Luton and District Association for the Control of Aircraft Noise
To minimise the number of people subjected to noise, and to limit the noise levels experienced by those who are, aircraft are expected to follow Noise Preferential Routes (NPRs). These are primarily defined for departing aircraft as arrivals are required to align with the runway 6 nautical miles (nm) from touchdown in to ensure a safe approach. They are usually embodied in the Standard Instrument Departure (SID) routes which aircrew are supposed to follow.
Aircraft can only follow the required routes to a limited accuracy so aircraft are permitted to fly within 1.5km of the route centre line. They are required to remain within these swathes until Air Traffic Control (ATC) re-directs (“vectors”) them onto their flight routes. This cannot happen below a specified height, usually 3,000 feet above mean sea level (amsl). On the Chiltern Hills around Luton, this is a little over 2,500 feet above much of the ground.
Some aircraft seem able to fly the required routes more accurately than others so we are working, with others, to try to find the causes of poor performance and to rectify them.
Westerly Departures
At Luton, the main noise reduction route requires that aircraft departing to the west turn left as soon as possible after leaving the ground to minimise the noise inflicted on people in south Luton. Over recent years, they have been turning later so that they fly further to the north than previously. Our map shows how the route and the permitted swathe (blue) were presented to the public in 2001 during the consultation on a new route to the north and the way it is now shown
Reproduced from the Ordnance Survey 1:50,000 scale map by permission of Ordnance Survey® on behalf of The Controller of Her Majesty's Stationery Office. © Crown copyright 2004. All rights reserved. Licence number 100042273.
(red) in the Airport’s publications. The instructions to pilots have not changed in this time and the blue route was being flown regularly 10 years ago.
The reasons for the change in flying behaviour are not yet clear but the importance of this failure to follow noise abatement procedures to residents of south Luton was highlighted in 2009 when the consultant who generates the noise contours for the Airport revised the track which aircraft were assumed to follow to more accurately reflect reality. This raised the number of people living within the 63 dBA Leq daytime noise contour tenfold.
Other tracking issues
In general, the NPR swathes avoid areas of high population. In recent years, departing aircraft have been over-flying towns such as Hemel Hempstead, Hitchin and Stevenage. Over Harpenden, aircraft departing from the runway to the east but turning to fly to the south west have been flying at least a mile further south across the town than in previous years. This has probably been a gradual development which has become more noticeable with the growth in numbers of flights.