Enroute Charts, Procedures and Holding

Enroute Ops
Enroute phase defined:
From the termination of the DP to the origin of the arrival procedure
There are a couple of ways to get there
Along victor airways
Direct routing from fix to fix

Vertical Airway Structure
Low altitude airways
Victor airways 1200 agl up to but not including 18,000 msl
High altitude airways
Jet routes 18,000 msl to 45,000 msl
Which are actually pressure alititudes because at FL180 you reset to 29.92
Above 45,000
Random operations

Air Route Traffic Control Center (ARTCC)
These are the centers that handle enroute
21 of them

Separation Standards
5 miles
1,000 if below FL290
2,000 if at or above FL290

Preferred IFR Routes
Usually connect the busier airports
Listed in the AFD
The DPs and arrivals usually hook up at both ends
They are available for both Victor airways and Jet routes
The object of this system is to speed traffic movement especially during busy times

Substitute Airways
Some places have planned routes for VOR outages

Tower Enroute Control
Usually applies to traffic below 10,000 feet
Established where busy airports are close to each other
Instead of being handed off to Center, Approach control hands off to Approach control
Descriptions are in the AFD
The Approach Control Area
The route
Highest altitude

Airway Route System
3 types of airways:

Airway Route System
3 different charts:
IFR enroute low altitude chart
IFR enroute high altitude chart
Terminal Area chart

Airway Route System
IFR low enroute charts
Published every 56 days

Low Enroute Chart
Minimum Enroute Altitude (MEA) –The lowest published altitude between radio fixes which assures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes. The MEA prescribed for a Federal airway or segment thereof, area navigation low or high route, or other direct route applies to the entire width of the airway, segment, or route between the radio fixes defining the airway, segment, or route.
Minimum Obstruction Clearance Altitude (MOCA)- The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments which meets obstacle clearance requirements for the entire route segment and which assures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR.
Minimum Crossing Altitude (MCA)- The lowest altitude at certain fixes at which an aircraft must cross when proceeding in the direction of a higher minimum en route IFR altitude (MEA).
Minimum Reception Altitude (MRA)- The lowest altitude at which an intersection can be determined.
Maximum Authorized Altitude (MAA)- A published altitude representing the maximum usable altitude or flight level for an airspace structure or route segment. It is the highest altitude on a Federal airway, jet route, area navigation low or high route, or other direct route for which an MEA is designated in 14 CFR Part 95 at which adequate reception of navigation aid signals is assured.
Off Route Obstruction Clearance Altitude (OROCA)- An off-route altitude which provides obstruction clearance with a 1,000 foot buffer in nonmountainous 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 navigational aids, air traffic control radar, or communications coverage.

Low Enroute Chart
Minimum Turning Altitude (MTA)- provides vertical and lateral obstruction clearance based on turn criteria over fixes, navaids, waypoints and charted route segments. Provides obstacle clearance for both turn anticipation and flyover protection by extending the primary and secondary obstacle clearance areas
Minimum IFR Altitude (MIA)- Minimum altitudes for IFR operations as prescribed in 14 CFR Part 91. These altitudes are published on aeronautical charts and prescribed in 14 CFR Part 95 for airways and routes, and in 14 CFR Part 97 for standard instrument approach procedures. If no applicable minimum altitude is prescribed in 14 CFR Part 95 or 14 CFR Part 97, the following minimum IFR altitude applies:
a. In designated mountainous areas, 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or
b. Other than mountainous areas, 1,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or c. As otherwise authorized by the Administrator or assigned by ATC.
Minimum Vectoring Altitude (MVA)- The lowest MSL altitude at which an IFR aircraft will be vectored by a radar controller, except as otherwise authorized for radar approaches, departures, and missed approaches. The altitude meets IFR obstacle clearance criteria. It may be lower than the published MEA along an airway or J-route segment. It may be utilized for radar vectoring only upon the controller’s determination that an adequate radar return is being received from the aircraft being controlled. Charts depicting minimum vectoring altitudes are normally available only to the controllers and not to pilots.

Low Enroute Chart
MEA change
Change over points
Mileage breakdown
Airway distance
Fix distance
DME distance
Blue airports
Green airports
Brown airports
Class C airspace

Low Enroute Chart
RNAV routes in blue
Denoted with a T
MEA for GNSS denoted with a G
8 NM wide
Expand at 4.5 degrees from origin
This means at 51 miles they become wider than 8 NM
VOR equipment check tolerance
360-179 odd thousands
180-359 even thousands
This gives 1000 feet vertical separation up to FL290
Above FL290 2,000 feet vertical separation
Except in the case of reduced vertical separation minima then it’s 1,000
The aircraft has to be equipped to take advantage of this reduced separation
LF airways expand at 5 degrees
At 49.6 miles they get wider

Primary obstacle clearance area is 8 NM
1,000 feet above the highest terrain in non-mountainous
2,000 feet above the highest terrain in mountainous
Secondary obstacle clearance area is 2 NM beyond the 8 NM
Secondary area extends 6.7 degrees from origin
Slants up starting 500 feet below the MEA and extends out to the boundary of the secondary area

Airway Route System
IFR high enroute altitude charts

High Enroute Chart
At and above FL180
Jet routes
RNAV Q routes

Airway Route System
Rules for off airway nav using navaids
Below 18,000 no more than 80NM apart
14,500 to 17,999 using H VORs in the conterminous US 200NM
18,000 to FL450 not more than 260NM
Above FL450 not more than 200NM
Off airway using RNAV
Have to be in radar contact
Pilot takes responsibility for navigation
Pilot must adhere to obstruction clearances

Random RNAV Routes
Rules for off airway random routes
File airport to airport
Appropriate suffix code
Begin at the end of the DP
End at the beginning of the arrival procedure
File for the SID or STAR
Define route by waypoints
Have at least 1 waypoint in each Center sector within 200NM from the boundary
Waypoint at each turn
Use as many waypoints as necessary to ensure accurate nav
Avoid prohibited and restricted airspace by 3NM

There are 2 types published
Fly-by waypoints
Fly-over waypoints

User defined waypoints
Communicated to ATC as radial and distance from nearest navaid or
Phantom waypoints
Old RNAV systems
Frequency, radial and distance
Floating waypoints
Usually for ATC purposes
ATC metering
Holding points
RNAV direct routing
Gateway waypoints
STAR origination points

Computer Navigation Fix
These are named using letters and numbers
They appear on approaches but not on the enroute charts
Sometimes denoted with an x
They include:
Unamed DME fixes
Beginning and ending points of DME arcs
Some FAFs on GPS overlay approaches

Required Navigation Performance
Has on-board alerting and monitoring to make sure its nav performance is being met
Allows for less separation
Allows you to fly curved approaches

Reduced Vertical Separation Minimums
Applies to flights between FL240 and FL410
Reduced to 1,000 feet vertical separation
Have to have certified altimeter and autopilot

Cruise Clearance
CRUISE- Used in an ATC clearance to authorize a pilot to conduct flight at any altitude from the minimum IFR altitude up to and including the altitude specified in the clearance. The pilot may level off at any intermediate altitude within this block of airspace. Climb/descent within the block is to be made at the discretion of the pilot. However, once the pilot starts descent and verbally reports leaving an altitude in the block, he/she may not return to that altitude without additional ATC clearance. Further, it is approval for the pilot to proceed to and make an approach at destination airport and can be used in conjunction with:
a. An airport clearance limit at locations with a standard/special instrument approach procedure. The CFRs require that if an instrument letdown to an airport is necessary, the pilot shall make the letdown in accordance with a standard/special instrument approach procedure for that airport, or
b. An airport clearance limit at locations that are within/below/outside controlled airspace and without a standard/special instrument approach procedure. Such a clearance is NOT AUTHORIZATION for the pilot to descend under IFR conditions below the applicable minimum IFR altitude nor does it imply that ATC is exercising control over aircraft in Class G airspace; however, it provides a means for the aircraft to proceed to destination airport, descend, and land in accordance with applicable CFRs governing VFR flight operations. Also, this provides search and rescue protection until such time as the IFR flight plan is closed.


  • žRequested by the pilot
  • žAllows the pilot to select altitudes (within reason)
  • —should still report changes to ATC
  • žMust maintain VFR altitude, cloud and visibility rules
  • žMust maintain IFR course and altitude minimums
  • žPilot assumes responsibility for traffic separation
  • žFile VFR-On-Top in altitude block of flight plan


Lowest Usable Flight Level
To ensure separation from the low altitude structure the lowest altitude is limited based on altimeter setting for that area
91.159 and 91.177

Enroute Reporting
Compulsory Reporting Points
When not in radar contact, you must report over fixes depicted on the Low Enroute chart
If on a direct airway report the fixes used to define the route
If reporting over a VOR the time is the first full reversal of the TO/FROM flag
Same with ADF
For a marker, take your time when first getting the signal then take your time losing the signal divide take the mean of those 2 times

Position Reporting Items
Type of flight plan
Eta to next fix
Name of next fix

13 Required Reports
AIM 5-3-2, 5-3-3
Memorize them babies

Communication Failure
FAR 91.185, AIM 6-4-1
If you’re VFR remain VFR and land as soon as practical
Even if your in Class A
If you’re IFR, continue the flight
(a) Route.
(1) By the route assigned in the last ATC clearance received;
(2) If being radar vectored, by the direct route from the point of radio failure to the fix, route, or airway specified in the vector clearance;
(3) In the absence of an assigned route, by the route that ATC has advised may be expected in a further clearance; or
(4) In the absence of an assigned route or a route that ATC has advised may be expected in a further clearance by the route filed in the flight plan.
(b) Altitude. At the HIGHEST of the following altitudes or flight levels FOR THE ROUTE SEGMENT BEING FLOWN:
(1) The altitude or flight level assigned in the last ATC clearance received;
(2) The minimum altitude (converted, if appropriate, to minimum flight level as prescribed in 14 CFR Section 91.121(c)) for IFR operations; or
(3) The altitude or flight level ATC has advised may be expected in a further clearance.

Communications Failure
7600 on the transponder
Try the last working frequency
Try 121.5
Monitor the closest VOR, they may talk to you that way

Communications Failure
Leaving the clearance limit 91.185
(i) When the clearance limit is a fix from which an approach begins, commence descent or descent and approach as close as possible to the expect-further-clearance time if one has been received, or if one has not been received, as close as possible to the estimated time of arrival as calculated from the filed or amended (with ATC) estimated time en route.
(ii) If the clearance limit is not a fix from which an approach begins, leave the clearance limit at the expect-further-clearance time if one has been received, or if none has been received, upon arrival over the clearance limit, and proceed to a fix from which an approach begins and commence descent or descent and approach as close as possible to the estimated time of arrival as calculated from the filed or amended (with ATC) estimated time enroute.

Leaving the Clearance Limit
Climbing and Descending
Start right away after getting the clearance
Exception: Pilot Discretion
Start when you want
Use a climb rate you want
You may temporarily level off
Although once you vacate an altitude you can’t go back
Normal climb
Climb at optimal rate until 1,000 feet below assigned altitude then use between 500 and 1500 fpm
Expedited climb
Request by ATC, use Vy
If you get a new altitude without the “expedite” then it’s canceled

The inbound to the fix coincides with the direction you are headed
Terrain separation is similar to the airway
1,000 feet of separation in the primary
500 feet tapering to 0 in the secondary

An ATC clearance requiring holding will include a few things:
1. Direction of holding from the fix in terms of the eight cardinal compass points (i.e., N, NE, E, SE, etc.).
2. Holding fix (the fix may be omitted if included at the beginning of the transmission as the clearance limit).
3. Radial, course, bearing, airway or route on which the aircraft is to hold.
4. Leg length in miles if DME or RNAV is to be used (leg length will be specified in minutes on pilot request or if the controller considers it necessary).
5. Direction of turn if left turns are to be made, the pilot requests, or the controller considers it necessary.
6. Time to expect further clearance and any pertinent additional delay information.

Usually get holding instructions at least 5 minutes before the clearance limit
If you’re within 3 minutes and have no further clearance call them
If the hold is not charted you should get the full holding instructions
Sundowner 60501 hold SE of Pelly on the 144 mag bearing from, expect further clearance 22:45 or sooner at pilot request
SE is the direction the 144 bearing is from Pelly, not the direction of the hold
The EFC is in case of lost comm
In those cases plan to leave the fix as close as possible to the EFC time
Standard holding patterns are right turns
So if no direction is indicated you are expected to know to do right turns

Some holding patterns are charted on the Low Enroute charts
If none is charted and you have no clearance you are expected to hold on the inbound course using right turns
You can be asked to hold at any fix or navaid at any time

Within 3 minutes or less start the speed reduction if needed
Some patterns have a speed published

At or below 14,000 1 minute inbound
Above 14,000 1 ½ minutes inbound
Timing for the outbound leg begins abeam the fix or wings level if you can not determine when you are abeam
Upon entry, the initial leg outbound should be flown 1 minute then adjusted based on your inbound leg time
DME and GPS holding gives distances in NM of the legs instead of minutes

Make all turns standard rate, 30 degrees or 25 degrees with a flight director, whichever is less
Triple your wind correction outbound
Use your heading to determine entry +-5 degrees

Holding pattern entry procedures:
(a) Parallel Procedure. When approaching the holding fix from anywhere in sector (a), the parallel entry procedure would be to turn to a heading to parallel the holding course outbound on the nonholding side for one minute, turn in the direction of the holding pattern through more than 180 degrees, and return to the holding fix or intercept the holding course inbound.
(b) Teardrop Procedure. When approaching the holding fix from anywhere in sector (b), the teardrop entry procedure would be to fly to the fix, turn outbound to a heading for a 30 degree teardrop entry within the pattern (on the holding side) for a period of one minute, then turn in the direction of the holding pattern to intercept the inbound holding course.
(c) Direct Entry Procedure. When approaching the holding fix from anywhere in sector (c), the direct entry procedure would be to fly directly to the fix and turn to follow the holding pattern.

žFor The Quiz

  • žThere will be a couple of low enroute charts, so study the map legend
  • žKnow your definitions
  • žKnow your lost comm stuff
  • žknow about change over points
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