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AIM

10/12/17

5

−1−14

Preflight

3.

An operational service volume has been

established for each class in which adequate signal
coverage and frequency protection can be assured. To
facilitate use of VOR, VORTAC, or TACAN aids,
consistent with their operational service volume
limits, pilot use of such aids for defining a direct route
of flight in controlled airspace should not exceed the
following:

(a)

Operations above FL 450 

− Use aids not

more than 200 NM apart. These aids are depicted on
enroute high altitude charts.

(b)

Operation off established routes from

18,000 feet MSL to FL 450 

− Use aids not more than

260 NM apart. These aids are depicted on enroute
high altitude charts.

(c)

Operation off established airways below

18,000 feet MSL 

− Use aids not more than 80 NM

apart. These aids are depicted on enroute low altitude
charts.

(d)

Operation off established airways be-

tween 14,500 feet MSL and 17,999 feet MSL in the
conterminous U.S. 

− (H) facilities not more than

200 NM apart may be used.

4.

Increasing use of self

−contained airborne

navigational systems which do not rely on the
VOR/VORTAC/TACAN system has resulted in pilot
requests for direct routes that exceed NAVAID
service volume limits. With the exception of
GNSS

−equipped aircraft, these direct route requests

will be approved only in a radar environment, with
approval based on pilot responsibility for navigation
on the authorized direct route. Radar flight following
will be provided by ATC for ATC purposes. For
GNSS

−equipped aircraft, ATC may approve a direct

route that exceeds ground based NAVAID service
volume limits; however, in a non

−radar environment,

the routing must be “point

−to−point,” defined as

navigation from a published point to a published
point, and navigational assistance will not be
available. (See subparagraph 5

−1−8d below.)

5.

At times, ATC will initiate a direct route in a

radar environment that exceeds NAVAID service
volume limits. In such cases ATC will provide radar
monitoring and navigational assistance as necessary.
For GNSS

−equipped aircraft, if the route is

point

−to−point, radar monitoring and navigational

assistance is not required. (See subparagraph 5

−1−8d

below.)

6.

Airway or jet route numbers, appropriate to

the stratum in which operation will be conducted,
may also be included to describe portions of the route
to be flown.

EXAMPLE

MDW V262 BDF V10 BRL STJ SLN GCK
Spelled out: from Chicago Midway Airport via Victor 262
to Bradford, Victor 10 to Burlington, Iowa, direct
St. Joseph, Missouri, direct Salina, Kansas, direct
Garden City, Kansas.

NOTE

When route of flight is described by radio fixes, the pilot
will be expected to fly a direct course between the points
named.

7.

Pilots are reminded that they are responsible

for adhering to obstruction clearance requirements on
those segments of direct routes that are outside of
controlled airspace. The MEAs and other altitudes
shown on low altitude IFR enroute charts pertain to
those route segments within controlled airspace, and
those altitudes may not meet obstruction clearance
criteria when operating off those routes.

d. Area Navigation (RNAV)/Global Navigation

Satellite System (GNSS)

1.

Except for GNSS

−equipped aircraft, random

impromptu routes can only be approved in a radar
environment. A random impromptu route is a direct
course initiated by ATC or requested by the pilot
during flight. Aircraft are cleared from their present
position to a NAVAID, waypoint, fix, or airport.
Factors that will be considered by ATC in approving
random impromptu routes include the capability to
provide radar monitoring and compatibility with
traffic volume and flow. ATC will radar monitor each
flight; however, navigation on the random impromp-
tu route is the responsibility of the pilot.
GNSS

−equipped aircraft are allowed to operate in a

non

−radar environment when the aircraft is cleared

via, or is reported to be established on, a
point

−to−point route. The points must be published

NAVAIDs, waypoints, fixes, or airports recallable
from the aircraft’s database. The distance between the
points cannot exceed 500 miles and navigational
assistance will not be provided.

2.

Pilots of aircraft equipped with approved area

navigation equipment may file for RNAV routes
throughout the National Airspace System and may be
filed for in accordance with the following procedures.

(a)

File airport-to-airport flight plans.

3/15/07

7110.65R CHG 2

AIM

2/28/19