GB840509A - Improvements relating to aircraft de-icing installations - Google Patents

Abstract

840,509. Aircraft icing and de-icing indicators. FAIREY CO. Ltd., July 15, 1958 [April 15, 1957], No. 12261/57. Class 4. An aircraft indicator includes a number of tell tale indicators operated automatically by external means sensing the onset of critical climatic conditions leading to icing, and/or sensing ice formation, and a dial bearing a pictorial representation of the aircraft and with several tell tale lamps located in various parts of the representation corresponding to the parts of the aircraft associated with various de-icing circuits to which the lamps are connected, each lamp being lit up as long as its associated de-icing circuit is energized. In Fig. 1, detector 20 is sensitive to ambient temperature and humidity, and when either of these conditions becomes critical, energizes a control system 21 which lights up the appropriate lamp T or H on the face of an indicator 23. When both conditions are critical, indicating impending icing, a further lamp I is lit up, and a signal passes on line 25 to a relay 26, provided a dynamic pressure responsive switch 32 is closed, which is the case when the flight speed is sufficient to prevent overheating of the deicing elements. Relay 26 when actuated operates a set of contactor devices 12 fed from the aircraft three phase power circuit 14 through an integrator device 13, and feeding three phase lines 11 supplying heating mats 10 located in various parts of the aircraft. Overheating of any one mat 10 sends a signal on one line 18 to operate cut-out relays 17 and light a warning lamp O. When the heating circuits are switched on, the integrator 13 operates a relay 33 to light a green lamp P. If a fault develops in one of the mats, the resulting lack of balance in the load transmitted by integrator 13 is arranged to operate relay 33 to switch off lamp P and light a red lamp L. The instrument 23 shown in part cross-section in Fig. 3, comprises a frosted glass or translucent plastic face 41, and an apertured backing plate 43, each aperture containing a lamp 45, and being shaped to conform to one of the areas into which the pictorial representation of the aircraft is divided. Each corresponding area of the actual aircraft has its own de-icing circuit. These areas on the representation are the propellers and spinner 51, 52, cowling 53, engine air intake guide vanes 55, wing leading edges 57, 58, wing main surfaces 60, 61, 62, 63, tail plane and fin leading edges 65, 66, 67, and tail plane and fin surfaces 69, 70, 71. Of these areas, the wing main surfaces 60-63, the propellers, spinner, and cowling 51-53, and the tail plane and fin main surfaces 69-71, are heated cyclically by means of switches 15 in the leads 11 controlled by a cycling motor 16 adjustable by the pilot, so that the heating cycle may be, say, 10 seconds on, 5 seconds off, or 30 seconds on, 15 seconds off. Further, the surfaces 60-63 are heated in successive order during the cycle. The other surfaces are continuously heated during deicing. The apertures in the plate 43 and the connections to the various lamps 45 are such that when any area of the aircraft is being heated, the corresponding area of the representation is illuminated from behind. For example, during de-icing, the four areas 60-63 are illuminated in sequence. In the case of continuously heated areas, the continuous flow of current may be indicated by a "flowing" illuminated chain line. In the instrument front face of Fig. 2 (not shown), the lamps L and P are situated in the centre of the aircraft representation, and the lamps H, T, I and O, one in each of the four quadrants into which the representation divide the instrument face. A switch 29 when closed manually by-passes relay 26, and provides de-icing of the propellers, spinner, cowling, and air intake at will, and a similar switch 30 provides de-icing of the remaining surfaces at will.