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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