FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1941
1941 - 1775.PDF
7th, 1941. FLIGHT c NIGHT brain which constitutes seeing. By the use of diaphragms with increas- ingly opaque filters in the object glass of the binocu- lars we can exercise the spotter, by day, in the combined effort of percep- tion and appreciation of aircraft targets, in condi- tions of confusion approxi- mating to those obtained in action at night. Scrutiny ' .• . It has been shown fiat small objects at extreme ranges and in difficult con- ditions of lighting require to be under observation for at least one second for the average eye and brain to detect their presence. All movements of the binocu- lars in searching an area of sky must therefore be carried out extremely slowly—in fact, at a rate not exceeding one field of view per second. An up- ward search such as that which we have shown to be required in the pro cesses of location may mean a movement repre- senting as many of three fields of view, each of which must be thoroughly scrutinised to ensure that the target is not in any one of them. Whilst scrutinising, the lateral movement must be con- tinued to keep pace with the moving target. To scrutinise each field ade- quately requires one second for the trained eye so that the process will take five seconds at the least. Consideration will be given, when carrying out this process, to the direction of flight. A combination of the two movements needs con- siderable practice to attain proficiency. To examine the field of view by day is a simple enough matter, but by -•',.'. ' •. • night a phenomenon exists which must be appreciated by the spotter if he is to suc- ceed. First, it must be realised that the eyes must be thoroughly dark-adapted (night efficient). It is estimated that from 12 to 40 minutes in complete darkness is re- quired to attain an efficient degree of night adaptation. Night fighter pilots adopt the habit of wearing dark glasses when awaiting action by night. The more difficult fact is that, whereas by day visual acuity is sharpest at the point of fixation, by night the opposite is true. The portion of the retina known as the macular region, which by day permits sharpest visual acuity at the point of fixation, becomes blind when the eye is dark-adapted. This fact was discovered very early by astronomers, who observed that stars appeared unmistakably brighter if looked at eccentrically. ARMSTRONG-WHIT- WORTH WHITLEY BRITISH BOMBERS : Lighted outlines of four operational types in service with Bomber Command. Views of our newer heavies such as Stirling, Halifax and Manchester are, for obvious ••:-.•-' reasons, not for publication. So when scrutinising a field of view by night, in order to perceive an object more clearly in the right-hand half of it, it is necessary to look in the left-hand half. In order to minimise the risk of failure to observe a target which may just be leaving the field of view of the binocu- lars, scrutiny must be carried out scientifically. The majority of targets will be approaching when engaged by a spotter and so the danger zone lies between nine and three o'clock of the field of view via 12 o'clock. If, there- fore, he first looks at six o'clock, he examines first most clearly that region in which the target may be about to disappear from his view. Then, according to the direction of flight, left or right, he will scrutinise round the field via five or seven o'clock. The process is a rapid one and can be carried out successfully with practice.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
