Runway: ATC Glossary

A glossary of common ATC terms, abbreviations and concepts.

Browse the glossary using this index

Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O
P | Q | R | S | T | U | V | W | X | Y | Z | ALL

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ALL

A

Aircraft Performance Category

The following extract from AIP explains the aircraft performance categories. This is provided for your awareness but is not assessed.

AIP ENR 1.5.1.2.1
The following categories, based upon V_at (except for CAT H), determine landing minima for aircraft:
CAT A speeds up to 90KT IAS.
CAT B speeds from 91KT to 120KT IAS.
CAT C speeds from 121KT to 140KT IAS.
CAT D speeds from 141KT to 165KT IAS.
CAT E speeds from 166KT to 210KT IAS.
CAT H (helicopters) see sub-section 1.3.

Note: V_at is the indicated airspeed at the threshold which is equal to the stalling speed V_so multiplied by 1.3 or the stalling speed V_s1gmultiplied by 1.23. Both V_so and V_s1g apply to aircraft in the landing configuration at the maximum certificated landing weight. If both V_so and V_s1g are available for an aircraft, the higher resulting Vat must be used.

C

Circling area

The area around an aerodrome within which an IFR aircraft may descend below the MDA during a non-precision approach, or below MSA during a visual approach, to position the aircraft for landing. The circling area is defined in AIP, below. It is a pilot responsibility and not required knowledge for ATC.

AIP ENR 1.5.1.7.3 Note 3
The circling area is determined by drawing an arc centred on the threshold of each usable runway and joining these arcs by tangents. The radii are 1.68NM for Category A, 2.66NM for Category B, 4.20NM for Category C, 5.28NM for Category D and 6.94NM for Category E. Runways less than 1,000M long are not
considered usable for Categories C,D and E.

CTA

Controlled airspace. Generic term referring to all classes of airspace where an ATC clearance is required.

D

DTI

Directed Traffic Information. A service provided by ATC where information about conflicting traffic is directed to individual aircraft (rather than via a general "all stations" broadcast). DTI is provided on an ongoing basis to IFR aircraft operating in Class G airspace; it is also available to VFR aircraft on request.

See also 'Traffic Statement'.

F

Frequency transfer

The instruction issued to an aircraft to contact the next ATC unit on a specified frequency. Except when transferring aircraft to a control tower, frequency transfers must not be initiated until the handoff has been accepted.

Keyword(s):

H

Handoff

The electronic proposal & acceptance of an aircraft data tag from one controller to another. The handoff is a separate action from a frequency transfer instruction issued to the aircraft. The handoff must be accepted by the receiving controller prior to issuing the frequency transfer.

L

LSALT

Lowest Safe Altitude - The lowest altitude that provides a minimum of 1000FT terrain & obstacle clearance at a given place. They are usually found as Route LSALTs, which provide a lowest safe altitude for a track between two points.

M

MSA

Minimum Sector Altitude. The lowest safe altitudes that provide 1000FT obstacle clearance within both a 10NM and 25NM radius of an aerodrome. These areas are known as 'sectors'. MSAs are displayed on Departure & Approach Plates (DAPs) and aircraft are only permitted to descend below the MSA under certain conditions.

MVA

Minimum Vectoring Altitude. The lowest altitude a controller may assign to a pilot under radar control. MVAs provide terrain & obstacle clearance as well as keeping the aircraft at least 500FT above the lower limit of controlled airspace.

O

OCTA

Outside controlled airspace. Informal term used when referring to operations in airspace that does not require a clearance.