MONDAY, DECEMBER 27, 1982
THE THREE SUB-SYSTEMS ARE CONNECTED BY CABLE TO A CENTRAL PROCESSING AND CONTROL UNIT AT THE AIRPORT METEOROLOGICAL OFFICE (AMO). DISPLAYS OF RUNWAY VISUAL RANGE AT EACH LOCATION ARE AVAILABLE AT THE AMO AS WELL AS AT THE AIR TRAFFIC CONTROL TOWER.
MR LAM EXPLAINED THAT IN MORE TECHNICAL TERMS, THE OPERATION OF THE TRANSMISSOMETER IS AS FOLLOWS:
THE PROJECTOR EMITS LIGHT PULSES OF HIGH ENERGY AND SHORT DURATION WITH CONSTANT PEAK INTENSITY AT A FREQUENCY OF ABOUT 90 FLASHES PER MINUTE. THE RECEIVER, WHICH IS ALIGNED WITH THE PROJECTOR AT A DISTANCE OF 150 METRES, RECEIVES THESE SHORT PULSES OF LIGHT AND CONVERT THEM INTO ELECTRICAL SIGNALS BY MEANS OF A PHOTO-DIODE.
THE ELECTRICAL SIGNAL, AFTER BEING AMPLIFIED, IS FED, THROUGH A TRANSMISSOMETER CONTROL ÚNIT, TO A VISIBILITY PÉN RECORDER AND ALSO TO THE RVR COMPUTER LOCATED IN THE AMO. INPUT TO THE COMPUTER ALSO INCLUDES THE GENERAL BACKGROUND LUMINANCE OF THE AERODROME MEASURED BY A SENSOR LOCATED AT THE BALCONY OF THE AMO, AND THE LEVEL TO WHICH THE HIGH INTENSITY RUNWAY LIGHTS ARE SWITCHED BY THE AERODROME CONTROL.
THE OUTPUT FROM THE COMPUTER IS THE DIGITISED RVR VALUE WHICH IS SENT TO THE MASTER DISPLAY UNIT. THE DIGITISED SIGNALS ARE IN TURN SENT TO +SLAVE+ DISPLAYS AT THE AERODROME CONTROL, THE APPROACH CONTROL, THE PAR (PRECISION APPROACH RADAR) POSITION, AND THE PILOT BRIEFING COUNTER IN THE AMO.
THE DISPLAY UNITS SHOW THE CURRENT RVR IN FOUR DIGITS, PRECEDED BY ONE OF THE SIGNS +, -, AND -, INDICATING THAT A REPORTED RVR HAS INCREASED, REMAINED UNCHANGED OR DECREASED SINCE THE LAST READING.
MR LAM SAID THE PRESENT SYSTEM HAS BEEN SERVING WELL. HOWEVER, TECHNOLOGICAL ADVANCES IN RECENT YEARS HAVE RESULTED IN EXTENSIVE MODIFICATIONS IN THE ELECTRONICS AND THE OPTICAL SYSTEM IN THE LATEST MODELS.
ALSO, BECAUSE SPARE PARTS FOR THE PRESENT SYSTEM ARE NO LONGER MANUFACTURED. IT IS LIKELY TO BECOME UNSERVICEABLE BY THE END OF 1984, HE SAID.
THE NEW SYSTEM WILL INCORPORATE THE LATEST TECHNOLOGICAL CHANGES TO PROVIDE THE NECESSARY OBSERVATIONS OF THE VARIOUS SECTIONS OF THE RUNWAY.
IT HAS THE SAME NUMBER OF TRANSMISSOMETERS BUT EACH TRANSMISSOMETER SYSTEM WILL INCLUDE A TRANSCEIVER UNIT AND A NUMBER OF REFLECTOR UNITS. ADDITIONAL REFLECTORS CAN BE FITTED TO THE TRANSMISSOMETERS WHICH CAN MEASURE METEOROLOGICAL VISIBILITY OVER TWO KILOMETRES.
MR LAM SAID THE NORMAL SERVICEABLE LIFE OF THE RVR SYSTEM IS ABOUT TEN YEARS. IF NECESSARY, THE SYSTEM CAN BE DISMANTLED AND REINSTALLED AT A NEW LOCATION AT AN ESTIMATED COST OF $50 000 AT CURRENT PRICES.