4/20/23
AIM
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 Equipment, 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
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 determines 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.
En Route Procedures
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