Why this altitude?

JCranford

JCranford

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JCranford
Look at the Texoma5.IRW departure from ZEMMA to IRW. The MEA is shown to be 11000. Correct?Compare that to the IFR Low chart. Nothing in the area is over about 3600.

1. Why is it so radically different than the Low chart
2. If I fly that SID I would be expected to comply with the MEA, right?
3. Why did ATC let me fly it yesterday at 5000?
 
JCranford said:
Look at the Texoma5.IRW departure from ZEMMA to IRW. The MEA is shown to be 11000. Correct?Compare that to the IFR Low chart. Nothing in the area is over about 3600.

1. Why is it so radically different than the Low chart
2. If I fly that SID I would be expected to comply with the MEA, right?
3. Why did ATC let me fly it yesterday at 5000?
Click to expand...

Just a comment that it would help for you to give some more info regarding departure airport, etc. so people can understand what you are asking about. Texoma5.IRW and ZEMMA allowed me to eventually find the SID, but it would have been easier if you'd given the airport...

Anyway, here's the departure procedure to which the OP is referring.
https://www.globalair.com/dtpp/globalair_06444texoma.pdf. It's a departure from KHQZ.

To answer your question, notice that the altitudes do not have over or underlines. That means they are recommended, not mandatory. Recomended because they apply more to the jets. For a contrast, check out the SUNOL8 departure from KSJC (my home drome) http://155.178.201.160/d-tpp/1704/00693SUNOL.PDF.

Notice that the SUNOL intersection must be crossed at 5000 feet as denoted by the lines above and below the altitude. After SUNOL, the recommended altitudes are 5000, but the absence of lines means that isn't mandatory.

The following is from the FAA Chart user's guide, page 77. https://www.faa.gov/air_traffic/fli...aero_guide/media/Chart_Users_Guide_12thEd.pdf

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JCranford said:
Look at the Texoma5.IRW departure from ZEMMA to IRW. The MEA is shown to be 11000. Correct?Compare that to the IFR Low chart. Nothing in the area is over about 3600.

1. Why is it so radically different than the Low chart
2. If I fly that SID I would be expected to comply with the MEA, right?
3. Why did ATC let me fly it yesterday at 5000?
Click to expand...

So, to directly answer your questions:

1. The SID altitudes are recommended (or expected), and apply more to the guys who will be going even higher. They are not mandatory due to the absence of over/under lines.
2. Yes, you must comply with MEA (or possibly the MOC at minimum if you coordinate with ATC). MEA also implies reception of NAVAID signals, and if you have GPS, you can sometimes get MOC instead of MEA if properly equipped.
3. You were allowed to fly at 5000 because 5000 is above MEA, and the SID altitudes are not mandatory.


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jimhorner said:
So, to directly answer your questions:

1. The SID altitudes are recommended (or expected), and apply more to the guys who will be going even higher. They are not mandatory due to the absence of over/under lines.
2. Yes, you must comply with MEA (or possibly the MOCA at minimum if you coordinate with ATC). MEA also implies reception of NAVAID signals, and if you have GPS, you can sometimes get MOCA instead of MEA if properly equipped.
3. You were allowed to fly at 5000 because 5000 is above MEA, and the SID altitudes are not mandatory.


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Click to expand...

One other thing. A SID gets you to an airway. Until you get there, MEA has no meaning (I believe) because MEA's are defined in the context of an airway. Before you get there, in a radar environment, MVA (minimum vectoring altitude) applies. That isn't on the charts.

91.177 always applies....


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That's blasting you through the fourth busiest terminal areas in the US. They're likely going to climb you to get you out of the way anyhow. The SID is there to avoid the controller from having to tell you that in detail.
 
Ya know... as an instrument student, the admonition to maintain situational awareness (esp. regarding terrain) and cross check against ATC instructions goes out the window with an uncharted MVA. "Ok, that's lower than it looks like I should be at, but hey... uncharted MVA".
 
It's because it's not really an MEA. It's a procedural altitude. A few years ago they started calling them MEA's on SIDS and STARS. it's brought up all kinds of questions just like yours. MOCA gets thrown in to the mix sometimes. They come up with new ways of charting it every now and then to supposedly clarify things. Some charts show it one way and others show it another way. They don't update them all at once when they come up with a new way to do it
 
Thanks guys. That makes sense. Sorry for leaving out the pertinent information of the departure airport information. It made it unnecessarily harder to answer my question.
 
Were you actually able to fly the SID, or did they just vector you towards the transition? Trying to get a feel for which ones they actually have us fly around here. We typically don't fly the actual JPOOL or HUBB at all; we just usually get a vector towards the filed route after the SID.
 
Since many OD the SIDs for the DFW airports are based off of MAVERICK or COWBOY VORs, it's almost always vectors along the direction of departure. I don't expect them to ever put us in the thick of things on the south end of KDFW.

From Denton headed to Houston, I always get JPOOL9.CLL but am vectored through the DFW Bravo until I get "Direct College Station VOR"

Great questions John!
 
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