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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