Aeronautical Information Manual (AIM), page 362

Index   361 -- Page 362 -- 363


aged due to increased workload for pilots to reprogram the
navigation system.

f. An RF leg is defined as a constant radius circular

path around a defined turn center that starts and ter-

minates at a fix. An RF leg may be published as part
of a procedure. Since not all aircraft have the capabil-
ity to fly these leg types, pilots are responsible for
knowing if they can conduct an RNAV approach with
an RF leg. Requirements for RF legs will be indicated
on the approach chart in the notes section or at the
applicable initial approach fix. Controllers will clear
RNAV-equipped aircraft for instrument approach
procedures containing RF legs:

1. Via published transitions, or

2. In accordance with paragraph e6 above, and

3. ATC will not clear aircraft direct to any

waypoint beginning or within an RF leg, and will not

assign fix/waypoint crossing speeds in excess of
charted speed restrictions.
Controllers will not clear aircraft direct to THIRD because
that waypoint begins the RF leg, and aircraft cannot be
vectored or cleared to TURNN or vectored to intercept the
approach segment at any point between THIRD and
FORTH because this is the RF leg. (See FIG 5-4-14.)
g. When necessary to cancel a previously issued
approach clearance, the controller will advise the pi-
lot "Cancel Approach Clearance" followed by any
additional instructions when applicable.

5-4-7. Instrument Approach Procedures

a. Aircraft approach category means a grouping of
aircraft based on a speed of VREF, if specified, or if
VREF is not specified, 1.3 VSO at the maximum
certified landing weight. V REF, V SO , and the
maximum certified landing weight are those values as
established for the aircraft by the certification
authority of the country of registry. A pilot must use
the minima corresponding to the category determined
during certification or higher. Helicopters may use
Category A minima. If it is necessary to operate at a
speed in excess of the upper limit of the speed range
for an aircraft's category, the minimums for the
higher category must be used. For example, an
airplane which fits into Category B, but is circling to
land at a speed of 145 knots, must use the approach

Category D minimums. As an additional example, a
Category A airplane (or helicopter) which is
operating at 130 knots on a straight-in approach must

use the approach Category C minimums. See the

following category limits:

1. Category A: Speed less than 91 knots.

2. Category B: Speed 91 knots or more but less
than 121 knots.

3. Category C: Speed 121 knots or more but
less than 141 knots.

4. Category D: Speed 141 knots or more but
less than 166 knots.

5. Category E: Speed 166 knots or more.

VREF in the above definition refers to the speed used in

establishing the approved landing distance under the
airworthiness regulations constituting the type
certification basis of the airplane, regardless of whether
that speed for a particular airplane is 1.3 VSO, 1.23 VSR, or
some higher speed required for airplane controllability.
This speed, at the maximum certificated landing weight,
determines the lowest applicable approach category for
all approaches regardless of actual landing weight.
b. When operating on an unpublished route or
while being radar vectored, the pilot, when an
approach clearance is received, must, in addition to
complying with the minimum altitudes for IFR
operations (14 CFR Section 91.177), maintain the
last assigned altitude unless a different altitude is
assigned by ATC, or until the aircraft is established on
a segment of a published route or IAP. After the
aircraft is so established, published altitudes apply to
descent within each succeeding route or approach
segment unless a different altitude is assigned by
ATC. Notwithstanding this pilot responsibility, for
aircraft operating on unpublished routes or while
being radar vectored, ATC will, except when
conducting a radar approach, issue an IFR approach
clearance only after the aircraft is established on a
segment of a published route or IAP, or assign an
altitude to maintain until the aircraft is established on
a segment of a published route or instrument
approach procedure. For this purpose, the procedure
turn of a published IAP must not be considered a
segment of that IAP until the aircraft reaches the
initial fix or navigation facility upon which the
procedure turn is predicated.

5-4-26 Arrival Procedures

Page 362 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   361 -- Page 362 -- 363