SubscribeNATS commission a new Time Distribution System from Time & Frequency Solutions
The Challenge
NATS provides en route air traffic control services to aircraft flying in UK airspace, and over the eastern part of the North Atlantic. It also provides services at fifteen of the UK's largest airports, including Heathrow, Gatwick and Stansted. This year NATS will safely handle more than two million flights carrying over 220 million passengers.
Under NATS two-centre strategy, the four existing en route Control Centres at Swanwick, West Drayton, Manchester and Prestwick will be rationalised into two centres at Swanwick and Prestwick.
The London Area Control Centre at Swanwick opened in 2002 and is the largest purpose-built air traffic control centre in Europe. The new Prestwick centre, currently under construction will open in 2009.
NATS' Requirement
NATS required a new Time Distribution System (TDS) to be installed at the London Swanwick centre, Hampshire to replace the existing system in operation at the London Terminal Control Centre, West Drayton.
To maintain stringent safety procedures the system was designed with a high level of built in resilience and will run in parallel with the West Drayton system to ensure a smooth transition.
A second system will be installed at NATS' Corporate and Technical Centre in Whiteley, Hampshire and will be used in its training and simulation facility. It does not require the same high level of redundancy as the Swanwick system but utilises the same principles and network management facilities to ensure ease of maintenance.
- Master clock system to interface with existing NATS equipment including voice recorders, CCTV, telephone system providing data in serial ASCII or NTP format
- Two GPS time reference inputs (from two locations) together with additional backup reference input from the Rugby MSF signal.
- Automatic changeover capability, with Master Time Source systems split between two equipment rooms in Swanwick to enable the highest level of resilience.
- Control and monitoring system, including test and diagnostics
- Commercial-Off-The-Shelf (COTS) solution.
The Solution
In order to fulfil the primary requirement of a master clock system, Time & Frequency Solutions' industry-proven M211 Modular Timing System was selected as the most appropriate for the task.
The M211 is a high-capacity flexible timing system designed for use applications where highly reliable time information is required. Nine separate module slots together with a large range of module options made it an ideal solution to the NATS requirement, where synchronisation of many different output interfaces was required. A five-button front panel keyboard allows direct equipment configuration and control with alphanumeric display of time, date and status. The equipment configuration is stored in non-volatile memory. The chassis is 3U high with a standard 19" rack mount.
Two separate M211 Modular Timing Systems were installed at Swanwick, one in each of the two equipment rooms. The units are configured to provide a dual redundant highly resilient timing source. Each M211 is equipped with an integral Global Positioning System (GPS) receiver with a feed from separate roof pod head-end antennas located at a distance from each other. Each M211 also had integral MSF receivers to ensure a time synchronisation source was available in the event that GPS signal was interrupted. A high stability internal oscillator provides an extremely accurate free running capability in the event of both synchronisation sources being unavailable.
Because of the high capacity of the M211s, sufficient space was made available within the chassis to fit IRIG-B and Timeon time code modules to interface with legacy systems. Serial modules and an Ethernet module were included in the M211 units to interface with companion systems.
Each M211 had outputs to three serial distribution units, which distribute the time to 20 displays. In order to meet NATS specific requirements the standard ATC console display was redesigned to fit with the London Terminal Control Centre desks.
The M211 master clocks feed a racked M210 Modular Timing System. These act as sub master clocks in the equipment rooms and distribute the time signal to other systems. Each sub master clock has been dedicated to a third party system to improve resilience.
Further redundancy is provided by cross-connections between the M211 masters and the sub-masters. In the highly unlikely event of a failure in a signal from one of the master clocks, the sub-masters will continue with no interruption to service.
Network Monitoring System
NATS also required a Network Monitoring System (NMS) and associated proprietary monitoring software.
A windows-based solution has been installed to enable centralised or remote monitoring and control of the Time & Frequency Solutions timing system and component parts by SNMP running over an Ethernet network.
Its user-friendly graphical interface with a visual representation of the TDS components allows for monitoring of status including alarms, software and hardware faults, errors and serial number details.
A separate Visual Software Interface (VIS) application is included which provides a visual representation of the Master and Sub-Master Clock's LCD panels. This application provides the user with the ability to remotely configure and control the units.
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