9/5/24
AIM
b.
ATC will express all speed adjustments in terms of knots based on indicated airspeed (IAS) in 5 or 10 knot
increments except that at or above FL 240 speeds may be expressed in terms of Mach numbers in
0.01 increments. The use of Mach numbers is restricted to aircraft with Mach meters.
c.
Pilots complying with speed adjustments (published or assigned) 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
FL 260
FL 270
FL 280
FL 290
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.
ATC Clearances and Aircraft Separation
4
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4
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