(2) ATM - ACAS & TCAS

Question 1

Aircraft with what criteria must be equipped with ACAS II? (2)

Answer 1

• MCTOM of >5700kg
• MOPSC of >19 passengers
• Turbine aircraft

Question 2

What equipment is only available to meet ACAS II? (1)

Answer 2

TCAS II

Question 3

What is ACAS? (2)

Answer 3

ACAS - Airborne Collision Avoidance System

“An aircraft system based on SSR transponder signals which operates independently of ground based equipment to provide advice to the pilot on potential conflicting traffic that are equipped with SSR transponders”

Question 4

What operational difference does TCAS II have, that TCAS I does not?

Answer 4

TCAS II WILL provide a Resolution to a conflict

Question 5

How is TCAS II & ACAS II used? (1)

Answer 5

Interchangeably

Question 6

What is TCAS? (2)

Answer 6

TCAS - Traffic & Collision Avoidance System

• Gives Traffic Information about other ‘cooperating’ aircraft which are displayed as various symbols in various colours
• Will tell you how to get out of the way - as long as the other aircraft is ‘cooperating’
• Uses range & Altitude data from transponders to determine possibility of collision
• Presents bearing information of aircraft intruding into your airspace (uses this information on the display only to assist in visual acquisition of an intruder
• When range and altitude of an intruder are computed and a collision risk is predicted, TCAS II will declare the intruder a “threat” and give manoeuvre advice in visual and aural form

Question 7

Transponder types working with TCAS (3)

Answer 7

Mode A/C transponders:
- Give both Traffic Advisory and Resolution Advisory
(only if Mode C available but any manoeuvre may not be in the logical sense)

Mode S transponders:
- ‘communicate’ with each other and ‘agree’ a course of action

No transponder:
- No TCAS alert

Question 8

What system key components does TCAS have? (5)

Answer 8

• Antennae
• TCAS Processor
• Transponder Control Panel
• Vertical Speed Indicator – Visual Display
• Voice Warning System “Traffic Traffic”

Question 9

How does the TCAS system operate? (2)

Answer 9

• A protected volume of airspace surrounds each ACAS II equipped aircraft
• Size of the protected volume depends on the altitude, speed, and heading of the aircraft involved in the encounter

Question 10

What target symbols are displayed on TCAS? (4)

Answer 10

• Hollow cyan (light blue) or white diamond – for other traffic
• Solid cyan (light blue) or white diamond – for proximate traffic
• Solid yellow or amber circle – for intruders (i.e. aircraft which trigger a TA)
• Solid red square – for threats (i.e. aircraft which trigger an RA)

Question 11

When does traffic class as Non-altitude reporting traffic? (1)

Answer 11

TCAS has no way of determining whether this is a ‘threat’ as no Mode C data is being transmitted

Question 12

When does traffic class as Non-threat traffic? (1)

Answer 12

A common display situation – usually with
multiple contacts

Question 13

When does traffic class as Proximity traffic? (1)

Answer 13

Any target within 6nm and within 1200ft

Question 14

When does traffic class as Traffic Advisory (TA)? (3)

Answer 14

• Traffic assumes “threat” status
• 20 – 48 secs before Closest Point of Approach (CPA)
• “Traffic Traffic”

Question 15

What are the pilot’s actions when encountering a TA? (3)

Answer 15

• Advised not to take avoiding action
• May request information from ATC
• Don’t routinely pass

Question 16

When does traffic class as Resolution Advisory (RA)? (3)

Answer 16

• Starts the conflict resolution process up to 35 secs before Closest Point of Approach (CPA)
• “Climb, Climb Now”

Question 17

What are the pilot’s actions when encountering a RA? (4)

Answer 17

• Pilots shall respond immediately
  (Disengage autopilot and respond within 5 seconds, unless doing so would jeopardise the aircraft)
• Restrict manoeuvres to the minimum necessary to solve conflict
• Advise ATC ASAP
• Return to original flight path when safe

Question 18

What limitations does TCAS have? (5)

Answer 18

1. Enhanced RA - <1450ft AGL - “Increase Descent”
2. Descend RA <1100ft AGL
3. All RAs - <1000ft AGL
4. All spoken messages - <500ft AGL
5. RAs some terrain avoidance systems or windshear warnings are active

Question 19

What can cause “Nuisance advisories”? (2)

Answer 19

• High vertical speed (Low level & congested airspace)
• Ground testing of transponders

Question 20

TCAS Advisories table diagram

Answer 20

Familiarise with the Aural messages

Question 21

What are the actions required from ATC when a RA is notified? (3)

Answer 21

• Do Not Issue Instructions to the Aircraft
• Cease provision of standard separation from affected traffic
• Should not routinely pass traffic information to aircraft conducting RA manoeuvres, or other aircraft affected by such manoeuvres

Question 22

When shall ATC resume responsibility for providing standard separation when the RA has cleared of conflict? (2)

Answer 22

• ATCO acknowledges a report from the flight crew that the aircraft has resumed the current clearance
• The controller acknowledges a report from the flight crew that the aircraft is resuming the current clearance and issues an alternative clearance which is acknowledged by the flight crew

Question 23

TCAS is the ONLY system that provides positive instruction to pilots to avoid a collision with other suitably equipped aircraft. True or False?

Answer 23

True

Question 24

What other systems may be available to the GA community? (2)

Answer 24

• TAS
• FLARM

**THEY DO NOT PROVIDE COLISION AVOIDANCE **