Airspace Structure

Airspace structure

As you already know there are two different types of airspace – controlled and uncontrolled.

In controlled airspace, aircraft in the air or on the ground, receive Air Traffic Control Service in accordance with the airspace classification.
In uncontrolled airspace, ALL aircraft do their own separation according to the General Rules.

• Flight Information Region (FIR)

A Flight Information Region is an airspace of defined dimensions in which Flight Information Service (FIS) and Alerting Service are provided. In this airspace, Countries are responsible for the provision of the Air Traffic Services (ATS). Very often they match the National boundaries, but for practical reasons, countries can delegate part of their airspace to their neighbours.

The ATS service in Tunisia is called “Tunis Information” (DTTC_FSS) and its frequency 128.900 MHz.

• Controlled Airspace

The controlled airspace are divided into the following types:

 – The Control zone (CTR)

A CTR is controlled airspace that starts from the surface (SFC) of the earth upwards to a specified upper limit. Only controlled aerodromes have a CTR.
On IVAO, a control zone is controlled by either a Tower controller, an Approach controller or an Area controller.

An example of Monastir (DTMB) CTR

              -The Control Area (CTA)

A CTA is a Controlled airspace extending upwards from a specified limit above the surface of the earth. It is a box of airspace that does not touch the surface of the earth.

IVAO training

           

              -Terminal Control Area (TMA)

A TMA is a Control Area normally established where airways and/or departure and arrival routes meet in the vicinity of one or more major aerodromes.

On IVAO, a TMA is controlled by either an Approach or an Area controller.

TMA of TUNIS which contains three aerodromes: Tunis Carthage (DTTA) Enfidha (DTNZ) and Monastir (DTMB).

              -Airway

An AWY is a Control Area or a part of it, shaped in the form of a corridor.

They have defined upper and lower limits, are usually 10nm wide and are equipped with VORs & NDBs for navigation. The airway name usually starts with a letter followed by number(s). If the route name is preceded by a U, it indicates an Upper Airway.

Example: Airway A411 / Upper route UA411.

IVAO training

           -ATS route

“ATS route” can mean either:
-an airway
-a controlled or uncontrolled route
-an arrival route
-a departure route
-etc.

An ATS route is defined by route specifications:

-an ATS route designator (name of the Airway, departure route, etc…)
-the track to or from significant points (waypoints)
-distance between significant points
-reporting requirements and
-the lowest safe altitude.

Standard Instrument Departure (SID)

An Instrument Flight Rule (IFR) departure route that links an aerodrome or a specified runway of the aerodrome with a specified significant point (normally) on an ATS route. This is mostly the airway at which the en-route phase of a flight begins.

Example: “SORAB 2D” departure Runway27 DTNZ Enfidha.

Standard Instrument Arrival (STAR)

An Instrument Flight Rule (IFR) arrival route that links a significant point, (normally) on an ATS route, with a point from which a published instrument approach procedure can be commenced.

Example: “ATLEL 1W” arrival to DTNZ Enfidha.

Area Navigation Route (RNAV route)

An ATS route (airway, departure route, arrival route, …) for aircraft that are RNAV equipped to navigate directly from waypoint to waypoint. These routes are mainly defined by intersections, but can also contain VORs & NDBs.

• Restrictions

Due to a specific activity (such as military flights, low level corridors for military jets, flight training, protection of historic buildings, satellite communication centers, nuclear powerplants…), some areas receive a special status.
The hours of operation are published in the Aeronautical Information Publication (AIP) or announced by NOTAM (NOtice To AirMen). Some areas may be activated anytime at very short notice and others are active 24 hours a day.

These special areas are identified by of a group of letters and figures as follows:

nationality letters for location indicators assigned to the State or territory which has established the airspace DT stands for Tunisia(HE- Egypt, LF- France, RJ- Japan, …)
a letter:

D for danger area
R for restricted area
P for prohibited area
a unique number for that area within the State or territory concerned.

Examples: DTP7, DTR4, HER108, LFD31, RJP15…

A danger area has the least degree of restriction, while the prohibited area is highly restricitive.

Special areas have no airspace classification.

Danger areas – D :

An airspace of defined dimensions within which activities dangerous to the flight of aircraft may exist at specified times. Despite the specific activity (air or ground firing, military jet combat training, intensive industrial activity) it remains at the discretion of the pilot to decide whether or not he can face the risk with a reasonable degree of certainty that it will not have serious consequences for his flight.

Dangerous area “DT D11” in Tunisian airspace.

Restricted areas – R :

An airspace of defined dimensions, above the land areas or territorial waters of a State, within which the flight of aircraft is restricted in accordance with certain specified conditions. You must comply with the conditions indicated in the flight information publications to be allowed to enter such airspace. Restrcited area’s are generally established when the risk level involved in the activities within the area is such that it can no longer be left to individual pilots to decide whether or not they want to expose themselves to such risk. In many cases the activities within a restricted area are not permanently present.

Restricted area “DT R2” in Tunisian airspace.

Prohibited areas – P :

An airspace of defined dimensions, above the land areas or territorial waters of a State, within which the flight of aircraft is prohibited. The prohibited area is completely forbidden to aircraft. It has therefore become general practice to establish such areas only to protect important State installations, critical industrial complexes whose damage as a result of an aircraft accident could assume catastrophic proportions (atomic power plants, sensitive chemical complexes) or especially sensitive installations which are essential for the national security.

Prohibited area “DT P7” in Tunisian airspace.

Classification of Airspace

The classification of airspace determines which flight rules apply and the minimum services that are to be provided in that airspace. There are 7 types of airspace; A to G, A being the most restrictive and G being the least restrictive.

In Tunisia we have A, D, F and G.

Class	Type of Flight	Separation	Contact ATC	Requires an ATC clearance	Speed limit
A	IFR only	separation from all aircraft	yes	yes	no
B	IFR	separation from all aircraft	yes	yes	no
	VFR	separation from all aircraft	yes	yes	no
C	IFR	separation from all aircraft	yes	yes	no
	VFR	separation from IFR but only traffic info about VFR	yes	yes	250 kt IAS below 10.000ft / FL100
D	IFR	separation from IFR but only traffic info about VFR	yes	yes	250 kt IAS below 10.000ft / FL100
	VFR	traffic info only	yes	yes	250 kt IAS below 10.000ft / FL100
E	IFR	separation from IFR only – traffic info about VFR [1]	yes	yes	250 kt IAS below 10.000ft / FL100
	VFR	traffic info only [1]	no [3]	no	250 kt IAS below 10.000ft / FL100
F	IFR	separation from IFR only [1] [2]	yes	no	250 kt IAS below 10.000ft / FL100
	VFR	no	no [3]	no	250 kt IAS below 10.000ft / FL100
G	IFR	no	yes	no	250 kt IAS below 10.000ft / FL100
	VFR	no	no [3]	no	250 kt IAS below 10.000ft / FL100

[1] as far as practical

[2] Air traffic advisory service

[3] On IVAO, ALWAYS CONTACT ATC WHEN you receive a “FORCE ACT”, whatever airspace Class you’re in, uncontrolled or not.