§ Captain Hewitson
asked the Minister of Transport and Civil Aviation the percentage availability of Cliffe and Gatwick, respectively, compared with London and their respective frequencies of visibility below 550 yards.
§ Mr. Boyd-Carpenter
When London Airport's visibility is below 440 yards Gatwick's is better on 55 per cent. of occasions.
No meteorological observations have ever been taken for Cliffe. Statistics are however available for Shoeburyness and very limited statistics for the Isle of Grain. These indicate that frequencies of visibility less than 550 yards in the winter months at the Isle of Grain and Shoeburyness are very similar. It is estimated that the frequency of fog at Cliffe is greater than at either the Isle of Grain or Shoeburyness, since Cliffe is nearer to London with consequent increase in smoke pollution. There is also a cement works half a mile south of the possible airport site.
When London Airport's visibility is less than 550 yards that at Shoeburyness is better on 55 per cent. of occasions and it is estimated that at Cliffe the percentage would be no greater than this.
Statistics for frequencies of visibility below 550 yards at all three places are not available, but taking 440 yards as the criterion there are the following observations covering 11 months in 1948–49, December to March, 1952–53, and October to March, 1953–54.
9 a.m. 12 noon 3 p.m. Gatwick 57 18 15 occasions with visibility below 440 yards Shoeburyness 51 19 15 London Airport. 72 26 22