700' vs 1200' Class E Airspace
08-15-2019, 07:23 AM
#1
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700' vs 1200' Class E Airspace
Most of the Sectional charts have a lot of ink on them, showing where the Class E airspace changes from 1200' to 700' AGL.
From a practical day-to-day user's viewpoint, why is that info even on the chart? I've yet to find anyone that cares or uses it. Maybe crop-dusters or some other niche users do?
Also, just curious what the altitudes were set at 700' and 1200'. Why not just call it all 1000', and be done with it?
It seems to make a fine point of changing the airspace when no one cares. What am I missing?
From a practical day-to-day user's viewpoint, why is that info even on the chart? I've yet to find anyone that cares or uses it. Maybe crop-dusters or some other niche users do?
Also, just curious what the altitudes were set at 700' and 1200'. Why not just call it all 1000', and be done with it?
It seems to make a fine point of changing the airspace when no one cares. What am I missing?
08-15-2019, 08:13 AM
#2
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My understanding, maybe someone can offer a better explanation:
The 700' Class E areas are around airports with an instrument approach and help separate the 1SM/Clear of Clouds VFR folks by increasing the distance-from-clouds minimums.
Without the 700' zone, you could fly an instrument approach with a solid overcast layer down to circling mins... you break out of the clouds and someone else is an instant collision hazard because they had "1SM visibility" and were just barely under the clouds in the traffic pattern.
A 1,000' Class E area like your suggestion would more likely entice people to just fly a 900' pattern under a 1,000' overcast layer, giving only 100' of separation when another aircraft breaks out of the clouds. Maybe people flying a 600' traffic pattern (to stay under a 700' overcast layer) is less likely in the eyes of the airspace planners. To your point about people not caring or using it though, that's a whole other issue.
That's my understanding, but I could definitely be wrong. I don't have any sources to cite.
The 700' Class E areas are around airports with an instrument approach and help separate the 1SM/Clear of Clouds VFR folks by increasing the distance-from-clouds minimums.
Without the 700' zone, you could fly an instrument approach with a solid overcast layer down to circling mins... you break out of the clouds and someone else is an instant collision hazard because they had "1SM visibility" and were just barely under the clouds in the traffic pattern.
A 1,000' Class E area like your suggestion would more likely entice people to just fly a 900' pattern under a 1,000' overcast layer, giving only 100' of separation when another aircraft breaks out of the clouds. Maybe people flying a 600' traffic pattern (to stay under a 700' overcast layer) is less likely in the eyes of the airspace planners. To your point about people not caring or using it though, that's a whole other issue.
That's my understanding, but I could definitely be wrong. I don't have any sources to cite.
08-15-2019, 09:10 AM
#3
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Originally Posted by Stoked27
My understanding, maybe someone can offer a better explanation:
The 700' Class E areas are around airports with an instrument approach and help separate the 1SM/Clear of Clouds VFR folks by increasing the distance-from-clouds minimums.
Without the 700' zone, you could fly an instrument approach with a solid overcast layer down to circling mins... you break out of the clouds and someone else is an instant collision hazard because they had "1SM visibility" and were just barely under the clouds in the traffic pattern.
A 1,000' Class E area like your suggestion would more likely entice people to just fly a 900' pattern under a 1,000' overcast layer, giving only 100' of separation when another aircraft breaks out of the clouds. Maybe people flying a 600' traffic pattern (to stay under a 700' overcast layer) is less likely in the eyes of the airspace planners. To your point about people not caring or using it though, that's a whole other issue.
That's my understanding, but I could definitely be wrong. I don't have any sources to cite.
The 700' Class E areas are around airports with an instrument approach and help separate the 1SM/Clear of Clouds VFR folks by increasing the distance-from-clouds minimums.
Without the 700' zone, you could fly an instrument approach with a solid overcast layer down to circling mins... you break out of the clouds and someone else is an instant collision hazard because they had "1SM visibility" and were just barely under the clouds in the traffic pattern.
A 1,000' Class E area like your suggestion would more likely entice people to just fly a 900' pattern under a 1,000' overcast layer, giving only 100' of separation when another aircraft breaks out of the clouds. Maybe people flying a 600' traffic pattern (to stay under a 700' overcast layer) is less likely in the eyes of the airspace planners. To your point about people not caring or using it though, that's a whole other issue.
That's my understanding, but I could definitely be wrong. I don't have any sources to cite.
Also, it's of note that any non-towered (not class D) airport that has a precision ILS has the dashed magenta class-E surface area, to protect the 200 foot ILS approach minimums.
Additionally, class D airspace has the weird key-shaped shaded magenta rings outside the class D circle and encompassing the ILS approach.
Lastly, these shaded magenta rings are not around airports that lack an instrument approach.
Not sure if this answers the OP question, but hope these observations add merit to the post above.
I've always been curious about this as well, but never could find a reference.
08-15-2019, 09:50 AM
#4
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Yes the 700’ Floor protects a non-precision approach while the normal 1200’ floor is for non-approach airports.
*Most* ILS airports have surface E but you do see some part-time tower D airports (BMI comes to mind) that revert to 700’ E when the tower is closed not surface E. Note that there are ILS approaches into that field.
*Most* ILS airports have surface E but you do see some part-time tower D airports (BMI comes to mind) that revert to 700’ E when the tower is closed not surface E. Note that there are ILS approaches into that field.
08-16-2019, 05:16 AM
#6
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Originally Posted by CaseTractor
Also, it's of note that any non-towered (not class D) airport that has a precision ILS has the dashed magenta class-E surface area, to protect the 200 foot ILS approach minimums.
10-19-2019, 06:52 AM
#7
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Originally Posted by EasternATC
This is not true.
Examples I was thinking of that do:
ELD
PBF
HOT
JBR
Example that does not:
BYH
But why does the fifth one not have the surface area protection for the ILS?
Random but good topic.
10-19-2019, 10:49 PM
#8
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Thanks for all of the excellent replies.
Ultimately, I suppose my question boils down to "practicality". Nothing really gets "protected"... and no one is actually tracking whether they need weather that will allow them to operate in 1200' airspace vs 700' airspace.
There should be a simpler way to do it.
Ultimately, I suppose my question boils down to "practicality". Nothing really gets "protected"... and no one is actually tracking whether they need weather that will allow them to operate in 1200' airspace vs 700' airspace.
There should be a simpler way to do it.
10-20-2019, 07:18 AM
#9
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As most folks know, the National Airspace System is a shared resource amongst many types of users. It is my understanding that Airspace changes require FAA rulemaking. Per Orders 8260.19 and/or 8260.3, instrument procedures “should” be contained within controlled airspace. There are exceptions, such as the far West pacific, like Pago Pago. There is not much traffic out there, but also minimal radar coverage. ADS-B implementation will change that. It is interesting to note that there are several different “flavors” of Class-E airspace with various floors and ceilings. I believe the basic expectation is that all NAS users will comply with the airspace requirements and thus the minimum level of safety (procedural separation of VFR & IFR aircraft) is maintained when “ATC Surveillance” is not in use.
10-20-2019, 01:57 PM
#10
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Pretty important distinction for helos in terms of obstacle clearance.
As far as Class E to the ground, my impression has always been it’s determined on a case by case basis. Good example is MSS, ILS to rwy 5 with two semi-busy HLZ’s and monster wires in close proximity to the airfield.
As far as Class E to the ground, my impression has always been it’s determined on a case by case basis. Good example is MSS, ILS to rwy 5 with two semi-busy HLZ’s and monster wires in close proximity to the airfield.
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