FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1937
1937 - 0146.PDF
52 FLIGHT. JANUARY 21, 1937. Croydon's first ultra-short wave approach and marker beacons have now been in action for some time. On the left is the control panel which also indicates whether the three transmitters are working properly. (Right) "You may take off ! " The look-out man at Croydon gives the take-off signal with the fixed signalling lamp on the control-fower gallery. Heston at once in order to report departure, destination and height. The short-range stations are, in fact, auxiliary stations for the benefit of pilots coming in to the airports on which they are placed and for the purpose of relieving the main station in the area concerned. All the existing control methods are based on that developed at Croydon, and a brief description of the work there will apply to that at the others. Eadio being the all-important medium of control, it should be explained, first of all, that, apart from those used for meteorological and other messages, there are three separate sets. One is used for telephony (in little demand nowadays), another for telegraphy and a third for short-range bad-weather work. The last is used only for communication with those machines, already in the controlled zone, whose pilots are preparing to land. In addition, there is the ultra-short wave repeater, which shows the control officer that the main and marker approach beacons are doing their work. Communications The principles of, and possible developments in, radio equipment are dealt with by Mr. Roderick Denman else where in this issue, and it is sufficient to explain that the long- and short-range D/F receivers have their aerials necessarily on the control tower itsdf, while the trans mitters work through the Mitcham station ; it would ob viously be dangerous to erect the tall masts which are necessary for transmitting power in the immediate vicinity of the airport. Teleprinter and normal land-line communi cation is used for inter-departmer.tal and inter-airport messages, while the familiar pneumatic message-tubs is used for the internal transport of written or teleprinted slips, all of which are filed for reference if necessary. In the main control office there is a large map of the London-Continent area, and the officer in charge keeps track of all the machines within this area by means of pins with identification flags—the direction of the flag showing whether a machine is outward- or inward-bound. All messages to and from the machines are handed to the officer, who moves the pins accordingly, or by his own estimation of progress. In poor visibility, for reasons of mental comfort and for the very necessary estimation of arrival time, a pilot always likes to obtain a check on his dead-reckon ing. Bearings are taken on him at a particular moment by Croydon, Lympne and Pulham, and these bearings are laid out on a special chart in the operators' room. The point of bearing intersection—which is almost invariably a small triangle, known as a "cocked hat"—gives the position of the machine at the moment when the bearings were taken. A position, or "fix," can be provided within a minute and a half of request, and as many as five plain bearings can be taken and transmitted within the same period of time. Once the pilot has been given permis sion to land during bad weather, he is led in on these bearings—given, in this case, by the short-range operator —and, if his machine has the necessary equipment, he makes his final approach down the short-wave beam. Eventually, two approach beacons will probably be in use at Croydon, transmitting in different directions, making it possible to complete a landing in other than calm condi tions almost straight off the glide path and without circling. At a busy airport some simple form of departure pro cedure is vitally necessary. At Croydon the pilot of an airline machine is given permission to leave the tarmac by the display of a panel, bearing an appropriate letter, on the control tower gallery. This means that the "ship's papers" are in order and that movement can safely be made. When the pilot reaches the take-off point he awaits a further signal, consisting of a white light projected from the tower by means of an Aldis lamp. This signal is necessary in order that the look-out man may see, before the take-off run is started, that no other machine is com ing in. Once in the air, the radio operator runs out the trailing aerial and tests his set. Croydon's chief : Air Commodore E. D. M. Robertson, D.F.C., the chief officer at our premier airport.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
