Heathrow noise abatement

[Jellied Eels]

Question from a ground observer - does wind/weather affect noise abatement? Have noticed on quiet days that more planes cruise quietly towards Heathrow, presumably on CDA, LP/LD. Yesterday & today, however, have seen jumbos swooping like swallows all over East/Southeast London, with lots of screech.

[HEATHROW DIRECTOR]

I think the answer to your query is - very little Despite what you imagine you are seeing, a/c fly similar CDA profiles on the approach day after day. Occasionally one might have to descend a little quicker than usual but not to the extent that you'd have Jumbos "swooping like Swallows"!! It simply doesn't happen.

[fadec_primary_channel]

During days of strong winds, on some aircraft types dependent upon configuration and weight, there can be a requirement for less thrust to maintain the assigned airspeed. Simply because we fly IAS, and the wind may give us 20-30 kts of the requirement.

This is only a minor point, and would endorse what HD has said already. :)

[Bigears]

fadec_primary_channel, I'm not a pilot, and at the risk of appearing stupid :rolleyes: , I don't understand your statement.
Can you point me towards an 'idiots guide'?
I would understand if it was relating to Ground Speed, but not airspeed.

[Bigears]

OK, since there is a deafening silence, I'll throw it open to anyone........am I as stupid as I look, or is there some flawed logic? :p

[Gonzo]

I'm with you, Bigears.

Airspeed is not affected by wind. Groundspeed is.

I think.:D

[expedite_climb]

Hmmm, i'd say theres a bit of both, simply because of the inertia that large jets have.

Wind often 'backs' (comes from a more anticlockwise direction), as you descend, and changes in direction coupled with inertia mean you may need less power, (albeit for a brief period).

Basically though, with no inertia, wind speed doesnt effect airspeed.

On a different note, is there a timetable published somewhere of which rwy is planned for use (i.e. north or south) somewhere ?

[Max Angle]

Headwind and tailwind does make a difference to the amount of thrust needed to fly an ILS. The glideslope is a fixed path in space which the aircraft has to follow and the rate of descent needed to do so depends on the speed the aircraft is moving down that path. A strong headwind means the a/c is slower down the glideslope and therefore needs a lower rate of descent to track the g/s.

A rough rule of thumb is 5 x groundspeed (or 10 x g/s /2)= rate of descent. ie gs=150 rod=750fpm.

Not sure that the thrust variation is enough to make much difference to the noise though.

[Point Seven]

Have to say, i'm very impressed with the science going on here. However, din't the pilot say that they fly INDICATED airspeed? And strong wind (all wind!) does contribute to this.:confused:

[refplus20]

Also in a strong wind situation, the airmass through which the sound is travelling would be moving away from the observer on the airfield watching approaching aircraft and consequently the noise level would be lower until the aircraft was abeam or past him. :p

[Lost_luggage34]

Just my tuppence worth ....

I wasn't aware that LHR had that much in the way of noise abatement - in practice that is.

I am a great lover of aviation and choose to leave within 10 miles of LHR. However, I do not believe sufficient alternation of westerley vs easterly landings and approaches is used.

It's great when we have a prevaling, albeit cold, easterly wind and activity is to the east. However, there are times when the wind component would allow more frequent useage of easterly operations.

Put that to the BAA and they send nice maps of SIDs and STARs. If you delve a little deeper you see that the noise monitoring terminals are (probably) stationed a tad too conveniently. There is no NMT near where I reside, yet any Dover departure to the West goes directly overhead.

Not a problem, I chose to live here. But when you consider that most of these flights are fuel-laden heaveys destined for the Middle/Far East or further afield, it makes one wonder. The main issue I have is when there is a delay and you have a 744 screeching overhead at 01:30am.

Bottom line, I think that more runway alternation could and should be utilised.

I am not a member of HACAN - nor would I ever be. Their focus seems purely on the affluent folks in Richmond etc. wrt arrivals in the early hours. The fact that they use council taxpayers money is also a huge turnoff.

Apologies for rambling.

[Point Seven]

Lost Luggage


Runway alternation rules at Heathrow are pretty strictly governed. It's not just a matter of air traffic picking a runway and using it. There is an annual plan of the correct alternation runway, for both easterly and westerly ops, and both night and day, published and distributed to all involved and this plan MUST be adhered to, unless there are met conditions or unservicabilities that preclude the correct runway being used. More alternation during the day would mean more delays for the aircraft (as it is quite a difficult procedure) and thus the flihgts would continue until later in the evening.

It should also be noted that in the Manual of Air Traffic Services for Heathrow, it states tat the preferential runway selection should be for Westerly operations unless the wind?met?unservicabilities cause otherwise. So if the wind is calm it is out of everyones hands as to the use of easterlies.

HOWEVER, as a final note, when Terminal 5 is finished and all of BA's ops are down by the 09R and 09L threshold doe s anyone out there think that they may lobby for Easterlies being the preferentail runway direction?:D

[Lost_luggage34]

Point Seven,
Thanks for that. But who makes the rules and why are they such ?

I stand by my original point regarding insufficient use of easterly landings/take-offs when the wind components allow. To me it simply doesn't happen when I believe it should or could.

For sure, the prevailing wind dictates westerly operations for the majority of the time. But in my limited opinion there could be and should more use of easterly operations. I have yet to find a decent answer to that question even from our friends at BAA.

As I've stated before, I am not complaining about it. I chose to live hear and thoroughly enjoy aviation and all that goes with it.

Cheers

LL

[foghorn]

Now that the Westerly preference rules have been changed, is the Cranford agreement still in force?

How significantly does that reduce the use of the Easterlies when the wind favours their use?

Sorry if these are dopey questions.

cheers!
foggy.

[Jerricho]

As far as I know, the Cranford Treaty is still in effect. On easterlies, Rwy 09L is used for arrivals, and 09R for departures. There are criteriea when this may be different (nav-aid unservicability, RVR problems etc...) as Point Seven discussed

Help me out here Tower Guys, but our tailwind component is a tailwind not exceeding 5 kts, with associated crosswind of 12 Kts, AND A DRY RUNWAY. I think the last bit can throw a spanner in the works, sorry LL_34. There is a graph we have available that allows the surface wind to be broken down, and shows what is accpetable before considering runway direction. There are times also when the wind at altitudes are such that even with a slight westerly component, it is very much easterly at alititudes (or vice-versa.......can have dramatic effects on landing rates!)

[expedite_climb]

Lost Luggage -

FYI - Every SID I have ever flown that has Noise monitoring points has them off to one side of the track, often at corners.

The reason is they are not monitoring how noisy an aircraft is, but whether it is maintaining the SID - which is the 'noise preferential routing'.

It is nice to see the 747's turning o/h us on those Dover SID's isnt it ? You're right though - easterlies are nice !:D :D

[Point Seven]

LL

I think that you're still missing the point a little bit. Easterlies CANNOT be employed simply because you, I or anyone else thinks that it may be quieter. There is a very real and tangible safety implication on the choice of runway in use. In the tower, we are very lucky in that (as yet) we are not yet governed by the airlines or the locals as to which end we should be landing on. It remains the decision of ATC and we make it based on the surface wind at the aerodrome, or IF THE WIND IS CALM (and I think that this may be the time that you're thinking of) we use the upper winds, for the benefit of a stable consistent approach. Easterly ops are not an answer to the perennial question of noise at EGLL.

In answer to the other questions, the Cranford agreement is still in place and the SIDs at Heathrow are there for noise abatement and are only to be deviated from is safety is an issue. This does not legislate for SAS pilots flying dodgy BPK's though.:= :=

[ATCO Two]

Wise words from Jerricho and Point Seven. The Cranford Agreement is still in place and only concerns DEPARTURES from 09L. As for SAS BPK departures, I MOR'd two this cycle and JD on the 4th floor is on the case!

[Lost_luggage34]

Thanks Point 7 - yes, I was particularly referring to CALM conditions. Also, hadn't fully considered the upper wind components.

[Banana99]

From Hansard 20/1/02

"Cranford Agreement
"Mrs. May: To ask the Secretary of State for Transport, Local Government and the Regions what plans he has to review the Cranford Agreement. [17794]
"Mr. Byers [holding answer 23 November 2001]: We recognise there is a case for reviewing the Cranford Agreement. We will do this next year in conjunction with the review of daytime westerly preference announced in the Terminal Five decision letter."