§ Sir M. Galpernasked the Minister of Aviation if he is satisfied with the present system of measuring visibility at airports during fog whereby an employee is stationed near the start of each runway, counts the lights he can see, and telephones the visibility to the control tower; and what research is in progress to establish a scientific method of measuring visibility.
§ Mr. Roy JenkinsThe present system is scientifically sound and, at present, we know of no better way of measuring what is known as Runway Visual Range (RVR).
Instrumental methods are not necessarily better. A transmissometer for instance can measure the opacity of the atmosphere over about 200 metres, but various corrections have then to be applied to the result to allow for such factors as background brightness and runway lighting intensity so as to derive in practical terms what the pilot is actually likely to see. At present, therefore, we prefer the present system. The Meteorological Office is nevertheless conducting trials of the latest instrument techniques and they will certainly be adopted if they are shown to be of value.
A considerable amount of research is also proceeding at the Blind Landing Experimental Unit, at the Royal Aircraft Establishment and at a number of airfields into various other methods of supplementing and improving present procedures, for example into the siting of RVR observing positions, into the value of increasing the number of such positions, 229W and into means of providing information on possible variations in visual range during the final stages of descent.