less noise with 4 degrees glideslope
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less noise with 4 degrees glideslope
just heard another discussion on the radio about noise plagued people around an airport and once more heard the song about the all solving solution: clean approach.
am working for an airline with strict stabilisation criteria and remember the criteria for such a clean approach given by stockholm airport: maximum 2 nm level flight.
what happens if anybody makes a level flight at minimum altitude fully configured will not be what sleeping people below want to hear and generally think that the clean approach concept does not really help as long as we pilots tend to be conservative (to add a year or two to the pilot time in just that company...)
here is my idea throwing in experience on the 320 on approaches down to 1000ft on a 5degrees and then changing back to 3degrees but asking you about your equipment to prove correctness of following statement:
most aircraft could use a 4 degrees glideslope with enough thrust for safety reasons when in an available final configuration but with less thrust than we use now and if last 5000ft (tbd) are flown in this final configuration stress levels will fall drastically not only for people below but also for pilots, especially, when tailwindlimits above 10kts as allowed nowadays on some airbus aircraft are cut back to 10kts to avoid idle landings...
(by the way, why not allow idle landings with an even steeper glideslope and decide at around 500ft based on runway conditions and GROUNDspeed about landing or go around - just another idea, not the thread!)
am working for an airline with strict stabilisation criteria and remember the criteria for such a clean approach given by stockholm airport: maximum 2 nm level flight.
what happens if anybody makes a level flight at minimum altitude fully configured will not be what sleeping people below want to hear and generally think that the clean approach concept does not really help as long as we pilots tend to be conservative (to add a year or two to the pilot time in just that company...)
here is my idea throwing in experience on the 320 on approaches down to 1000ft on a 5degrees and then changing back to 3degrees but asking you about your equipment to prove correctness of following statement:
most aircraft could use a 4 degrees glideslope with enough thrust for safety reasons when in an available final configuration but with less thrust than we use now and if last 5000ft (tbd) are flown in this final configuration stress levels will fall drastically not only for people below but also for pilots, especially, when tailwindlimits above 10kts as allowed nowadays on some airbus aircraft are cut back to 10kts to avoid idle landings...
(by the way, why not allow idle landings with an even steeper glideslope and decide at around 500ft based on runway conditions and GROUNDspeed about landing or go around - just another idea, not the thread!)
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fuelevap:
Won't work in the U.S. for airline airports. The FAA is hard over on 1,000 feet per mile max vertical descent and definately not engines at idle from 1,000, feet agl until in the flare. The 1,000 feet max v/s came from an NTSB recommendation.
most aircraft could use a 4 degrees glideslope with enough thrust for safety reasons when in an available final configuration but with less thrust than we use now and if last 5000ft (tbd) are flown in this final configuration stress levels will fall drastically not only for people below but also for pilots, especially, when tailwindlimits above 10kts as allowed nowadays on some airbus aircraft are cut back to 10kts to avoid idle landings...
I have slight doubts if this will make approaches much quieter. One might think that one degree will keep the planes higher and enable steeper descent with less power without any further implications, but in fact there are several.
- In my company, it is a requirement at the stabilization gate to have the engines run under a minimum power (10% Torque on the DH8D) to shorten the spool-up in case of need. So the aircraft will need to be stabilized at the approach speed, not still reducing towards it, at 1000ft AAL. Now a steeper approach angle makes speed reduction much harder, usually requiring the early use of flaps, the extension of the landing gear and possibly also increased prop RPM (above 4 degrees, we are even required to have the landing configuration with maximum flaps, prop RPM and the gear down when intercepting the glideslope) - and all this does not exactly reduce the noise emissions. Quite the opposite actually. On the Fokker, a 4 degrees approach may also require the use of the speed brake for the entire approach. While the engines may run at idle power only during the speed reduction, I am under the impression that a few percent of power more or less have a way lower effect on noise than extended flaps or landing gears - these are the other main source of noise on an aircraft.
-Resulting from the previously written, such a 4 degrees approach will on average be flown much slower than a standard 3 degrees ILS. Keeping in mind that aircraft separation on the approach is not measured in minutes but in miles, it seems logical that such a 4 degrees approach will reduce the airport traffic capacity by a noticeable margin. Now this will not lead to less traffic but typically will cause holdings and other delays at rush hours. Consequently, more fuel will be burnt unnecessarily.
So in my eyes, implementing a 4 degrees approach where not mandated by terrain will likely not even bring a small-scale effect in decreasing the noise burden on those living in the approach sector, but will come at the price of increased fuel burn and therefore pollution.
- In my company, it is a requirement at the stabilization gate to have the engines run under a minimum power (10% Torque on the DH8D) to shorten the spool-up in case of need. So the aircraft will need to be stabilized at the approach speed, not still reducing towards it, at 1000ft AAL. Now a steeper approach angle makes speed reduction much harder, usually requiring the early use of flaps, the extension of the landing gear and possibly also increased prop RPM (above 4 degrees, we are even required to have the landing configuration with maximum flaps, prop RPM and the gear down when intercepting the glideslope) - and all this does not exactly reduce the noise emissions. Quite the opposite actually. On the Fokker, a 4 degrees approach may also require the use of the speed brake for the entire approach. While the engines may run at idle power only during the speed reduction, I am under the impression that a few percent of power more or less have a way lower effect on noise than extended flaps or landing gears - these are the other main source of noise on an aircraft.
-Resulting from the previously written, such a 4 degrees approach will on average be flown much slower than a standard 3 degrees ILS. Keeping in mind that aircraft separation on the approach is not measured in minutes but in miles, it seems logical that such a 4 degrees approach will reduce the airport traffic capacity by a noticeable margin. Now this will not lead to less traffic but typically will cause holdings and other delays at rush hours. Consequently, more fuel will be burnt unnecessarily.
So in my eyes, implementing a 4 degrees approach where not mandated by terrain will likely not even bring a small-scale effect in decreasing the noise burden on those living in the approach sector, but will come at the price of increased fuel burn and therefore pollution.
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I fly into LCY with 5.5deg glideslope.
To do this, drag has to be used to stop the engines "idling". On the RJ/146 it was the airbrake. On the EMB190 it is the lift spoilers.
So thrust settings are not much less than on a normal approach.
I would not like (or be allowed) to do an idle thrust approach.
Think how long it takes for the engines to spool up on take off.
Imagine on approach with idle thrust as suddenly your airspeed goes from Vref +5 to Vref -5. It will be a very uncomfortable few seconds before you get any help from your engines to regain that speed.
To do this, drag has to be used to stop the engines "idling". On the RJ/146 it was the airbrake. On the EMB190 it is the lift spoilers.
So thrust settings are not much less than on a normal approach.
I would not like (or be allowed) to do an idle thrust approach.
Think how long it takes for the engines to spool up on take off.
Imagine on approach with idle thrust as suddenly your airspeed goes from Vref +5 to Vref -5. It will be a very uncomfortable few seconds before you get any help from your engines to regain that speed.
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Approach idle mitigates a good deal of that snag. MABH on my jet is 17" as I recall.
In my airline we class anything over 3.2 degree's as a steep approach and it must be flown fully stabilised from the FAF. The real issue would be slowing the jet if you didn't especially in turbulence or with a tailwind. Can't really see decelerated approach's happening at 4 degree's somehow
In my airline we class anything over 3.2 degree's as a steep approach and it must be flown fully stabilised from the FAF. The real issue would be slowing the jet if you didn't especially in turbulence or with a tailwind. Can't really see decelerated approach's happening at 4 degree's somehow
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To manage the energy at 4 degree GPA, the slat/flaps/speed brake noise would likely negate any benefits regarding noise abatement...
Cant see many 4 engine or heavies making a steep slope like that, most of the time, we are trying to reduce the GPA to 2.8/2.5 to manage a descent queue...
few guidance systems are set up for that...
Cant see many 4 engine or heavies making a steep slope like that, most of the time, we are trying to reduce the GPA to 2.8/2.5 to manage a descent queue...
few guidance systems are set up for that...
Last edited by FlightPathOBN; 4th Sep 2012 at 16:12.
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Whilst the actual thrust used to perform a steep approach may be very similar to a standard approach, the (ground) noise footprint is smaller. But the best advice to people affected by aircraft noise is to move back to where you came from. Do not buy your next house near a F
g airport. The majority of airport noise is generated by whingers who shortly after moving house close to a well established airport, start to complain about the noise of aircraft. Another top tip to tits like these would be - Don't move close to a tanning factory or refuse handling centre if you don't like bad smells, etc.
Another solution might be to spread the noise about a bit, bit that is not possible because of "noise abatement procedures". At certain airports this means that for certain houses, for a minimum of seven miles out, they will be hit with noise by every single approach. Sounds more like a noise maximisation procedure to me.
PM
g airport. The majority of airport noise is generated by whingers who shortly after moving house close to a well established airport, start to complain about the noise of aircraft. Another top tip to tits like these would be - Don't move close to a tanning factory or refuse handling centre if you don't like bad smells, etc.Another solution might be to spread the noise about a bit, bit that is not possible because of "noise abatement procedures". At certain airports this means that for certain houses, for a minimum of seven miles out, they will be hit with noise by every single approach. Sounds more like a noise maximisation procedure to me.
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exactly...like you didnt realize there was an f'n airport there when you moved in!
we have some interesting results using the marine inversion layers to bounce the sound around...
I have seen people cover their house with tin foil to reflect the sound, at least I think thats why they are doing that....
we have some interesting results using the marine inversion layers to bounce the sound around...
I have seen people cover their house with tin foil to reflect the sound, at least I think thats why they are doing that....
Last edited by FlightPathOBN; 4th Sep 2012 at 22:11.
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I have lived around a busy airport, I moved. Do you really want to submit to idiots who complain about noise and depreciation when they made a concious decision to live there in the first place????
fuelevaporator, sorry to disappoint you, but this has already been thought of and extensively tested in the 1970s.
RAE Bedford (BLEU/Flight Systems) conducted steep approach and landing trials, and two-stage (segmented) approaches with HS 748 and BAC 1-11 aircraft.
Some of the tests were in conjunction with the FAA, and sought solutions for B727 / Trident size aircraft during regional operations. Tests were extended to 1011 sized aircraft and used MLS for approach guidance.
The general findings were that 748 / 1-11 aircraft could autoland from 5-6 deg straight in approach – demonstrated with use of MLS, but heavier aircraft needed to change to a flatter approach at a suitable point. The absolute minimum for this was 300ft with autopilot/autothrust control, but for manual flight a 1000ft changeover was required. These values also considered combinations of steep, curved / segmented approaches. Some tests were flown at LGW and IIRC, LHR when experimental Doppler MLS was installed.
Whist the conclusions confirmed practicality and showed many noise benefits, the implementation requiring precision approach aids (MLS), matched lighting, revised airspace, and co-ordination with non-compatible aircraft, prevented implementation.
Also there were on-going engine and airframe noise reduction programs which showed similar benefits.
RAE Bedford (BLEU/Flight Systems) conducted steep approach and landing trials, and two-stage (segmented) approaches with HS 748 and BAC 1-11 aircraft.
Some of the tests were in conjunction with the FAA, and sought solutions for B727 / Trident size aircraft during regional operations. Tests were extended to 1011 sized aircraft and used MLS for approach guidance.
The general findings were that 748 / 1-11 aircraft could autoland from 5-6 deg straight in approach – demonstrated with use of MLS, but heavier aircraft needed to change to a flatter approach at a suitable point. The absolute minimum for this was 300ft with autopilot/autothrust control, but for manual flight a 1000ft changeover was required. These values also considered combinations of steep, curved / segmented approaches. Some tests were flown at LGW and IIRC, LHR when experimental Doppler MLS was installed.
Whist the conclusions confirmed practicality and showed many noise benefits, the implementation requiring precision approach aids (MLS), matched lighting, revised airspace, and co-ordination with non-compatible aircraft, prevented implementation.
Also there were on-going engine and airframe noise reduction programs which showed similar benefits.
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when they made a concious decision to live there in the first place????
I recall talking with the then Boeing aerodromes specialist years ago. His story was along the lines of "the most efficient way to plan for a significant domestic village/town/city development 20 years in the future .. is to plan for a significant airport development 10 years in the future ..."
At least Melbourne (YMEL) was put out in the sticks with planning restrictions in a futile attempt to limit the problem. For the first few years, things were great .. now it's a real bind to meet the various noise requirements.
I recall talking with the then Boeing aerodromes specialist years ago. His story was along the lines of "the most efficient way to plan for a significant domestic village/town/city development 20 years in the future .. is to plan for a significant airport development 10 years in the future ..."
At least Melbourne (YMEL) was put out in the sticks with planning restrictions in a futile attempt to limit the problem. For the first few years, things were great .. now it's a real bind to meet the various noise requirements.
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With the automatic snitch reports on acars if your surface winds were a 10 knot tailwind but 500 ft winds were 20 + you would have US airplanes going around all the time because they couldn't exceed 1,000 fpm. Don't screw with something that works.
The INTERSCAN Microwave landing System was developed and proven back in the late 70's by Australia's CSIRO, it allowed nearly unlimited approach tracks and variable approach angles but sadly was never adopted for widespread use.
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FPOBN:
The U.S. standard was 2.5 degrees, which worked great for Connies, DC-6s, and the like. But, it was too shallow for the jet transports. Thus all standard ILSes were converted to 3.0 degrees in the early 1970s, with 3.1 degrees being the max for Approach Category D.
Cant see many 4 engine or heavies making a steep slope like that, most of the time, we are trying to reduce the GPA to 2.8/2.5 to manage a descent queue...
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My experience on the A320 is that the aircraft will settle at about 160kts with flap 2 and more or less idle power. At 4 miles drop the gear and the last two stages of flap and at 1000 ft the aircraft is stable with power is coming on nicely. I suspect a 4 degree glideslope would require approach idle only, not an ideal solution.
At 160 kts that's 1100 fpm in calm winds just to stay on the glideslope; 950 ft/min at 140 kts.
At 160 kts that's 1100 fpm in calm winds just to stay on the glideslope; 950 ft/min at 140 kts.
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I agree with a couple of posters above - stuff 'em. If these idiots are silly
and dumb enough to move into areas of well-known airport noise because
of the cheaper rent/mortgages then they can double-glaze their windows
and tiles or just move out. Bitching and moaning about it is their problem
and no-one else's. Why should we get pulled to the office on Level 3 QAR
busts just because of the unwashed?
and dumb enough to move into areas of well-known airport noise because
of the cheaper rent/mortgages then they can double-glaze their windows
and tiles or just move out. Bitching and moaning about it is their problem
and no-one else's. Why should we get pulled to the office on Level 3 QAR
busts just because of the unwashed?
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I'm guessing the Cat 1 DA would go up on a 4 degree slope, as autolands aren't permitted on that slope then Cat 2/3 ops are out - Wouldn't like to visit in the typical scandinavian winter!
At MRS on a 4 degree slope, most configure totally prior to the glide... Lots of noise!
At MRS on a 4 degree slope, most configure totally prior to the glide... Lots of noise!
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At least Melbourne (YMEL) was put out in the sticks with planning restrictions in a futile attempt to limit the problem. For the first few years, things were great .. now it's a real bind to meet the various noise requirements.
Current standard for Airbus RNP is 2.8 GPA so they can manage the energy...
CDA will help with this, but good luck with CDA in the US...
Last edited by FlightPathOBN; 5th Sep 2012 at 20:34.
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Noise
Interesting discussion. As I posted in another thread, the newer by-pass engines of today are very quiet, so whats the fuss about.
Some points : The CFIT manual published by Airbus recommends glide slopes angles of between 3 and 3.7 degrees for jet transport, that is a gradient of between 318 and 392 feet per NM. 2.8 is too flat.
4 degrees =424 ft/nm
5.5 degrees (LCY) = 582 ft/nm
8.9 degrees =950 f/nm
For 1000 ft/nm the gradient would be 9.4 degrees, NUTS !!
Remember the recommended max is 3.7 degrees, 392 ft/nm
Even with approach idle on new jets, the spool up time is 6 to 8 seconds.
The microwave landing system (MLS) never worked well in rain. The signals were bent and unreliable, that's why it is not used today.
Blame week politicians for allowing the building of houses too close to airports. Trouble with that lot is no training for the job. Just the soap box talk, then we vote them into power.
Some points : The CFIT manual published by Airbus recommends glide slopes angles of between 3 and 3.7 degrees for jet transport, that is a gradient of between 318 and 392 feet per NM. 2.8 is too flat.
4 degrees =424 ft/nm
5.5 degrees (LCY) = 582 ft/nm
8.9 degrees =950 f/nm
For 1000 ft/nm the gradient would be 9.4 degrees, NUTS !!
Remember the recommended max is 3.7 degrees, 392 ft/nm
Even with approach idle on new jets, the spool up time is 6 to 8 seconds.
The microwave landing system (MLS) never worked well in rain. The signals were bent and unreliable, that's why it is not used today.
Blame week politicians for allowing the building of houses too close to airports. Trouble with that lot is no training for the job. Just the soap box talk, then we vote them into power.