ICASC_Paper_on_Flight_inspection_Intervals_IFIS_template_issue_1doc.doc

Where good correlation cannot be established the

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Where good correlation cannot be established the flight inspection interval remains at six months. An internal DSNA document approved by the French CAA describes the policy and techniques to be applied both by local ground maintenance units and DTI flight inspection unit in order to use correlation for the extension of ILS flight inspection interval. A summary of the procedures that are followed is provided below: After commissioning and each routine flight inspection, the following parameters are recorded: For Localiser: Tests points on the transmitter Monitor values (course, width and clearance) Alignment recorded along the runway with a portable receiver. Alignment – For CAT III, Far Field Monitor DDM value. Width values at dedicated points beside the runway, located at minimum 1km from the antenna. For Glide Path: Test points on the transmitter Monitor values (course, width and clearance) Phase and amplitude relationship s between lower and middle antenna, and between lower and upper antenna. Those measureme nts are carried out on the threshold. After commissioning the following ground maintenance intervals are adopted: For Cat I, there are 2 maintenanc es types: biannual and annual For Cat III, there are 4 maintenanc es types: weekly, monthly, biannual and annual. The biannual maintenance carried out by ground maintenance, replaces the 180 day flight inspection. If during this maintenance, all measurements are close to those performed just after the commissioning flight; the flight inspection interval may remain at one year. Otherwise, if there is the slightest doubt, a flight inspection is requested to investigate. Experience has shown that this policy significantly increases the safety, because during the annual flight inspection, there is a cross check between airborne and ground measurement. If there is discrepancy between the measurements, flight inspectors and ground personnel have to explain the causes of this malfunctioning, before any adjustment of the ILS parameters. There are essential conditions to implement a correlation policy to extend Flight inspection interval: The flight inspectors and ground personnel have: o Si mi lar an d ap pr op ria te en gi ne eri ng qu ali fic ati on s o Si mi lar ly ac cu rat e me as uri ng eq ui p me nt There are no potential changes to the environmen t that will affect the correlation. Changes in the Operating Environment [1] §1.15.7 Despite all the advances in ILS technology, the effects of the electromagnetic environment external to ILS facilities cannot always be detected by the ground maintenance. Localizer far-field monitors do provide some far-field performance indications, but are
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only able to monitor the local environment on and near the runway. After a facility has been commissioned and between periodic inspections, encroachment can occur around the airport. This could cause signal quality degradation from RF interference or reflecting objects.
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