Section 2. Class D Airspace Standards
17-2-1. CONFIGURATION
a. A Class D airspace area shall be of sufficient
size to:
1. Allow for safe and efficient handling of
operations.
2. Contain IFR arrival operations while
between the surface and 1,000 feet above the surface
and IFR departure operations while between the
surface and the base of adjacent controlled airspace.
b. Size and shape may vary to provide for 1 and 2
above. The emphasis is that a Class D area shall be
sized to contain the intended operations.
17-2-2. AIRPORT REFERENCE POINT/GEOGRAPHIC POSITION
a. The Class D airspace boundary should normally
be based on the airport reference point (ARP) or the
geographic position (GP) of the primary airport. The
ARP/GP is the center of the airport expressed in
coordinates and should be incorporated into the
surface area's legal description.
b. If a Class E surface area is established in
conjunction with a part-time Class D area, the areas
should normally be coincident. Explain any
differences in the rulemaking documents.
NOTE-
Under certain conditions, the ARP/GP can change. If this
occurs, the airspace should be reviewed to ensure the
instrument procedures are still contained within existing
airspace.
17-2-3. SATELLITE AIRPORTS
a. Using shelves and/or cutouts to the extent
practicable, exclude satellite airports from the
Class D airspace area (see
FIG 17-2-3).
b. Satellite airports within arrival extensions may
be excluded using the actual dimensions of the
TERPs trapezoid.
c. Do not exclude airports inside the TERPs
primary obstruction clearance area of the
procedure(s) for which the surface area is being
constructed or when the exclusion would adversely
affect IFR operations.
17-2-4. ADJOINING CLASS D AIRSPACE
AREAS
Designate separate Class D airspace area for airports
in proximity to each other. A common boundary line
shall be used so that the airspace areas do not overlap.
When operationally advantageous, the common
boundary separating adjacent Class D areas may be
eliminated if the areas are contained in an existing
Class B or Class C airspace area controlled by the
same IFR ATC facility.
17-2-5. DETERMINING CLASS D AREA
SIZE
The size of a Class D area, and any necessary
extensions, is determined by the use of a 200 feet
per NM climb gradient and information obtained
from the person responsible for developing instrument procedures (see
FIG 17-2-1).
NOTE-
Normally, the person responsible for developing
instrument procedures for civil and U.S. Army airports is
a FAA Aviation Standards Airspace Evaluation Specialist.
A military representative handles all other military
procedures.
17-2-6. DEPARTURES
a. When diverse departures are authorized, design
the Class D area using a radius of 3.5 NM plus the
distance from the ARP/GP to the departure end of the
outermost runway (see
FIG 17-2-1).
b. When specific departure routes are required, the
routes will determine the shape of the Class D area.
Use the 200 feet per NM climb gradient procedure in
subparagraph a. above and
FIG 17-2-2 plus 1.8 NM
either side of the track(s) to be flown.
c. In areas with rising terrain, apply the procedures
reflected in
FIG 17-2-2.
17-2-7. ARRIVAL EXTENSION
a. A Class D area arrival extension shall be
established to the point where an IFR flight on an
instrument approach can be expected to descend to
less than 1,000 feet above the surface.
b. When multiple approach procedures are
established using the same initial approach course,
but with different 1,000-foot points, the extension
length shall be based on the approach requiring the
greatest distance. Consistent with safety and
operational feasibility, if an adjustment to the
1,000-foot point can be made to eliminate or shorten
an extension, the specialist shall coordinate with the
person responsible for developing the instrument
approach to request the adjustment.
c. The width of the extension shall 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 an altitude
below 1,000 feet above the surface. However, if the
primary area widens between the point where the
flight leaves 1,000 feet and the airport, the widened
portion of the primary area located outside the basic
surface area radius shall be used for the extension.
These extensions shall, in all cases, extend to a
minimum of 1 NM on each side of the centerline.
d. If all arrival extensions are 2 NM or less, they
will remain part of the basic Class D area. However,
if any extension is greater than 2 NM, then all
extensions will be Class E airspace.
17-2-8. VERTICAL LIMITS
Class D areas should normally extend upward from
the surface up to and including 2,500 feet AGL. The
altitude shall be converted to MSL and rounded to the
nearest 100 feet. However, in a low density or
non-turbo aircraft traffic environment, a vertical
limit of 2,500 feet AGL may be excessive and a
lower altitude should be used.
NOTE-
The nearest 100 feet means that 49 feet and below shall be
rounded down and 50 feet and above shall be rounded up.
17-2-9. COMMUNICATIONS
Communications capability must exist with aircraft,
that normally operate within the Class D Surface
Area down to the runway surface of the primary
airport (the airport upon which the surface area is
designated). This communication may be either
direct from the ATC facility having jurisdiction over
the area or by rapid relay through other communications facilities which are acceptable to the ATC
facility having that jurisdiction.
17-2-10. WEATHER OBSERVATIONS AND
REPORTING
a. Weather observations shall be taken at the
primary airport during the times and dates the
Class D airspace is active. A federally certified
weather observer or a federally commissioned
automated weather observing system (this includes
all FAA and NWS approved and certified weather
reporting systems) can take the weather observation.
The weather observer shall take routine (hourly) and
special observations. An automated weather
observing system can provide continuous weather
observations.
b. Scheduled record and special observations
from weather observers or automated weather
reporting systems shall be made available to the ATC
facility(s) having control jurisdiction over the
Class D designated surface area. This can be
accomplished through Automated Flight Service
Station/Flight Service Station (AFSS/FSS),
Longline Dissemination, National Weather Service
(NWS), or other FAA-approved sources. Facilities
that require weather reports from satellite airports
may enter into a letter of agreement (LOA) with the
associated AFSS/FSS, airline/contract observer,
airport management, etc.
NOTE-
1. At ATC sites where non-Federal employees perform
weather duties, the appropriate FAA office shall ensure
that the reporting and dissemination requirements
applicable to National Weather Service and FAA
publication standards are followed.
2. In facilities where direct access to automated weather
observing systems is not available, controllers will apply
the provisions of FAAO 7110.65, Air Traffic Control.
17-2-11. LOSS OF COMMUNICATION OR
WEATHER REPORTING CAPABILITY
a. If the capabilities outlined in paragraph
17-2-9 and/or paragraph
17-2-10 are temporarily
out of service for an active Class D Surface Area, a
Notice to Airmen shall be issued stating the
temporary loss of the affected service.
b. However, if it is determined that the capabilities
are consistently unavailable, a Notice to Airmen shall
be issued, as described above, and rulemaking action
initiated to revoke the Surface Area, as appropriate.
c. The FPO needs to be kept informed of any
planned action, especially when instrument approach
procedures (IAP) are involved, so as to assess the
impact on published approaches. The Standards
Specialist may decide changes are needed in the IAP,
dependent on possible new altimeter source and other
considerations. These changes will have an effect on
the airspace action required; e.g., minimums may be
raised, or procedure may be canceled.
FIG 17-2-1
CLASS D AREA RADIUS FORMULA
Class D AREA RADIUS FORMULA
RADIUS
ARP/GP = AIRPORT REFERENCE POINT AND/OR GEOGRAPHIC POSITION
EOR = END OF OUTERMOST RUNWAY
6076 = ONE NAUTICAL MILE IN FEET
200 FEET PER NAUTICAL MILE = STANDARD CLIMB GRADIENT
D = DISTANCE IN FEET FROM ARP/GP TO EOR 3.5 MILES = DISTANCE
REQUIRED FOR DEPARTURE TO REACH 700-FOOT CLASS E AIRSPACE USING
STANDARD CLIMB GRADIENT
(700/200)
2.5 MILES = DISTANCE REQUIRED FOR DEPARTURE TO REACH 1200-FOOT
CLASS E AIRSPACE USING STANDARD CLIMB GRADIENT
((1200 - 700)/200)
THE FORMULA CAN BE EXPRESSED AS: R = D/6076 + 3.5
Example:
At Airport A, the distance from the geographic position to the end of the outermost runway
is 4,023 feet; therefore, assuming flat terrain, the radius is calculated as:
R = 4023/6076 + 3.5 = .662 + 3.5 = 4.162 = 4.2
The radius for the 700-foot Class E airspace becomes: 4.2 + 2.5 = 6.7
RISING TERRAIN
In the above example, an aircraft departing to the west would reach the lateral boundary of the
surface area without reaching 700 feet AGL and, in effect, leave controlled airspace. To ensure that
the lateral boundary of the Class D area is congruent with the beginning of the 700-foot Class E
airspace, the specialist shall:
a. Search the Class D area's radius circle for the highest terrain.
b. Calculate the MSL height of the aircraft by adding 700 feet to the airport elevation.
c. Compare MSL altitudes of the aircraft versus the highest terrain to determine if the
aircraft has reached the overlying or adjacent controlled airspace. If not, increase the size
of the Class D area, as necessary, to contain the departure.
NOTE-
When terrain, obstacles, or procedures prohibit departures in portions of the basic surface area, a terrain search is not
necessary in that area and that height is not used in the computations.
FIG 17-2-3
EXAMPLES OF SATELLITE AIRPORTS EXCLUDED FROM SURFACE AREA AIRSPACE AREAS
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