08/11/2014

Emirates increases capacity and noise to Dubai.

On the site of Geneva airport Emirates announces increased capacity to Dubai, using only the larger Boeing B777 aircraft.


The actual Emirates statement indicates that as from this month, August 2014, only the large model Boeing  777-300ER aircraft will be used. In fact, the change already happened last month: the last flight of the smaller Boeing 777-200ER was at the end of June.

Out of curiosity, I checked what was the typical noise of these two models of aircraft when overflying the ARAG noise station in Vernier. Strangely, the larger aircraft makes a lot more noise than the smaller one: I calculate the typical values as 85 dBA for the 777-300ER, against 81 dBA for the 777-200ER. Because the measurments of ddBA (decibBels noise mode A) are logarithmic, with an increase of 3 dBA implying a doubling of the noise, this means that a single larger aircraft makes more noise than two simultaneous smaller aircraft.

Another way of looking at noise is to divide the noise equally among the passengers, thus giving a value per passenger. Doing this for the larger aircraft, which can typically carry 386 passengers in a three-class configuration, gives a value of 59 dBA per passenger seat. For the smaller aircraft, with a typical capacity of 314 passengers, the calculation comes out at 56 dBA. In other words, twice as much noise per passenger. Thus, for the airport neighbours, there will overall be more noise.

How does this compare to the workhorses of the airport, the Airbus A319 and A320? Surprisingly, the average takeoff noise over Vernier for an A319 seems to be about 76 dBA. Since an A319 carries around 100 passengers, this gives a noise per passenger of 56 dBA per passenger: virtually the same as the smaller Boeing B777. Thus, there is an equivalence of noise per passenger between the two. However, now that Emirates is using only the larger aircraft, there will actually be more noise for the same number of passengers.

Another question is what is the noisiest aircraft using Geneva airport as a scheduled flight (we exclude the odd military aircraft and some ancient aircraft)? Unsurprisingly, this is the Air China flight to Beijing: a very long flight requiring a full fuel load. The actual aircraft being used are the Airbus A330-200, which have a typical capacity of 253 passengers.The same measurements of noise indicate typically 91 dBA for a takeoff over Vernier: careful readers will see that this is the equivalent of no less than four Boeing 777-300ER aircraft. The same noise per passenger calculation gives a value of 67 dBA, as against 59 dBA for the Boeing 777-300ER and 56 dBA for the smaller Boeing 777-200ER. Quite a difference!

The lesson of all this is that having larger aircraft does not necessarily decrease the overall noise in all cases. It is probably true when (as sometimes happens) a large wide-body aircraft is used for a short distance (some winter ski flights to Geneva from London do this). It does, however, reduce the number of flights for an equivalent number of passengers. This fact would have been relevant many years ago, when the nuisance measured with a Noise and Number (NNI) formula was in use. However, for a long time now the unique measurement method is of "Equivalent Noise", measured over fixed periods.

19:52 Posted in Noise around Geneva airport, Noisy aircraft | Permalink | Comments (1) | |  del.icio.us | | Digg! Digg |  Facebook

Comments

"Since an A319 carries around 100 passengers"

Not really...

Posted by: Romain | 08/25/2014

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