XN000022-1974-04-10 — Page 14

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WEDNESDAY, APRIL 10, 1974

GROOVING OF RUNWAY TO START NEXT NOUTH

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WORK ON GROOVING KAI TAK RUNWAY IS EXPECTED TO START SHORTLY TO ENSURE GREATER SAFETY FOR AIRCRAFT LANDING, THE HON. JAMES RUBSUN, SECRETARY FOR THE ENVIRONMENT, SAID TODAY.

REPLYING TO A QUESTION BY THE HON. SZETO WAI IN LEGISLATIVE COUNCIL MR. ROBSON SAID THAT TENDERS FOR THE GROOVING PROJECT HAD BEEN RECEIVED UN MARCH 29 AND HE HOPED THAT A CONTRACT WOULD BE AWARDED TODAY SO THAT WORK COULD START NEXT MONTH.

+IN THIS EVENT THE ENTIRE RUNWAY SHOULD BE GROOVED BY THE END OF AUGUST,+ HE SAID.

MR. ROBSON EXPLAINED THAT DANGER TO AIRCRAFT LANDING DURING HEAVY RAIN WAS NOT ONLY POSED BY SLIPPERINESS, BUT ALSO BY +AQUA PLANING+--- THAT IS, A FILM OF WATER BUILDING UP BETWEEN THE TYRES OF THE AEROPLANE AND THE SURFACE OF THE RUNWAY SO THAT THERE IS NO DIRECT CONTACT BETWEEN THEM, WITH A SUBSEQUENT LOSS OF FRICTION AND BRAKING POWER.

THE CUTTING OF SHALLOW GROOVES ON THE RUNWAY SURFACE CAN HELP TU PREVENT AQUA PLANING BY BREAKING UP THE FILM OF WATER, AND PROVIDING A RUUGH SURFACE FOR BETTER BRAKING PERFORMANCE, HE SAID.

GROOVING HAD BEEN CARRIED OUT ON THE RUNWAY IN 1971, BUT THESE GROOVES WERE OVERLAYED LAST YEAR BY A STRENGTHENING LAYER OF BITUMINJUS MATERIAL, WHICH MUST BE ALLOWED TO SETTLE BEFORE IT COULD BE GROOVED. GRIT BLASTING AND OTHER METHODS HAD BEEN TRIED OUT ON A SMALL SCALE TO IMPROVE THE SITUATION, BUT THEY PRODUCED LITTLE EFFECT.

+TRIAL GROOVES WERE ALSO CUT AT PERIODIC INTERVALS AND KEPT UNDER OBSERVATION TO CHECK WHEN IT WOULD BE POSSIBLE TO START GROOVING, + MR. RUBSON ADDED.

DANGER OF SLIPPERINESS COULD BE REDUCED IF RAIN WATER WAS SHED FROM THE RUNWAY AS QUICKLY AS POSSIBLE. +THIS COULD BE ACHIEVED BY INCREASING THE CROSS FALL OF THE SURFACE OF THE RUNWAY WHICH IN FACT WAS DONE LAST YEAR WHEN THE KAI TAK RUNWAY WAS STRENGTHENED B LAYING AN ADDITIONAL THICKNESS OF BITUMINOUS MATERIAL OVER THE OLD SURFACE.+

MR. ROBSON SAID THAT AQUA PLANING COULD ALSO BE AVOIDED BY PROVIDING A LONGER LENGTH OF RUNWAY.

TWO EXTENSIONS WERE COMPLETED AT THE KAI TAK RUNWAY LAST YEAR, GIVING AN EXTRA 500 FEET OF EFFECTIVE RUNWAY SURFACE, AND PROVIDING A SIGNIFICANT MARGIN OF SAFETY AGAINST OVERRUN TYPE ACCIDENTS.

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