AIM

8/15/19

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En Route Procedures

pilot can resolve. Some variables which must be
considered are turn radius, wind effect, airspeed,
degree of turn, and cockpit instrumentation. An early
turn, as illustrated below, is one method of adhering
to airways or routes. The use of any available cockpit
instrumentation, such as Distance Measuring Equip-
ment, may be used by the pilot to lead the turn when
making course changes. This 

is consistent

 with the

intent of 14 CFR Section 91.181, which requires
pilots to operate along the centerline of an airway and
along the direct course between navigational aids or
fixes.

b.

Turns which begin at or after fix passage may

exceed airway or route boundaries. FIG 5

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contains an example flight track depicting this,
together with an example of an early turn.

c.

Without such actions as leading a turn, aircraft

operating in excess of 290 knots true air speed (TAS)
can exceed the normal airway or route boundaries
depending on the amount of course change required,
wind direction and velocity, the character of the turn
fix (DME, overhead navigation aid, or intersection),
and the pilot’s technique in making a course change.
For example, a flight operating at 17,000 feet MSL
with a TAS of 400 knots, a 25 degree bank, and a
course change of more than 40 degrees would exceed
the width of the airway or route; i.e., 4 nautical miles
each side of centerline. However, in the airspace
below 18,000 feet MSL, operations in excess of
290 knots TAS are not prevalent and the provision of
additional IFR separation in all course change
situations for the occasional aircraft making a turn in
excess of 290 knots TAS creates an unacceptable
waste of airspace and imposes a penalty upon the
preponderance of traffic which operate at low speeds.
Consequently, the FAA expects pilots to lead turns
and take other actions they consider necessary during
course changes to adhere as closely as possible to the
airways or route being flown.

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6. Changeover Points (COPs)

a.

COPs are prescribed for Federal airways, jet

routes, area navigation routes, or other direct routes
for which an MEA is designated under 14 CFR
Part 95. The COP is a point along the route or airway
segment between two adjacent navigation facilities or
waypoints where changeover in navigation guidance
should occur. At this point, the pilot should change

navigation receiver frequency from the station
behind the aircraft to the station ahead.

b.

The COP is normally located midway between

the navigation facilities for straight route segments,
or at the intersection of radials or courses forming a
dogleg in the case of dogleg route segments. When
the COP is NOT located at the midway point,
aeronautical charts will depict the COP location and
give the mileage to the radio aids.

c.

COPs are established for the purpose of

preventing loss of navigation guidance, to prevent
frequency interference from other facilities, and to
prevent use of different facilities by different aircraft
in the same airspace. Pilots are urged to observe COPs
to the fullest extent.

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7. Minimum Turning Altitude (MTA)

Due to increased airspeeds at 10,000 ft MSL or above,
the published minimum enroute altitude (MEA) may
not be sufficient for obstacle clearance when a turn is
required over a fix, NAVAID, or waypoint. In these
instances, an expanded area in the vicinity of the turn
point is examined to determine whether the published
MEA is sufficient for obstacle clearance. In some
locations (normally mountainous), terrain/obstacles
in the expanded search area may necessitate a higher
minimum altitude while conducting the turning
maneuver. Turning fixes requiring a higher minimum
turning altitude (MTA) will be denoted on
government charts by the minimum crossing altitude
(MCA) icon (“x” flag) and an accompanying note
describing the MTA restriction. An MTA restriction
will normally consist of the air traffic service (ATS)
route leading to the turn point, the ATS route leading
from the turn point, and the required altitude; e.g.,
MTA V330 E TO V520 W 16000. When an MTA is
applicable for the intended route of flight, pilots must
ensure they are at or above the charted MTA not later
than the turn point and maintain at or above the MTA
until joining the centerline of the ATS route following
the turn point. Once established on the centerline
following the turning fix, the MEA/MOCA deter-
mines the minimum altitude available for
assignment. An MTA may also preclude the use of a
specific altitude or a range of altitudes during a turn.
For example, the MTA may restrict the use of 10,000
through 11,000 ft MSL. In this case, any altitude
greater than 11,000 ft MSL is unrestricted, as are
altitudes less than 10,000 ft MSL provided
MEA/MOCA requirements are satisfied.