Advanced Continuous Descent Approach (A-CDA), also known as the "Green Approach" is allowing Boeing 737s in Europe to use a new landing approach that reduces fuel consumption, which in turn reduces the amount of CO2 and NOx emission by approximately 20%. The Green Approach is the result of GE Aviation's Systems participation in Europe's NUP2+ project, in which select 737 aircraft in Sweden were allowed to employ GE's Flight Management System (FMS) to fly the aircraft at idle thrust from cruise through landing. Green approaches also deliver measurable noise reduction for the surrounding communities. As a result, SAS and the Swedish government have agreed to expand the Green Approaches to the other busier airports in Sweden, and plans are being discussed with more airlines and ATM authorities to allow its use during city-pair operations between Stockholm and aerodromes within core-Europe.
AIPAIP — Aeronautical Information Publication: a publication issued by, or with the authority of, a state and containing information of a lasting character essential to air navigation.
AirwayAirway: a control area in the form of a corridor, normally 10 nautical miles wide, delineated by navigation aids (eg beacons).
CDA (Continuous Descent Approach)Continuous Descent Approach (CDA) or Optimized Profile Descent (OPD) is a method by which aircraft approach airports prior to landing. It is designed to reduce fuel consumption and noise compared with a conventional approach and involves maintaining a constant three degree descent angle during landing, until meeting the Instrument Landing System (ILS).
Continuous Descent Approach starts ideally from Top of Descent, i.e. at cruise altitude, and allows the aircraft flying its individual optimal vertical profile down to runway threshold. Some airports apply constraints to this individual optimal profile such as imposing a constant descent angle (e.g. 3 degree) or starting the CDA only after having left the holding pattern (e.g. London, at about 7000 feet) due to Air Traffic Management constraints.
CDA has historically had many critics who believed they were impractical at busy airports in crowded airspace. These criticisms were partially dispelled by the introduction of true CDA at several busy airports, including Los Angeles International Airport (LAX).
Chapter 2, 3 and 4 aircraft noise categoriesThe International Civil Aviation Organisation (ICAO) defines aircraft noise categories known as 'Chapters'. The Chapter of an aircraft is based upon noise measurements taken at the time of it's noise certification, taking account of its size and the number of engines. The noisiest category of aircraft, Chapter 2, has been banned from operating in Europe since 2002. Since 1977, all jet, and large non-jet, aircraft have been built to meet ICAO Chapter 3 standards, although stricter Chapter 4 standards are now in place for aircraft certified after 2006.
Some older, noisier aircraft types whilst meeting Chapter 3 requirements, only just comply with the standard and are significantly noisier than most modern aircraft. These have become known as 'Marginally Compliant aircraft' (MC3). The definition of marginal compliance was formalised by the EU in 2002 as being a cumulative margin of not more than 5 decibels upon Chapter 3 standards.
There are separate noise certification schemes for small propeller aircraft and for helicopters. What does this all mean in plain English? Not very much, but broadly the manufacturer measures the actual noise levels of each aircraft type they manufacture at three certification points ('approach', 'sideline' and 'flyover' – or more simply coming towards, passing by and going away!) and these measurements are used to determine whether the aircraft is classified as Chapter 2, 3 or 4. A large, modern 4 engine aircraft may well be classified as Chapter 4 but it can still be a lot noisier than a smaller Chapter 2 or Chapter 3 aircraft! Confused? We are too!
Chicago ConventionChicago Convention (see also ICAO ): Convention signed in December 1944 which sets out the framework on which air services operate in order that "international air transport services may be established on the basis of equality of opportunity and operated soundly and economically". Established the ICAO.
dB (The decibel) and dB(A) (the 'A weighted decibel')Sound is measured in decibels (dB) which follow a logarithmic scale because our perception fits such a representation – a sound which we rate as twice as loud as another is measured 10 decibels higher. In aircraft terms, a plane which produces 80 dB on flyover will be perceived as twice as noisy as one which produces only 70 dB. A decibel is one tenth of a bel, named for Alexander Graham Bell, and is used in its place because it represents the smallest change we can detect under laboratory conditions; a difference of 3dB between aircraft is generally regarded as the minimum we will be aware of.
Sound is usually measured on an "A-weighted" basis, dB(A), which means that the sound pressure waveform picked up by a microphone is put through a filter which weights it to mimic the variations in sensitivity of the human ear to the different frequencies within it. However, this ignores low frequency vibration which is annoying and can generate audible noise by, for example, rattling windows and doors.
ILS (Instrument Landing System)An ILS is an instrument approach system that provides precise navigational guidance to an aircraft approaching and landing on a runway. It is particularly useful in poor visibility conditions. Gatwick has two ILS approaches to the East and West of the main runway.
LdenDirective 2002/49/EC requires EU Member States to measure noise using the Lden noise metric. In the same way that we now measure the fuel consumption of our cars against the standard European 'urban', 'extra urban' and 'combined' cycles, Lden is used as a standardised European way of representing an equivalent (average) sound level over a full annual cycle / period. Because noise at night is causes a greater perceived nuisance, the Lden average is calculated by adding a +5 dB weighting for noise events in evenings and a +10 dB weighting for noise events at night.
Confused? Not surprising! Average noise levels can be a real trap. What is more annoying to you:
- – Periods of loud noise interspersed with periods of comparative silence or steady noise which merges into the background?
- – Noise at night or noise in the daytime?
- – High frequency noise or low frequency noise?
- – Noise with a particular and distinctive tone or any old noise?
- – Noise for a month followed by a month of comparative silence or just steady noise?
Lden is, of course, just an 'average' noise over 12 months, whatever that means!
Leq or LAeqThe term Leq is shorthand for 'equivalent continuous noise level', which is a parameter that calculates a constant level of noise with the same energy content as the varying acoustic noise signal being measured. The Leq is an energy mean of the noise level averaged over the measurement period and often regarded as an average level (see the figure below). In the UK, the averaged A-weighted Leq, or LAeq (often abbreviated to 'Leq'), for the 16-hour period 0700-2300 (local time), is used as the airport noise exposure index.
Confused? Not surprising! See Lden - average noise levels can be a real trap and means very little!
NOTAMNOTAM: Notice to Airmen: a notice containing information about the establishment, condition or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel concerned with flight operations. It is issued in the UK by the Aeronautical Information Service (AIS). A NOTAM Class 1 is distributed by means of telecommunications; a NOTAM Class 2 is distributed by slower and cheaper means.
NPRsNoise Preferential Routes (NPRs) or Preferred Noise Routes (PNRs) are pre-defined routes for aircraft leaving an airport. Departing aircraft are asked to stay within defined corridors and wherever possible these are generally kept away from the most densely populated areas. See diagram below showing the NPRs for Gatwick Airport
P-RNAV is a set of requirements that cover procedures, design principles and aircraft capabilities that enable more precise navigation. This can lead to environmental benefits from increased route flexibility.
SlotSlot: a particular time allocated to an airline to land or take-off from a particular airport. The allocation of slots at co-ordinated airports in the European Union is governed by EC Regulation 95/93 which aims to provide for neutral, transparent and non-discriminatory slot allocation at the more congested Community airports through a co-ordinator independent of Government, airlines and airports. In the United Kingdom the slot co-ordinator is Airport Co-ordination Limited (ACL).
UKAIPThe UK Aeronautical Information Package (UKAIP) is the set of 'rules' which govern the use of UK airspace – equivalent to 'the Highway Code for pilots'
The UK AIP, AIP Supplements and AIC, together with AIP Amendments are issued by NATS and any changes to UKAIP are published on a monthly cycle in the form of AIRAC notices.
For airports such as London Gatwick (EGKK) UKAIP consists of 'Textual Data' and 'Charts Related to the Airport'. These documents are the instruments which are used to inform air operators and flight crew how and where to fly and how and where to take directions from Air Traffic Control. Unfortunately, they are rather complex, use acronyms and specialist terms very heavily and therefore tantamount to impossible for the layman to understand.which set out requirements for stacking.