Section 6, Chapter 4 - Radar Safety Nets Flashcards
What are the key characteristics and purpose of a Radar Safety Net in ATM systems?
A Radar Safety Net in ATM systems:
- Caters for unplanned events.
- Uses information from ground-based and airborne components to automatically generate alerts requiring immediate attention.
- Alerts controllers to increased safety risks for aircraft in their operational environment.
- Aids controllers by producing alerts according to predetermined rules, acting like an ‘electronic colleague’.
Note: Safety nets contribute to overall safety but should not be relied upon solely for safe operation due to inherent limitations.
What types of alerts are generated by safety nets and what do they signify?
Safety nets generate the following types of alerts:
- Genuine Alerts: Indicate that one or more aircraft are exposed to a particular hazard according to the rule set.
- Nuisance Alerts: Generated according to the rules but are operationally inappropriate, often due to lack of knowledge of aircraft intentions (e.g., STCA for two aircraft climbing and descending towards each other but will be separated).
- False Alerts: Do not correspond to a situation requiring attention or action (e.g., caused by split radar tracks and radar reflections).
- Failed Alerts: An alert that is not produced but is operationally desirable and should have been produced according to the rule set.
What should a controller do when a safety net alert is displayed?
When a safety net alert is displayed, the controller should:
- Immediately assess the situation.
- If necessary, take positive action to resolve the situation without delay.
How is a safety net failure indicated and what actions should be taken?
A safety net failure is indicated by SNMAP being highlighted in red within the General Information Window (GIW). The DEO and WM must be informed as soon as practicable.
What are the guidelines for handling audible warnings generated by safety net alerts?
Guidelines for handling audible warnings:
- Alerts produce an audible warning via speakers in the equipment cabinet.
- ATCOs must not alter the volume on the speakers at any time.
- An audible alarm can be independently enabled for each of the following groups:
- ‘Sensor Alerts’ Group: STCA, AFDA, AIW, DAIW, MSAW
- ‘SSR Emergencies’ Group: EMG, RCF, HIJ
What are the code allocations for different flight operations to manage safety net alerts?
Code allocations for managing safety net alerts are:
- 7030: Local VFR conspicuity in EGAA CTR (to avoid nuisance AIW alerts).
- 7031 - 7040: Designated as VFR/SVFR codes (excluded from some safety nets).
- 7046 - 7047: Designated as IFR codes (included in all safety nets).
How can the visual representation of safety nets be displayed on EUROCAT?
To display the visual representation of safety nets on EUROCAT:
- Select ASD Tools.
- Go to Map Select.
- Choose the S_NETS tab.
How does the Short Term Conflict Alert (STCA) system work and what is its operational status on EUROCAT displays?
The Short Term Conflict Alert (STCA) system:
- Predicts aircraft tracks in a three-dimensional manner for a specified time period using current aircraft tracks.
- Is always active on all displays and processes information from all sensors feeding the EUROCAT system.
- Can display an alert using CROWSSR data even if the BELFAST sensor is selected.
What are the operating parameters and excluded SSR codes for the Short Term Conflict Alert (STCA) system?
STCA Operating Parameters:
* Inclusion Areas: All STCA Inclusion Areas must be switched on (System > Area Control > STCA - select all areas).
* Alert Criteria: STCA alerts if predicted separation between aircraft will be less than 2NM and/or 600ft.
* Purpose: Assists in preventing collisions, not for loss of separation.
* Monitoring Area: Approximately within which EGAA may provide a radar service.
Lateral Parameters:
* Outside CAS: Up to 42.5NM (plus ~5NM buffer zone)
* Inside CAS: Up to 60NM (plus ~5NM buffer zone)
Vertical Parameters:
* Operational Range: FL016 to FL245
Excluded SSR Codes:
* 0000: SSR Data Unreliable
* 1177: London FIS
* 3301 - 3303: Swanwick Military Special tasks
* 3310 - 3367: Swanwick Military
* 4250 - 4257: EGAC Codes
* 6040 - 6177: Swanwick Military
* 6101 - 6157: Swanwick Military
* 6501 - 6577: CRC Scampton
* 7000: Conspicuity Code
* 7001: Low Level Climbout
* 7002: Danger Area general
* 7004: Aerobatics
* 7005: High energy manoeuvres
* 7006: Operators TRA
* 7401: Scottish FIS
What is the method of alert for the Short Term Conflict Alert (STCA) system?
If STCA is activated:
- Line 1 of the target labels of all relevant aircraft will show ‘STCA’.
- The target and label will blink, and the speed vectors will be switched on.
- The alerts box will be displayed on screen with the following parameters:
- Impending alert: 50 seconds from conflict.
- Actual alert: 30 seconds from conflict.
What actions should a controller take in response to a Short Term Conflict Alert (STCA)?
In response to an STCA, a controller should:
- Immediately assess the situation.
- Take positive action to restore separation if necessary, without delay.
Additional Notes:
STCA is a safety net and does not replace the controller’s responsibility to provide standard separation as detailed in MATS Part 1 and Part 2.
Alerts may or may not require positive action from the controller.
Controllers should not rely on Downloaded Aircraft Parameters (DAP), especially Downloaded Selected Altitude, due to potential issues such as autopilot failure or incorrect pressure settings.
In the event of a TCAS RA report from a pilot, controllers must respond according to procedures detailed in MATS 1.
What are the known limitations and causes of nuisance/false alerts for the Short Term Conflict Alert (STCA) system?
Known limitations and causes of nuisance/false alerts for STCA:
- STCA is SSR based; no alert will be generated if a transponder mode C is not displayed.
- Attention is required at lower altitudes as STCA on EUROCAT is based on STANDARD pressure (1013 hPa) rather than QNH.
Impact of Pressure Changes:
Lower QNH (below 1013 hPa):
* The base of the STCA monitoring area is lowered.
* STCA warnings occur at lower than expected levels.
* Example: At 983 hPa, FL016 equates to ~700ft ALT, causing extra STCAs against circuit traffic.
Higher QNH (above 1013 hPa):
* The base of the STCA monitoring area is raised.
* Loss of STCA warnings at lower levels.
* Example: At 1043 hPa, FL016 equates to ~2500ft ALT.
How is a failure of the STCA safety net indicated and what actions should be taken?
Failure of the STCA safety net is indicated by SNMAP being highlighted in red within the General Information Window (GIW). The DEO and WM must be informed as soon as practicable.
What is the purpose of the Approach Funnel Deviation Alert (AFDA) and how does it operate?
The Approach Funnel Deviation Alert (AFDA) is intended to warn a controller that an approaching aircraft has deviated from the safe approach centerline and/or glidepath. The AFDA safety net actively monitors all final approach tracks and will still generate alerts even when a different runway is selected via the graphical interface window ARW.
What are the operating parameters for the Approach Funnel Deviation Alert (AFDA) system and how does it indicate an alert?
The Approach Funnel Deviation Alert (AFDA) system initiates an alert when an aircraft moves outside the defined volume of airspace below and/or either side of the final approach. An AFDA alert will be shown on line 1 of the target label.
Operating Parameters for Different Runways:
- Runway 07: 6.5NM - 1.5NM
- Runway 17: 6.5NM - 1.5NM
- Runway 25: 8NM - 1.5NM
- Runway 35: 8NM - 1.5NM
Note: The distance at which AFDA monitoring begins varies depending on the runway due to terrain and associated step-down fixes.
