GM6 to AMC2 ATS.TR.255 Operations on parallel or near-parallel runways

MONITORING CONTROLLER With reference to point (l) of AMC2 ATS.TR.255:

(a)Independent operations on parallel runways can only be conducted if there are means to ensure that the objectives of the air traffic services would be fulfilled in a manner similar to what the application of separation minima (vertical or horizontal) would achieve.

(b)Considering the geometry of two aircraft operating simultaneously on the parallel runways, while longitudinal separation is applied between aircraft approaching the same runway, a lateral separation is needed between the aircraft operating on parallel approaches for the most critical scenario: two aircraft at the same time on each final approach.

(c)To provide the acceptable lateral separation in such circumstances, an NTZ is established. The NTZ is considered to provide the lateral separation from the moment vertical separation between aircraft on adjacent approaches no longer exists until aircraft have landed. The responsibility of air traffic controllers is to closely monitor the progress of the flights and to immediately react when an aircraft deviates towards the NTZ boundary.

(d)In that sense, the tasks of these air traffic controllers (referred to as ‘monitoring controllers’), are as follows:

(1)to ensure that the NTZ is not penetrated when vertical separation is reduced;

(2)to instruct aircraft observed to overshoot the turn-on or to continue on a track which will penetrate the NTZ to return immediately to the correct track;

(3)to ensure that the applicable minimum longitudinal separation between aircraft on the same final approach course or track is maintained;

(4)if no dedicated radio channels are available for the monitoring controllers to control aircraft until landing, to transfer communication with the aircraft to the respective channel of the aerodrome air traffic controller before either of the two aircraft on adjacent final approach tracks intercepts the glide path or vertical path for the selected instrument approach procedure. In this case, the controllers monitoring the approaches to each runway are provided with the capability to override transmissions of aerodrome control on the respective radio channels for each arrival flow;

(5)if dedicated radio channels are available for the monitoring controllers to relay the landing clearances received from the aerodrome air traffic controller, or when the aerodrome air traffic controller informs that visual separation can be applied, to transfer the communications to the aerodrome air traffic controller;

(6)when an aircraft is observed penetrating the NTZ, to instruct the aircraft on the adjacent final approach course or track to immediately climb and turn to an assigned altitude/height and heading (break-out procedures) in order to avoid the deviating aircraft. Where PAOAS criteria are applied for the obstacle assessment, the monitoring controller will not issue the heading instruction to the aircraft below 120 m (400 ft) above the runway threshold elevation, and the heading instruction will not exceed 45 degrees track difference with the final approach course or track; and

(7)to terminate monitoring when either:

(i)visual separation is applied provided that procedures ensure that both monitoring controllers are advised whenever visual separation is applied; or

(ii)the aircraft has landed or, in case of a missed approach, is at least 1 NM beyond the departure end of the runway and adequate separation with other traffic is established.

(e)When there is a large deviation from the final approach track, communication between the controllers and pilots involved is critical. For independent parallel approaches, monitoring controllers are required, for each runway, with separate control frequencies. The monitoring controller(s) can transmit on either of these frequencies, automatically overriding transmissions by the other aerodrome air traffic controllers, or can use dedicated radio channels, if available. It is essential that a check of the override capability at each monitor position be performed prior to the monitoring controllers assuming responsibility of the position. The air traffic services provider should take steps to ensure that, in the event of a deviation, the monitoring controller will be able to contact the deviating aircraft and the endangered aircraft immediately. This will involve studying the proportion of time during which communications are blocked.

(f)Monitoring of approaches to no more than two runways by a single monitoring controller may be permitted if determined by a safety assessment and approved by the competent authority, as described below.

(g)During simultaneous independent approach operations, participating aircraft are established on guidance to instrument approach procedures which have been designed to not interfere with one another. By remaining on their guidance, the aircraft are, by design, not threats to each other, and are considered separated. If either aircraft deviates from its lateral path defined by its assigned instrument approach, separation is no longer assured. To protect against operational errors, system or equipment failures, etc., Simultaneous Operations on Parallel or Near-Parallel Instrument Runways (SOIR) procedures require the monitoring controller to provide intervention as necessary. Monitoring controllers are required to identify and respond to such traffic transgressions in a timely manner to protect proximate traffic and minimise collision risk. Their responsibility is to recognise a deviation from a cleared lateral path, determine a manoeuvre for any nearby traffic that might be threatened by this deviation that will avoid a collision, and transmit this manoeuvre instruction to the threatened aircraft. If there is no threatened traffic, or after the threatened traffic has begun its escape manoeuvre, the monitoring controller will also attempt to instruct the deviating aircraft.

(h)The time budgeted for recognition by monitoring controller of potential collision during non-nominal events in simultaneous parallel approaches is in the order of seconds. System-generated alerts to the monitoring controller that can differentiate quickly and accurately between normal and non-nominal situations will be an enabling element of the operation. The region known as NTZ is used to provide air traffic controllers with time to identify that one aircraft on a simultaneous approach may threaten the other and to then take appropriate action to avoid a collision. Normally, a dedicated monitoring controller is assigned to each approach during simultaneous operations. However, since a single NTZ is defined in the space between simultaneous approaches, it may be possible for a single controller to effectively monitor and correct any transgressing aircraft. Approval of an alternate to the otherwise-required approach-specific monitor control positions should consider, as a minimum, the following elements unique to a specific approach pairing:

(1)Approach geometry complexity:

(i)displaced thresholds which cause non-coincident altitudes along the parallel tracks;

(ii)use of curved course transitions to final; and

(iii)short finals.

(2)Traffic mix and density:

(i)mix of light-heavy traffic necessitating varying longitudinal wake spacing; and

(ii)approach speed variations.

(3)Arrival rate and density:

(i)total traffic volume versus approach capacity; and

(ii)flow management consistency with traffic demand.

(4)Available levels of system automation:

(i)conformance monitoring tools; and

(ii)non-transgression alerting.

(5)Availability of back-up systems to provide continuity of:

(i)communication;

(ii)approach navigation (approach technology);

(iii)surveillance (independent, redundant sources); and

(iv)interdependency of CNS.

(6)The impacts of local meteorological conditions and other environmental factors:

(i)inversion on final that can cause wake vortices to not dissipate;

(ii)excessive tailwind;

(iii)high cross-winds;

(iv)gusty winds; and

(v)inconsistent wind patterns (e.g. caused by nearby obstacles or terrain).