GB626543A - Improvements in means for detecting ice-formation on aircraft - Google Patents

Abstract

626,543. Aircraft icing indicators. FAULKNER, A. W. April 15, 1947, No. 10044. [Class 4] An icing detector for aircraft has an air inlet consisting of a large number of perforations 11 distributed along a part of the leading edge of a plane or fin of the aircraft, the perforated part being composed of the same material and having the same surface finish as the unperforated part, and a duct leading from said inlet to an outlet at a part of the aircraft, not facing the airstream, which is not liable to ice formation at least until sometime after it has taken place at the air inlet, the detector also including a warning device responsive to changes in the air velocity through or to the difference in the air pressures at the ends of said duct. In Fig. 2, the detector includes an anemometer rotor 14, mounted in the duct 13 and driving a small generator 14<SP>1</SP>, abnormal fall in the voltage produced thereby causing a warning indicator to operate. In Fig. 3, the invention is applied to an aircraft fitted with de-icing apparatus of the type described in Specification 622,778. The air duct 19 leads from perforations 11 at the edge of the blister 15 to a chamber 20 on one side of a diaphragm 21. A restricted byepass pipe 30 leads from chamber 20 to a chamber 22 at the back of the diaphragm, the air then passing to outlet holes 24 in column 25 that may be heated by a filament 26. Under non- icing conditions, the pressure of the air in front of the diaphragm deflects it sufficiently to hold two electric contacts 28, 29, closed. When a substantial number of the holes 11 have become blocked by ice, reduction of pressure in chamber 20 permits the diaphragm 21 to open contacts 28, 29, thereby actuating a warning device. In the Provisional Specification, it is stated that means may be provided for feeding a supply of de-icing fluid to the duct to prevent any icing of its interior, a shutter may be fitted behind the perforations to prevent entry of dust in normal atmosphere conditions, and a heated pitottube may be exposed directly to the airstream near to the perforations to provide a measurement of the characteristic pressure at that point. Specification 563,148 also is referred to.