less noise with 4 degrees glideslope

[fuelevaporator]

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!)

[aterpster]

fuelevap:

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...

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.

[Tu.114]

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.

[renard]

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.

[Ashling]

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

[FlightPathOBN]

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...

[Piltdown Man]

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:mad: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

[FlightPathOBN]

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....:oh:

[grounded27]

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????

[safetypee]

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.

[john_tullamarine]

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.

[bubbers44]

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.

[zlin77]

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.

[aterpster]

FPOBN:

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...

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.

[Fursty Ferret]

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.

[Slasher]

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?

[Cough]

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!

[FlightPathOBN]

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.

Exactly why we werent allowed to publish the RNP tracks for MEL, especially the EO missed, as the people in Diggers Rest didnt want 'an airplane on fire going over their house'

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...

[thermostat]

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.

[Cough]

MLS unreliable in the rain? Please could you inform NATS/CAA so they can stop me doing one (last week) in the (heavy) rain...

[FlightPathOBN]

thermostat,

2.8 degrees too flat, that is crap...

note that criteria max GPA for CAT C is 3.6 and CAT D is 3.1 degrees MAX!

For CAT D, we use 2.8 as the standard...

With baro-vnav, the min effective GPA is 2.5. That drives where you see the NA below temp, with 3.1 driving the NA above temp.

MLS never took off because the accuracy of the typical system is not much better than GPS. Heathrow has a custom system, and is used instead of the ILS in low vis situations...but its still DME/Precision.

The US no longer has any MLS procedures on the books...

[Boslandew]

The article about the Airbus 318 landing at LCY gives the runway length at LCY as 1199 metres/3650 feet which are very precise figures obviously quoted from somewhere. According to the UK AIP chart it is 1508 metres/4947 feet. Have I missed something?

[Squealing Pig]

Boslandew
http://www.ead.eurocontrol.int/eadbasic/pamslight-4D786E5D2E5C70A53E6895EB52019501/7FE5QZZF3FXUS/EN/AIP/AD/EG_AD_2_EGLC_en_2012-08-23.pdf Table 2.13 shows TORA as 1199m

SP

[Boslandew]

SP Many thanks. So its the difference between TORA and actual runway length. I've been out of the loop for 13 years, can't remember all the abbreviations.

The writer did say runway length.

[safetypee]

MLS works fine in rain.
The FAA favoured GPS only after fighting for world leadership of the MLS design with an inferior system, then discovering that the costs of re-equipping was not justified by their requirement for Cat 3. Thus the already funded GPS was selected as being capable of achieving Cat 3 integrity in the future at lower cost.

MLS was demonstrated at 1 deg glidepath showing interference free operation, and for potential military / helicopter applications.

The LCY runway was initially limited to 1199m to comply with the ICAO code 2 runway requirements (1200m limit). This provided the necessary lateral obstacle free zones and distances to the water hazards in the event of lateral or longitudinal runway excursion. With evolving common sense it has been possible to lengthen some aspects the runway whilst maintaining obstacle clearance (height of parked aircraft tails) and providing alternative overrun protection.
Runway extension to the West is not easy due to the (real) approach obstacles, but to the East with the absence of the mythical East London River Crossing Bridge the approach could be adjusted. The 5.5deg slope is retained for noise reasons.

[aterpster]

safety pee:

MLS works fine in rain.
The FAA favoured GPS only after fighting for world leadership of the MLS design with an inferior system, then discovering that the costs of re-equipping was not justified by their requirement for Cat 3. Thus the already funded GPS was selected as being capable of achieving Cat 3 integrity in the future at lower cost.

All I know about FAA MLS in the mid-1970s was the airlines wouldn't touch it. They had just spent a bundle on fail-active autholand tied to high-quality ILSes.

GPS can do great curved paths although I am not sure where those would be required at the major airports that have CAT III, at least in the U.S.

[thermostat]

Attack, attack, attack. Seems that some PPruners are only happy when on the defensive. Too bad we can't discuss items without the attacks.
Cough : That was my understanding when they were trying to develop the MLS system many years ago.
FlightpathOBN : Don't shoot the messenger. I am quoting from the Airbus CFIT manual. Due to many landing accidents in the past, research shows the 3 to 3.7 degree slope to be the best angles for large jet transport. That does not mean that some chart producers won't produce charts with less than 3 degrees. It's just not as safe as the larger angles, obviously. Airbus spent millions of $$ to develop the FPA system which I thought was the best invention in years. Instead of dragging the aircraft in on final with high power at 2.8 deg, why not fly down the slope at a more comfortable 3 deg. with more clearance from obstacles? Safety first.
I don't understand your bravo-nav statement. Please explain.
Why does the USA no longer have a MLS system? Again please explain.
Safetypee. What type of aircraft uses the 5.5 deg slope ?
AND PLEASE, NO MORE ATTACKS !!!!!!!!!!!!!!!!!!!!!!!!!!

[BN2A]

Bring back Concorde, the VC10, the 707, the Trident, etc etc etc....

Creates a bit of perspective!!

:D

[aterpster]

BN2A:

Bring back Concorde, the VC10, the 707, the Trident, etc etc etc....

Creates a bit of perspective!!

Next to the Concorde the "water wagon" version of the 707 would bring tears to your eyes as your ears shut down.:)

[Slasher]

I think its time to show the kids what a REAL jet sounded like back in the
days when we flew 'em. Ensure yer speakers/headset are up full blast.......


gwel7Ulmrvs

Ah that JT8D grunt - still brings a tear to me eye!

[FlightPathOBN]

thermostat,

Are you a pilot?

I am not sure what about baro-vnav you dont understand.

The reason why the US doesnt use MLS was already answered by several posters.

[safetypee]

MLS – the original concept of MLS was as the ICAO standard approach aid to replace ILS.
In the late 1970s ILS was projected to suffer co-channel interference problems with a rapidly expanding industry. Most Cat 1 operations could tolerate some interference, but for Cat 2 and particularly Cat 3 this was seen as a major safety issue for autocoupled approaches.
History shows otherwise, with a less than anticipated runway expansion, and lower Cat 3 demand, also that modern ILS / auto flight systems and careful ILS location reduces the problem.
The US won the MLS competition for the system design (time ref scanning beam) which like other systems could offer area navigation type approaches, but the straight-in ILS replacement was the priority, and this, particularly for Cat 1 and the urgent safety upgrade of NPAs to ILS, could be met by the emerging GPS with FMS R Nav.
The FAA quietly dropped MLS in favour of GPS, leaving Europe to solve the higher integrity problems for Cat 3 ILS. Some US views will claim GPS capable Cat 3, but perhaps the integrity is not yet as that required in Europe.

What type of aircraft uses the 5.5 deg slope ?
Some time since I visited LCY:-
Originally Dash 7 at 7.5 deg, then BAe146 / Avro RJ (all variants) at 5.5 deg.
Fokker tried the F70 (not very successfully ?), Saab 340, and other turboprops … ???
Airbus 318, and several Biz Jet types … .

Flight Path Angle (FPA) is a useful instrument aid, but its use during approach and landing requires knowledge of where the intended point of touchdown is.
Hence some of the first applications were displays on HUD where the FPA could be overlaid on the runway – but this also required a marker which designated the required flight path angle, so that when all were coincident the aircraft was on the correct approach path.
The similar head-down application requires an electronic (ground referenced) glideslope to determine the point of landing, hence use of FPA as/with a FD.

[DaveReidUK]

What type of aircraft uses the 5.5 deg slope ?
Some time since I
visited LCY:-
Originally Dash 7 at 7.5 deg, then BAe146 / Avro RJ (all
variants) at 5.5 deg.
Fokker tried the F70 (not very successfully ?), Saab
340, and other turboprops … ???
Airbus 318, and several Biz Jet types …

Not forgetting one of the commonest types that you will see at LCY - the ERJ-170.