GB446983A - Ice accretion indicator for aircraft and internal combustion engines - Google Patents

Abstract

446,983. Apparatus for indicating ice formation on aircraft. SWAN, A., GRIFFITH, A. A., and HELMORE, W., Royal Aircraft Establishment, South Farnborough, Hampshire. Dec. 21, 1934, No. 36608. [Class 4] [See also Groups XXVII and XXIX] An ice-accretion indicator comprises a warning-device, means for actuating said warning-device, a device responsive to ice formation having a part on which ice forms when ice forming conditions prevail, which ice is arranged to constitute an element in the means bv which said warning device is actuated. In one form, Figs. 1 and 2, as applied to an aircraft the means responsive to ice formation comprise a diaphragm 24 secured between the two halves of a casing forming upper and lower pressure chambers which communicate by conduits 9, 27 respectively with forwardly opening passages 15, 16 formed in a cylindrical member 14 of which the axis is disposed in the direction of motion. Passage 16 is adapted to be readily obstructed by ice-laden air by means of a plug 18 having a small inlet aperture 19. A balance plug 20 with an aperture 21 is inserted in tube 15, and each passage also communicates with the atmosphere by means of a screwed plug provided with a bleed hole. Diaphragm 25 carries centrally a pip 34 adapted to engage the free end of a spring blade 35 secured to the diaphragm housing by an insulated bolt 36 secured at its outer end to a lead 39 of an electric cable 13. Spring blade 35 is arranged to make contact, on downward deflection of the diaphragm which occurs on obstruction of orifice 19, with an adjustable contact member 40 connected by a conducting-strip 43 with a terminal 48 connected to cable lead 47. A heating-coil 8 is would around the cylindrical member 15, one end being connected to strip 43 and the other to cable lead 53. As shown in Fig. 3, the warning-device comprises a lamp 57 disposed in a circuit comprising a battery 56, a main switch 55 and a relay-operated switch 58. Switch 58 which is closed on downward movement of the diaphragm also serves to establish the circuit of heater coil 8 whereby the ice obstruction in passage 16 is thawed and diaphragm 24 is restored to its neutral position. A modified form of this device is described in which the cylindrical member is disposed in the induction pipe of the aircraft engine. In this case the bleed holes are omitted since the passages are subjected to suction and the electric circuit is simplified by the omission of the heater and relay. According to further modifications the warning-device may be operated mechanically, and a horn or indicating- needle for instance forming part of the air-speed indicator may be substituted for the lamp. The heating-coil may be manually instead of automatically controlled. The element responsive to ice formation may comprise an apertured part e.g. a piece of gauze disposed in the air stream in such manner that when the apertures become blocked the wind resistance of such part increases and the part is moved to initiate the warning-signal.