ILS-33
According to the international recommendations of the International Civil Aviation Organisation (ICAO), aircraft must land on runway 33 (from the south) whenever the tailwind component reaches 5 knots for aircraft approaching the main runway 15 (from the north).
Civil Aviation receives real-time wind data measured at the airport, as well as forecasts from the meteorological services. The wind data measured at the airport is available here. These values can vary significantly from one location to another.
The tailwind component is the decisive factor. It is derived from the breakdown of the crosswind and tailwind. (Example: For a wind speed of 8 knots from a direction of 290°, the tailwind component is greater than 5 knots relative to the runway centreline for northbound landings, which are at 160°.)
Any change in runway use has the direct consequence of reorganising the airspace for aircraft on approach or take-off. To ensure flight safety, such short-term changes, particularly when traffic is heavy, are undesirable. Furthermore, weather forecasts for the coming hours must also be taken into account.
Civil Aviation guides pilots using radar in the southern Jura region. This is where the precision approach with ILS 33 begins at a minimum altitude of 1,700 metres above sea level. The landing follows a level flight phase followed by a descent path at an angle of 3.5° along the axis of runway 33. The fly-over heights are approximately 1,100 m above ground level at Balsthal, approximately 700 m above ground level at Birstal, and approximately 300 m above ground level at Binningen and Allschwil.
ILS 33 is defined by the runway heading (330°) and a glide path angle of 3.5°. This definition complies with the international standards set by the ICAO.
Analysis of radar tracks shows that pilots follow the glide path with a high degree of accuracy (near Birstal, deviations can be as much as 100 metres).
These differences stem partly from the different types of aircraft. Thus, a larger aircraft will appear lower than a small one. Furthermore, observations are sometimes misleading depending on the observer’s position relative to the horizon. So, depending on whether one sees an aircraft ‘touching’ the treetops or disappearing behind a building, the impression will not be the same.
Scheduled cargo and passenger aircraft may take off between 06:00 and 24:00 and land between 05:00 and 24:00. Certain specific categories (charter flights, general aviation, etc.) are subject to additional restrictions.
There have always been southerly landings. But they were carried out according to a special visual approach procedure in the vicinity of the airport. Since 20 December 2007, this has been replaced by the new instrument landing system ILS 33.
General
History
Very soon after the first flights, pilots sought to push their limits in poor weather conditions. The development of commercial aviation—first for mail, then for cargo and passengers—encouraged them to do so.
Since 1961, IFR has been mandatory for all public air transport flights in Europe.
Details
Instrument flight therefore allows pilots to fly in conditions of reduced visibility, such as cloud (icing clouds, thunderstorms, fog, etc.), enabling them to fly through or avoid such conditions as necessary.
A pilot operates a flight in accordance with Instrument Flight Rules (IFR) when they adhere to a set of rules that enable them, with the aid of their instruments and air traffic control, to:
maintain the aircraft in a flight-specific configuration (attitude, speed)
follow a route prescribed by air traffic control (to ensure separation from terrain, obstacles, other aircraft, etc.)
comply with published regulations and procedures
To do this:
the aircraft must be equipped with specific instruments (radio, transponder, direction finder (indicates direction), autopilot, de-icing system, etc., all of which must be duplicated)
the pilot must have completed and passed the relevant training, and their skills are regularly tested and their licence validated.
Generally, there are two pilots in the cockpit, who are in constant contact with an air traffic controller who monitors the flight on their radar screen and ensures that the aircraft maintains a safe distance from other obstacles (adverse weather conditions, other aircraft, terrain, etc.).
As a general rule, an IFR flight must submit a filed flight plan (FPL). This FPL must be submitted at least sixty minutes in advance to the body responsible for air traffic control at European level, Eurocontrol, via an air traffic control unit (e.g. air traffic control centre). To be able to land at an airport using this technique, both the aircraft and the airport must be equipped with the
necessary technical equipment that provides information regarding azimuth, glide path and distance.
Basel-Mulhouse Airport is equipped with an Instrument Landing System (ILS) on Runway 15 and Runway 33.
Civil aviation airspace has a structured layout. Broadly speaking, the upper zone, above approximately 6,000 metres above sea level, is reserved for traffic operating under instrument flight rules (IFR). In the lower zone, flights may also be conducted under what are known as visual flight rules (VFR), whereby the altitude and speed of the flight path are selected with the aid of a map and compared in flight with landmarks on the ground (relief, roads, settlements, etc.). In doing so, the VMC standards regarding minimum visibility and cloud separation must be strictly observed in order to comply with the principle of ‘see and be seen’ (so-called ‘Visual Meteorological Conditions’).
Below a flight altitude of 300 metres above ground level or up to 900 metres above sea level, flights must be conducted outside the clouds and ground visibility must be maintained. The minimum required horizontal visibility is 1.5 kilometres. Above this altitude, a cloud separation of 1,500 metres horizontally and 300 metres vertically must be maintained. The minimum required horizontal visibility is 5 kilometres up to an altitude of 3,000 metres above sea level and 8 kilometres above that.
Pilots must observe further regulations and restrictions when flying in so-called ‘controlled airspace’ (airport control zones, defined air routes, special restricted zones, etc.).
The minimum flight altitude above ground level is 150 metres.
However, different regulations apply in the vicinity of airports, built-up areas and specific sites.
For visual flight rules (VFR) flights, the minimum clearance height above ground level depends on various factors, including population density, the height of obstacles, and proximity to an airport.
As a general rule, built-up areas may only be flown over at an altitude of 300 metres or more and within a radius of 600 metres from the highest obstacle.
However, depending on the size of the built-up area, higher minimum flight altitudes may be required.
Furthermore, numerous additional restrictions are set out in official aeronautical publications, which pilots must be aware of and comply with when planning flights. This is particularly true for night flights where visibility is reduced.
Fuel dumping is an exceptional procedure carried out only in circumstances where passenger safety requires the aircraft’s weight to be reduced prior to landing.