Plane tyres

THE ARTICLE by Patrick Forman (page 14, January 16) attributes to me the statement "the safe life of a carcass is not much more than the life of its first tread". I have in fact never said this.

What I have said is that in the case of car tyres the carcass may become unprotected against the effects of fatigue due to loss of antidegradant during the first retread life.

I have been at pains to point out that the safe retread limit for aircraft tyres is not known and this is why I have urged the need to establish both the service usage and retread limits for aircraft tyres which, as Patrick Forman points out, must be a major potential source of accidents in the modern aircraft.

In the absence of such experimental evidence, however, I have advocated that the retread limit should be less than six. In my opinion, in the case of the wide-bodied aircraft it should not be more than four.

However, I emphasise again that judgment is no substitute for experimental evidence which, in the present case, is readily accessible, given appropriate funding. Ironically, the cost of this research is only a minute fraction of the cost of a modern aircraft.

Gerald Scott
Professor of Polymer
Science and Technology
University of Aston
Birmingham