FRUIT isnt always good for you!

EUROCONTROL, the Brussels based European coordinators of Air Traffic Management activities, have purchased the first of the new generation S3DR-E data recorders, to be installed on the Airbus Beluga aircraft.

The recorder is to be used for monitoring and recording high bandwidth analogue radar video signals received from a Rockwell Collins TCAS receiver, as well as GPS position, altitude and time. The recorder is to be used as part of an overall programme to ascertain the actual levels of RF pollution from 1090MHZ FRUIT (see sidebar) that exist over core European airspace.

The Airbus Beluga aircraft fleet is the ideal platform for making these recordings since the aircraft make daily scheduled trips between Hamburg (Germany), Toulouse (France), Filton and Broughton (UK) carrying Airbus fuselage segments between the partner factories of Airbus Industries.

The recorder will be configured to allow EUROCONTROL to make consistent daily recordings over defined regions of airspaces and to compare and contrast the levels of FRUIT over time.

The introduction of Mode-S secondary surveillance radars throughout Europe is now in full swing and the benefits promised by Mode-S should become apparent. The improvement in FRUIT levels that result from Mode-S have already been theoretically proven using sophisticated simulation tools, but this will be the first time that a solid state data recorder with sufficient data recording capacity has been available to carry out a detailed assessment of the actual situation as experienced by an aircraft operating in the congested European airspace.

Under the contract, SES are also providing a dedicated ground data extraction facility, built from the SES REVEAL product, which will allow the hundreds of Gigabytes of recorded data to be effectively managed.

What is Mode-S Secondary Surveillance Radar?

Secondary Surveillance Radar is an established technology in which ground stations communicate with and "interrogate" transponders, carried by all commercial aircraft, to uniquely identify the aircraft for air traffic control purposes. The technology has been widely used since the 1960's, but in its original form was quickly identified as suffering from limitations due to signal interference and limited capacity.

Mode S (Selective) is the solution to these interference and capacity problems. It is a datalink technology using discretely addressed interrogations. Unlike traditional secondary surveillance, the interrogations that ground sensors send aircraft include the identification (address) of the target plane. The selective identification of targets for interrogations ensures that aircraft only respond when required to. Therefore the number of transmissions that are generated by each aircraft is kept to an appropriate minimum.

FRUIT - (False Returns Unsynchronised in Time)

FRUIT replies are unwanted replies received by an interrogator from transponders responding to other interrogators. Such replies, if they are received at the same time as a wanted reply, have the potential to degrade or corrupt the reply and therefore affect the correct operation of the interrogator. The amount of FRUIT will depend on the distributions of the aircraft in the environment and the number of interrogations replied to by each aircraft. Consequently, FRUIT replies will generally increase in proportion to the number of aircraft and interrogators operating in the environment.