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Aviation History
1975
1975 - 1743.PDF
FLIGHT International, 4 September 1975 337 • D S q I warucs for business pilots AFTER MANY years of promise—but little action—avionics for busi ness and light aircraft are beginning to develop, taking advantage of micro- circuitry and other by-products of the electronics boom outside aviation. In all fields there are rapid and exciting advances for the private or company pilot, from the cheapest nav/ com sets up to the sophisticated airline-style equipment, which can cost as much as one small aircraft. Many of these advances are to be seen at the Flight Cranfield Show, which opens today (September 4). Traditionally new concepts in avionics are seen first in the US. This is simply because both the industry and the market place are there and it often does not pay a manufacturer to seek British certification for a new system until it has been fully accepted in the US, especially if that equipment is in any way innovative. Trends in operating demands are leading to changes in light-aircraft avionics. These are not as immediately exciting as some of the latest cosmetic changes, but show how rapidly air transport has developed in the last few years. Radios with 720 channels (25kHz channel spacing) are now appearing in the UK. It is not so long ago that a 12- or 20-channel set was adequate in the UK for most VFR work, and 120 channels were sufficient for IFR. This was satisfactory until the frequency-separation problems caused by the use of more and more stations required the introduction of 50kHz channel spaced radios (360 channels). Now 25kHz spacing is appearing in the US and it will un doubtedly be introduced in Europe before long. This raises an interesting procedural point. It has long been air- traffic philosophy to invent phrases to abbreviate R/T talk. We are now faced with the possibility of a very long (and therefore easily mistaken) command, such as "continue with London, one-two-seven-decimal-seven- two-five." Maybe one day this will be abbreviated to a three-figure channel number. Plans are ready in the UK for the implementation of 25kHz spac ing, but the CAA has not yet decided on a date for the introduction. Also becoming more and more common in light aircraft—and manda tory in increasing areas of airspace— is the transponder. A few years ago this unit was prohibitively expensive for the general-aviation sector, but now full 4096-code systems are com petitively priced. The Mode C trans ponder (altitude reporting) is becom ing accepted as a useful ATC tool, especially now that so much of the UK is covered by compatible RCA introduced the Primus-40 weather radar, left, at the Paris Air Show. Digital electronic techniques give optimum range and target definition. The planar aerial can be tilted 15" either side of the horizontal The Sperry Stars flight instruments, above, introduce a new standard of clarity. The range is now standard on the Cessna Citation secondary surveillance radar. Here, for once, the UK leads the world with 4096-code requirements and the transponder can be fully utilised in UK airspace. Ground proximity warning systems (GPWS) have been made mandatory for air-transport aircraft and it is probable that the lower weight limit covered by the legislation (presently 15,000kg) will be eventually reduced. For the moment, however, the CAA has no plans for such an extension to the regulations. Nevertheless it tells Flight that it would encourage any company, particularly those operating to AOC standards, to fit GPWS. Two further items of avionics which are becoming cheaper as technology advances are weather radar and the radio altimeter. Digital-circuitry weather radar can be useful both as a bad-weather detector and for locat ing masts and other isolated struc tures. The digital technology now being employed in this area allows longer range detection and better
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