PPRuNe Forums

PPRuNe Forums (https://www.pprune.org/)
-   Spectators Balcony (Spotters Corner) (https://www.pprune.org/spectators-balcony-spotters-corner-52/)
-   -   Heathrow Approach Path (https://www.pprune.org/spectators-balcony-spotters-corner/525519-heathrow-approach-path.html)

krsmith 13th Oct 2013 12:40

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


DaveReidUK 13th Oct 2013 21:33


But a colleague assured me that I was mistaken and that all aircraft overflying Sheen are already aligned with the southern runway.
He is correct. You are mistaken.


They both stated that planes landing at Heathrow were aligned with the runway centerline when they passed over Sheen.
They are correct. Aircraft are required to join the ILS at or above 2500 feet (3000 feet at night). That means that they must be on the runway centreline by around 8nm from the runway during the daytime - roughly by the time they are over Putney.


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?
The "no-fly" zones made little or no difference to the flightpaths of aircraft by the time they had reached Putney.


Does Heathrow’s set a specific ILS azimuth approach for incoming flights?
If you mean "is the ILS offset from the centreline of the runway?", the answer is No.


I reckon a couple of pints at the Hare and Hounds are resting on the answer – but who will be buying?
Looks like the drinks are on you.

MarianA 14th Oct 2013 09:38


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.

That five degree fan is the area in wich the localizer signal can reliably be received by the equipment on the aircraft. The target then is to fly down the centre line of that fan, any deviation from that will show in the cockpit and be quickly corrected.

The direction of that transmitted centreline is fixed at installation of the system and in the majority of cases it is pointing down the extended centreline of the runway the system is guiding aircraft to. ILS systems can be installed at an angle from a runway, but that is only done where terrain or other obstructions require it and that offset-angle is then fixed as well and cannot be changed without physically moving and realigning the antenna-array.

In theory it would be possible to instruct crews to fly the localizer at a constant deflection of x and thus follow not the line the transmitter is pointing at but come in at a slant. I believe that is never done.

You would need multiple ILS system installation to the same runway to achieve any noticeable spread of flight paths at that stage. That is never done either.

HEATHROW DIRECTOR 14th Oct 2013 12:35

<<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 suspect that what you are seeing are aircraft landing on both runways, which may occur under certain conditions during early morning.

<< how are navigational systems such as VOR and Satnav used to turn flights into the ILS beam at the right point? >>

All aircraft flying into Heathrow are radar controlled. Instructions from ATC include changes of heading, speed and altitude and the position at which aircraft join final approach varies greatly depending on traffic. It may be 8 miles or it may be 15 miles. To achieve the maximum landing rate, speed control is applied on final approach until aircraft are about 4 miles from the runway.

HTH

c52 14th Oct 2013 14:20

I have a dozen questions I'd like to ask on this topic - surely there's a book available to explain it all. Anyone got any ideas? The best I can find is from Ian Allen, published in 1998.

Talkdownman 14th Oct 2013 14:33

Have a little play with Heathrow Webtrak. That will show you where all the planes have been. Then you can see just how skilled Heathrow Directors have to be...

Allow a little time for it to load. Have fun!

Oh, and Kevin, mine's a pint of Doom Bar...Cheers!

c52 14th Oct 2013 14:42

It's from watching FR24 that my questions arise.

Gonzo 14th Oct 2013 15:03

c52, ask away....

c52 14th Oct 2013 15:39

here's a few...

why do most flights get to LHR via Lambourne when most of the world is not to the north-east?

why are there days (with decent weather) when all the stacks are full for hours on end and other days when holding is the exception?

why do some US/Canada/Dublin flights arrive via Ockham?

why would two consecutive flights to Singapore turn right and left on leaving LHR?

how much disruption is caused by the 1500 runway swap, and how much when the runway changes from 09 to 27 or vv?

when LHR's capacity is stated as 498000 movements per year (I think), how is that calculated? Not on the basis of an arrival and a departure every minute from 06:00-23:00.

Why do aircraft fly Biggin-Epsom-almost back to Biggin before lining up with the runway? It makes for a lot of unnecessary noise and pollution over London and I've have thought the purpose could be served just as well by flying out east until it's time to turn onto the approach.

Why do some planes cross the centreline on their approach - e.g. Ockham to ~Edgware?

Do aircraft flying to say Farnborough or Biggin Hill have a sort of dedicated tunnel to fly through, or are they directed to avoid whatever other traffic is around at the time?

Most Detling departures fly past Biggin at < 8000', but a few are well clear at 10-12000'. Couldn't they all get that high to avoid inbound traffic?

The first time I took off on 09R at Heathrow we were warned we'd be making an extremely sharp right turn immediately after take-off for noise abatement reasons. That duly happened - but they don't do it now. Why not? (It was a MAS 747).

HEATHROW DIRECTOR 14th Oct 2013 15:52

Over to you Gonzo. You've done it now!!

Hartington 14th Oct 2013 16:01


The first time I took off on 09R at Heathrow we were warned we'd be making an extremely sharp right turn immediately after take-off for noise abatement reasons. That duly happened - but they don't do it now. Why not? (It was a MAS 747).
Not related to Heathrow but some years ago I was on a United 777 from San Francisco to London. UA have the ability to pipe the ATC into channel 9 on the IFE and I was listening as we taxied out. As we approached the runway the controller asked "can you accept a shorline 9 departure" to which the answer was an immediate "yes" followed by ATC asking "are you sure". There was then a delay before our pilots once again said they could accept the departure. We lifted off and immediately turned right; the normal long haul departure from 28R back to London being straight over the peninsular to the ocean and then a right turn.

The point is that just because you haven't experienced the same departure as the MAS one since it happened doesn't mean it never happens.

Defruiter 14th Oct 2013 16:56

I can answer some


why do most flights get to LHR via Lambourne when most of the world is not to the north-east?
Traffic doesn't just route via LAM from the North East. Anything coming from the east of Heathrow tends to come in via LAM. (Holland, Belgium, Germany, eastern block, Russia, Scandinavian countries, the far east etc). BIG traffic tends to come in from parts of France/Spain, Italy, Africa and other countries to the south east. OCK traffic tends to come from over the pond, parts of France/Spain, South America. BNN traffic tends to come from across the pond and UK domestic destinations.


why are there days (with decent weather) when all the stacks are full for hours on end and other days when holding is the exception?
There are lots of factors. Could be due to weather, airline schedules, atc staffing, the list is endless.


why do some US/Canada/Dublin flights arrive via Ockham?
Over the atlantic ocean are a series of tracks, called NAT tracks. As there is no radar over the ocean, aircraft must fly on these prescribed tracks at certain altitudes, several minutes apart. The tracks tend to be aligned with the wind. If the jet stream is further north, the tracks are northerly (so the planes have the wind behind them when coming east bound). if the jet stream is to the south, the tracks are southerly. So when tracks are northerly, aircraft tend to come in over scotland and down the UK into BNN, and when they are southerly, aircraft tend to come in over Wales and the South west into OCK.


why would two consecutive flights to Singapore turn right and left on leaving LHR?
Depends on the route that they have planned to fly. There can be lots of different routes to get to the same place. Airlines will plan on the best route for that aircraft on that particular day, taking into account lots of factors such as weather conditions, fuel required, aircraft weight etc. The aircraft turning right off 27s (left off 09s) is leaving UK airspace via Clacton, the aircraft turning left off 27s (right off 09s) is leaving UK airspace via Dover.


how much disruption is caused by the 1500 runway swap, and how much when the runway changes from 09 to 27 or vv?
From a radar point of view, switching from 27L to 27R or vice versa causes very little disruption, if any. The only complicated bit is working out which aircraft is last/first on either runway. When switching from 09 to 27 or vice versa, things can get very complicated. I don't know what disruption is caused on the ground, I'm not a tower controller. Someone else will have to answer that.


Why do aircraft fly Biggin-Epsom-almost back to Biggin before lining up with the runway? It makes for a lot of unnecessary noise and pollution over London and I've have thought the purpose could be served just as well by flying out east until it's time to turn onto the approach.
It's all to do with the set up of the airspace. Heathrow isn't the only airport in London.


Do aircraft flying to say Farnborough or Biggin Hill have a sort of dedicated tunnel to fly through, or are they directed to avoid whatever other traffic is around at the time?
They fly on prescribed routes, which keep clear of other airports traffic (to a degree!)


Most Detling departures fly past Biggin at < 8000', but a few are well clear at 10-12000'. Couldn't they all get that high to avoid inbound traffic?
Unfortunately not. All aircraft climb at different rates. We have to ensure that planes are kept either 3 miles or 1000ft apart. A lot of the time, there just isn't the room to get them going up and away from the inbound aircraft, so they are stuck low down.


I'm sure others will chip in with ones I've missed, or to add more content :)

DaveReidUK 14th Oct 2013 17:14

And a few more:


why do some US/Canada/Dublin flights arrive via Ockham?
As far as transatlantic arrivals concerned, their routes over the ocean (the NAT tracks) very from day to day depending on the winds - some days they are much further north/south than other days, which will affect where they enter UK airspace and therefore which approach routing (STAR) they arrive at Heathrow via (i.e. Ockham or Bovingdon).

Bear in mind also that the USA and Canada are very large countries. If you look on a globe you can see that the Great Circle route from West coast points such as San Francisco and Vancouver goes much further north that the GC routes from, say, New York or Boston.


The first time I took off on 09R at Heathrow we were warned we'd be making an extremely sharp right turn immediately after take-off for noise abatement reasons. That duly happened - but they don't do it now
But they do.

Whenever Heathrow is operating on easterlies, departures are normally from 09R, and when the NAT tracks are southerly (see above), departures to the USA will usually head out over South Wales, which involves a 180 degree right turn on departure onto the Compton SID. Gonzo and/or HD will explain the challenges that ATC face keeping those departures clear of inbounds coming off the stacks, which results in around two-thirds of 09 CPT departures going technically "off-track".

Look at WebTrak for last Friday (11 October) from 16:30 and you will see half a dozen successive departures to YUL, EWR, ATL, LAX, BOS, JFK) doing just that - and note also the two SAN and YEG departures that turn left after takeoff and head north.

This is worth a read:

http://www.heathrowairport.com/stati...partures11.pdf

Defruiter 14th Oct 2013 17:24

09 CPT departures don't fly the SID at all (Though there may be occasions when they do, but these are few and far between.) They get airborne on a heading. They conflict with the arrival stream. If they followed the SID, they would almost be flying backwards up the ILS. Apparently, they've been trying to change this SID for 20+ years...

DaveReidUK 14th Oct 2013 17:36


09 CPT departures don't fly the SID at all (Though there may be occasions when they do, but these are few and far between.)
Well around a third of CPT departures from 09R are classed as "on-track", which means that they have stayed within the NPR lateral swathe that extends 1.5km either side of the SID track.

DaveReidUK 14th Oct 2013 17:52

One more:


how much disruption is caused by the 1500 runway swap, and how much when the runway changes from 09 to 27 or vv?
The first part has already been answered. Changing ends, from easterlies to westerlies or vice versa, typically involves a gap of around 8 minutes between the last landing in the original direction and the first in the opposite direction.

Again, if you want to see an example on WebTrak, look at last Saturday evening (12 October) from 17:25 onwards.

Gonzo 14th Oct 2013 18:01

Well, that was easy.

Next?

DaveReidUK 14th Oct 2013 18:39

Last one:


when LHR's capacity is stated as 498000 movements per year (I think), how is that calculated? Not on the basis of an arrival and a departure every minute from 06:00-23:00.
The limit of 480,000 ATMs per year is a planning constraint dating from the T5 decision. Here's how it works:

http://www.acl-uk.org/UserFiles/File...e%203%20v2.pdf

HEATHROW DIRECTOR 14th Oct 2013 19:12

I think they call it "thread drift" Gonzo!

HEATHROW DIRECTOR 14th Oct 2013 19:15

<<Changing ends, from easterlies to westerlies or vice versa, typically involves a gap of around 8 minutes between the last landing in the original direction and the first in the opposite direction.>>

8 minutes? What's going on? When I was there we'd have been shot for that.


All times are GMT. The time now is 15:22.


Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.