Heathrow Approach Path
13 October 2013
From Kevin Smith, SW14
Can someone explain how flights bound for Heathrow Airport are marshalled? I live directly beneath an approach path to one of Heathrow’s two runways so I must declare a personal interest.
East Sheen is 12 miles due East of Heathrow’s Southern runway. So I have had plenty of time to observe both the precision with which incoming flights can pass line astern over the same two or three houses then migrate a little further north to give some respite from the noise. This modest transition is quite apart from, runway rotation.
But a colleague assured me that I was mistaken and that all aircraft overflying Sheen are already aligned with the southern runway. So to settle the matter, I contacted the Heathrow press office while he contacted a professional pilot. They both stated that planes landing at Heathrow were aligned with the runway centerline when they passed over Sheen.
But Heathrow’s recent ‘noise respite trial’ surely depends on the ability to direct incoming flights around the two noise relief zones terminating in neighbouring Putney? So I searched the Internet for a possible answer and found that the ILS localiser, used to guide aircraft in the end of the runway, projects a fan-shaped beam with an azimuth angle of five degrees at its apex.
At Sheen, 12 miles from Heathrow, the localiser beam would have a lateral spread of one mile (2π12 miles x 5/360) and this fits with what I see. Early morning flights often take a southerly route bordering Richmond Park, then later flights are moved to just north of the Upper Richmond Road. I have often tracked this transition while walking from my doorstep to the Upper Richmond Road.
So can you clarify the matter for us? Does Heathrow’s set a specific ILS azimuth approach for incoming flights? And if so, how are navigational systems such as VOR and Satnav used to turn flights into the ILS beam at the right point? I reckon a couple of pints at the Hare and Hounds are resting on the answer – but who will be buying?
Kevin Smith