a bit of an odd question for those who understand the runway alternations system and how wind affects it please.....
I'm going to Heathrow tomorrow for the day as I'm picking up my neighbour off SIA318 around 7pm. The runway alternation schedule says landing 27L until 3pm assuming wind is suitable.
It's the wind that is causing me a problem. The forecast is showing wind of around 15mph (or knots - not sure which BBC use) from approximately the south-east rising to 40mph by 3pm but by then from the south.
I believe LHR prefer to operate on 27s wherever possible and will even use 27s with a slight tailwind (5kts from memory) so are those winds likely to cause a switch to easterly (09) ops. I'm not expert at wind direction / speed components but logic says to me that a 15kt wind from the south east will cause a 7.5kt easterly component and enough to cause a switch to 09 operations - am I right please?
I'm assuming that by 3pm when they switch runways and the wind is southerly they will be landing on 27R anyway so it's up to 3pm that I'm trying to pre-guess. I'm trying to plan my day and locations and to me it's not clear cut at present. With showers forecast (and continuous rain later until dark) I don't want to be too far from my car).
MTIA
Andy
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Heathrow likely runway in use tomorrow (16-01-2020)
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Heathrow likely runway in use tomorrow (16-01-2020)
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Re: Heathrow likely runway in use tomorrow (16-01-2020)
It might be worth stopping somewhere just before you get there and having a look at FR24 to see which runway they're using.
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Re: Heathrow likely runway in use tomorrow (16-01-2020)
I shall when I get off the M25 if I can't see them departing/landing anyway. I just want to have a cunning plan ready.
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Re: Heathrow likely runway in use tomorrow (16-01-2020)
I can usually work it out with a good degree of certainty but it look so marginal I can't be sure. My best guess is 09s from around 10am until 3pm but I'm nowhere near certain.
As a 'suits all options' I will probably end up at the football club so I have my car there and if they are on 09s I can get departure shots of sorts (not as good as Feltham park though and if they are landing on 27L that's equally good. After 3pm it becomes a pain with 27R arrivals though AND very wet!
As a 'suits all options' I will probably end up at the football club so I have my car there and if they are on 09s I can get departure shots of sorts (not as good as Feltham park though and if they are landing on 27L that's equally good. After 3pm it becomes a pain with 27R arrivals though AND very wet!
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- PorkScratching
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Re: Heathrow likely runway in use tomorrow (16-01-2020)
As you say, Heathrow prefer the 27s and will keep operating on them with up to a 5kt tailwind component.
The relationship between relative wind angle and wind component is not linear (they are vector components for those that like maths!). This means that for winds that are 45 degrees from the direction of travel, the crosswind and headwind/tailwind components are approx 0.7 of the wind speed, not 0.5. So if landing on 27L with the wind from the southeast at 15mph (the BBC weather uses mph by default), then the tailwind component will be ~11mph, which is significantly more than 5kt, so I would expect Heathrow to be using the 09s.
If the wind does veer to a southerly during the day, and they are using the 09s to start with, it's probable that they will switch to the 27s. But it does depend on the what the winds actually do, and the gusts, and operational considerations too, so they may not do what you expect.
The relationship between relative wind angle and wind component is not linear (they are vector components for those that like maths!). This means that for winds that are 45 degrees from the direction of travel, the crosswind and headwind/tailwind components are approx 0.7 of the wind speed, not 0.5. So if landing on 27L with the wind from the southeast at 15mph (the BBC weather uses mph by default), then the tailwind component will be ~11mph, which is significantly more than 5kt, so I would expect Heathrow to be using the 09s.
If the wind does veer to a southerly during the day, and they are using the 09s to start with, it's probable that they will switch to the 27s. But it does depend on the what the winds actually do, and the gusts, and operational considerations too, so they may not do what you expect.
Last edited by PorkScratching on Wed Jan 15, 2020 2:21 pm, edited 1 time in total.
- andygolfer
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Re: Heathrow likely runway in use tomorrow (16-01-2020)
many thanks Nick, that helps no end. Hopefully I can keep a step ahead of any changes.
I think I can understand the maths of the components- I can vaguely remember my trigonometry and cosines etc!
Andy
I think I can understand the maths of the components- I can vaguely remember my trigonometry and cosines etc!
Andy
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Re: Heathrow likely runway in use tomorrow (16-01-2020)
thanks for the help guys
In the end it was 27s all day. In fact they were landing on 27L right through until 7pm rather than switching to 27R at the usual 3pm. don't know the reason but it made things easier for me. I'm guessing it was an issue with the ILS gear on 27R ut that IS only a guess.
In the end it was 27s all day. In fact they were landing on 27L right through until 7pm rather than switching to 27R at the usual 3pm. don't know the reason but it made things easier for me. I'm guessing it was an issue with the ILS gear on 27R ut that IS only a guess.
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