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uta999
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LHR Easterly Preference

Fri Feb 12, 2016 11:45 am

To get the third runway built, why doesn't Heathrow Airport Limited offer to ban approaches over the city completely?

This would allow two of the 09 runways for arrivals, while departures use 27 out to the west, so avoiding London.

With three runways, each a mile apart and nearly 12000' long, it is possible to operate in most wind conditions using an easterly preference for landings.

Ideally, all runways could be used in mixed mode, so there would not be the constant stream we have now.

It could even enable 24-hour operation, as the approach is largely over open countryside, similar to LGW. They appear to get away with more movements at night.

If Heathrow did operate normally during the night, there would not be the huge early morning peak of arrivals. Its this peak and the one in the evening that cause local traffic problems, pollution and noise. At the moment, airport staff, greeters and passengers are competing for the same road space with commuters and parents taking their kids to school. These are the very same local people moaning about aircraft noise/pollution.

The fact that there is no unemployment, high salaries and rising house prices because of their proximity to Heathrow Airport escapes them.
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mmo
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RE: LHR Easterly Preference

Fri Feb 12, 2016 1:36 pm

Quoting uta999 (Thread starter):
o get the third runway built, why doesn't Heathrow Airport Limited offer to ban approaches over the city completely?

You do realize most airlines have tailwind and crosswind limits that are below what the manufacturer has. 10Knot tail winds are fairly common while depending on the aircraft some have 15. My question to you is where would the flights go when the winds are out of limits? Your proposal has a complete ban on flying over the city.
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uta999
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RE: LHR Easterly Preference

Fri Feb 12, 2016 3:19 pm

The average year-round wind speed at Heathrow is less than 7 Knots from the south west.

The runways are 12000' long. This means 99% of the time aircraft would not need to fly over London during the approach.

A slight tail wind during landing is not a death trap, as some would like you to believe. It simply means the ground speed is higher. This is not a problem for today's aircraft, tyres, brakes and more efficient runway surface.

It could also be the case that flying with the wind, rather than into it would be less turbulent during the flare.
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glen
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RE: LHR Easterly Preference

Fri Feb 12, 2016 4:32 pm

Quoting uta999 (Reply 2):
The average year-round wind speed at Heathrow is less than 7 Knots from the south west.

An average wind of 7 kts means, there are many days with little or much more wind. And it's not the average wind which is the problem. It is the actual wind of every single landing. As mmo already mentioned most aircraft have a certified limit of 10 kts tailwind.
So there would be many days making it impossible to land. And with winds close to the limit I see a lot of go-arounds leading directly over the city...

Quoting uta999 (Reply 2):
It could also be the case that flying with the wind, rather than into it would be less turbulent during the flare.

Turbulence has nothing to do if you are going with or against the wind. If the air you are moving through with your aircraft is disturbed, you will have turbulence.

Quoting uta999 (Reply 2):
A slight tail wind during landing is not a death trap

No, it's not a death trap, but it is more problematic than a headwind landing. As you mentioned, during tailwind landing your groundspeed is higher. On a fixed glideslope this also means a higher rate of descend, which doesn't make the landing easier. The number of hard landings would probably increase.


Quoting uta999 (Thread starter):
Ideally, all runways could be used in mixed mode, so there would not be the constant stream we have now.

This system would be very intolerant for errors, especially in such a dense airspace as London.
In todays system the traffic on take-off an the one on approach are seperated. At higher altitudes, where departure and arrival routes cross each other (which they have to, as aircraft arrive from and depart to all directions), in- and outbound traffic is safely separated by different altitudes these routes are flown.
With your proposal you have hundreds of aircraft climbing and descending on opposite direction in very close proximity. There would be no tolerance for navigational errors. Well, when there will be a collision, at least the aircraft will fall into open countryside...

[Edited 2016-02-12 08:34:02]
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mmo
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RE: LHR Easterly Preference

Fri Feb 12, 2016 4:34 pm

Quoting uta999 (Reply 2):
A slight tail wind during landing is not a death trap, as some would like you to believe. It simply means the ground speed is higher. This is not a problem for today's aircraft, tyres, brakes and more efficient runway surface.

It could also be the case that flying with the wind, rather than into it would be less turbulent during the flare.

I think you are missing my point and trying to use average as the gold standard for runway operations.

First of all, the 10 knot tailwind limit that is imposed by the regulatory authorities with respect to the specific airlines ops spec. It is not some fluffy limit at all. It is a very "hard" limit and you can not violate the limit.

The average wind speed you quote is really meaningless. If I have a wind of 25 knots of wind, say 090/25 and the 4 days where the wind is 0/0 the average wind is 5 knots. So what? The fact remains the wind exceeded the limit on one day. You can not operate with that wind component. In addition, there are wind limits for CATIIIb approaches. Granted, you don't normally have to worry about low vis on very windy days but it can and does happen. Again, what do you do on those days where the wind is 11 knots?

Quoting uta999 (Reply 2):
A slight tail wind during landing is not a death trap, as some would like you to believe. It simply means the ground speed is higher. This is not a problem for today's aircraft, tyres, brakes and more efficient runway surface.

Are you aware of brake energy limits and the effect of additional groundspeed (airspeed) has on the energy generated? It is a big deal and I disagree with your statement. Landing with a tailwind presents all sorts of problems. Completely different thrust reduction technique for the crew, problems when coming back on an emergency landing right after takeoff. And please explain a "more efficient runway surface". That's a new one on me.

Quoting uta999 (Reply 2):
It could also be the case that flying with the wind, rather than into it would be less turbulent during the flare.

Again, could you explain this phenomena? I have found if there is turbulence at low levels it really doesn't make what any direction you are landing. Also, in gusty winds, if you are hand flying the thrust levers you have all sorts of wind additives to add. Now we are increasing the groundspeed even more.
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Florianopolis
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RE: LHR Easterly Preference

Fri Feb 12, 2016 4:50 pm

Just to make sure I understand, you're proposing something like LAX's "over-ocean" operations, as described here?

Quoting uta999 (Thread starter):
If Heathrow did operate normally during the night, there would not be the huge early morning peak of arrivals

I tend to think LHR's AM arrivals peak coincides with natural preferences, not airport rules. In other words, in the absence of rules, people would prefer to not arrive at 3 AM.

Quoting uta999 (Reply 2):
It could also be the case that flying with the wind, rather than into it would be less turbulent during the flare.

Airplane has no idea. But going down a glideslope in a tailwind does make your descent rate faster for the same descent angle. There is a significant reduction in turbulence if you don't go rolling off the end of the runway at high speed, however.
 
kdhurst380
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RE: LHR Easterly Preference

Tue Feb 16, 2016 12:55 am

It's a nice idea but it wouldn't happen, apart from being against most of not all airlines SOPs, averages are a very small part of the story. It's also worth remembering that whilst Heathrow's runways are the longest of any civilian airport in the UK, both easterly ends have displaced threshold, reducing actual landing distance.

It would be less significant for smaller aircraft, but Heathrow sees more VLA's (very large aircraft) than any other airport in Europe, these take a fair bit of energy to slow down.
 
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Jetlagged
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RE: LHR Easterly Preference

Thu Feb 18, 2016 5:54 pm

Quoting uta999 (Thread starter):
To get the third runway built, why doesn't Heathrow Airport Limited offer to ban approaches over the city completely?

That would mean all takeoffs are towards the city. Where is the gain? The approach side is much quieter than the takeoff side. Under your scheme (where all takeoffs and landings would be opposite to the generally prevailing wind) the suburbs to the east of Heathrow would always get takeoff noise.

Also, tailwind landings will also mean tailwind takeoffs. A lose-lose situation.

Since the 1960s Heathrow has operated with a westerly preference. Tailwinds up to 5 knots are accepted when the wind is from the east. This is the exact opposite of what you suggest. It is done so the more densely populated eastern side of the airport gets less takeoffs than the western side.

http://www.heathrow.com/noise/heathrow-operations/wind-direction
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