossing restriction at WEBAD. A turbojet would be subject to the 12,000′ crossing restriction at BRUSR.

    Much of this is academic since a “descend via” clearance isn’t all that common. And rarer for pistons. But it would be nice to have a clear understanding of it.

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  12. Mark Kolber on Jan 28, 2014

    BTW John, did you get a chance to discuss with CLT TRACON?

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  13. Dan Chitty on Jan 28, 2014

    Mark,

    I think I misread the AIM.

    I agree with you that descend via is not limited to only STARs with crossing restrictions but also to STARs with MEAs and or MOCAs. In the case of a STAR with only MEAs and or MOCAs (no crossing restrictions), and descend via is issued, the pilot would be cleared to descend on the STAR profile as long as the pilot remains at or above the MEA and or MOCAs.

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  14. Wes Beard on Jan 29, 2014

    There is a brand new FAA InFO bulletin released today talking about climb via and descend via clearances:

    http://content.govdelivery.com/attachments/USAFAA/2014/01/29/file_attachments/266243/InFO12014.pdf.

    Straight from the attached text: .

    “Descend Via” is an abbreviated ATC clearance that requires compliance with a published procedure lateral path and associated speed restrictions, and provides a pilot-discretion descent to comply with published altitude restrictions. The “bottom altitude” on a STAR or STAR runway transition is the lowest published or ATC assigned altitude authorized and is not to be mistaken for the minimum en route altitude (MEA).

    Going back tot he MAHEM TWO ARRIVAL into Phoenix the lowest altitude you can descend to would be on the narrative page (which isn’t shown in the IPH pg. 4-24). If that segment was also in the enroute structure you cannot descend to the MEA based on the low enroute chart but only that altitude listed on the STAR.

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  15. Mark Kolber on Jan 29, 2014

    Thanks Wes. Unfortunately, it really doesn’t add anything. Is still begs the question whether the published segment altitudes on the chart are, in the words of the bulletin, the “bottom altitude,”i.e., the “lowest published … altitude authorized.” Or is it an MEA, which the “bottom altitude” is “not to be mistaken for.”

    Before you come to the easy answer that the legend refers to it as an MEA, recall Dan’s initial question and my example where each of us shows an actual SID and STAR with supposed MEAs that are thousands of feat higher than the real MEA.

    Going back to MAHEM, what narrative page? That’s part of my gripe with the IPH discussion – an example that says to vertically navigate after Mahem intersection, when there is nothing on the chart after Mahem that provides any latitude information. Then a reference tin the sample chart to a second page that may have information applicable to the example but doesn’t exist. (I’m sure one or two others looked and found there is currently no MAHEM arrival into Phoenix; there is a very similar — replacement? — arrival, COYOT TWO, but it doesn’t provide much help because it is an arrival for which ATC is not supposed to give a “descend via” clearance).

    That’s an issue with every “official” explanation of “descend via” I have seen. Not one points to a chart and says, “this is an altitude that means something in a ‘descend via’ clearance and that is one that doesn’t.”

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  16. Wes Beard on Jan 30, 2014

    Take the Johns Three Arrival into Charlotte, NC. The clearance received is “Proceed direct to HMV descend via the Johns Three Arrival”. You are authorized to proceed direct to HMV and follow both the lateral and vertical portion of the STAR.

    You will cross SHINE at 12,000/250kts. After JOHNS you can descend and maintain 5,000. Most pilots will 20+ miles to descend that 7,000 feet to 5,000 putting them between FOSSE and CEDOX when they reach 5,000′

    The IVANE Two Arrival in KCLT is a newer style RNAV STAR but the concept is the same with a descend via clearance. You will cross ESENE at 6000 and since there is no more altitudes on the chart you will stay at 6,000 feet until further clearance is received.

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  17. Mark Kolber on Jan 30, 2014

    Wes, you and I agree completely on how this would be flown – the 5,000 ft altitude after JOHNS being a “pilots discretion” procedure altitude that the pilot would descend toward.

    My gripe is that none of the FAA materials explain it in that way.

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  18. Wes Beard on Mar 04, 2014

    An NBAA explanation of how climb via and descend via clearances should be followed. It looks that the bottom altitude on the RNAV STARs is not the MEA for the procedure as I previously stated but the altitude associated with the waypoint.

    In the Johns Three arrival into KCLT, the “bottom altitude” a pilot can descend to with a descend via clearance looks to be 12,000ft/250kts at SHINE intersection.

    http://www.nbaa.org/ops/cns/pbn/climb-via/

    A link directly to the PPT presentation that explains it much better.
    https://s3.amazonaws.com/nbaa/ops/cns/pbn/climb-via/NBAA-Pilot-Briefing-Climb-Via-Descend-Via-Speed-Adjustments-2.00-20140228.pptx

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