XN000022-1982-12-27 — Page 2

NEW RUNWAY VISUAL RANGE SYSTEM FOR AIRPORT

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THE ROYAL OBSERVATORY HAS BEEN GIVEN THE GO-AHEAD BY THE FINANCE COMMITTEE TO EQUIP THE HONG KONG INTERNATIONAL AIRPORT WITH A NEW RUNWAY VISUAL RANGE (RVR) SYSTEM WHICH INCORPORATES THE LATEST TECHNOLOGICAL CHANGES IN THE FIELD.

THE NEW SYSTEM, COSTING ABOUT $2 MILLION, IS EXPECTED TO BE OPERATIONAL BEFORE THE END OF 1984, REPLACING THE PRESENT SYSTEM WHICH HAS BEEN IN SERVICE SINCE 1974.

MR H.K. LAM, SENIOR SCIENTIFIC OFFICER AT THE OPERATIONS AND METEOROLOGICAL SERVICES BRANCH OF THE ROYAL OBSERVATORY, SAID RVR INFORMATION, TOGETHER WITH DATA ON THE HEIGHT OF THE CLOUD BASE, THE HORIZONTAL VISIBILITY AND OTHER WEATHER CHARACTERISTICS, ASSISTS THE PILOT IN DECIDING ON WHAT PROCEDURES TO USE IN HIS TAKE-OFF OR LANDING OPERATION,

RUNWAY VISUAL RANGE, HE SAID, IS DEFINED AS THE MAXIMUM DISTANCE IN THE DIRECTION OF TAKE-OFF OR LANDING AT WHICH THE RUNWAY LIGHTS OR MARKERS DELINEATING THE RUNWAY CAN BE SEEN BY THE PILOT AT A HEIGHT CORRESPONDING TO THE AVERAGE EYE-LEVEL OF THE PILOT AT TOUCHDOWN.

ACCORDING TO THE REQUIREMENTS OF THE INTERNATIONAL CIVIL AVIATION ORGANISATION (ICAO), RVR INFORMATION SHOULD BE INCLUDED IN ROUTINE METEOROLOGICAL REPORTS AND DISSEMINATED TO AIR TRAFFIC CONTROLLERS AND PILOTS OF APPROACHING AND DEPARTING AIRCRAFT.

THE ICAO ALSO STATES THAT SUCH REPORTS SHOULD BE TRANSMITTED WITHIN 15 SECONDS OF THE OBSERVATION WHICH GAVE RISE TO THE REPORTS.

MR LAM SAID GENERALLY, RUNWAY VISUAL RANGE COULD BE OBTAINED BY A HUMAN OBSERVER MEASURING THE DISTANCE TO THE FURTHEST LIGHT THAT HE COULD SEE FROM ONE SIDE OF THE RUNWAY. THIS METHOD, BASED ON THAT DEVELOPED BY THE BOARD OF TRADE IN THE U.K., WAS INTRODUCED AT THE HONG KONG AIRPORT ON JANUARY 1, 1970.

HOWEVER, MR LAM EXPLAINED THAT IT IS DIFFICULT TO COUNT LIGHTS AT LONG DISTANCES, SAY BEYOND 1 000 METRES, AND SOMETIMES

IT IS NOT FEASIBLE TO SEND OBSERVERS TO THE RUNWAY POSITION AT SHORT NOTICE UNDER ADVERSE WEATHER CONDITIONS.

THERE IS ALSO THE ADDED DIFFICULTY THAT THE HUMAN OBSERVER METHOD PROVIDES NO CONTINUOUS RECORD AND THE OBSERVATIONS ARE SUBJECT TO PERSONAL DISCREPANCIES SO THAT IT IS NOT EASY TO MEET THE REQUIREMENT OF ICAO FOR REPORTING ALL CHANGES IN RVR WITHIN 15 SECONDS.

FOR THESE REASONS, THE HONG KONG AIRPORT OPERATIONS COMMITTEE DECIDED THAT THE ROYAL OBSERVATORY SHOULD INVESTIGATE AND PROVIDE RVR MEASURING EQUIPMENT AT THE HONG KONG AIRPORT.

THE PRESENT RVR SYSTEM, INSTALLED IN 1974 AFTER MUCH CAREFUL TECHNICAL RESEARCH AND INVESTIGATION, CONSISTS OF THREE SETS OF TRANSMISSOMETERS - EACH COMPRISING A RECEIVER AND A PROJECTER LOCATED AT THE THRESHOLDS AND IN THE MIDDLE OF THE RUNWAY.

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