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Questions / Answers

Why are planes noisier on certain days?

The noise an aircraft makes mainly depends on what type of plane it is and the engine it uses; whether it is taking off or landing; how far away it is; and weather conditions (such as wind force and direction, temperature, humidity levels and atmospheric pressure). How noisy a plane seems depends on the individual listener, how susceptible they are to hearing it as it goes over, and other sounds around them. As a result, in a single location planes might seem noisier to you some days than others, depending on the type of aircraft in operation, whether it’s landing or taking off, the runway being used, weather conditions and what you’re doing at that moment.

Why don’t planes always face the same way when they are taking off and landing?

Planes usually travel into the wind when they take off or land. This way, they are quicker to reach the speed they need to take off, and they have more lift. Landing into the wind helps them gradually put on the brakes and reduces the distance they then travel on the runway. This is why runways can be used both ways in a single day – it all depends on the direction and speed of the wind, both on the ground and at altitude. Air traffic control decides which runway should be used and the direction a plane needs to travel in.

Why don’t planes all follow the same flight path?

There are various factors that affect the slightly different paths planes take when they arrive at or depart from the airport:

  • Weather conditions: wind direction and force, atmospheric pressure and other conditions have a direct influence on planes’ trajectories and the time it takes them to get into the air. 
  • The aircraft type, and the size of its load: depending on how much they are carrying, two identical planes with identical engines will take different lengths of time to get in the air. Even if they have travelled the same distance from the runways, they won’t both reach the height they need to cruise towards their destination at the same time. 
  • Aircraft speed: speed has a direct influence on the curving path a plane takes as it travels through the air. This is why two aircraft with different speeds that start climbing at the same point will follow different trajectories.
  • Air traffic safety: to keep aircraft safe, they need to maintain a minimum distance from each other, horizontally and vertically. Airways and published flight paths take into account instruments’ and equipment’s levels of precision when they set out the range of space that aircraft can occupy (planes don’t follow strict lines like trains on a railway track).
  • The air navigation procedure used for approaches and departures. 
     
Can the Airport use two runways at the same time during busy periods?

No, because Bordeaux Airport’s runways intersect. However, runways can be used in both directions in a single day, depending on wind direction and speed – air traffic control makes that decision.

Do planes sometimes dump fuel in the atmosphere?

Fuel dumping is a very rare occurrence. It happens only when the plane’s weight needs to be quickly reduced so an emergency landing can be performed for passengers’ safety.  This might be the case on long-haul flights that need to land shortly after take-off for technical reasons or due to a passenger emergency.

Fuel-dumping can only be done over sparsely populated areas and at a height of at least 2,000 m. The fuel is vaporised into tiny droplets so that it can then evaporate and disperse into the atmosphere. 

Only major carriers operating long-haul flights that have to land shortly after take-off might need to dump fuel. The reason planes do this is that, because they haven’t consumed much fuel on their journey so far, they might be heavier than the authorised weight for landing. 

Sometimes you might spot white trails at the tips of a plane’s wings as it takes off or lands. These aren’t caused by fuel dumping - in fact, they are made of condensed water vapour. They occur when the air is humid and the flaps at the back of the wings are extended (this is particularly common during landing). 

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