Originally Posted by
LookingForAJob
It's mainly to do with the size of the aircraft relative to the ILS signal. When an aircraft is close (within a few hundred metres) to the LLZ antenna it can have a significant effect on the signal for aircraft flying the approach because it it blocking and reflecting much of the signal that is being transmitted, at five miles from touchdown, for example, the size of an aircraft relative to the signal is tiny and will have no noticeable impact on the signal for following aircraft. ATC procedures, particularly those used in LVP, ensure that preceding landing aircraft have vacated the runway (and so are out of the main area that can affect the signal) and departing aircraft have passed over the LLZ antenna before an approaching aircraft reaches a point where the impact on the signal is operationally significant. In practise, it is not uncommon for there to be little 'blips' or wobbles in the LLZ in good weather conditions because the LVP restrictions are not in force and aircraft/vehicles do have an effect on the LLZ signal.
All ILS antennas have what are known as sensitive areas and critical areas and it is these that are protected and, if aircraft or vehicles go into them which may result in a noticeable effect on the LLZ signal. Size of the aircraft is also relevant - in some cases the areas to be protected are larger for B747 and A380 aircraft than for other types. There's lots of good information on ILS protection on Wikipedia and Skybrary so I won't try to replicate it here.
Yes, I know there´s a lot of info about the critical and sensitive areas of the ILS. But they all refer to the vehicles or aircraft ¨on ground¨, not about several Aircraft on the LOC. I know there are tons of airports like Zurich or Heathrow where they have 4 o 5 planes on final But is there any advisory or information about the interference on LOC signals when this approaches are made? any aircraft in the world performed a go around due to signal lost?