Clearances

Definition

A clearance is an official instruction issued by Air Traffic Control (ATC) that authorizes an aircraft to proceed under specific conditions in controlled airspace. Receiving a clearance means the pilot is permitted to operate as instructed — but it does not relieve the pilot of responsibility for collision avoidance unless separation is explicitly provided (e.g., under IFR).

Types of Clearances

Type	Description	Example Phraseology
Start-up Clearance	Authorization to start engines (at large airports)	“Start-up approved for OE-ABC”
Taxi Clearance	Instructions for ground movement to runway or stand	“Taxi to holding point runway 27 via Alpha and Bravo”
Takeoff Clearance	Authorization to take off from a runway	“Runway 27, cleared for takeoff”
Landing Clearance	Permission to land	“Runway 08, cleared to land”
Enroute Clearance (IFR)	Full routing and level authorization for IFR flights	“Cleared to Salzburg via WPT1, climb FL90”
Approach Clearance	Authorization to commence an instrument or visual approach	“Cleared ILS approach runway 16”
Crossing Clearance	Permission to cross a runway, taxiway, or airspace sector	“Cross runway 34, report vacated”
Level or Climb/Descent Clearance	Instruction to change altitude or flight level	“Climb FL100” / “Descend 4000 ft QNH 1015”

Phraseology Patterns

Clearances must follow ICAO phraseology for clarity and legal validity. Key verbs include:

“Cleared” → Authorization to execute a specific procedure
“Taxi” → Movement on the ground
“Hold short” → Do not enter or cross specified area
“Line up” → Enter runway and hold position
“Contact” → Change frequency
“Report” → Provide specific information when condition is met

Readback Requirement

All ATC clearances must be read back verbatim by the pilot to confirm correct understanding. Controllers will correct any readback errors.

Example:
ATC: “OE-CVC, cleared to land runway 08, wind 090 degrees 6 knots”
Pilot: “Cleared to land runway 08, OE-CVC”

Conditional Clearances

Used when a clearance depends on a certain condition being met:

“Behind landing Cessna on final, line up and wait runway 27”
“After the crossing vehicle, taxi to holding point runway 22”

Important: The condition must be fulfilled before executing the clearance.

I am a new element

Clearance Limits

Some clearances (e.g., IFR) include a clearance limit — a point up to which the aircraft is authorized to proceed. The pilot must hold or request further clearance if unable to continue beyond that point.

Cancellation or Modification