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Session 12: Legacy Navaids

Solution to Coverage Issues Created by Large Hangars
Hervé Lenquette, DSNA/DTI, France; Bertrand Spitz, ENAC, France
Location: Regency Ballroom
Date/Time: Friday, Apr. 20, 10:45 a.m.

The airport of St Nazaire is equipped with a 13 element dual frequency localizer operated in Cat 1.
The addition of 2 large hangars (200x27m and 145x24m or 656x89 ft and 476x79 feet) has created an out of tolerance coverage DDM which has not been detected at the first flight inspection. Pilots reported false capture when flying some approach trajectories.
A new flight inspection detected the issue and a solution had to be found.
This coverage issue was in fact coming from the reflected clearance signal by the hangars interacting with the clearance signal on the opposite side of the runway. Reducing a clearance/clearance disturbance is quite challenging.
This presentation is going to show how this issue has been solved by using asymmetric clearance radiation patterns. This asymmetric radiation patterns are obtained by using the standard antenna distribution unit (ADU) and can be applied to any existing antenna systems. Just the CSB and SBO feedings to the ADU have been modified.



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