Patent EA-002165-B1 (EA)
Title: Method and apparatus for detection of ice accretion
Inventor: HOLMEN HANS KRISTIAN
IPC: B64D15/20
Filed: 1998-10-14
Abstract: 1. Method for detection of conditions involving a risk of ice formation on the surface of aircraft in movement, based on temperature measurement, the surface temperature is measured with temperature measuring elements (Dtl,Dt2,Dt3) disposed in at least two surface points (P1,P2,P3,P4) characterized in that one of the surface points (P2) is disposed downstream in relation to another surface point (P1) as seen in the general direction of air flow in the surface region at the points, in that the recording of the temperature difference between points in a normal situation for the aircraft concerned and its velocity, altitude, climbing/desending relationsships, dry air, as well as the absolute temperature is taken as a basis for the detection and a corresponding indication being presented to the aircraft pilot or crew, and that subsequently recorded temperature differences are related to the temperature difference in the normal situation for detection and indication of risk of ice formation. 2. Method according to claim 1, characterized in that deviations in the level of subsequently recorded temperature differences (61-64) in relation to the temperature difference in the normal situation, are taken as a basis for the detection and the indication, preferably on the basis of level deviations over and beyond a predetermined value. 3. Method according to any one of claims 1-2, characterized in that the time derivative of recorded temperature differences (61-64) is taken as a basis for the detection and the indication. 4. Method according to any one of clams 1-3, characterized in that at least one temperature measuring element is located at a stagnation point or region (Pl) at the surface of the aircraft. 5. Method according to any one of claim 1-4, characterized by the employment of temperature measuring elements that in pairs consist of a differential temperature measuring element (Dtl and DtZ, respectively), and that an absolute temperature element (PtlOO) is located preferably adjacent to the differential temperature measuring element (P3). 6. Method according to claim 5, characterized by the employment of two or more differential temperature measuring elements (fltl,Dt2,Dt3). 7. Method according to any one of claims 1-6, characterized in that a relatively strong increase in the absolute temperature is used for warning about ice formation having started. 8. An apparatus for detection of conditions involving a risk of ice formation at the surface of aircraft in movement of claim 1, comprising at least two temperature measuring elements (Dtl,Dt2,Dt3) disposed at different surface points (P1,P2,P3,P4), characterized in that the temperature measuring elements are disposed in points, one of which (P2) is situated downstream in relation to another point (Pl) as seen in the general direction of air flow in the surface region at the points, the apparatus comprises means (70) for recording the time curve or development of the temperature difference between the points, and means (70,71) for detection and corresponding indication based on the recording, one of temperature measuring element (PtlOO) indicates the absolute temperature and means for detection and indication at the instrument panel for the pilot or crew. 9. Apparatus according to claim 8, characterized in that at least one temperature measuring element is located at a stagnation point or region (Pl) at the surface of the aircraft. 10. Apparatus according to claim 8 and 9, characterized in that at least some temperature measuring elements in pairs consist of differential temperature measuring elements (Dtl,Dt2), and that an absolute temperature element (Ptlo0) is located preferably adjacent to a differential temperature measuring element (P3). 11. Apparatus according to claim 10, characterized by comprising two or more differential temperature measuring elements (Dtl,Dt2,Dt3). 12. Apparatus according to any one of claims 8-11, characterized in that one or more temperature measuring elements is/are mounted underneath the heat conductive outer skin of the aircraft.