David Learmount ('Banana Skins', Flight International, 14-20 May) exposes the dilemma of airports when they, rather than airlines, aircraft and engine makers, are at the sharp end in dealing with local communities over the issues of environment and capacity.
ICAO Assembly Resolution 33(7) encourages contracting states not to use operating restrictions as the first resort in reducing noise nuisance. But, apart from limited scope for land-use measures around many European airports, are other elements of the so-called Balanced Approach to Aircraft Noise Reduction real or illusory?
Noise certification standards, with progressively tougher limits, have been a central plank of ICAO policy since the adoption of Annex 16 Volume I. But does noise measured and classified during aircraft certification offer an unambiguous relationship to operational noise performance? Standards do not define worst case test conditions, nor are the procedures used in certification flown in everyday operations. In reality, for example, most airlines employ thrust de-rate at take off, with power settings adjusted for mass, airport altitude, temperature, etc. There are benefits in fuel savings, emissions (another important environmental consideration) and engine maintenance costs, but a trade-off in shape and size of the noise footprint. And yet, 33(7) also states that operating restrictions should be based on noise performance as determined by the certification procedures (Annex 16 Volume I).
Also, is it feasible to make more extensive use of specially tailored operational procedures at individual airports? At least the widely adopted practice of designing standard instrument departures or arrivals (SIDs or STARS) to avoid direct over-flight of communities means that all crews/operators know what they will face and can be ready for it.
But operating procedures generally redistribute noise rather than reduce it. Airlines want to keep things simple, so they face as few unknowns or variations as possible for crews and aircraft types, across all their destinations. And of course safety concerns remain paramount in determining and varying such procedures.
Martin Wright
Sutton, UK
Source: Flight International
