Class G (14,500 feet) and a few other airspace questions

7 Answers

1. 
   

   
   

   Scott Kanlyn on Feb 13, 2011

   Skyhawk,
   In answer to your questions;
   1. Class G to 14,500′ is pretty rare these days. You usually have to go into the plains (Montana, South and North Dakota have quite a bit) to find any that extends that high.
   2. Short Answer: Maybe
   Long Answer: Flight following always depends on two things: ATC coverage and workload. When flying in areas that are G to 14,5000′ you are usually away from large terminal areas and thus, radar and voice coverage can be limited at lower altitudes. When you find class G airspace to 14,500′ you will notice victor airways carved through it. Back in the day (before GPS), most IFR traffic was forced to follow these Victor Airways, thus why they carved out class E airspace. Thesedays with GPS, people are going IFR direct all over the place, including through class G.
   This is also the reason you will see minimum reception altitudes on IFR charts. Minimum reception altitude refers to the altitude you need to be at to get a navigation signal (not to be confused with communication signal). If you have to be at 7,000 ft. to get a VOR signal, imagine what altitude you might potentially need to be at to get ATC radar or voice coverage(which isn’t published anywhere).
   3. Class B airspace, when initially designed were meant to all be standard “upside down wedding cakes”. Class B extends to 10,000 MSL in most cases. Denver, for example extends to 12,000′. Class C and D airports which are significanly less busy than B are more custom tailored and many times lie under a class B. In theory you could have class C or D higher than a class B, but I do not believe there are any areas with airports at that high of an elevation and that close to a class B to be above its airspace.
   4. I’ve never seen what your referring too and not quite sure I understand. I think the lowest airport in the US is Furnace Creek at -210 AGL, but its not a class D.
   Cheers,
   Scott Kanlyn

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   Ben on Feb 13, 2011

   4) I believe the …..[-16]….you are referring to on some class delta airspaces is for Delta airports whose airspace underlie Charlie or Bravo – Example:
   New Smyrna (KEVB) look it up on http://www.skyvector.com it has [-12] but this is because it underlies the outer shelf of Daytona Beach’s class Charlie and is therefore ‘squashed’ in underneath.
   Same deal for Kissimmee (KISM) – except this time it is squashed under Bravo airspace.
   It does NOT mean “Negative 1200MSL” or AGL or anything else…that’s just a misconception and a rather ridiculous one at that.
   For an example of a “normal” Delta without the brackets is Bartow – (KBOW) which goes up to “26” or 2600MSL which in turn is usually the standard 2500ftAGL rounded up by 100ft and converted to MSL…..hence the 2600MSL for Bartow.

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3. 
   

   
   

   Dave on Feb 14, 2011

   4) [-16] means “Up to, but not including, 1600 ft,” whereas [16] means “Up to, and including, 1600 ft.” Which is why you normally see the “negative” number when the airspace is below another. The overlying airspace will start at that altitude. In New Smyrna’s case, it’s airspace, and Ormond Beach’s (KOMN) for that matter, stop at 1199 ft. Daytona’s (KDAB) will start at 1200 and go up to 4000.

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4. 
   

   
   

   Jon on Feb 14, 2011

   4) A quick look at the legend on your sectional will show that a minus ceiling value indicates a ceiling up to, but not including, that value.  As Ben said, it’s usually because of overlying airspace.  Technically, it’s because a chunk of air can only be one kind of airspace.  For example, the class D airspaces of GKY and GPM are under DFW’s class B.  Since a tiny part of GKY’s airspace and a larger part of GPM’s airspace intersect the 2000′ DFW shelf, they have to be defined as “up to but not including 2000′ “.

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5. 
   

   
   

   Wesley Beard on Feb 14, 2011

   I’m going to answer the questions missed in the other posts.
   1) I’ve never come across an airport surrounded by Class B or C airspace where the overlying airspace is Class G up to 14,500 feet.  Granted, I’m only a student pilot.  But, has anyone ever come across this?  In my part of the country, I hardly ever encouter Class G extending above 1,200 feet.  Is it rare that Class G would extend upwards to 14,500 feet? 
    
   Class G airspace most likely does not exist above Class B, C or D airspace.  There are only a few instances of that I know of that have Class G above class E airspace.  Aim 3-2 has a diagram clearly showing only Class E above those airspaces.  Unfortunately, I cannot find the exact place that confirms my instinct though.  If you were to look to the east of KDUG on skyvector you would see “Ceiling 13,000” talking about the ceiling of class E airspace.  So Class G extends from 13,001ft to 14,499.9ft.  Why… I don’t have a clue.
    
   You might be surprised to see how much of the country still has Class G extending up to but not including 14,500ft.  On a NACO low enroute chart, any shaded brown depicts Class G up to 14,5000.

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6. 
   

   
   

   Kent Shook on Feb 15, 2011

   Using the low enroute and looking for brown/blue, it’s easy using ForeFlight to see that there is no airspace where class G is up to 14.5 near the lateral limits of a class B or C. About the closest looks to be Salt Lake City, which has some 14.5 G to the southwest and east maybe 45-50 miles away from KSLC.
    

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7. 
   

   
   

   Kent Shook on Feb 15, 2011

   I should also point out one reason WHY there isn’t G overlying B or C: Most B or C airspace exists due primarily to airline traffic. The airlines must fly IFR, and the FAA wants them in controlled airspace, lest a model airplane, ultralight, small airplane, etc. pop out of nowhere from behind a cloud (remember, reduced cloud clearance and vis requirements in class G). So, for the most part, wherever there’s radar coverage and airplanes flying IFR, there’s going to be class E airspace. Class G is truly uncontrolled – the wild west. ATC can’t/won’t tell you what to do in class G, and there is very little traffic in class G. (A common IFR clearance departing an uncontrolled field that doesn’t have class E to the ground will include the words, ‘upon entering controlled airspace, fly heading xxx’ or the like – They don’t tell you what to do prior to that.)
    
   This is all a convoluted way of saying that where safety dictates, airspace is likely to be controlled – and that means Class E or “better” (D, C, B, A). Due to the traffic near C and B airspaces, they want that surrounding area to remain controlled airspace.
    
   And now I’ve got this wild idea that I should go file IFR through some 14.5 E at a lower altitude and see what I’m told by ATC, if anything.
    

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