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LHR - Steeper Approaches trial 14 September 2015

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LHR - Steeper Approaches trial 14 September 2015

Old 24th Aug 2015, 08:41
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RAE Bedford conducted extensive noise trials 1975-85 which showed significant benefits with increasing approach angle. IIRC the BAe146/Avro RJ AFM has a table of angle vs noise for the full landing config.
One aspect of noise was the aircraft configuration. Engine noise reduction was generally understood, but the effect of the airframe less so; this was studied with overflight tests and a few Tristar ‘under-flights’ below a large noise monitor suspended from a helicopter.

Bedford also studied wake vortex, but I don’t recall any specific trials with steep approach, or any concerns that any change of approach path would significantly affect the wake.
I recall a study of the LHR 27R ‘famed’ vortex from a hangar (bakery?) with a SW wind which affected aircraft on short finals.

There were also operational studies at LHR with split operations where ‘STOL’ (steep approach) capable aircraft would land long, >3,500ft from a steep approach (4.5 deg), with heavy traffic on a normal, or slightly elevated approach. The different approach paths provided wake separation such that normal runway capacity limit spacing could be used for all types. Guidance was with ILS/MLS and PAPI.
These studies were revisited with the advent of the BAe146 at LCY, but not pursued as only a few aircraft were then STOL capable and even fewer operated at LHR. The situation and balance of traffic may now have changed enough to reconsider.

There should little or no concerns about aircraft operation or wake vortex from the LHR trials providing there is no need to change from the normal landing configuration; the noise benefits from 3.2 deg would be most noticeable at distant locations.
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Old 24th Aug 2015, 10:01
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The object of reducing noise on approach, IMHOm is to reduce the noise effect to the highest number of people. I still suggest that this can better be achieved by starting at higher platform height rather than a steeper approach from a lower height. Given ATC's perquisite to control a/c so they intercept from below this can lead to some pilots dragging it in. Leaving a STAR (IAF) fix from 6000' on a continuous descent, possibly with LOC & G.S. intercept close together at 10nm, with gear down no earlier than 5nm, would create a low noise foot-print. This is what we did on very basic B732 with no radar; so surely in today's wizz-bang all bells & whistles a/c it should be a doddle. Tinkering with the last 6-8nm seems a sticking plaster on a more serious problem.
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Old 25th Aug 2015, 09:04
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I live a few miles from Southampton Airport.

If a similar trial was happening here, I just calculated the aircraft would be about 90 feet higher overhead and thus 0.50dB quieter. I don't think any of the local residents would notice, not even me who is used to looking up at aircraft.

I gather the numbers are quite close to the natural glide angle for some jets, hence the mention of CDA. More drag and power is going to have to happen in the latter part of the approach though, and there will be limits to how close that transition can be brought.

So the trial will have negligible effect on the people most affected.

I don't think the human ear and brain can notice a 0.5 dB difference in a few seconds let alone a few days. Like guessing the weight of two cakes a few grams different. What is the PR point of promising an improvement that will turn out to be imperceptible?

I thought I would check my assertion about levels. I found discussion on a hifi type forum, where they proposed tests with 1 dB plus or minus or zero change in mid piece. Some discussion of which music or just pink noise. Someone said that 0.5 to 3 dB is said to be undetectable. Nobody actually polled any results. The discussion closed with someone talking of reading about a test with MRI scanning of people told to imagine they were sampling an expensive wine, and there was raised activity in parts of the brain that sense pleasantness. Placebo effect.

So the people who suggest this trial has already been deemed a success may well be right. But maybe it just depends on telling enough people.

Last edited by aox; 12th Oct 2017 at 22:43.
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Old 26th Aug 2015, 09:29
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Chaps,


I live in Sandhurst Berkshire, where I moved in 94, after growing up in Hounslow, between (what was then) 28L and 28R approaches.
Aircraft noise does not bother me in the slightest, but local Facebook groups are going all "nimbyish" over it.
Am I likely to really see ANY difference when I wake up on 14th September?
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Old 26th Aug 2015, 10:03
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Originally Posted by scudpilot
Am I likely to really see ANY difference when I wake up on 14th September?
The official line is that "visually the aircraft may appear slightly higher and quieter (1-2dB on average)".

See link in post #60.

Oh, and the trial doesn't start until 17th September.
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Old 30th Aug 2015, 18:07
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Originally Posted by DaveReidUK
Well somebody would have been behind those trial steep approaches, with the trailing aircraft obviously at 3°, but whether they were at the standard or increased separation (or maybe used the parallel runway to avoid wake issues), I haven't been able to find out.

Where's Gonzo when you need him?
Standard separation and it was a trial for the night jet ban slots. Eg. Land before 0602LT.

On our fleet and in our airline the aim is a CDA.
For our fleet this works well with Gear Down at 2000ft. 160kts-4Miles. stable around 1100ft.

VA is particularly bad at dragging their way in over London with gear down. Noisey in Barnes!!
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Old 30th Aug 2015, 19:22
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Originally Posted by Shaka Zulu
Standard separation and it was a trial for the night jet ban slots. Eg. Land before 0602LT.
OK, so presumably the BAW12/26/56 arrivals then, as they are the only A380 landings before 0600.

Any idea of the dates involved?
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Old 18th Sep 2015, 03:33
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just in case you missed it and reviving

thread


BBC NEWS | UK | UK Politics | Heathrow expansion plans unveiled
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Old 18th Sep 2015, 03:35
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Heathrow's new angle to win over neighbours: Planes to use a steeper landing as they descend in bid to cut noise levels
Heathrow Airport announces plans for steeper landing approach for planes
Planes currently descend at an angle of three degrees on final approach
From September 14, angle of 3.2 degrees will be introduced on a trial basis
Measure introduced in a bid to cut noise levels for west London residents
By EMMA GLANFIELD FOR MAILONLINE
PUBLISHED: 05:28, 11 August 2015 | UPDATED: 08:45, 11 August 2015

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Heathrow Airport has announced plans to introduce a steeper approach for planes coming in to land in a bid to cut noise levels.
Airplanes at Europe's busiest airport currently descend at an angle of three degrees on their final approach.
However, from September 14, an angle of 3.2 degrees will be introduced on a trial basis until mid-March next year.
The measure is part of 10 steps being trialled at the west London airport in a bid to improve noise levels for residents.
Heathrow Airport has announced plans to introduce a steeper landing approach in a bid to cut noise levels in west London. From September, an angle of 3.2 degrees will be introduced over the current three-degree angle
+3
Heathrow Airport has announced plans to introduce a steeper landing approach in a bid to cut noise levels in west London. From September, an angle of 3.2 degrees will be introduced over the current three-degree angle
'The steeper the angle, the less time an aircraft spends at low altitudes, which means that fewer people should be affected by higher levels of noise,' airport authorities explained in a briefing document.
'The trial will assess the operational and noise implications of slightly steeper approaches.'
The international standard approach for most airports in the world is set at three degrees, except for obstacle clearance - such as buildings or mountains.
Officials at London's Heathrow believe a steeper angle is possible and will lead to quieter approaches to the airport.
If adopted permanently, Heathrow will become the only airport in the UK to introduce such measures. It comes after a similar procedure was introduced at Frankfurt Airport in Germany.
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Other noise-reducing measures being implemented at Heathrow include allowing fewer plans to land and take off after 11pm.
Heathrow said it is also trying to encourage airlines to use 'modern, quieter planes' and has adopted noise insulation schemes around the airport.
Matt Gorman, director of sustainability and environment at the airport, said: 'Heathrow has changed, and taken a new approach to addressing our impacts on communities, including when it comes to noise.
'Our blueprint to cut aircraft noise has been driven by feedback from local communities.
'Its role is to challenge the industry to think innovatively about ways to reduce noise.
Heathrow Airport released this noise contour graphic to show how noise levels have reduced since 2011
+3
Heathrow Airport released this noise contour graphic to show how noise levels have reduced since 2011
Officials at London's Heathrow believe a steeper angle is possible and will lead to quieter approaches to the airport. Mobile noise monitors have been specially deployed for the duration of the trial, which ends next March
+3
Officials at London's Heathrow believe a steeper angle is possible and will lead to quieter approaches to the airport. Mobile noise monitors have been specially deployed for the duration of the trial, which ends next March
'Steeper approaches are just one step in the right direction, and along with other quieter operating procedures and incentives to bring quieter aircraft into operation, will ensure fewer people are affected by noise, even with an expanded airport.'
However, John Stewart, chairman of Hacan – a group which opposes expansion of Heathrow – said the new measures would offer little improvement.
He told The Times: ‘Increasing the angle will have some impact, and the cumulative effect of the plans set out in the blueprint will be felt on the ground, but the effect will be very small.’
Mobile noise monitors have been specially deployed for the duration of the trial and a report will be issued at the end to summarise the findings.
It comes as the Government considers whether to approve a third runway at Heathrow or expand air capacity in southeast England at another airport such as London Gatwick. A decision is expected by the end of the year.
The issue has proved highly controversial, drawing opposition from figures including London Mayor Boris Johnson, partly over concerns about noise in the densely populated area of west London over which many Heathrow flights take off and land.
A commission looking into the issue published a report last month strongly backing a third runway at Heathrow.

Read more:
Heathrow outlines new approach to cut noise | The Times


Read more: Heathrow planes to use a steeper landing as they descend to cut noise levels | Daily Mail Online
Follow us: @MailOnline on Twitter | DailyMail on Facebook
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Old 18th Sep 2015, 08:57
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Originally Posted by victor tango
However, from September 14, an angle of 3.2 degrees will be introduced on a trial basis until mid-March next year.
The trial was in fact due to start yesterday (17th) with the new AIRAC, though Heathrow initially put out an incorrect press release with the 14/9 start date.
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Old 18th Sep 2015, 09:01
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<<In 1986 there were very few flights after 8.30 pm at night. >>

I had been working there for 14 years by then and I do not recall "very few flights after 8.30pm".
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Old 18th Sep 2015, 21:30
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<<In 1986 there were very few flights after 8.30 pm at night. >>

I had been working there for 14 years by then and I do not recall "very few flights after 8.30pm".
And in 1986, BAC1-11's 707's, DC-8, 727 were in common operation.
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Old 19th Sep 2015, 09:54
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Steeper approach LHR - 18 SEPT

As pax, I experienced a steeper approach into LHR on !8 Sept. Ended in a "robust" landing and fairly fierce breaking. Do not know wind conditions - light storms and turbulence over southern counties. Frequent "robust" landings will not enhance LHR's case with pax. Sadly not likely to appease resident groups or politicians with their own agenda.
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Old 19th Sep 2015, 10:09
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Originally Posted by DIA74
As pax, I experienced a steeper approach into LHR on 18 Sept.
Out of interest, what was the airline/flight number?
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Old 19th Sep 2015, 10:44
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DIA74 Sorry I'm lost there.
Ended in a "robust" landing and fairly fierce breaking.
What broke?
What is the connection between a 7% steeper approach and a robust landing?
How did you know it was a steeper approach? Did the Nigel announce it or could you see the difference? I have to admit flying as a pax into Malaga RWY 13 I can't feel nor see any real difference to RWY 31.
As for robust landings - yes they happen! Anywhere.

As a pilot, flying a steeper approach, even 0.2 deg I always err on the safer side and configure earlier to avoid any FDM alerts. More drag = more aerodynamic noise and more engine noise. Pointless.
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Old 19th Sep 2015, 10:55
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For those observing different operators' application of configuration/stabilisation in a B77W at or close to MLW full configuration is required to achieve 160/4. So for their may be a slight improvement with the 3.2. Though not on a lower than ISA day!
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Old 19th Sep 2015, 23:10
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Hi aox

any chance you could pm me your calcs?

I don't want to challenge them online or anything - its just that I did an OU Course many moons ago and sound propagation & attenuation - including airfield footprints, were a significant part of the syllabus.

thanks
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Old 20th Sep 2015, 00:06
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Not sure it needs a PM of details

At any given point on the approach path the aircraft on a 3.2 degree slope will be about 6% higher than the 3 degree slope

Sound attenuates with distance squared, measured as 20 log (r2/r1) decibels, where r2/r1 is the ratio of the distances, in this case half a decibel

That will apply to below the flight path; for places a bit off to the sides then the proportionate change in distance will be less.

Last edited by aox; 20th Sep 2015 at 00:46.
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Old 20th Sep 2015, 06:42
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Originally Posted by aox
Sound attenuates with distance squared, measured as 20 log (r2/r1) decibels, where r2/r1 is the ratio of the distances, in this case half a decibel
As a general rule, that's true. Whether it's the net effect here depends on all other things being equal.

The nub of this thread seems to suggest that they won't necessarily be.
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Old 20th Sep 2015, 09:00
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Originally Posted by DaveReidUK
As a general rule, that's true. Whether it's the net effect here depends on all other things being equal.

The nub of this thread seems to suggest that they won't necessarily be.
Well, that's treating the sound as a point source, and non-directional.

Maybe someone can say whether they think those are too simplistic or poor assumptions. Yes it's moving, and continuous, but at any moment the sound reaching the observer has come from a specific point.

I also suggest that the greatest saving, due to 6.6% extra distance, will be where the aircraft is directly overhead. Where the observer is out at the side the increase in distance will be less. At say half a mile sideways aircraft on 3.2 and 3 degree approach angles are only about 1.5% different in distance from the observer. At one mile to the side this is 0.44%

A 1 or 2 dB difference is difficult for people to distinguish between two sounds played a few seconds apart. A few hours apart, assuming the trial starts at the beginning of one morning, only specialist instruments can compare. And locations half a mile and one mile to the side of the approach line will experience 0.12 dB and 0.04 dB differences. Utterly imperceptible. Where do the 2dB claims come from?

If the chosen angle means that aircraft are nearer to a pure glide approach and thus using less or idle power until the point of deploying more drag then yes that will be quieter, but two sounds the same level at source will not be distinguished by human ear and brain.

So are we talking about being able to use less power? Is that why prospective savings are greater?

What is a typical glide angle of these things? Has it worsened from 20 to 18 to justify a steeper angle being chosen? Will they also consider a range of slightly steeper angles for stronger winds?

Last edited by aox; 22nd Sep 2015 at 10:02.
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