Acas sample

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AIRBORNE COLLISION AVOIDANCE SYSTEM (ACAS)

Transcript of Acas sample

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AIRBORNE COLLISION AVOIDANCE SYSTEM (ACAS)

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1. From 1 July 2003, all turbine-engine commercial air transport aeroplanes of a maximum certificated mass in excess of 15000 kg or with a maximum approved passenger seating configuration in excess of thirty (30) passengers, shall be fitted and operated with serviceable equipment meeting ACAS II specifications. (121.05.15)2. From 1 January 2005, all turbine-engine commercial air transport aeroplanes of a maximum certificated mass in excess of 5 700 kg or with a maximum approved passenger seating configuration in excess of nineteen (19) passengers, shall be fitted and operated with serviceable equipment meeting ACAS II specifications.

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SCOPE

1. Introduction.2. ACAS II Principles.3. Cockpit Presentation.4. Aural Annunciations.5. Use of ACAS indications.

7. Controls and Displays.8. Collision Avoidance Logic.9. Additional changes.

6. Standard Phraseology.

EXAMINATION

1. Multiple answer format.2. 90% passmark.

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INTRODUCTIONACAS II is a system used for detecting and tracking aircraft in the vicinity of your own aircraft. It interrogates their transponders, analyzing the replies to determine range, bearing, and if reporting altitude, the relative altitude of the intruder. Should a possible collision hazard exist, it issues visual and audio advisories to the crew for appropriate vertical avoidance maneuvers.

ACAS is unable to detect any intruding aircraft without an operating ATC transponder (operating in Mode A and C) or a Mode S transponder.

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ACAS II issues two types of advisories:

Traffic Advisory (TA). Showing the intruding aircraft's relative position and altitude with a trend arrow to indicate if it is climbing or descending. The display is usually a dedicated instrument.Resolution Advisory (RA). Showing the required vertical speed to avoid an airborne collision. The display is incorporated in the VSI.

INTRODUCTION

ATC procedures will continue to be the primary means of ensuring aircraft separation.

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ACAS logic based on two main concepts:1. The warning time, which is based on the time-to-go to the Closest Point of Approach (CPA)2. The sensitivity level, which is a function of the altitude.

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When RA triggered:1. Computes most appropriate vertical manoeuvre to achieve target vertical miss distance (600 ft).2. Tries to prevent vertical crossing RA’s.3. Advisory strength continuously evaluated and modified if necessary.

Multiple threat encounter:1. Attempts to resolve in single RA.2. Otherwise with a composite RA of non-contradictory climb and descend.

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COCKPIT PRESENTATIONThe cockpit presentation provides limited information on adjacent traffic, TA’s and RA’s, and aural annunciations. The traffic information display system is designed to aid visual acquisition of an intruder.

ACAS display center

2 NM range circle

Display range

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RA -Vertical rate to be avoided

RA - Required vertical rate

COCKPIT PRESENTATION

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Off scale traffic

Non-altitude

reporting traffic

COCKPIT PRESENTATION

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COCKPIT PRESENTATION

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Example of “envelope” at FL 090

300 kts closure rate.

COLLISION AVOIDANCE LOGIC

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ADDITIONAL CHANGES

ACAS II Bulletin No 5 – October 2004

“Pilots shall respond immediately by following the RA as indicated, unless doing so would jeopardise the safety of the aeroplane”

“Pilots shall follow the RA even if there is a conflict between the RA and an ATC

instruction to manoeuvre”

“Visually acquired traffic may not be the same traffic causing an RA. Visual perception

of an encounter may be misleading, particularly at night.”

“Pilots shall not manoeuvre in the opposite sense of an RA”

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SUMMARYACAS is a “last resort” tool designed to

prevent mid-air collisions.ATC procedures to provide flight safety

must continue.

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END