Contents:
   EN ROUTE OPERATIONS
---Flight standards are set by Title 14 of the Code of Federal Regulations (CFR)
---En route is segment from termination point of departure procedure to origination point of arrival procedure

EN ROUTE NAVIGATION
---National Airspace System (NAS) consists of lowest from base of controlled airspace to 18,000 MSL
---Second stratum extends from 18,000 MSL to Flight Level (FL) 450
---Third stratum extends from FL 450 and above is for random, point-to-point navigation
---Under IFR pilots must fly the center of airways or direct between navaids or fixes defining a route
---All restrictions allow traffic avoidance as necessary

AIR ROUTE TRAFFIC CONTROL CENTERS (ARTCC)
---Twenty ARTCCs have 20 to 80 sectors defined by traffic, airways and workload
---The Code of Federal Regulations (CFRs) require pilots to monitor appropriate frequencies
---National Aeronautical Charting Office (NACO) makes charts with Centers, Sectors and frequencies
---Flights are handed-off as passage requires to new frequency and sector.
---Controller gives the pilot the name of the agency, frequency required for handoff
---Pilot makes contact by naming the agency, aircraft call-sign, and altitude situation
---Charted frequencies can be used for ‘Pop-up' flight plan filing
---En route pilots are responsible for obstacle, traffic avoidance and situational awareness

PREFERRED IFR ROUTES
---Use of preferred routes as designed by ATC moves traffic ‘better' by avoiding high traffic areas
---Preferred routes seem designed for highest traffic situations to divert all neighboring traffic
---Present ARTCC system can predict congestion and choke points and hold traffic on the ground
---Preferred IFR routes are published in the A/FD
---Some preferred routes begin at a fix that you will get to by way of a vector
---The FAA computer will give you a preferred route whether you want it or not. so take it and change later
Notes:
---There are no preferred routes that take a flight even close to the San Francisco Class Bravo airspace
---Once into the preferred routing you should seek any ‘corner cutting' options on each handoff
---One way around areas such as the Los Angeles Basin is to file inside and amend out an edge route later
---I once filed an 80 mile direct flight through the basin that took 215 miles of routes and vectors.

SUBSTITUTE EN ROUTE FLIGHT PROCEDURES
---ARTCCs establish substitute airways and route segments when facilities are shutdown or fail.
---Scheduled shutdown of facilities is anticipated by NOTAM otherwise as required
---Substitute airways must be in controlled airspace and be flight inspected by FAA
---Minimum en route and maximum en route with temporary reporting points are provided and tested
---A minimum reception altitude (MRA) is determined for each temporary reporting point.

TOWER EN ROUTE CONTROL (TEC)
---If you can fly without using ARTCC you can file an IFR tower en route between city pairs far apart
---When on a TEC flight plan you remain in approach control airspace
---All tower en route city pairs are listed in the A/FD with direct routing between navaid facilities
---Coded identifiers for the route can be used instead of filing the route

AIRWAY AND ROUTE SYSTEM
---The present en route system is based on VHF airway/route navigation system

MONITORING OF NAVIGATION FACILITIES
---AFSS and ARTCC sectors determine the operational status of navigation facilities based on internal tests
---Prior to any flight, a pilot should check notices to airmen (NOTAMS) regarding performance of navaids

LOW FREQUENCY AIRWAYS/ROUTES (LF)
---In Alaska only
---Range does not have the line-of-sight limitation of VHF frequencies

VHF AIRWAYS/ROUTES
---May have Maximum Authorized Altitudes because of radio limitations
---The Change Over Point (COP) between VHF navaids is midway unless otherwise charted

VHF EN ROUTE OBSTACLE CLEARANCE AREAS
---Obstacle clearance areas for the en route flight are identified as primary, secondary and turning areas
---Navigation airway is 4.5 or 6.7 NM to each side based upon factors of accuracy and probability
---The accuracy is 4.5 degrees out to 51 miles 95% of the time meaning 5% of the time you exceed 4nm
---The accuracy is 6.7 degrees out to 51 miles 99% of the time when airway is 12 miles wide.

PRIMARY AREA
---The primary obstacle clearance area of an airway is 4 NM to each side of center 1000' above obstacles
---Differences is clearance areas exist where a dogleg occurs or Change Over Points (COP) are unequal
--- In mountainous areas (actually hilly) the obstacle clearance area is 2000' above obstacles
---In some locations the 2000' may be reduced to 1700' or even 1500'
---Precipitous terrain
---Weather phenomena
---Pressure differentials
---Type and distance between navaids
---Weather services
---Altimeter setting accuracy
---1000' over manmade obstacles if not subject to low pressure Bernoulli Effect

SECONDARY AREA
---Extends 2NM beyond 8NM primary area to each side giving total of 6NM each side of center line
---The secondary obstacle clearance plane begins at a point 500' above the obstacle basis for the primary area and angles out for two miles and up another 500 feet. Draw it to see it.
---Pilots are expected to lead turns before a fix (Figure 3-13)

NAVAID SERVICE VOLUME
---The use of the term volume is a GovSpeak misleading and potentially dangerous way of saying how far a radio signal may be used. They think of radio signals as being in a cylinder. Do you?
---Maximum distances vary with altitude and obstacles obstructing line of sight signals
---12000 and below (terminal facilities) 50NM
---Below 18000 80NM
---14500 to 17999 200NM
---18000 to FL 450 260NM
---Above FL450 200NM
---If cleared to a facility beyond your range by ATC they will monitor your flight with radar

NAVIGATIONAL GAPS

---Exist called MEA gap can still be approved for a distance related to altitude with one gap per airway
---MEA steps are limited to one step between facilities
---A navigational gap is not identified on the chart by distances from navaids

CHANGE OVER POINTS (COP)
---Normal COP is midway between navaids unless otherwise depicted on chart with numerical legs
---The COP assures navaid reception at IFR minimum altitude
---The COP affects the primary and secondary obstacle clearance areas
---Offset COP and dogleg segments of airways result in a flare in the width at the COP

IFR EN ROUTE ALTITUDES
---Altitudes selected for adequate signal to keep flight within route widths
---IFR FARs requires that pilots fly at or above IFR minimum altitudes on IFR flights
---Mountainous areas require IFR flight 2000' above the obstacle within 4NM of airway centerline
---Non-mountainous areas minimum IFR altitude is1000' above any obstacle within 4NM centerline
---Exception: Within 22NM of VOR pilot can fly down to Minimum Obstacle Clearance Altitude (MOCA)
---Climbing to higher Minimum IFR Altitude (MIA) must begin at the first point that is higher.
---When obstruction exists begin climb so as to get vertical separation from terrain
---The Minimum Crossing Altitude (MCA) applies to the VOR point as published
---On an IFR flight and cleared to VFR on top flight at or above minimum IFR altitudes must be maintained
---Minimum IFR altitudes apply to all IFR flights regardless of weather conditions

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