Airspace & Charts Overview

See also: Finding Legal Sites With Google

Exploring new areas by PPG is an experience in freedom seldom even imagined just a few short years ago. As with most freedoms it carries some extra responsibility…one of those is making sure you’re in allowable airspace.

The PPG Bible has a far more thorough and detailed treatment of the subject but this should a provide a working knowledge of how to determine if the air above is legal. Barring a knowledgeable local pilot, the best way to learn the “where of legal air” is to purchase and become familiar with the Aeronautical Sectional Chart for that area. Big cities have more detailed versions covering just their vicinity called VFR Terminal Area Charts…and they more detailed. 

Sectional and Terminal Area charts are available from the local airports, the Internet, and pilot shops such as Sporty's for about $8 each. New, updated ones come out every 6 months and must be used to avoid blundering into newly added restricted airspace (of which there is much lately).

FAR 103

Among other things, this short regulation says we must stay out of class A, B, C, D and some E airspace, prohibited and restricted areas, and other airspace as given by a notice to airman (NOTAM). There is also an admonition on the charts to stay out of charted wildlife areas. 

We can fly in many of these airspace classes but must have prior permission by the controlling facility.

There are also visibility and cloud clearance requirements based on what kind of airspace we operate in.

The best way to learn this information would be a session or two with a certified FAA flight instructor. Next best would be some good videos such as "The Complete Airspace Review" and "VFR Cross Country Flying"...both from the well known producer of such flicks, King Schools (www.kingschools.com). They are about $30 each.

Getting the Info

While the sectional chart is a great source of information, it is also the least current. They are printed every six months and new airspace frequently pops up or changes frequently. A necessary source of info for some of these tips is the Flight Service Station (FSS).

NOTAM's

There are times when prohibited airspace is created temporarily. That is when a Notice to Airmen (NOTAM) is issued restricting overflight during the affected time for listed locations and altitudes. In the current security environment, adherence to these are critical. 

NOTAM information can be obtained by calling a Flight Service Station (FSS) at 1.800.wx-brief. Tell them you're an ultralight, where and when you want to fly and they'll give you any pertinent info. A bonus of this call is that you'll also be able to get weather around your area if desired (just ask for an abbreviated briefing with local weather, forecast and NOTAMS).

One example of when airspace will become off-limits by NOTAM is whenever the president or other dignitary comes to town: they don’t want private planes or ultralights (us) buzzing about for obvious reasons. They will specify a bunch of areas and times that will cover the expected route, including alternate routes they will travel. Nowadays these are taken extremely seriously; blundering into one might be a one-time mistake.

Another time airspace is NOTAM’d off-limits is after a natural disaster. This is an effort to keep the area clear for rescue or relief traffic. These cases are usually going to be obvious because the disaster creating the airspace will be all over the news.

The boundaries will frequently be in the form of a radial and distance from a VOR (see offset above).

Here's an example (reference the excerpt): a truck carrying propane explodes on the highway southwest of Vero Beach. The highway is closed and a rescue/firefighting operation gets underway. FAA managers, at the request of local officials, will close the airspace over the area by issuing a NOTAM - prohibiting overflight below 2000’ and within 2nm (nautical miles) of an area defined by the 210° radial at 7nm. Flying there would be particularly dangerous due to disaster related air traffic and would guarantee yourself special attention:  everybody in officialdom knows you’re not supposed to be there.

A VOR (VHF Omnidirectional Range) station is used for aircraft navigation and by air traffic controllers to reference airspace such as that listing restricted areas. The reason why we might care about it is 1) to know that airplanes congregate overhead - it's good to avoid above about 800' AGL and 2) we can easily describe locations using distance and direction from it. Such reference can be useful when getting permission to fly in controlled airspace.

The the location of the station and it’s compass rose are pointed at by (#2). The name of the VOR (VERO BEACH) and it’s controlling agency (St Petersburg) are at (#1).

The degrees of the compass rose are in 5 degree increments and, space permitting, are labeled every 30 degrees. The (#3) above points to the 090, 120, 150, 180 and 210 degree lines of the VRB VOR.

If, for example, a NOTAM listed prohibited airspace on the 210 degree radial, at 7nm (nautical miles) with a radius of 2nm, that would be the area depicted by the black dotted circle out the 210° radial. The black dots were added here for clarity. These location won’t be on the charts, that is why they use a radial/distance to mark them.

The ABC’s of Keeping Clear

The most relevant piece of knowledge regarding airspace is that almost anywhere you go, you're probably launching in G airspace at the surface with E airspace overlying it 700' (or 1200') overhead. Minimum for that airspace require remaining clear of clouds and having at least a mile visibility. When you pop into E airspace, airplanes are more likely to be found tere and you must maintain at least 3 mile visibility and stay 500' below, 2000' to the side and 1000' above any cloud.

Class A airspace is above 18000’...no problem staying clear of that. Class B is where the big airplanes land. There are only a handful of these around the country surrounding the largest airports and generally we wouldn’t want to go anywhere near them. Unfortunately they do usually block out otherwise usable launches that are indeed far enough away, so we must go to the chart.

The usual analogy of the three dimensional chunk of air carved out by a “B” is the upside down wedding cake (diagramed left). Near the airport it goes right down to the surface, as you get further away from the primary airport the floor goes above ground level, allowing us to fly in that area. That would be flying beneath “B” airspace and is perfectly legal. 

For example, in the above depiction there is a ring with 80 over 40. That means the B airspace goes from 4000' above sea level (ASL) to 8000' ASL. So in the area of that ring you could fly up to 4000'. Keep in mind all those little airplane guys know that and will frequently squeeze around these rings just below those altitudes.

The area where it has 80 over SFC means from the surface up to 8000'. That is the off-limits area for launching (or flying into at any altitude). 

Class C and Terminal Radar Service Areas

Class C is designated just like class B but with a magenta line instead of blue. It has altitudes depicted in the same way with a floor and ceiling and is just as prohibited

These airports, like the their larger "B" brethren have an approach control facility associated with them.

Before airspace was designated into the alphabetic descriptions (for compliance with world standards) there were distinct names for each type. One that remains is the Terminal Radar Service Area (TRSA). 

To the right is the Rockford, IL TRSA. There is not quite enough traffic to be a class "C" and It is designated with a dark gray line. It is permissible to fly in this airspace without talking to anyone although there will be a control tower and class D airspace near the center (dashed blue lines) which is prohibited (unless you have permission, of course). 

Tower Airports and Class D

Airports with control towers are blue and those with no tower  are magenta (purple). Furthermore an airport with a control tower will generally have a blue dashed line around it. That line designates “class D” airspace which prohibits our operations  (unless we talk to them).

The class D airspace typically goes up 2500' above ground level (AGL) and the above-sea-level (ASL) altitude is depicted in the box. The DPA airport (left) shows 33 which is 3300' ASL. The airport elevation is 758. When aviation charts use italics it usually is to indicate elevations referencinv mean sea level (MSL and ASL are the same thing). This includes airports, mountains and obstructions.

Legally you could fly right above the DPA airport at 3400' ASL. While legal this would be complete folly because airplanes will be taking off and landing at the airport and many will be overflying for the same reason...they don't have to talk to anyone. It is some very crowded airspace and they're not looking for essentially stationary ppg's.

Note also in the DPA example the 100/40 near the top of the picture. This airport underlies Chicago's very busy O'Hare airport, the floor of who's B airspace is at 4000'. So everyone not talking to either the DPA tower or O'Hare approach is squeezing between 3300' and 4000' MSL. 

Military Airspace

There are many flavors of airspace where the military stakes a claim. Most of it is actually not forbidden zone but given the nature of their use it would best be avoided. All military airspace is designated the same way with rows of parallel lines in either blue or red (see MARIAN MOA below for an example).

There are also VR and IR's which are Visual Routes and Instrument Routes. These thin gray lines are not restricted legally but be aware they frequently fly very low and fast along them (up to 270 mph!). 

Prohibited and Restricted areas generally are no-no’s. Flying in one of these while it’s in use would be utter folly. But even these may allow flight…they are in effect from different altitudes (sometimes only high up) and different times or days. This information is usually located on the chart. If planning on flying in one of these areas you must call the Flight Service Station (FSS) at 800 WX-BRIEF to verify the times though. The sectionals come out every 6 months and these times are updated every 56 days so the chart’s info could be old. Tell the FSS briefer you’re an ultralight pilot and he will find out whether it’s “hot”. He has a direct line usually to the controlling agency (usually the enroute “center”) and will relay the information to you…and the call is free!

Alert areas, Controlled Firing areas and MOA’s do not actually prohibit flight…they are there as a warning that military operations will be conducted and pilots should “look out”. Keep in mind some military training involves low-altitude helicopter or jet training where they do various “nap-of-the-earth” type work. That would put them smack in the middle of our favorite altitudes. 

Wildlife Areas

These are not actually prohibited but the admonishment on the charts requests pilots to remain at least 2000' AGL when overflying them. They are designated in blue with a solid line that has dots running along just inside the line. 

In the example to the left, the Verde River Bald Eagle Breeding Area roughly follows a river. This area is about 2 miles wide. Note that it overlaps another, rectangular shaped, wildlife area south of it (whose name is not shown).

Class E & G Airspace

Generally all of our flying is going to be in this airspace. We can legally take-off, fly around in, and land in both E & G airspace. The difference between the two is only in the required cloud clearance and visibility requirements. The vast majority of the United States is covered by G (the least restrictive) and then E on top of that...meaning that our freedom to fly is indeed bountiful. In those few areas, mostly out west, where G airspace has not cap shown, the top is still 14,500 with E above that. The practical difference is negligible because visibility and cloud clearance requirements are the same.

In most areas of the country the G airspace goes from the surface up to 1200' AGL. If there's a nearby airport that sometimes gets lowered to 700' AGL. Above the G airspace is E which has more restrictive visibility requirements but we can certainly fly in it.

Near airports where airplanes are likely to be letting down on an instrument approach, the floor of E airspace lowers to 700 feet. That is depicted by a shaded magenta outline. In the example around Pontiac airport it is a circle but sometimes it has weird shapes with extensions that stick out.

Class E Surface Area

Some airports are not quite busy enough to have a control tower but are still busy. They may have the Class E airspace lowered to the surface as depicted by dashed magenta lines. The example at right, Truth or Consequences airport in New Mexico shows a shaded magenta area around it, which lowers the E airspace to 700' AGL then, inside that is a dashed magenta ring that lowers the class E to the surface.

We are specifically prohibited from flying here without permission.

Another example is where a control tower airport has extensions around it where Class E is lowered to the surface. Aurora, shown at right with the inset, is one example. The blue area is the class D and the magenta area is class E to the surface. The coloring was added only in the inset for clarity.

Permission comes from the control tower where applicable, approach control if it's near a large airport, or the Air Route Traffic Control Center which handles traffic everywhere else.

Mode C

Around most of the busy class B airspace areas there is a 30 mile ring that says "Mode C". This has no bearing on our ability to fly inside that ring.

The mode C "veil" pertains to certified aircraft with an electrical system and stipulates that they must have a transponder with altitude encoding. That equipment transmits to the radar controllers their altitude along with some other information. We, as ultralights, are exempt from this requirement. Obviously we do have to stay out of the various layers of the class B airspace.

Surveying

Sometimes I've found myself in a new area and one of the first tasks is to buy a chart if I don't have one. Then by comparing what's on the chart with the road map I can make sure I'm legal from an airspace perspective.

On a couple occasions the places where I really wanted to fly were in someone's class D airspace. So far I have been able to secure permission by adhering to agreed upon times, altitudes and routes.