At the bottom of this page is a map of the proposed hold or stack. It gives an indication of the area affected by these proposals. Before looking at it, you should bear a few things in mind:
- Aircraft initially join the stack at the lowest available level. As more aircraft join, they are allocated circuits at higher intervals. As the stack empties, the higher aircraft descend and exit the holding pattern. Each stack can contain up to 8 aircraft at any one time, although NATS claims 'this will not happen regularly' (part E para 2.2), which is somewhat short of saying it will happen rarely.
- The black line is the 'the published centre line of the route' (nats.co.uk), not its complete limit. In reality the aircraft will not flight neatly along this thin line. NATS admits that 'aircraft will have planned to fly along such a route but in practice they often do not' (part D para 2.5)
- The black line is the flight path for aircraft at the highest level i.e. 14,000 feet, not the lowest and noisiest level of 7,000 feet. NATS does not provide any maps of where those low level flight paths will be, but has suggested that the circle will get smaller and smaller as the planes descend. Aircraft at higher levels fly more quickly, so lower aircraft have to take a shorter route to keep the correct distance. NATS says 'the circuit shown should be considered the widest extent of the holding pattern, and so holding aircraft may be seen anywhere within it' (part E para 2.21)
- Aircraft will fly shortened routes if they are given clearance to land. Not all aircraft will queue in this pattern, and some will take short-cuts across and within the marked area at a lower level i.e. as low as 6,000 feet. NATS says 'aircraft leaving the hold often follow truncated circuits' (part E para 2.21) they also say 'When holding is not required, aircraft may follow a descent path that takes them on a direct route beneath parts of the hold. Therefore, the lowest height for aircraft in the hold [7,000ft] is not necessarily the lowest height that aircraft may be seen in the geographical location of the hold." (part E para 3.5)
- Further route maps provided by NATS suggest that the aircraft will exit the stack at its southwestern corner. There is no clear indication where aircraft will join the stack, other than from the east, and then fly anti-clockwise.
- Look here for a postcode search to see how low the planes will be above your area. Make sure you click on 'proposed' routes to see how things will change.
Extract from NATS TCN Consultation Document Part E: CAMBRIDGESHIRE, SUFFOLK & NE SUFFOLK AREA