XN000022-1982-03-21 — Page 4

SUNDAY, MARCH 21, 1982

MICROWAVE MODEL STUDY ON LEI YUE MUN BRIDGE ******

THE DIRECTOR OF CIVIL AVIATION HAS SIGNED AN AGREEMENT WITH THE UNIVERSITY OF SYDNEY (AUSTRALIA) FOR A MICROWAVE MODEL STUDY INTO THE EFFECT OF THE PROPOSED LEI YUE MUN BRIDGE ON THE ACCURACY OF THE GLIDEPATH OF THE INSTRUMENT LANDING SYSTEM FOR RUNWAY 31 AT HONG KONG INTERNATIONAL AIRPORT.

THE INSTRUMENT LANDING SYSTEM IS A RADIO NAVIGATIONAL AID USED TO GUIDE AIRCRAFT IN LOW CLOUD-BASE AND POOR VISIBILITY CONDITIONS, THE GLIDEPATH IS AN ELEMENT OF THE SYSTEM WHICH DEFINES A SLOPE OF 3 DEGREES FROM THE HORIZONTAL ALONG WHICH THE AIRCRAFT DESCENDS.

THE ACCURACY OF THE GLIDEPATH SIGNAL IS SUSCEPTIBLE TO DEGRADATION BY REFLECTIONS AND RE-RADIATIONS FROM OBSTRUCTIONS SUCH AS A BRIDGE AT LEI YUE MUN, WHICH IF BUILT, WOULD BE A MASSIVE STRUCTURE WITHIN THE RADIATION COVERAGE OF THE GLIDEPATH AERIAL.

+THE OBJECTIVE OF THE MICROWAVE MODEL STUDY IS TO ENSURE THAT THERE WILL BE NO OUT-OF-TOLERANCE ABERRATIONS ON THE GLIDEPATH AND TO MINIMISE THE EFFECT OF THE BRIDGE ON GLIDEPATH ACCURACY BY CHOOSING AN APPROPRIATE BRIDGE DESIGN,+ A SPOKESMAN FOR THE CIVIL AVIATION DEPARTMENT SAID.

+THE UNIVERSITY OF SYDNEY HAS BEEN ASKED TO PRODUCE MODELS AT ABOUT 1/90TH SCALE OF THE GLIDEPATH ANTENNA, THE NEIGHBOURING TERRAIN, BUILDINGS AND THE PROPOSED LEI YUE MUN BRIDGE WITH THE FREQUENCY OF THE GLIDEPATH RADIATION PROPORTIONATELY INCREASED TO SIMULATE THE ELECTROMAGNETIC CHARACTERISTICS OF THE REAL SYSTEM, HE ADDED.

MEASUREMENT OF THE GLIDEPATH PERFORMANCE WITH THE PRESENCE OF THE SCALED BRIDGE WILL THEN BE CARRIED OUT ON THE MODELS.

+SEVERAL BRIDGE DESIGNS AND CONSTRUCTION METHODS WILL BE SIMULATED TO DETERMINE WHICH WILL HAVE THE LEAST EFFECT ON THE GLIDEPATH ACCURACY, THE SPOKESMAN SAID.

THE STUDY IS EXPECTED TO TAKE ABOUT TEN MONTHS TO COMPLETE.

THE UNIVERSITY OF SYDNEY, WHICH HAS BEEN COMMISSIONED AS A CONSULTANT TO UNDERTAKE THE STUDY, HAS HAD MANY YEARS OF EXPERIENCE IN THE FIELD OF MICROWAVE MODEL STUDY AND HAS A TEST RANGE AVAILABLE FOR USE.

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