ALAN Sangster's ideas on the development of all-electric airliners are fanciful indeed, dependent on aeroengines "incorporating motor/generator sets employing high-temperature superconducting technology and advanced cryogenic cooling".

Questions include, first, whence the fundamental power will come for manufacturing, developing and testing such new engines.

Secondly, manufacturing new alloys and sophisticated tooling, all dependent on electricity in vast amounts, cannot reduce fossil fuel consumption. The answer could only be nuclear power, manufactured using fossil fuels.

Realisation of his ideas would depend on wholly new, as-yet undreamed-of power generation, manufacturing techniques and safety concepts. Pipe dreams indeed.

Meanwhile, in the foreseeable future, would it all be worth the effort and expense? At present, surely not, since the role of greenhouse gases as the main cause of climate changes is controversial, despite the confidence of the converted; there is no proof at all that domestic and industrial decarbonisation will offset changes, which have featured since the birth of planet earth.

Mr Sangster is wishing for the impractical and impossible and, indeed, for now, the unnecessary.

(Dr) Charles Wardrop,

111 Viewlands Road West, Perth.