Question on Sectionals

[Huggyu2]

Sectionals have magenta areas (one edge is "hard" and the other "soft") that delineate where the floor of controlled airspace goes from 1200 AGL to 700 AGL. Who uses/needs this info? Are there really that many pilots that need that info?
It's not something I've ever found I need to know while navigating around, but I'm sure it's beneficial to someone. Can you give me an example of how you would use this info to your benefit?

 

[CA1900]

Sure: You're in a Skyhawk, cruising at 1,000 feet, beneath a 1200-foot overcast layer. Perfectly legal -- you're in Class G airspace. But not once you get to the shaded magenta area, because above 700 feet you're now in Class E, and need 500 feet below the clouds. You'll have to go around it, or go lower if terrain permits.

The short answer is that it's to keep VFR traffic out of the instrument approach corridors on crappy days. (You'll notice these areas are over nontowered airports, typically. Note that some of them are kind of "keyhole"-shaped, to correspond with the final approach courses.)

 

[mattpilot]

It has to do with the difference of cloud clearence/visibility requirement.

The Class E drop down to 700ft AGL protects the airspace for IFR flyers from low flying Class G flyers who use the reduced requirements to "scud run" - in theory. In practice, i don't really know anyone who is crazy enough to go flying in such poor conditions that low anyway. Although it is fun... wait.. did i just say that?

 

[FN FAL]

Sectionals have magenta areas (one edge is "hard" and the other "soft") that delineate where the floor of controlled airspace goes from 1200 AGL to 700 AGL. Who uses/needs this info? Are there really that many pilots that need that info?

It's not something I've ever found I need to know while navigating around, but I'm sure it's beneficial to someone. Can you give me an example of how you would use this info to your benefit?

You need to know where controlled airpace begins in the event that you are flying on instruments outside of controlled airspace, so that you will know where you are not authorized to be.

 

[MauleSkinner]

It has to do with the difference of cloud clearence/visibility requirement.

The Class E drop down to 700ft AGL protects the airspace for IFR flyers from low flying Class G flyers who use the reduced requirements to "scud run" - in theory. In practice, i don't really know anyone who is crazy enough to go flying in such poor conditions that low anyway. Although it is fun... wait.. did i just say that?

Hi Matt, my name is David. You now know somebody who is "crazy enough" to go flying at 600-700 feet all day long. It's safe enough if you're willing to put in the effort to navigate properly and keep your eyes open for uncharted towers and traffic.

As to Huggyu2's orignal question, yes, that's the primary reason...VFR visibility and cloud clearance requirements change when you get into controlled airspace, and you need to know where those airspace changes are in order to be legal AND to ensure that you're properly separated from IFR traffic. Remember, too, that instrument approaches usually take you below 700 feet AGL, so IFR traffic can be in the underlying uncontrolled airspace as well...use caution.

No, I don't recommend flying down there to just everybody...as I stated earlier, it takes substantial extra effort to maintain the level of safety. You can't just hit "direct to" on the GPS and turn on the autopilot.

Fly safe!

David

 

[mattpilot]

Hi Matt, my name is David. You now know somebody who is "crazy enough" to go flying at 600-700 feet all day long. It's safe enough if you're willing to put in the effort to navigate properly and keep your eyes open for uncharted towers and traffic.

Hi david. I was trying to be subtle in my last sentence - the one with the smiley.

 

[MauleSkinner]

Hi david. I was trying to be subtle in my last sentence - the one with the smiley.

Subtlety is lost on me...I'm a "blunt instrument" kind of guy

 

[NW_Pilot]

It has to do with the difference of cloud clearence/visibility requirement.

The Class E drop down to 700ft AGL protects the airspace for IFR flyers from low flying Class G flyers who use the reduced requirements to "scud run" - in theory. In practice, i don't really know anyone who is crazy enough to go flying in such poor conditions that low anyway. Although it is fun... wait.. did i just say that?

Hey, matttpilot I am NW_Pilot Nice to meet ya! Now you know another that is that crazy! and Yea it's a blast!

 

[heph224]

Sectionals have magenta areas (one edge is "hard" and the other "soft") that delineate where the floor of controlled airspace goes from 1200 AGL to 700 AGL. Who uses/needs this info? Are there really that many pilots that need that info?
It's not something I've ever found I need to know while navigating around, but I'm sure it's beneficial to someone. Can you give me an example of how you would use this info to your benefit?

As you can see, the class E drops to 700 around airports. Think about it, if the airport elevation is 0 MSL, and you are flying a TP at 1000 MSL and it's an uncontrolled field (no communication is required) what if someone is on a right downwind for runway 9 and another person is on a left downwind for runway 27 and there is small cloud on the downwind leg which both pilots navigate around ( class G 1sm COC ). This can cause a very dangerous environment especially with low vis and uncontrolled airports. Therefore, the magenta lines drops the floor of class E to 700 in order for airplanes converging in the TP and around the airport to have higher vis and coc mins.

This is also for IFR purposes, IFR pilots need to know and prefer to get into controlled airspace ASAP after departure, especially when getting a clearance from an RCO or such.

 

[Huggyu2]

Great! I thought there might be more to it than I was missing.
Next set of questions: since this is purely to allow pilots to get different VFR WX mins:
- do that many pilots really fly around a bare VFR mins, below 1200' AGL? I see that at least one on this forum does, but are there really enough to warrant all of this?
- If the WX is low enough that you need to duck down below 1200' AGL or even 700' AGL to navigate around the country on a regular basis, why wouldn't you just go above it, or file IFR (yes, I know it's a lot of fun).
- I know none of you wrote the rules (you just abide by them), but maybe you CFI/CFII types have some background knowledge on this: why not just have the floor be a compromise of about 1000' AGL, and be done with this 700'/1200' complexity? Does having a single altitude really adversely affect a bunch of flyers (crop dusters maybe)?
- Is it just me, or do others find having so much magenta all over the sectionals make the sectionals cluttered? I know I'd sure like it if I could buy Sectionals that didn't have all of that on them.

Don't think I don't like flying low. I just don't see a big reason to have two different altitudes when one compromise altitude (1000') would seem to work for everyone. Educate me, folks!

 

[mlifly]

The reason for the lower altitude (700' agl) is to keep IFR flights on an approach procedure, inside controlled airspace longer. This is evident at some airports where the magenta line is not a perfect circle around the entire airport, but instead it is a rectangle extension aligned with a runway. Most of the time it is found at class D airports that go class E after hours.

 

[mattpilot]

- do that many pilots really fly around a bare VFR mins, below 1200' AGL? I see that at least one on this forum does, but are there really enough to warrant all of this?

There's a lot of people doing pipeline/powerline patrol. Also, Helicopters like class G airspace, because we can fly around with no visibility requirement at all (just enough to see and avoid others &obstacles).

Furthermore, What if you file IFR out of an uncontrolled airfield, but there is no RCO on that field? Well, with an instrument rating, you are allowed to fly IFR in class G airspace without a clearence. So to get your clearence, you take off, stay in class G airspace until you can reach center or someone else to get your IFR clearence. While it definitely isn't safe to go INTO clouds that low, what you can do is get much closer to clouds while trying to get a radio signal.

- If the WX is low enough that you need to duck down below 1200' AGL or even 700' AGL to navigate around the country on a regular basis, why wouldn't you just go above it, or file IFR (yes, I know it's a lot of fun).

Helicopters like to stay close to the ground. The problem with climbing in helicopters is, you will need to lean the mixture, and nobody likes to do that during flight. Furthermore, IFR equipped helos are some expensive machines.

Also, airplanes doing pipeline/powerline patrols are often low-tech with little instrumentation. Can't send them into the soup.

- I know none of you wrote the rules (you just abide by them), but maybe you CFI/CFII types have some background knowledge on this: why not just have the floor be a compromise of about 1000' AGL, and be done with this 700'/1200' complexity? Does having a single altitude really adversely affect a bunch of flyers (crop dusters maybe)?

As you said, i didn't write the rules, so i'm just laying out my best guess to each of your question.

Why not 1000'AGL? Because 1000AGL is often the minimum altitude you need to stay about congested area. I know, its a beotch . So 1200agl to allow some freedom of movement, and 700AGL so IFR flyers have more protection on approach.

- Is it just me, or do others find having so much magenta all over the sectionals make the sectionals cluttered? I know I'd sure like it if I could buy Sectionals that didn't have all of that on them.

Doesn't bother me. I've learned to "ignore" them. They are useful if your trying to find out real quick if your destination airport has an IFR approach. The only time i reaaaallly pay attention to them is if i'm in a helicopter. I like staying in class G.

 

[MauleSkinner]

- do that many pilots really fly around a bare VFR mins, below 1200' AGL? I see that at least one on this forum does, but are there really enough to warrant all of this?
- If the WX is low enough that you need to duck down below 1200' AGL or even 700' AGL to navigate around the country on a regular basis, why wouldn't you just go above it, or file IFR (yes, I know it's a lot of fun).

Yes, there are quite a few pilots down there, as Matt indicated...as to going above it, or filing IFR, a lot of those airplanes are non-electric, no gyro (or like my Maule, with just a turn needle for gyros), or otherwise not legal or safe to fly above or in the clouds. Icing and embedded thunderstorms are REALLY good reasons not to go in the clouds if you're not properly equipped. (no, I don't fly around embedded thunderstorms with 800-ft ceilings and a mile visibility, but the airspace down there is useful.)

Performance limitations, pilot currency and qualification...the list gets pretty long if you think about it.

Fly safe!

David

 

[Huggyu2]

Matt / Maule,
Great feedback. Thank you for the clear layout.