I have a silly radar question.
According to the European Aviation Safety Agency (EASA) when two (or more) aircraft with the same (duplicate) ICAO 24-bit aircraft address are operating within range of a specific Mode S interrogator, then potentially hazardous situations can arise:
* One (or more) of the aircraft involved may be assessed by the Mode S interrogator to be a false or reflected echo, and subsequently ignored. These aircraft will not then be displayed to air traffic controllers.
* In the case of aircraft whose flight paths cross, the identification labels of those aircraft may inadvertently ‘swap’ (i.e. replace one another) on air traffic controllers displays, thereby presenting controllers with incorrect information and creating the possibility of misidentification.
The text above is taken from EASA Safety Information Bulletin July 4, 2011:
http://ad.easa.europa.eu/blob/SIB_20.../SIB_2011-14_1
There is a significant number of planes flying with bad aircraft addresses:
AIRFRAMES.ORG - Aircraft Database - incorrect ICAO 24-bit addresses
My questions are:
* Did anybody ever seen the duplication effects or knows why they occur?
* Can the two duplication effects combine to create one displayed path consisting of data points of one plane until the crossing point and of the other plane afterwards? At the crossing point the displayed path may have a turn or a corner.
My guesses for the explanations are respectively:
* the SSR software automatically deletes points it considers erroneous
* the label assignment algorithm gets confused by the path crossing