This article is divided into the following 5 parts:
- History Describing the Need for Noise Abatement Procedures
- Calculations For Reference Points
- Test procedures
1. History Describing the Need for Noise Abatement Procedures
Standards and Recommended Practices for Aircraft Noise were first adopted by the Council on 2 April 1971 pursuant to the provisions of Article 37 of the Convention on International Civil Aviation (Chicago, 1944) and designated as Annex 16 to the Convention. The Annex was developed in the following manner:
The Sixteenth Session of the Assembly, Buenos Aires, September 1968, adopted the following Resolution:
- The problem of aircraft noise is so serious in the vicinity of many of the world’s airports that public reaction is mounting to a degree that gives cause for great concern and requires urgent solution;
- The noise that concerns the public and civil aviation today is being caused by increase in traffic of existing aircraft;
- The introduction of future aircraft types could increase and aggravate this noise unless action is taken to alleviate the situation;
- The Fifth Air Navigation Conference of ICAO held in Montreal in November 1967 made certain recommendations, based on the principal conclusions of the International Conference on the Reduction of Noise and Disturbance Caused by Civil Aircraft (“The London Noise Conference”) held in London in November 1966, with the objective of concluding international solutions to the problem through the machinery of ICAO; and
- The Assembly has noted the action being taken by the Council, in consultation with States and the appropriate international organizations, to give effect to the recommendations of the Fifth Air Navigation Conference, as reported to the Assembly by the Secretary General;
1.1 The Assembly resolves to instruct the Council:
- To call an international conference within the machinery of ICAO as soon as practicable, bearing in mind the need for adequate preparation, to consider the problem of aircraft noise in the vicinity of airports;
- To establish international specifications and associated guidance material relating to aircraft noise;
- To include, in appropriate existing Annexes and other relevant ICAO documents and possibly in a separate Annex on noise, such material as the description and methods of measurement of aircraft noise and suitable limitations on the noise caused by aircraft that is of concern to communities in the vicinity of airports; and
- To publish such material on a progressive basis, commencing at the earliest possible time.
In response to Assembly Resolution, a Special Meeting on Aircraft Noise in the Vicinity of Aerodromes was convened in Montréal (November–December 1969) to examine the following aspects related to the problems of aircraft noise:
- Procedures for describing and measuring aircraft noise
- Human tolerance to aircraft noise
- Aircraft noise certification
- Criteria for establishment of aircraft noise abatement operating procedures
- Land-use control
- Ground run-up noise abatement procedures
Based on the recommendations of the Special Meeting on Aircraft Noise in the Vicinity of Aerodromes, draft International Standards and Recommended Practices for Aircraft Noise were developed and, after amendment following the usual consultation with the Contracting States of the Organization, it was adopted by the Council to form the text of Annex 16.
With the development of Standards and Recommended Practices dealing with the control of aircraft engine emissions, it was felt that all provisions relating to environmental aspects of aviation should be included in a single document. Accordingly, it was agreed that Annex 16 would be retitled as
- “Environmental Protection” as Volume I of the Annex would contain the existing provisions (Third Edition) of Annex 16
2. “Aircraft Noise” as Volume II should contain the provisions related to aircraft engine emissions of Annex 16.
In reference to Assembly Resolution A33-7, the balanced approach to noise management consists of identifying the noise problem at an airport and then analyzing the various measures available to reduce noise through the exploration of four principal elements:
- Reduction at source
- Land-use planning and management
- Noise abatement operational procedures
- Operating restrictions
with the goal of addressing the noise problem in the most cost-effective manner.
- Bypass ratio: The ratio of the air mass flow through the bypass ducts of a gas turbine engine to the air mass flow through the combustion chambers calculated at maximum thrust when the engine is stationary in an international standard atmosphere at sea level.
- Powered-lift: A heavier-than-air aircraft capable of vertical take-off, vertical landing, and low-speed flight, which depends principally on engine-driven lift devices or engine thrust for the lift during these flight regimes and on non-rotating aero foil(s) for lift during horizontal flight.
- State of Design: The State having jurisdiction over the organization responsible for the type design.
- State of Registry: The State on whose register the aircraft is entered.
- Subsonic Aero plane: An aero plane incapable of sustaining level flight at speeds exceeding flight Mach number of 1.
- Type Certificate: A document issued by a Contracting State to define the design of an aircraft, engine or propeller type and to certify that this design meets the appropriate airworthiness requirements of that State.
Note: Noise certification is granted or validated by the State of Registry of an aircraft on the basis of satisfactory evidence that the aircraft complies with requirements that are at least equal to the applicable Standards specified in this Annex.
Items required for Noise Certification are:
- Name of state
- Title of Noise document
- Nationality or Common mark and Registration sign
- Manufacturer and Manufacturer’s designation of aircraft
- Aircraft serial number
- Engine’s manufacturer, type and model
- Maximum Takeoff Mass in Kgs
- Propeller and Propeller type driven aircraft
- Maximum Landing Mass, in Kgs
- The chapter and section of this Annex according to which the aircraft was certificated
- Additional modifications incorporated for the purpose of compliance with the applicable noise certification Standards.
- The lateral/full-power noise level in the corresponding unit for documents issued under Chapters 2, 3, 4, 5, 12 and 14 Annex 16
- The approach noise level in the corresponding unit for documents issued under Chapters 2, 3, 4, 5, 8, 12, 13 and 14 Annex 16
- The flyover noise level in the corresponding unit for documents issued under Chapters 2, 3, 4, 5, 12 and 14 Annex 16
- The overflight noise level in the corresponding unit for documents issued under Chapters 6, 8, 11 and 13 Annex 16
- The take-off noise level in the corresponding unit for documents issued under Chapters 8, 10 and 13 Annex 16
- Date of issuance of noise certificate document
- Statement of compliance
- Signature of issuing authority
Each chapter (2 to 14) of Annex 16 has Guidelines and Restrictions for efficient use of different kind, type, and age of aircrafts. Every chapter of the document is further divided into following parts (some chapters have further divisions as required):
- Noise evaluation measures
- Noise measurement points
- Maximum noise levels
- Test procedures
Relevant chapters for jet and large propeller driven aircrafts:
4. Calculations For Reference Points
4.1 Noise Evaluation Levels
The noise evaluation measure is the Effective Perceived Noise Level (EPNL) in EPNdB.
The EPNL “is a single number evaluator of the subjective effects of aircraft noise on human beings”.
The EPNL is the perceived noise level:
- Adjusted for spectral irregularities,
- Adjusted for the duration of noise.
4.2 Reference Noise Measurement Points
- Lateral full-power reference noise measurement point: The point on a line parallel to and away from the runway center line, where the noise level is a maximum during take-off.
The orange points on the image above shows the Lateral full power reference noise measurement points at different location for correct noise measurement.
The distance of these points from runway centre line, may vary for the purpose of noise measurement for different Chapters (2-14) of Annex 16.
- Flyover reference measurement point: The point on the extended centre line of the runway and at a distance away from the start roll.
The orange points on the image below shows the Flyover reference noise measurement point at a distance from the start roll on the runway centre line.
- Approach reference noise measurement point: The point on the ground, on the extended centre line of the runway, and at a distance from the threshold. On level ground this corresponds to a position vertically below the 3° descent path originating from a point beyond the threshold.
The orange points on the image above shows the Approach reference noise measurement point which is at runway centre line, some vertical distance below the 3 degrees glide path and at a distance prior to the runway threshold.
4.3 Maximum noise levels:
All noise levels are in EPNdB (effective permissible noise level in Decibels) and the weight (MTOM=Maximum take off mass) is in 1000kgs
If the maximum noise levels are exceeded at one or two measurement points
- The sum of excesses shall not be greater than 3 EPNdB.
- Any excess at any single point shall not be greater than 2 EPNdB.
- Any excess shall be offset by corresponding reductions at the other point or points.
5. Test procedures
- Mass: The mass of the aeroplane at brake release shall be the maximum take-off mass at which the noise certification is requested.
- Engine thrust: Average engine take-off thrust or power shall be used from the start of take-off to the point where the height mentioned in the respected chapters has been documented above runway.
- Engine thrust 2 (cutback): Upon reaching the height specified above, the thrust or power shall not be reduced below that required to maintain a climb gradient of 4 per cent, and in the case of multi-engine aeroplanes, level flight with one engine inoperative, (whichever thrust or power per engine is greater).
- Engine thrust 3: For the purpose of determining the lateral full-power noise level, the reference flight path shall be calculated on the basis of using full take-off power throughout without a thrust or power reduction.
- Speed: The speed shall be the all-engines operating take- off climb speed and shall be at least V(2) + 10 kt but not greater than V(2) + 20 kt.
- Glide path: The aeroplane shall be stabilized and following a 3° glide path.
- Speed: A steady approach speed of V(REF) + 10 kt, with thrust and power stabilized, shall be maintained.
- Mass: The mass of the aeroplane at the touchdown shall be the maximum landing mass at which noise certification is requested.
- Configuration: The most critical configuration (that which produces the highest noise level) shall be used.
5.3 Atmospheric Conditions
The reference procedures shall be calculated under the following reference atmospheric conditions:
- Sea level atmospheric pressure of 1013.25 hecto Pascals
- Ambient air temperature of 25°C, (i.e., ISA + 10°C Relative humidity of 70 per cent)
- Zero wind (most desirable)
- No precipitation
- Ambient air temperature between -10°C and 35°C Relative humidity between 20% and 95%
- Wind speed not above 12 kt and crosswind speed not above 7 kt at 10 m above ground (if present)
- No anomalous atmospheric conditions that would significantly affect the measured noise levels
Go where you feel the most alive !!