RETREADS FOR AIRCRAFT

Press, Volume CVII, Issue 31564, 29 December 1967, Page 5

RETREADS FOR AIRCRAFT

JJETREADED tyres are today generally accepted in every part of the world. Acceptance is based on proven reliability: a cheaper article is a dangerous econ-

omy if it is likely to fail at a crucial moment.

The tyre industry caters for all demands, giving each type of tyre the design strength to do its particular job. Modem aircraft tyres, which are subjected to exceptionally demanding stresses, have an especially vital function.

An article on the reconditioning of these tyres, by the manager of a specialist reconditioning firm in Melbourne, Australia, appears in "Rubber Developments,” journal of the Natural Rubber Producers’ Research Association. England. When an intercontinental jetliner comes in to land the tyres hang motionless until the moment of contact with the runway. In cushioning the initial impact, they accelerate from standstill to almost 2000 r.p.m. in a split second. They then deflect under a static load of 17 tons a tyre imposed at 150 m.p.h. Momentum continues to load the tyres, while jet thrust reversers and brakes are brought into play to stop the aircraft in about 40 seconds. The aircraft then taxis at about 30 m.p.h. to the ter minal, which may be up to two miles away.

The heat generated by the braking and subsequent taxiing causes the temperature in the bead area of lhe tyre to rise to about 160 degrees Fahrenheit. The tyre has while the aircraft discharges its passengers, refuels and re-

loads, before another two nr so miles of taxi-ing is followed by a further two in.lns' take-off—in which the tyre accelerates to 200 m.p.h. 'in about one minute. At the end of the run. air temperature inside the tyro reaches about 140 degrees Once airborne, the landing gear is retracted until wanted again and at around 35,000 ft the tyres are subjected to long periods of intense cold Natural rubber is chosen for aircraft tyre treads because good abrasive resistance, together with good heat resistance and adhesive properties, is essential. All jet aircraft tyres are tubeless and here again natural rubber is chosen for the inner tubeless liner of the tyre because, in the temperature extremes to which such tyres are subjected, it provides adequate air retention properties.

When fitted to a Bieing 707, DCB or Convair 880, the average tyre can withstand the landing and take-off cycle more than 100 times before the tread is worn away. This represents a period of perhaps 30 days, depending on the aircraft’s operating schedule. The tyre can then Jbe reconditioned, but not like a car or truck tyre. It is a highly-specialised job which can be earned out in only a few specialised plants. With jet aircraft tyres there is a tremendous inbuilt strength. As a result, aircraft tyres can be reconditioned several times.