Section 3. Transitional Airspace Area Criteria

18-3-1. DEPARTURE AREA

a. The configuration of Class E airspace for departures is based on either specific or diverse departure routings and determines whether the Class E airspace will be circular or oriented in one or more specific direction(s).

b. A climb gradient of 200 feet per NM must be applied to determine the size of all Class E airspace for departures, and when necessary departure extensions. Specific departure areas with a base of 700 feet require the airspace 1.8 NM each side of the track centerline. Departure areas with a base of 1,200 feet require 4 NM each side of the track centerline.

c. When a surface area does not exist, the climb gradient must be applied from the departure end of the outermost runway to determine the width of the 700-foot Class E airspace and the beginning of the 1,200-foot Class E airspace.

d. The lateral boundary of a 1,200-foot Class E airspace that overlies the waters within 12 NM of the coast of the 48 contiguous states and Alaska, excluding the Alaskan Peninsula west of longitude 160 degrees, must terminate at 12 NM.

e. In the western states where the floor of controlled airspace is 14,500 MSL or 1,500 AGL, the 1200-foot airspace should be route oriented and normally only necessary between the 700-foot Class E airspace and the closest adjacent existing controlled airspace.

NOTE-
Where diverse departures are authorized, the 700-foot Class E airspace will normally be a 2.5 NM radius beyond the radius of the basic surface areas. This standard does not apply to surface areas associated with Class C airspace.

18-3-2. LENGTHY DEPARTURE CLASS E AIRSPACE EXTENSIONS

If lengthy Class E airspace extensions are established for departing flights, they must include the additional airspace within lines diverging at angles of 4.5 degrees from the centerline of the route radial beginning at the associated NAVAID. In planning such extensions, the same frequency protection considerations involved in airway planning must be included.

NOTE-
The 4.5-degree angle leaves an 8 NM wide area at 51 NM from the associated NAVAID.

18-3-3. ARRIVAL AREA

The point at which a flight can be expected to leave 1,500 feet above the surface on an instrument approach and the width of the primary obstruction clearance area must be obtained from the office responsible for developing the instrument approach.

18-3-4. ARRIVAL EXTENSION

Class E airspace extension with a base of 1,200 feet above the surface and 4 NM each side of the track centerline must be established to contain the flight path of arriving IFR flights at altitudes at least 1,500 feet or higher above the surface.

a. To determine length of an arrival extension, one needs:

1. The point at which a flight can be expected to leave 1,500 feet above the surface.

2. The airspace needed to contain arriving IFR operations at 1,500 feet and higher above the surface.

b. The extension length must be based on the approach requiring the greatest distance when multiple approach procedures (e.g., NDB/ILS) are established using the same approach course but with different final approach altitudes.

c. The width of the extension must be equal to the width of the TERPS primary obstruction clearance area at the point where an IFR flight on an instrument approach can be expected to descend to less than 1,500 feet above the surface. However, if the primary area widens between the point where the flight leaves 1,500 feet and the airport, the widest portion of the primary area must be used for the extension. Extensions must, in all cases, extend to a minimum of 1 NM on each side of the centerline, although the primary obstruction clearance area extends less than 1 NM from the centerline.

d. The extension width must be based on the approach requiring the greatest width when multiple approach procedures (e.g., NDB/ILS) are established using the same approach course.

18-3-5. PROCEDURE TURN PROTECTION

Class E airspace extensions must be established for the protection of low altitude procedure turn areas as follows:

a. Procedure turns authorized to a distance of 5 NM or less:

1. The boundary on the procedure turn side is 7 NM from, and parallel to, the approach course.

2. The boundary on the side opposite the procedure turn side is 3 NM from, and parallel to, the approach course.

3. The outer limit is established at 10 NM outbound from the procedure turn fix.

b. Procedure turns authorized to a distance greater than 5 NM:

1. The boundary on the procedure turn side is 8 NM from, and parallel to, the approach course.

2. The boundary on the side opposite the procedure turn is 4 NM from, and parallel to, the approach course.

3. The outer limit is established at 16 NM outbound from the procedure turn fix. This length is extended 1 NM and the width is widened .2 (2/10) of a NM for each NM beyond 10 NM that the procedure turn is authorized.

18-3-6. DETERMINING BASE ALTITUDES

In determining the base altitude of Class E airspace designated to encompass procedure turns, it is only necessary to consider governing terrain within the TERPS primary obstruction clearance area, excluding the entry zone, rather than terrain within the entire rectangular areas specified above.