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AIM

10/12/17

4

−4−8

ATC Clearances and Aircraft Separation

numbers is restricted to turbojet aircraft with Mach
meters.

c.

Pilots complying with speed adjustments are

expected to maintain a speed within plus or minus
10 knots or 0.02 Mach number of the specified speed.

d.

When ATC assigns speed adjustments, it will

be in accordance with the following recommended
minimums:

1.

To aircraft operating between FL 280 and

10,000 feet, a speed not less than 250 knots or the
equivalent Mach number.

NOTE

1. On a standard day the Mach numbers equivalent to
250 knots CAS (subject to minor variations) are:
FL 240

−0.6

FL 250

−0.61

FL 260

−0.62

FL 270

−0.64

FL 280

−0.65

FL 290

−0.66.

2. When an operational advantage will be realized, speeds
lower than the recommended minima may be applied.

2.

To arriving turbojet aircraft operating below

10,000 feet:

(a)

A speed not less than 210 knots, except;

(b)

Within 20 flying miles of the airport of

intended landing, a speed not less than 170 knots.

3.

To arriving reciprocating engine or turboprop

aircraft within 20 flying miles of the runway
threshold of the airport of intended landing, a speed
not less than 150 knots.

4.

To departing aircraft:

(a)

Turbojet aircraft, a speed not less than

230 knots.

(b)

Reciprocating engine aircraft, a speed not

less than 150 knots.

e.

When ATC combines a speed adjustment with

a descent clearance, the sequence of delivery, with the
word “then” between, indicates the expected order of
execution.

EXAMPLE

1. Descend and maintain (altitude); then, reduce speed to
(speed).

2. Reduce speed to (speed); then, descend and maintain
(altitude).

NOTE

The maximum speeds below 10,000 feet as established in
14 CFR Section 91.117 still apply. If there is any doubt
concerning the manner in which such a clearance is to be
executed, request clarification from ATC.

f.

If ATC determines (before an approach

clearance is issued) that it is no longer necessary to
apply speed adjustment procedures, they will:

1.

Advise the pilot to “resume normal speed.”

Normal speed is used to terminate ATC assigned
speed adjustments on segments where no published
speed restrictions apply. It does not cancel published
restrictions on upcoming procedures. This does not
relieve the pilot of those speed restrictions which are
applicable to 14 CFR Section 91.117.

EXAMPLE

(An aircraft is flying a SID with no published speed
restrictions. ATC issues a speed adjustment and instructs
the aircraft where the adjustment ends): “Maintain two two
zero knots until BALTR then resume normal speed.”

NOTE

The ATC assigned speed assignment of two two zero knots
would apply until BALTR. The aircraft would then resume
a normal operating speed while remaining in compliance
with 14 CFR Section 91.117.

2.

Instruct pilots to “comply with speed

restrictions” when the aircraft is joining or resuming
a charted procedure or route with published speed
restrictions.

EXAMPLE

(ATC vectors an aircraft off of a SID to rejoin the procedure
at a subsequent waypoint. When instructing the aircraft to
resume the procedure, ATC also wants the aircraft to
comply with the published procedure speed restrictions):
“Resume the SALTY ONE departure. Comply with speed
restrictions.”

CAUTION

The phraseology “Descend via/Climb via SID” requires
compliance with all altitude and/or speed restrictions
depicted on the procedure.

3.

Instruct the pilot to “resume published

speed.” Resume published speed is issued to
terminate a speed adjustment where speed restric-
tions are published on a charted procedure.

NOTE

When instructed to “comply with speed restrictions” or to
“resume published speed,” ATC anticipates pilots will
begin adjusting speed the minimum distance necessary
prior to a published speed restriction so as to cross the
waypoint/fix at the published speed. Once at the published