08/28/2012

A better aircraft landing path

The residents living around Nernier want incoming flights to stop coming over their town. They have made a perfectly reasonable proposition.


In the evening of the 21 August in Nernier I attended the Annual General Meeting of AFRAG, the association for french people living around the airport, in particular those living around Nernier (close to Yvoire). This association was formed around 2001, the time when the federal concession for the airport was up for renewal (for another 50 years). Their particular complaint was that they were being overflown, at low altitude, by aircraft landing at Geneva airport, and that this was resulting in noise and atmospheric pollution. They wanted aircraft to stay towards the centre of the lake.

As an outcome of the discussions, including a judgement of the federal tribunal, Geneva airport was requested to take part in a study to propose such a flight path, coming down the centre of the lake. Over a long period of time this study was made, and proposed a path essentially coming down exactly the centre of the lake, i.e. the dividing line between Switzerland and France. A great deal of effort and expense was devoted to establishing how much the level of noise would be affected on both sides of the lake.

Unfortunately (for AFRAG), the proposition was defined as a segmented approach, including a relatively short segment in the region just off Tannay, from a point called LEMAN to a point called FAF. However, this segment was too short to be compatible with international rules, which require a minimum segment length of 5 nautical miles.Thus, when the Swiss federal office, OFAC, was requested to authorise it, the request was turned down. It is the belief of many people, including almost all AFRAG members, that this was what the airport wanted all the time.

However, things are not always what they seem. Aircraft do not all come over the guidance beacon in St Prex, then make a long and continuous glide path to the airport. Instead, they come from many directions and join the glide path at many different points. On seeing this, some experts in AFRAG were able to make an approach proposal entirely compatible with the segment rules and which would provide relief for Nernier.

The big coincidence of exactly that day, 21 August, came because the AFRAG president, Dr Georges Ryser, noticed a big aircraft coming in over the other side of the lake in the morning. He asked me to investigate this, so I verified which aircraft it was and on what trajectory it came. I found that it was the incoming Swiss flight from New York, and that its trajectory was exactly compatible with the AFRAG proposal. You can look at this in more detail by clicking on this picture.

20120821_LX023_att.jpg

The AFRAG proposal is simplicity in itself, and could have been proposed years ago. The picture shows the short segment from LEMAN to FAF (Final Approach fix). AFRAG simply proposes that FAF be simply moved to LEMAN (suppressing the short segment). With that, aircraft which do approach from afar, over the St Prex radio beacon (SPR), stay over the lake, making a turn of not more than 10° at a given turn point, then anothe turn of at most 10° at the new FAF/LEMAN point. This 10° limit is an important factor in aircraft approaches.

What is clear from this actual approach of the Swiss Airbus A330 from New York is that the AFRAG proposal is perfectly reasonable, since the flight joined the axis of the runway very late: it could just as easily have come in over the moved FAF point. It is equally clear that it could not have included any element of danger: when you have a few hundred passengers on a big aircraft you do NOT take any risks.

So what will happen next. Being a pessimist, I expect no results. Large organisations like the airport hate to be forced to change anything, so they will either entirely ignore the new proposal or quibble about little things for years, so that any judgement is eternally delayed.

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