Class D / E / G / TSRA

[PilotMikeTX]

I just skimmed this thread so forgive me if it's already been mentioned, but a point to remember regarding Class D areas with part time control towers is that when the tower is closed, sometimes the airspace within the lateral limits of the Class D becomes a Class E Surface Area (think of it as the dashed blue circle becomes a dashed magenta circle). But that's not always the case, it could be a Class E with floor 700AGL or I supposed technically it could be Class E with floor 1200AGL or even Class G (and it would not have to be out in the middle of nowhere with no instrument approach as you'll see.) You'll find that information in the A/FD.

Let's look at Stinson Muni KSSF:

STINSON MUNI (SSF) 6S UTC6(5DT) N29°20.22 W98°28.27 SAN ANTONIO
577 B S4 FUEL 100LL, JET A L–19C
RWY 09–27: H4835X100 (ASPH) S–12, D–20 MIRL (NSTD) 0.3% up W IAP, AD
RWY 09: REIL. Thld dsplcd 206. P–line. RWY 27: REIL.
RWY 14–32: H4128X100 (ASPH) S–12, D–20 MIRL 0.5% up
NW
RWY 14: REIL. VASI(V2R)—GA 4.0° TCH 57. Thld dsplcd 584.
Trees.
RWY 32: REIL. VASI(V4L)—GA 3.0° TCH 60. Thld dsplcd 372.
Trees.
AIRPORT REMARKS: Attended 1300–0400Z‡. Numerous acft operating
at or above 2,500 MSL in the Stinson Class D airspace under the
control of San Antonio approach. PAEW adjacent all twys and ramp
areas Mon–Fri 1300–2359Z‡. Rwy 09–27 NSTD MIRL; thld lgts
located 30 in from dsplcd thld. Rwy 09 REIL located 30 in from
dsplcd thld. Rwy 14 REIL OTS indef. MIRL Rwy 09–27 and Rwy
14–32 preset medium intensity when twr closed. ACTIVATE VASI
Rwy 32—CTAF.
WEATHER DATA SOURCES: ASOS (210) 927–9391. LAWRS.
COMMUNICATIONS: CTAF 118.2 UNICOM 122.95 ATIS 128.8
SAN ANGELO FSS (SJT) TF 1–800–WX–BRIEF. NOTAM FILE SSF.
R SAN ANTONIO APP/DEP CON 125.7 CLNC DEL 121.7
TOWER 118.2 (1300–0400Z‡) GND CON 121.7
AIRSPACE: CLASS D svc 1300–0400Z‡ other times CLASS G.
RADIO AIDS TO NAVIGATION: NOTAM FILE SAT.
SAN ANTONIO (H) VORTACW 116.8 SAT Chan 115 N29°38.64 W98°27.68 174° 18.4 NM to fld. 1160/8E.
HIWAS.
(L) VORW 108.4 SSF N29°15.50 W98°26.61 334° 4.9 NM to fld. NOTAM FILE SSF.
VOR unusable:
111°–149° byd 10 NM
150°–159° byd 7 NM
160°–170° all altitudes
205°–235° all altitudes

You'll note that the airport lies in Class D airspace while the tower is in operation, then it is in Class G airspace. Technically they are correct in that the airport--the part that is dirt and concrete that has a fence around it--is in Class G airspace. But if you look at a sectional, you'll see that the airport lies within the giant shaded magenta blob that surrounds the greater San Antonio area. So the airspace above the airport is only class G to 700AGL.

[Bruce Fenstermacher]

But that's not always the case, it could be a Class E with floor 700AGL or I supposed technically it could be Class E with floor 1400AGL or even Class G (and it would not have to be out in the middle of nowhere with no instrument approach as you'll see.) You'll find that information in the A/FD.

PilotMikeTX I think you meant to type 1200AGL not 1400AGL in the above statement.

PilotMikeTX is correct and brings up a good point. Class D airspace does not always revert to Class E to the surface. You do have to look in the Airport Facility Directory to find what it reverts to.

The hours of operation of control towers, if not 24 hours, is on the edge panel of the charts but for what the airspace reverts to you will have to go to an AFD. Some of us barely have a current chart let alone an AFD. If you find yourself without an AFD in the middle of the night when the towers are generally closed, if you use the rules for Class E to the ground you won't go wrong.

Those of us who need to know the benefits ( ) of departing an airfield at night in Class G under a 700ft ceiling if that is what the airspace has actually reverted to, will have an AFD.

[PilotMikeTX]

Thanks for catching that. I was tired last night. I think where it will get you into trouble as a vfr pilot is if you come cruising into a traffic pattern at 800 feet under a 1000' ceiling...then the $1000 (or 30 day) question becomes "Do I need to be 500 feet below or clear of clouds?" Chances are nobody gives a crap one way or the other, but there's always the possibility that there is a regional airliner or charter jet hoding short with an FAA inspector on the jumpseat. A friend of the family had his airline career put on hold for about 7 years for doing just that. For IFR pilots, the situation usually involves canceling IFR, when you're not quite legal to do so. While there is no requirement for part 91 operators to have a current chart of A/FD on board, the PIC is ultimately responsible at the end of the day.

14CFR91.103
Each pilot in command shall, before beginning a flight, become familiar with all available information concerning that flight...

Oh, and I should also add that while TRSA participation is voluntary, the controllers sure get bent out of shape when you don't volunteer to participate. I always give them a call.

[jrenwick]

...I think where it will get you into trouble as a vfr pilot is if you come cruising into a traffic pattern at 800 feet under a 1000' ceiling...then the $1000 (or 30 day) question becomes "Do I need to be 500 feet below or clear of clouds?"

Perfect! I assume you won't have any heartburn if I steal this and use it in my ground school this week! Airspace is one of the more difficult subjects, and I think this will help the Class E complexity come alive for them a little better. Thanks!!!

Now I'll share something I teach, which I got from one of my instructors (Kyle and Becky, I'll bet you have this!). How do you keep it straight in your head what the VFR cloud separation and visibility minimums are? FAR 91.155 shows a table of minimums for each class of airspace. The table is very repetitious, because organizing it by airspace class is really a poor way to try to remember it. Instead, I teach it this way to VFR pilots:

You have two basic VFR minimum requirements: low, and high.

Low is 500' below, 1000' above, 2000' horizontally, and 3 miles visibility (1/2=.5, if that helps as a memory aid).
High is 1000' above, 1000' below, 1 mile horizontally, and 5 miles visibility.
Commit those two things to memory. Now:

At or above 10000' MSL, the high minimums apply.
Below 10000' MSL, the low minimums apply.
If this is all you can remember, you'll always be legal. There are just a few exceptions that will let you fly with lower minimums. Here are the exceptions:

1. In Class B airspace, the cloud separation miminum is simply clear of clouds (because ATC is providing separation for all aircraft, VFR and IFR alike).
2. In Class G airspace at night, the standard low and high minimums still apply. But during the day --
a. 1200' AGL or lower, 1 mile and clear of clouds -- even if you're above 10000' MSL.
b. Above 1200' AGL, it's low minimums except the visibility requirement drops to 1 mile.

Here's a chart my instructor gave me to help visualize this, if it helps:

Wx_Min.gif

John

[PilotMikeTX]

Cool. I printed that thing out and made a pterydactyl out of it.

Airspace is hard to learn. Just about the time I had the ARSA's and TCA's figured out, they changed it on me. Then they did the same thing with the weather reporting.

I think it would be easier if everyone got an instrument rating with their private ticket like the military kids, but I could probably get voted off the island for saying that out loud. If it weren't for those IFR SOBs we could just do whatever we wanted whenever we wanted.

I was taught "3 [Cessna]152's" and "5 [F-]111's" Of course, there's generation of students who have probably never seen an F-111, and there are probably some who don't know what a 152 is.

"I got you's glass panel right heah, kid."

[AR Dave]

Hey I didn't see the printable attachment - thanks!

Attachment

[Bruce Fenstermacher]

Just remember the 1200'AGL in the triangle can also be 700ft AGL

[jrenwick]

Just remember the 1200'AGL in the triangle can also be 700ft AGL

No, that line across the bottom of the triangle is meant to represent the feature of Class G airspace where the cloud clearance requirements change at 1200' AGL. Not to be confused with the boundary between Class G and Class E airspaces, which is also a change in VFR minimums, but not the same.

See? I think we can all agree the FAA has made all this much too hard!

John

[voorheesh]

The triangle doesn't mention an interesting exception to airports under Class G Airspace at night where you can fly with 1 mile visibility and clear of clouds if you remain within 1/2 mile of the runway. Before you blame the FAA entirely for these confusing rules, you should consider how rulemaking actually works. Public comments, particularly those from alphabet groups have a big influence in rulemaking and this is where compromises are struck which allows those who "have to have 1 mile at night or need 1 mile when flying within 1200' of a 12500' mountain" get to have their piece of the action. The rule ends up with many "exceptions" just to keep those guys happy. Incidentally, the FAA does not have a tape measure to enforce these visiblity rules. About the only way you can get busted for a visiblity violation is for ATC to catch you in airspace where they can prove what the visibility value is. Class E surface areas are good examples because a lot of inexperienced pilots forget that if the reported wx is less than ceiling 1000 and vis 3 miles you need special VFR or IFR to enter or depart an otherwise non towered airport. While few pilots get violated for busting other visiblity rules, many of them end up at accident sites and those are usually fatal. You would be surprised how many of these pilots are actually highly experienced, many with ATPs. Its always kind of sad to hear their families and friends talk about what "great pilots" they were. We should all know the FARs but use much higher minimums to keep safe.

[Bruce Fenstermacher]

No, that line across the bottom of the triangle is meant to represent the feature of Class G airspace where the cloud clearance requirements change at 1200' AGL.

OK John were is the line on the triangle for when Class G ends at 700ft AGL and Class E starts. The majority of the Glass G airspace around me ends at 700 ft AGL and very little at 1200 ft AGL but you can find some of the 1200 ft variety if you try.

[jrenwick]

OK John were is the line on the triangle for when Class G ends at 700ft AGL and Class E starts. The majority of the Glass G airspace around me ends at 700 ft AGL and very little at 1200 ft AGL but you can find some of the 1200 ft variety if you try.

The diagram isn't trying to show that. It's only trying to show what VFR minimums apply in which airspaces, and you have to look at a sectional chart to know where Class G ends and Class E begins. Class G airspace is represented by the lower left (night) and lower right (day) triangles. Controlled airspace below 10K' is represented by the middle triangle, and everything above 10K' (controlled or uncontrolled) is represented by the top one.

Class G is different from the others, having four different sets of VFR minimums within itself that change at two different altitude boundaries (1200 AGL and 10000 MSL) and one temporal one (defined by civil twilight).

Here's a fairly devious question from the FAA Private Pilot knowledge test: "(Refer to Figure 23, area 1.) The visibility and cloud clearance requirements to operate over Sandpoint Airport at less than 700 feet AGL are:
A. 3 miles and 1000 feet above, 500 feet below, and 2000 feet horizontally from each cloud.
B. 3 miles and clear of clouds.
C. 1 mile and 1000 feet ablve, 500 feet below, and 2000 feet horizontally from each cloud."
(Sandpoint Airport in the figure has a magenta fuzzy circle around it, so it's Class E down to 700 AGL.)
The correct answer is A. You have to assume on your own that it's night time, otherwise none of the answers are correct for Class G airspace below 1200 AGL (which includes below 700 AGL). I'm not sure this question is still in the active pool, but we're teaching it anyway, because it's in the guide book.

By the way, I won't try to argue that this is the absolute best way to represent VFR minimums. I tell students that the definitions you have to know are in FAR 91.155, and if there's any question, you should go there. The chart is just a memory aid, and different depictions or mnemonics will work better for different people. This is just one more tool in the kit, and it will work better for some than for others.

John

[AR Dave]

Above 14,500 MSL is Class E - up to 18,000 MSL.
So why 14,500? Why not start it at 10,000 MSL, where the weather minimums change?
Between Anchorage and Valdez, one could fly up to 14,500 in Class G. Guess that could come in handy if you needed to fly around a 12,000 mtn, with only 1 mile of visibilty. So why are there Class G circles up here over the Beaufort, Sea?

[voorheesh]

14500' is the old continental control area. All airspace above 14500' is E or A. I couldn't see your chart too well but if there is a stand alone magenta circle, that would indicate Class G to 700' and then Class E (within the magenta boundaries) up to the floor of Class A.

[PilotMikeTX]

Dave, those aren't really areas of Glass G airspace (to 14,500), but rather they show the borders of the Class E airspace (above 1200AGL). You'll notice that there are airways passing through the areas between those funny blue polygons. Airways are automatically Class E airspace from 1200-18,000 5nm either side of the centerline. The process doesn't place areas of Class G airspace, rather we started with the entire country having Class G to 14,500, then carved out areas of other types of airspace. An area that is still Class G from the surface to some height only exists because it hasn't been replaced by some other airspace...yet. That's how you end up with those funky shapes up there.

In fact, those blue shaded areas are almost impossible to find in the lower 48. There are a few in remote mountainous areas out west. When I was instructing and I wanted to show a student an example, I had to get out a Brownsville or El Paso sectional, because it is depicted on the border. The ADIZ "dots" are actually co-located with the blue shaded border.

[AR Dave]

I really appreciate all the discussion on Airspace! My instructor is going to be suprised when I start telling him about Airspace. I've been pouring over the FAR/AIM, Sectionals, and etc.. Once ya'll got me going in the right direction, I became interested. It helped that I have a pilot coworker that is learning them at the same time, so we kept challenging eachother. Oh yeh, well what about this - you're flying over the Aluetian Islands and the weather drops to 2 miles visiblity - - - that kind of stuff.