08/15/2010

Friday 13th : aircraft noise and a mystery

Friday 13th was unusually bad for aircraft noise: the Boeing 747 cargo plane was even noisier than the Air Mauritius Airbus A340. It also included a mystery noise event: can you help solve it?


Friday nights are always noisy for people living under the axis of the runway at one end or the other (or both!). Friday 13 August was no exception, with the Air Mauritius A340-300 being, for once, not the noisiest aircraft of the day. That honour was reserved for the Boeing 747-400 of Jade Cargo International (that one described by the airport as of a new generation and therefore producing less noise and less pollution).

In terms of measured noise at the ARAG measurement station at the Versoix Town Hall (Mairie) the 87 dBA of the Jade 747 beat the noise of the Air Mauritius A340 by 3 dBA (meaning that it was twice as noisy). In turn, the A340, a class III aircraft, beat the venerable McDonnell Douglas MD82 of SAS by 2 dBA, despite this latter aircraft being in the (noisier) class II. All of these were noisier than the three transatlantic Boeing 767 aircraft.

When aircraft take off over Vernier the measurements are much higher, because the mearurement station at Vernier is only about 1.3 km from the end of the runway, whereas the Versoix Town Hall is 4.3 km from the end of the runway. As a result, at Vernier there are sometimes measurements as loud as the Air Mauritius (the transatlantic flights, for example). At Versoix, however, the difference is that an Airbus A340-300 climbs much more slowly than the other aircraft, so the noise drops off much less rapidly. Unfortunately, also, the A340 has to cross the alps, thus frequently necessitating a loop around the Geneva, Vaud and neighbouring France countryside before a sufficient height has been reached.

It would be really nice to see the detailed measurements made by the official airport measuring station near Bellevue (about 1.6 km from the end of the runway), but this information seems to be a jealously garded secret.

And the mystery noise event? Well, the noise measurements of the two Versoix microphones, a microphone at Ferney-Voltaire and one in Meyrin, all seem to suggest that there was a takeoff at around 23h50. However, the detection system registered no definite takeoff. There is some evidence to suggest that it was the aircraft registered as LX-GEX, a Bombardier BD-700 belonging to Global Jet Luxembourg, but in the first detected transponder emission, at 23h50, it called itself flight SVW12EX and was already at an altitude of 4450 feet. So did the pilot not switch on the transponder before and during the takeoff? Would this be allowed?

I will ask the airport and report back here, but do not hold your breath waiting for an answer!

 

10:46 Posted in Noisy aircraft | Permalink | Comments (0) | Tags: jade, mauritius, airport, geneva | |  del.icio.us | | Digg! Digg |  Facebook

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