FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1973
1973 - 0092.PDF
FLIGHT International, II January 1973 Avionics Radar recorders THERE HAS ALWAYS BEEN A NEED to record the information shown on radar displays, but until recently the only method of doing so was by pho tography. This was far from satisfac tory since, even though automatic ex posures could be made, they could only sample the radar picture at inter vals, whereas the requirement has always been for a continuous rec ording. With the advent of video tape it is now possible to record everything the radar sees as it occurs, and to play it back immediately or store it for future use. As a result a variety of require ments for radar recording are now be ginning to arise. The applications are numerous but the significant ones are readily de fined. Probably the most important is training. To be able to record a radar story and then play back the result can be of great value for the training of operators. No simulator can pro duce the difficult fluctuating echoes, masked by clutter, exactly as they would be seen by the operator, per haps sitting in a bumpy aircraft with heavy rain squalls all but blanking his display. With suitable equipment it is possible to record a great variety of phenomena and eventually to amass a whole library of records, each show ing a real situation. The records can then be played back on to the same type of display, and if necessary in the same environment, while the instruc tor explains to the trainee operators what the echoes are, what caused the interference, what the operator should have done to minimise it, and so on. Various types of jamming can be recorded and fed into "live" radar to teach the operator what to do when his picture is degraded by ECM. Alternatively, real radar records can be fed into simulators or trainers in order to provide realistic situations. The Ferranti Radot, which is used for radar operator training at HMS Dryad, the Royal Navy's navigational school, uses this method. An expansion of the training aspect is to record military exercises and use the records at the subsequent de briefing. How many times does one hear on such occasions "You were quite close to the target, how was it you did not see it on your radar?" The probable reply is "I don't know." The record is then played back and it should be possible to determine whether or not the echo did show and whether the operator was at fault. Apart from its use for checking operators, the radar record can be easily arranged to show a complete tactical situation as seen in the air craft or ship, thus greatly facilitating the subsequent analysis. Radar recorders can also be of use in air traffic control and a few authori ties are experimenting with them. When an incident, for example an air- miss, occurs the record of the appro priate ATC display is played back and the procedures examined to see how the event occurred. In spite of the fact that it is now mandatory for voice communication in ATC to be taped, the recording of traffic-control radars has not yet been made obligatory. ATC controllers appear not to like the idea and generally put forward the argument that a large quantity of tape would have to be used, since any recording must be continuous to be of any value. Most video sets only have sufficient tape for 60min or 90min recording, but there is no reason why two recorders should not be used in sequence with automatic switching from one to the other. The stowage of tape might cause a prob lem, but each tape could be wiped and used again after, say, 48hr if no inci dent was reported. This technique is of course commonly used with acci dent data recorders, where the tapes are normally stored for 28 days before being used again. A somewhat similar situation exists in the recording of harbour radars. Decca, which supplies the majority of British ports with their radars, also provides a recorder for each. The radar plots are recorded continuously and the tapes kept for 24hr, in what appears to be a very similar traffic- control organisation. Probably the only airfield in the world to have adopted continuous radar recording is Kai Tak in Hong Kong. In aircraft, and less frequently in ships, it might be possible to record echoes of various different types of aircraft, ship and missile. The records could be played to operators as fre quently as needed to enable them to recognise similar echoes when seen in real situations. Radar recorders can also be of value in times of radar silence. Owing to the risk of interception, some radio plans call for no transmission until the enemy is actually encountered. Under these circumstances it is vital to ensure that the radar will work when it is switched on. A recorder could be connected and feed into the system a previously made record. The whole radar, except the transmitter, could The EMI Type RR.IOO is a typical radar recording system. This company's work began with a requirement for test-gear at Britain's West Drayton ATC Centre. An airborne recorder is being built for MRCA trials, and "spin-off" applications include the investigation offish shoals then be checked before entering the critical stage of the flight. Yet another application is the test ing of radars in service. When check ing a radar, particularly a new one, it is necessary to investigate its per formance when operating under ser vice conditions. With airborne radars this is often difficult, since there may not be room for test personnel in the aircraft. By recording the picture the behaviour of the equipment can be examined at leisure with suitable test instrumentation. A radar recorder consists basically of a video tape-recorder and an inter face or conversion unit, i.e. a device to extract the necessary information from the radar and feed it to the tape recorder, or vice-versa. The three main parameters required to produce a recording are the video signal itself, trigger or synchronising pulses which define the length of each "picture frame" on the tape, and the aerial azimuth angle measured from the direction of motion of the aircraft or ship. In addition, arrangements are usually made to add time, geographi cal position, course and speed, height and, if necessary, a voice channel with, for example, a running commentary. The equipment now available provides recording comparable with the original, with virtually no degradation of quality. To play back, the interface unit is connected to a radar display of the same type as the original from which the record was taken. The record then unfolds in the display as it appeared originally and at the same rate. It is usually possible to increase the play back speed, or the record can be stopped for comment or discussion, or moved forward in slow motion. Unfortunately there is little uni formity in radar characteristics, and
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
