The en route chart excerpt depicts three published RNAV jet
routes: J804R, J888R, and J996R. [Figure 2-45] The R suffix
is a supplementary route designator denoting an RNAV
route. The overlapping symbols for the AMOTT intersection
and waypoint indicate that AMOTT can be identified by
conventional navigation or by latitude and longitude
coordinates. Although coordinates were originally included
for aircraft equipped with an inertial navigation system
(INS), they are now a good way to cross check between
the coordinates on the chart and in the flight management
system (FMS) or global positioning system (GPS) databases
to ensure you are tracking on your intended en route
course. The AMOTT RNAV waypoint includes bearing and
distance from the Anchorage VORTAC.
Random RNAV Routes
Random RNAV routes are direct routes that are based on
RNAV capability between waypoints defined in terms of
latitude or longitude coordinates, degree-distance fixes,
or offsets from established routes or airways at a specified
distance and direction. Radar monitoring by ATC is required
on all random RNAV routes. Random RNAV routes can
only be approved in a radar environment. Factors that
are considered by ATC when approving random RNAV
routes include the capability to provide radar monitoring
and compatibility with traffic volume and flow. ATC radar
monitor each flight; however, navigation on the random
RNAV route is the responsibility of the pilot.
Pilots flying aircraft that are equipped with approved area
navigation equipment may file for RNAV routes throughout
the NAS and may be filed for in accordance with the
following procedures:
1. File airport-to-airport flight plans.
2. File the appropriate RNAV capability certification
suffix in the flight plan.
3. Plan the random route portion of the flight plan
to begin and end over appropriate arrival and
departure transition fixes or appropriate NAVAIDs
for the altitude stratum within which the flight is
conducted. The use of normal preferred DPs and
STAR, where established, is recommended.
4. File route structure transitions to and from the
random route portion of the flight.
5. Define the random route by waypoints. File route
description waypoints by using degree distance fixes
based on navigational aids that are appropriate for
the altitude stratum.
6. File a minimum of one route description waypoint
for each ARTCC through whose area the random
route is flown. These waypoints must be located
within 200 NM of the preceding center’s boundary.
7. File an additional route description waypoint for
each turnpoint in the route.
8. Plan additional route description waypoints as
required to ensure accurate navigation via the filed
route of flight. Navigation is the pilot’s responsibility
unless ATC assistance is requested.
9. Plan the route of flight so as to avoid prohibited and
restricted airspace by 3 NM unless permission has
been obtained to operate in that airspace and the
appropriate ATC facilities are advised.
Note: To be approved for use in the NAS, RNAV equipment
must meet the appropriate system availability, accuracy,
and airworthiness standards. For additional guidance
on equipment requirements, see Advisory Circular (AC)
20-138C, Airworthiness Approval of Positioning and
Navigation Systems. For airborne navigation database,
see AC 90-105, Approval Guidance for RNP Operations
and Barometric Vertical Navigation in the U.S. National
Airspace System.
Pilots flying aircraft that are equipped with latitude/
longitude coordinate navigation capability, independent
of VOR/ TACAN references, may file for random RNAV routes
at and above FL 390 within the conterminous United States
using the following procedures:
1. File airport-to-airport flight plans prior to departure.
2. File the appropriate RNAV capability certification
suffix in the flight plan.
3. Plan the random route portion of the flight to
begin and end over published departure/arrival
transition fixes or appropriate NAVAIDs for airports
without published transition procedures. The use of
preferred departure and arrival routes, such as DP
and STAR where established, is recommended.
4. Plan the route of flight so as to avoid prohibited and
restricted airspace by 3 NM unless permission has
been obtained to operate in that airspace and the
appropriate ATC facility is advised.
5. Define the route of flight after the departure fix,
including each intermediate fix (turnpoint) and
the arrival fix for the destination airport in terms
of latitude/longitude coordinates plotted to the
nearest minute or in terms of Navigation Reference
System (NRS) waypoints. For latitude/longitude
filing, the arrival fix must be identified by both the
latitude/ longitude coordinates and a fix identifier
as shown in the example below.
MIA1 SRQ2 3407/106153 3407/11546 TNP4 LAX5
1Departure airport
2Departure fix
3Intermediate fix (turning point)
4Arrival fix
5Destination airport
Or:
ORD1 IOW 2 KP49G 3 KD34U 4 KL16O 5 OAL6 MOD2 7
SFO8
1Departure airport
2Transition fix (pitch point)
3Minneapolis ARTCC waypoint
4Denver ARTCC waypoint
5Los Angeles ARTCC waypoint (catch point)
6Transition fix
7Arrival
8Destination airport
6. Record latitude/longitude coordinates by four
figures describing latitude in degrees and minutes
followed by a solidus and five figures describing
longitude in degrees and minutes.
7. File at FL 390 or above for the random RNAV portion
of the flight.
8. Fly all routes/route segments on Great Circle tracks.
9. Make any in-flight requests for random RNAV
clearances or route amendments to an en route ATC
facility.
Figure 2-46. Excerpt of authorized areas of en route operation.
SAMPLE NOT FOR ACTUAL USE
The 48 contiguous United
States and the District of
Columbia
Canada, excluding Canadian
MNPS airspace and the areas
of magnetic unreliability as
established in the Canadian
AIP
SPECIAL REQUIREMENTS:
Note 1 - B-737 Class II navigation operations with a single long-
range system is authorized only within this area of en route
operation.
Note 3 - Only B-747 and DC-10 operations authorized in these
areas.
Note 1
Note 3
Authorized areas of
en route operation
Limitations, provisions,
and reference paragraphs
Off-Airway Routes
14 CFR Part 95 prescribes altitudes governing the operation
of aircraft under IFR on Federal airways, jet routes, RNAV low
or high altitude routes, and other direct routes for which a
MEA is designated. In addition, it designates mountainous
areas and COPs. Off-airway routes are established in the
same manner and in accordance with the same criteria
as airways and jet routes. If a pilot flies for a scheduled air
carrier or operator for compensation or hire, any requests for
the establishment of off-airway routes are initiated by the
company through the principal operations inspector (POI)
who works directly with the company and coordinates FAA
approval. Air carrier authorized routes should be contained
in the company’s Operations Specifications (OpSpecs) under
the auspices of the air carrier operating certificate. [Figure
2-46]
Off-airway routes predicated on public navigation
facilities and wholly contained within controlled airspace
are published as direct Part 95 routes. Off-airway routes
predicated on privately owned navigation facilities or
not contained wholly within controlled airspace are
published as off-airway non-Part 95 routes. In evaluating
the adequacy of off-airway routes, the following items are
considered: the type of aircraft and navigation systems
used; proximity to military bases, training areas, low level
military routes; and the adequacy of communications
along the route.
Commercial operators planning to fly off-airway routes
should have specific instructions in the company’s
OpSpecs that address en route limitations and provisions
regarding en route authorizations to use the GPS or other
RNAV systems in the NAS. The company’s manuals and
checklists should include practices and procedures for
long-range navigation and training on the use of long
range navigation equipment. Minimum equipment lists
(MELs) and maintenance programs must address the long
range navigation equipment. Examples of other selected
areas requiring specialized en route authorization include
the following:
• Class I navigation in the United States Class A
airspace using area of long range navigation system.
• Class II navigation using multiple long range
navigation systems.
• Operations in central East Pacific airspace.
• North Pacific operations.
• Operations within North Atlantic (NAT) minimum
navigation performance specifications (MNPS)
airspace.
• Operations in areas of magnetic unreliability.
• North Atlantic operation (NAT/OPS) with two engine
aircraft under 14 CFR Part 121.
• Extended range operations (ER-OPS) with two
engine aircraft under 14 CFR Part 121.
• Special fuel reserves in international operations.
• Planned in-flight re-dispatch or re-release en route.
• Extended over water operations using a single long-
range communication system.
• Operations in reduced vertical separation minimum
(RVSM) airspace.
Off-Route Obstruction Clearance Altitude
An off-route obstruction clearance altitude (OROCA) is
an off-route altitude that provides obstruction clearance
with a 1,000-foot buffer in non-mountainous terrain areas
and a 2,000-foot buffer in designated mountainous areas
within the United States. This altitude may not provide
signal coverage from ground-based NAVAIDs, ATC radar,
or communications coverage. OROCAs are intended
primarily as a pilot tool for emergencies and SA. OROCAs
depicted on en route charts do not provide the pilot with
an acceptable altitude for terrain and obstruction clearance
for the purposes of off-route, random RNAV direct flights
in either controlled or uncontrolled airspace. OROCAs
are not subject to the same scrutiny as MEAs, minimum
vectoring altitude (MVAs), MOCAs, and other minimum IFR
altitudes. Since they do not undergo the same obstruction
evaluation, airport airspace analysis procedures, or
flight inspection, they cannot provide the same level of
confidence as the other minimum IFR altitudes.
When departing an airport VFR intending to or needing to
obtain an IFR clearance en route, you must be aware of the
position of your aircraft relative to terrain and obstructions.
When accepting a clearance below the MEA, MIA, MVA,
or the OROCA, you are responsible for your own terrain/
obstruction clearance until reaching the MEA, MIA, or MVA.
If unable to visually maintain terrain/obstruction clearance,
pilots should advise ATC and state intentions of the flight.
[Figure 2-47]
NOT FOR NAVIGATION
Figure 2-47. Off-route obstacle clearance altitude.
Figure 2-48. Random RNAV route.
For all random RNAV flights, there needs to be at least one
waypoint in each ARTCC area through which you intend
to fly. One of the biggest problems in creating an RNAV
direct route is determining if the route goes through special
use airspace. For most direct routes, the chances of going
through prohibited, restricted, or special use airspace
are good. In the United States, all direct routes should be
planned to avoid prohibited or restricted airspace by at
least 3 NM. If a bend in a direct route is required to avoid
special use airspace, the turning point needs to be part
of the flight plan. Two of the most prominent long range
navigation systems today include FMS with integrated GPS
and stand-alone GPS. The following example is a simplified
overview showing how the RNAV systems might be used
to fly a random RNAV route.
Shown in Figure 2-48, the aircraft is northeast of Tuba City
VORTAC at FL 200 using RNAV (showing both GPS and
FMS), RNAV direct on a southwesterly heading to Lindbergh
Regional Airport in Winslow. As the pilot is monitoring his
or her position and cross-checking the avionics against the
high altitude en route chart, he or she receives a company
message instructing to divert to Las Vegas, requiring a
change in the flight plan as highlighted on the depicted
chart excerpt.
During the flight deck review of the high and low altitude
en route charts, the pilot determines that the best course
of action is to fly direct to the MIRAJ waypoint, 28 DME
northeast of the Las Vegas VORTAC on the 045° radial. This
places the aircraft 193 NM out on a 259° magnetic course
inbound, and may help to avoid diverting north, allowing to
bypass the more distant originating and intermediate fixes
feeding into Las Vegas. The pilot requests an RNAV random
route clearance direct MIRAJ to expedite the flight. Denver
Center comes back with the following amended flight plan
and initial clearance into Las Vegas:
“Marathon five sixty four, turn right heading two six zero,
descend and maintain one six thousand, cleared present
position direct MIRAJ. ”
The latitude and longitude coordinates of the aircraft’s
present position on the high altitude chart is N36 19.10
and W110 40.24 as the course is changed. Notice the GPS
moving map (upper left), the FMS control display unit
(below the GPS), and FMS map mode navigation displays
(to the right of the GPS) as the flight is rerouted to Las Vegas.
For SA, the pilot makes note that the altitude is well above
any of the OROCAs on the direct route as the flight arrives
in the Las Vegas area using the low altitude chart.
Monitoring of Navigation Facilities
VOR, VORTAC, and instrument landing system (ILS) facilities,
as well as most NDBs and marker beacons installed by the
FAA, are provided with an internal monitoring feature.
Internal monitoring is provided at the facility through
the use of equipment that causes a facility shutdown if
performance deteriorates below established tolerances.
A remote status indicator also may be provided through
the use of a signal-sampling receiver, microwave link, or
telephone circuit. Older FAA NDBs and some non-Federal
NDBs do not have the internal feature, and monitoring is
accomplished by manually checking the operation at least
once each hour. FAA facilities, such as automated flight
service stations (AFSSs) and ARTCCs/sectors, are usually
the control point for NAVAID facility status. Pilots can query
the appropriate FAA facility if they have questions in flight
regarding NAVAID status, in addition to checking NOTAMs
prior to flight, since NAVAIDs and associated monitoring
equipment are continuously changing.
Navigational Gaps
A navigational course guidance gap, referred to as an
MEA gap, describes a distance along an airway or route
segment where a gap in navigational signal coverage
exists. The navigational gap may not exceed a specific
distance that varies directly with altitude, from 0 NM at sea
level to 65 NM at 45,000 feet MSL and not more than one
gap may exist in the airspace structure for the airway or
route segment. Additionally, a gap usually does not occur
at any airway or route turning point. To help ensure the
maximum amount of continuous positive course guidance
available when flying, there are established en route criteria
for both straight and turning segments. Where large gaps
exist that require altitude changes, MEA “steps” may be
established at increments of not less than 2,000 feet below
18,000 feet MSL, or not less than 4,000 feet at 18,000 MSL
and above, provided that a total gap does not exist for the
entire segment within the airspace structure. MEA steps are
limited to one step between any two facilities to eliminate
continuous or repeated changes of altitude in problem areas.
The allowable navigational gaps pilots can expect to see
are determined, in part, by reference to the graph depicted
in Figure 2-49. Notice the en route chart excerpt depicting
that the MEA is established with a gap in navigation signal
coverage northwest of the Carbon VOR/DME on V134. At
the MEA of 13,000, the allowable navigation course guidance
gap is approximately 18.5 NM, as depicted in Figure 2-49.
The navigation gap area is not identified on the chart
by distances from the navigation facilities. Proper flight
planning will help pilots prepare for MEA gaps by insuring
that appropriate maps are available as they may need
to dead reckon through the gap. Calculating the ground
track (with adjustments for winds) before and after the gap
will also help to stay on course when navigational course
guidance is not available.
NAVAID Accuracy Check
The CFRs and good judgment dictate that the equipment
of aircraft flying under IFR be within a specified tolerance
before taking off. When approved procedures are available,
they should be used for all equipment inspections.
VOR Accuracy
VOR accuracy can be checked by using any of the following
methods: VOR test facility signal (VOT), VOR checkpoint
signs, dual VOR check, or airborne VOR check.
VOT
The VOT is an approved test signal and is located on an
airport. This enables the pilot to check the VOR accuracy
from the flight deck before takeoff. Listed below are the
steps used for a VOT:
1. Tune the VOR receiver to the VOT frequency. VOT
frequencies can be found in the CS. [Figure 2-50]
These frequencies are coded with a series of Morse
code dots or a continuous 1020-cycle tone.
Sample: Enter with MEA of 13,000 feet. Read allowable gap 18.5 NM.
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Allowable navigation course guidance gap (NM)
NOT FOR
NAVIGATION
MEA of airway or route segment (thousands of feet)
Figure 2-49. Navigational course guidance gaps.
VOR test facilities (VOT)
Facility Name .............................. Type VOT
(Airport Name) ...........Frequency Facility Remarks
Bradlay Intl .................... 111.40 G
Bridgeport ..................... 109.25 G
Groton ........................... 110.25 G
Hartford ......................... 108.20 G
Figure 2-50. VOR test facilities (VOT) frequencies.
Figure 2-51. VOR checkpoint signs.
VOR 116.4
147° 4.1 NM
DME and VOR check radial
2. On the VOR, set the course selector to 0° and the
track bar (TB) indicator should read center. The TO
FROM indicator should read FROM.
3. Set the course selector to 180° and the TO-FROM
indicator should read TO and the TB should then be
centered.
Note: Determining the exact error in the receiver is done
by turning the track selector until the TB is centered and
noting the degrees difference between 180° or 0°. The
maximum bearing error with the VOT system check is plus
or minus 4° and apparent errors greater than 4° indicate
that the VOR receiver is beyond acceptable tolerance.
VOR Checkpoint Signs
Many aerodromes have VOR checkpoint signs that are
located beside the taxiways. [Figure 2-51] These signs
indicate the exact point on the aerodrome that there is
sufficient signal strength from a VOR to check the aircraft’s
VOR receiver against the radial designated on the sign.
Listed below are the steps to use at a VOR checkpoint:
1. Tune the proper VOR frequency.
2. Identify the VOR frequency.
3. Set the published radial on the course deviation fl
indicator (CDI). r
4. Confirm that the TB is centered. t
o5. Check the needle sensitivity by changing the
omnibearing select (OBS) 10° each way.
6. Set the reciprocal of the radial and check the TO TFROM flag change. n
7. The maximum permissible difference between f
aircraft equipment and the designated radial is 4° i
and 0.5 NM of the posted distance. s
Dual VOR Check
If a VOT or VOR checkpoint is not available and the aircraft is
equipped with dual VORs, the equipment may be checked
against one another by tuning both sets to the VOR facility
at the same time and noting the indicated bearings to that
station. [Figure 2-52] A difference greater than 4° between
the two VORs indicates that one of the receivers may be
out of tolerance.
Airborne VOR Check
OR equipment can also be checked for accuracy while in
ight b
y flying over a fix or landmark located on a published
adial and noting the indicated radial. Variances of more
han 6° from the published radial should be considered out
f tolerance and not be used for IFR navigation.
NDB Accuracy Check
he pilot must identify an NDB before using it for
aviga
tion, and continuously monitor it while using it
or an instrument approach. The lack of an IDENT may
ndicate that the NDB is out of service, even though it may
till be transmitting (for instance for maintenance or test
purposes). If an incorrect IDENT is heard, then the NDB
should not be used.
RNAV Accuracy Check
RNAV accuracy checks may differ depending on the
different type of equipment and manufacturer. When
available, all written procedures should be followed.
Figure 2-52. Instrument panel with dual VORs.