Air Traffic Control Clearances and Procedures
Anatomy of a clearance
Use the CRAFT mnemonic: Clearance limit, Route, Altitude, Frequency, Transponder. A clearance is not authority to deviate from a regulation; ATC cannot clear you below minimums or into unsafe conditions. Items that must be read back include altitudes, headings, radials, frequencies, runway assignments, hold-short instructions, and 'line up and wait.' 'Cleared as filed,' 'cleared direct,' and abbreviated clearances all have specific meanings you should be able to state precisely.
Key procedures
A void time means you must be airborne before it or obtain a new clearance. A cruise clearance authorizes descent to the minimum IFR altitude for the segment and, at the destination, an approach - no separate approach clearance is required. A 'cleared for the approach' issued with an altitude restriction obliges you to maintain that altitude until established on a published segment. Expect-further-clearance (EFC) times matter for fuel and for lost-communication planning. 'Expect' clearances are not clearances.
Worked example
'Citation 12AB, cleared for the ILS runway 27 approach, maintain 3,000 until established on the localizer, cleared for the approach.' You must read back the altitude and the approach clearance, hold 3,000 until the localizer is intercepted and you are established, then descend on the glideslope.
Trap: believing an approach clearance cancels a previously assigned altitude or authorizes descent below the DA/MDA; it does not. Another common trap is confusing an ODP with a SID - an ODP is flown only without a radar vector or SID.