Flashcards in S6, C4 - Radar Safety Nets Deck (30):
A safety net displays the following characteristics:
1. It caters for unplanned events
2. It makes use of information from ground-based and airborne components of the ATM systems to automatically generate alerts that require immediate attention
3. It has the sole purpose of alerting controllers to the increased safety risks for aircraft in their environment of operations
Safety nets are provided to...
...aid a controller by producing alerts according to a predetermined set of rules.
They do not use any data which is hidden from the controller to produce alerts and should be thought of as an electronic colleague that occasionally points out a hazardous situation which may otherwise have gone unnoticed.
Safety nets can contribute to the overall level of safety, but due to inherent limitations they shall not be relied upon to provide a safe operation.
Alerts generated by safety nets may be considered to be any of the following:
A) genuine alerts - generated when , according to the rule set, the system determines that one or more aircraft are exposed to a particular hazard
B) nuisance alerts - generated according to the rules set but are considered to be operationally inappropriate. Safety nets have no knowledge of aircraft intentions and will therefore alert on occasions that are unnecessary (e.g. STCA for 2 aircraft climbing/descending towards each other but will be level separated)
C) false alerts - those which do not correspond to a situation requiring particular attention or action (e.g. Caused by split radar tracks and radar reflections)
Additionally an alert which is not produced but is operationally desirable and should have been produced according to the rule set is known as a failed alert.
In the event of any safety net alert being displayed, the controller shall without delay:
- immediately assess the situation
- if necessary, take positive action to resolve the situation
Failure of any of the safety nets will be indicated by...
...SNMAP being highlighted in red within the general information window (GIW)
The DEO and WM must be informed ASAP.
Alerts will produce an audible warning.
ATCOs must not alter the volume on the speakers at any time.
An audible alarm can be enabled independently for each of the:
- sensor alerts group i.e. STCA AFDA AIW DAIW MSAW
- SSR emergencies group i.e. EMG RCF HIJ
The following codes are assigned to aid safety nets:
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)
A visual representation of the safety nets are shown on...
...the EUROCAT by selecting ASD Tools - Map Select - S_NETS tab
STCA works on the basis of...
...prediction of aircraft tracks in a 3D manner for a specified time period using the current aircraft tracks.
STCA is always active on all displays and will process information from all sensors feeding the eurocat ie an alert may be displayed using CROWSSR dads even though the Belfast sensor is selected
Which STCA areas shall be switched on?
All STCA inclusion areas shall be switched on (System...Area Control...STCA - select all areas)
STCA will alert if it predicts that the separation between aircraft will be...
...less than 2nm and/or 600ft
The configuration of the STCA is to assist in...
...prevention of collisions, not for loss of separation.
STCA monitors the approximate area...
...within which EGAA may provide a radar service.
OCAS to 42.5nm (plus 5nm buffer zone)
Inside CAS to 60nm (plus 5nm buffer zone)
FL016 to FL245
The following SSR codes are excluded from STCA processing:
0000 - SSR data unreliable
1177 - London FIS
3301-3304 - Swanwick Military special tasks
3310-3367 - Swanwick military
4250-4257 - EGAC codes
4610-4667 - Scottish military radar
6040-6077 - London military radar
6101-6107 - London military radar
6110-6137 - Scottish military radar
6140-6147 - London military radar
6150-6157 - Scottish military radar
6401-6457 - Swanwick military radar
6501-6577 - CRC Scampton
7000 - conspicuity code
7001 - low level climb out
7002 - danger area general
7004 - aerobatics
7005 - high energy manoeuvres
7006 - operators TRA
7401 - Scottish FIS
If the 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 within the following parameters:
- impending alert: 50s from conflict
- actual alert: 30s from conflict
In the event an STCA is displayed the controller shall...
...immediately assess the situation and, if necessary, take positive action to restore separation without delay.
STCA is a safety net, it in no way replaces controller responsibilities to provide standard separation as detailed in M1 and M2.
Alerts may or may not require positive action to be taken by the controller.
Controllers should not rely on DAPs, especially DSA as:
1. The autopilot may fail to capture the level assigned to the pilot (at which the pilot should initiate manual control)
2. The aircrew may have the wrong pressure setting e.g. 060 is displayed but the controller has no confirmation as to whether or not that is FL60 or 6000ft altitude.
It should be noted that in the event of a TCAS RA report from a pilot, controllers are to respond IAW the procedures as detailed in M1
Known limitations and nuisance/false STCA alerts:
The STCA safety net is SSR based, in the event that a transponder Mode C is not displayed, no alert will be generated.
Particular attention must be paid to the lower altitudes as the STCA function on eurocat is based on standard pressure 1013 rather than QNH.
Since the STCA lower level is fixed at FL016, extreme changes in pressure will manifest in the following ways:
1. When the QNH is lower than 1013, the base of the STCA monitoring area will be LOWERED
2. STCA warnings will occur at lower than expected levels
(Eg if the QNH were 983hpa FL016 would equate to approx 700ft altitude so may cause extra STCA alerts)
3. When the QNH is higher than 1013 the base of STCA monitoring will be RAISED. This will cause a loss of STCA warnings at lower levels
(Eg if the QNH were 1043hpa FL016 would equate to approx 2500ft altitude)
Failure of STCA will be indicated by...
...SNMAP being highlighted in red within the GIW.
The DEO and WM must be informed ASAP
The AFDA is intended to...
...warn a controller that an approaching aircraft has deviated from the safe approach centreline and/or glidepath.
The AFDA actively monitors...
...all final approach tracks and hence alerts will still occur when a different runway is selected via the graphical interface window ARW
An AFDA will be initiated and an alert shown on line 1 of the target label when...
...the aircraft moves outside the defined volume of airspace below and/or either side of final approach.
AFDA exists on all runways with the following operating parameters:
The distance at which AFDA monitoring begins is different depending on the runway due to the presence of terrain and associated step down fixes.
The glideslope tolerance is set at 0.75 degrees below the nominal approach path for all runways.
Final approach centreline + 0.1nm either side of track, and 2 degrees lateral angle (diagram in M2, 6-22)
The following SSR codes are excluded from AFDA processing:
0000 SSR data unreliable
0023 SAR Ops
0026 special tasks
0035 selected Helis
0037 Royal heli
7030 VFR conspicuity
7031-7040 VFR squawks
7041-7043 UKP squawks
7045 EGAA monitoring code
7200 Navy ship
In order to benefit from the AFDA safety net, the following IFR codes should be assigned:
AFDA will trigger an actual alert if it detects the that...
...the aircraft is below and/or either side of the FAT.
There is no AFDA impending alert.
The presence of an AFDA in no way reduces or replaces...
...a controllers responsibility to monitor approaching aircraft and take appropriate action if the controller believes the aircraft is dangerously positioned at any time as per M1
AFDA limitations/nuisance alerts:
Since the AFDA safety net operates based on the touchdown point and the runway centreline, there is an increased possibility of nuisance alerts from non-precision and pilot interpreted approaches.
Nonetheless, controllers shall assess each alert accordingly.
AFDA is SSR based, in the event that a transponder Mode C is not displayed, no alert will be generated.
Failure of AFDA will be indicated by...
...SNMAP being highlighted in red within the GIW.
The DEO and WM are to be informed ASAP.