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AIM

10/12/17

4−4−5

ATC Clearances and Aircraft Separation

routing and an alternative clearance if VFR−on−top

is not reached by a specified altitude.

c. A pilot on an IFR flight plan, operating in VFR

conditions, may request to climb/descend in VFR

conditions.

d. ATC may not authorize VFR−on−top/VFR

conditions operations unless the pilot requests the

VFR operation or a clearance to operate in VFR

conditions will result in noise abatement benefits

where part of the IFR departure route does not

conform to an FAA approved noise abatement route

or altitude.

e. When operating in VFR conditions with an ATC

authorization to “maintain VFR−on−top/maintain

VFR conditions” pilots on IFR flight plans must:

1. Fly at the appropriate VFR altitude as

prescribed in 14 CFR Section 91.159.

2. Comply with the VFR visibility and distance

from cloud criteria in 14 CFR Section 91.155 (Basic

VFR Weather Minimums).

3. Comply with instrument flight rules that are

applicable to this flight; i.e., minimum IFR altitudes,

position reporting, radio communications, course to

be flown, adherence to ATC clearance, etc.

NOTE−

Pilots should advise ATC prior to any altitude change to

ensure the exchange of accurate traffic information.

f. ATC authorization to “maintain VFR−on−top”

is not intended to restrict pilots so that they must

operate only above an obscuring meteorological

formation (layer). Instead, it permits operation above,

below, between layers, or in areas where there is no

meteorological obscuration. It is imperative, howev-

er, that pilots understand that clearance to operate

“VFR−on−top/VFR conditions” does not imply

cancellation of the IFR flight plan.

g. Pilots operating VFR−on−top/VFR conditions

may receive traffic information from ATC on other

pertinent IFR or VFR aircraft. However, aircraft

operating in Class B airspace/TRSAs must be

separated as required by FAA Order JO 7110.65,

Air Traffic Control.

NOTE−

When operating in VFR weather conditions, it is the pilot’s

responsibility to be vigilant so as to see−and−avoid other

aircraft.

h. ATC will not authorize VFR or VFR−on−top

operations in Class A airspace.

REFERENCE−

AIM, Paragraph 3−2−2 , Class A Airspace

4−4−9. VFR/IFR Flights

A pilot departing VFR, either intending to or needing

to obtain an IFR clearance en route, must be aware of

the position of the aircraft and the relative

terrain/obstructions. When accepting a clearance

below the MEA/MIA/MVA/OROCA, pilots are

responsible for their own terrain/obstruction clear-

ance until reaching the MEA/MIA/MVA/OROCA. If

pilots are unable to maintain terrain/obstruction

clearance, the controller should be advised and pilots

should state their intentions.

NOTE−

OROCA is an off−route altitude which provides obstruc-

tion clearance with a 1,000 foot buffer in nonmountainous

terrain areas and a 2,000 foot buffer in designated

mountainous areas within the U.S. This altitude may not

provide signal coverage from ground−based navigational

aids, air traffic control radar, or communications

coverage.

4−4−10. Adherence to Clearance

a. When air traffic clearance has been obtained

under either visual or instrument flight rules, the

pilot−in−command of the aircraft must not deviate

from the provisions thereof unless an amended

clearance is obtained. When ATC issues a clearance

or instruction, pilots are expected to execute its

provisions upon receipt. ATC, in certain situations,

will include the word “IMMEDIATELY” in a

clearance or instruction to impress urgency of an

imminent situation and expeditious compliance by

the pilot is expected and necessary for safety. The

addition of a VFR or other restriction; i.e., climb or

descent point or time, crossing altitude, etc., does not

authorize a pilot to deviate from the route of flight or

any other provision of the ATC clearance.

b. When a heading is assigned or a turn is

requested by ATC, pilots are expected to promptly

initiate the turn, to complete the turn, and maintain the

new heading unless issued additional instructions.

c. The term “AT PILOT’S DISCRETION”

included in the altitude information of an ATC

clearance means that ATC has offered the pilot the

option to start climb or descent when the pilot wishes,