FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1961
1961 - 1085.PDF
FLIGHT, 10 August 1961 187 SYSTEM SURVEY Smiths Apply ATR Casing DURING the SBAC Display last year Smiths Aviation Divisionexhibited components of the new electronic equipment cases they had developed to American ARINC specification No 404 and BritishATEC specification 201. The components and appropriate mount- ing trays can now be bought "off the shelf" for any of thestandard boxes up to 1 ATR, in both short and long versions. In the aircraft, the assembled electronic box is supported in themounting tray secured to cross-rails which are shock-mounted on the airframe structure at spacings recommended by the aircraftmanufacturers. The boxes are not individually shock-mounted. Electrical connections are made by multi-way plug sockets at therear of the case which mate with equivalent units on the tray. Dowel pins align the connectors and are also positioned to preventinsertion of the wrong box. It is now widely accepted that the British Standards Specification BSR.l is obsolete; accordingly,British manufacturers have largely adopted ARINC form factors. ATR shapes and sizes can be mounted closer together, are easy toremove for maintenance and lend themselves well to modern pro- duction techniques, particularly those using miniaturized modules. Smiths have applied the ATR sizes extensively to their systempackaging, and they make what is probably the largest single appli- cation of ATR equipment—American or British—in the multiplexautomatic flight-control system for the de Havilland Trident. All the electronic units of this system will be packaged in accordancewith ARINC Spec. 404, using Smiths' own hardware. In addition, the Trident radio, navigation and electrical units contained inother manufacturers' ATR cases will be carried in Smiths ATR mounting trays and associated junction boxes. The provision of a set of standard components from which boxesof various ATR sizes can be assembled has already made possible an appreciable reduction in cost and man-hours within SmithsAviation Division itself. Without standard cases, considerable time must be spent on the design of boxes in a number of differentdepartments. The Smiths boxes are so arranged that, on removal of the covers, electrical and mechanical components, cable forms andconnectors are all fully accessible. Base-plate assemblies and top Decca roller map 9273, left, and 9267, above. They are respectively manually set and Dopp/er- controlled channels allow for use of full-size chassis and modules, eitherseparately or in combination. Extruded aluminium sections are employed wherever extrastrength is needed; and maximum longitudinal stiffness is inherent from fixings in two planes at front and rear panels. Normal ventila-tion from bottom to top is ensured by perforated base-plates and covers made of simple, one-piece pressings in light alloy, piercedall over with a mosaic of £in holes. A f ATR cover made from 0.036in-thick material would have 2,500 pierced holes, giving aseven per cent saving in weight. Smiths have developed special junction boxes which can beremoved from the top of the mounting tray, even when the tray is situated on the bottom shelf, without damaging the wiring. Junc-tion boxes can also be joined together into "families," reducing the number of wires run externally along the rear of the racking.Indexing pins on each box can be interchanged with blanking screws to make any combination of indexing listed in the ARINCspecification. The three pictures below show some of the units of the Tridentflight control system in Smiths ATR cases. The flight compass amplifier is mounted in a short £ATR case. The electronic unit ofthe master compass, not shown, is mounted in a short $ATR case which is subsequently bolted end-to-end to the presentation unitto form a single long ATR case. The PVD amplifier, shown below, has lightening holes in the base-plate and end cover, as well asperforations in the top cover, to allow virtually unrestricted flow of ventilating air through the case from bottom to top. One pictureshows the three tiers of junction boxes which will connect the cases of the Trident flight control system. Behind them is the largeblack case of the main junction box for the whole system. Decca Roller Maps Two examples of pictorial roller-map devices proposed byDecca for military aircraft not equipped with Decca Navigator are illustrated above. Intended for dead-reckoning and track-keeping in strike aircraft, they are small and light; and one of them can be placed in front of an instrument panel and used withmanual information inputs only. The rollers will accommodate up to 4,800 miles of "one-million" topographical map strip on which apointer shows lateral track displacements. Groundspeed and lateral displacement are manually set on one roller map or coupledto Doppler on the other type. Trials have proved, it is stated, very successful. Smiths ATR coses applied (left, 'upper and [lower) to the PDV amplifier and flight compass amplifier. Below are the junction boxes, with the main junction box behind, for the flight-control system of the Trident, mounted in the final assembly jig
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
