Air Traffic Services
Air Regulations · Chapter 4 · DGCA CPL and ATPL
Who looks after you in the air, how much protection each block of airspace gives, and what happens when an aircraft goes silent.
Remember
- ATS has 5 jobs, done by 3 services: ATC (collisions and flow), FIS (information), Alerting (search and rescue).
- Classes A to G: protection drops down the alphabet. Only C separates VFR from IFR; G separates no one.
- In India, Class C is 4000 ft to FL285 around busy airports, and Class D extends up to 30 NM around them.
- FIR letters are the vowels A E I O: Mumbai, Kolkata, Delhi, Chennai.
- Emergency phases climb in severity: INCERFA (30 min), ALERFA, DETRESFA.
What is ATS for, and who does each job?
5 jobs, 3 services
Five objectives (a to e) are split between three services. Tap a box with + to see the parts.
- Air Traffic Services 5 objectives, 3 services ATS has five objectives (a to e), met by three services: air traffic control (a, b, c), flight information (d) and alerting (e).
- Air Traffic Control objectives a, b, c The service that accomplishes objectives a, b and c. It is divided into area, approach and aerodrome control.
- a. Prevent collisions between aircraft The first job of ATC.
- b. Prevent collisions on the manoeuvring area With other aircraft and obstructions on the ground. Only aerodrome control covers this.
- c. Expedite and keep an orderly flow Keep traffic moving efficiently.
- Three units area, approach, aerodrome ATC is split into area, approach and aerodrome control, each handling a different part of a controlled flight.
- Area control a, c ATC for controlled flights, except the parts handled by approach and aerodrome control. It achieves objectives a and c and is provided by an area control centre.
- Approach control a, c ATC for the arrival and departure parts of controlled flights. It achieves objectives a and c.
- Aerodrome control a, b, c The only unit that also covers objective b.
- Flight Information Service objective d The service that accomplishes objective d. It goes to all aircraft likely to be affected that receive ATC or are otherwise known to the ATS units.
- d. Advice and information for safe, efficient flight Includes SIGMET, volcanic and radioactive cloud, navigation aid and aerodrome information.
- ATIS broadcast, max 30 seconds Each new message takes the next letter of the spelling alphabet. Not broadcast on an ILS voice channel.
- Alerting Service objective e The service that accomplishes objective e. It covers all aircraft with ATC, others on a flight plan or known to ATS as far as practicable, and any aircraft subject to unlawful interference.
- e. Notify search and rescue Tell SAR organisations about aircraft that need help, and assist them.
- Works in 3 phases INCERFA, ALERFA, DETRESFA When an aircraft gets into trouble, ATS tells the rescue coordination centre straight away. Emergencies come in three stages: uncertainty, alert and distress.
- Air Traffic Control objectives a, b, c The service that accomplishes objectives a, b and c. It is divided into area, approach and aerodrome control.
Memory hook: CIA: Control, Inform, Alert.
Takeaway: Collisions and traffic flow belong to ATC. Advice belongs to FIS. Calling SAR belongs to Alerting.
How much protection does each airspace class give?
Classes A to G
Each step down the alphabet removes protection. * A and B are under consideration in India.
| Class | Who may fly | Who is separated | Service | Clearance needed | 250 kt below 10,000 ft | Radio |
|---|---|---|---|---|---|---|
| A* | IFR only | Everyone from everyone | ATC | Yes | Not applicable | All |
| B* | IFR and VFR | Everyone from everyone | ATC | Yes | Not applicable | All |
| C | IFR and VFR | IFR from all; VFR from IFR | ATC | Yes | VFR only | All |
| D | IFR and VFR | IFR from IFR | ATC + traffic info | Yes | All | All |
| E | IFR and VFR | IFR from IFR | ATC for IFR | IFR only | All | IFR |
| F | IFR and VFR | IFR kept apart from IFR where possible | Advisory | No | All | IFR |
| G | IFR and VFR | Nobody | Information only | No | All | IFR |
Memory hook: A to G is a ladder going down: less control on every rung.
Takeaway: A and B separate everyone. C separates VFR from IFR. D and E separate IFR from IFR only. F is advisory. G is information only.
Can you work out the class from what a flight receives?
Find the class
Read each case and press the stamp that applies.
This lesson is part of the Core plan. See plans
How is India's airspace divided?
FIR, CTA, CTZ
A side view of one FIR. Tap each number.
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What does “up to 30 NM around Class C airports is Class D” mean?
India: C and D
Busy Indian airports get a core of Class C, wrapped in a ring of Class D.
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Flying VFR into India's Class C: what must you do?
VFR into Class C
Answer in order before you enter.
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Who gives which ATC service, to whom?
Who gives ATC
Who gets it, who gives it, who is separated. Tap + to open each.
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Must you read it back?
Read it back?
Tap an item, then the box it belongs in.
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What does FIS give you, and what is in ATIS?
FIS and ATIS
Flight information, then the ATIS broadcast. Tap + to open each.
This lesson is part of the Exam-Ready plan. See plans
What happens when an aircraft goes quiet?
Emergency phases
The alerting service escalates through three phases. Each one is triggered by time or by what is known.
This lesson is part of the Core plan. See plans
How does the alerting service run?
Alerting service
From the first sign of trouble to the rescue centre.
This lesson is part of the Exam-Ready plan. See plans
How does flow management work in India?
Flow management
One command centre, flow positions at the busiest airports. Tap each number.
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How are India's four FIRs named?
FIR letters
Each Flight Information Region has a vowel and a block of numbers for its temporary areas.
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How do you read an airport code like VIDP?
VIDP
Four letters, three jobs. Tap each part.
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How many letters for each chart indicator?
Chart indicators
Find the item, read across.
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Can you fly through it?
P, R, D, TSA, TRA
Five kinds of special airspace, from closed to crossable.
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What do the letters around an ATS route mean?
Route designator
An example route, UL301F. Tap each part.
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How protected is each class, and how do routes work?
Airspace and routes
Four views: the classes, the timings, the border strip and the route rules.
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Which flight plan for a local or cross-country flight?
Which flight plan?
Answer about the flight you are planning.
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Numbers to know
Numbers
The figures examiners like, in one list.
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Pairs that catch students out
Don't mix up
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Test yourself
Ten questions from this chapter.
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