Aeronautics and astronautics – Aircraft structure – Ice prevention
Reexamination Certificate
2000-05-03
2002-02-19
Jordan, Charles T. (Department: 3644)
Aeronautics and astronautics
Aircraft structure
Ice prevention
Reexamination Certificate
active
06347767
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to detection of conditions involving a risk of ice formation on the surface of aircraft in movement, based on temperature measurement. More specifically the invention comprises both a method and an apparatus in various embodiments, intended to avoid the problems represented by such ice formation.
When there is referred to aircraft here, there is in the first instance the question of airplanes and secondly other forms of aircraft, including helicopters, which also to a high degree can be subject to icing. In particular icing on the helicopter rotor can be very dangerous.
DESCRIPTION OF THE RELATED ART
Previously there are many proposals directed to the detection of ice layers being deposited on the surface of aircraft. Examples of known methods of interest in this respect, are U.S. Pat. No. 5,521,584 and perhaps in particular U.S. Pat. No. 5,313,202.
U.S. Pat. No. 5,313,202
The patent specification takes as a starting point that the aircraft part collides with undercooled water drops existing in the air space where the part is moving. The collision results in attachment of the water drops to the aircraft part and the drops are converted into ice as a consequence of this collision. When the water freezes to ice energy is liberated in the form of heat so that the ice will have a temperature higher than the environment while the ice is formed. Ice is formed at 0° C. This region of the aircraft part that is being covered with ice or that has been covered with ice still not being completely frozen out, therefore will have a temperature that is higher than the environment and accordingly also higher than the regions still not being covered by ice. This difference in temperature, between for example the leading edge of a helicopter rotor being in a process where ice is built up—and portions of the same rotor where still no ice has attached, according to the patent specification can be recorded by means of a particular contact-free detector that records the difference in infrared radiation from the regions with ice in relation to the radiation from the ice-free regions.
Nowhere in the patent specification it is mentioned that freezing can commence in front of the aircraft part, and the sensitivity of an IR detector as shown, will not be suitable in order to measure the influences on the aircraft part from temperature differences due to freezing of very small droplets of undercooled water in the air space outside the actual aircraft part—i.e. droplets being too small to be able to attach to the aircraft part by the freezing-out. Therefore the solution can not be employed for warning about any risk of icing.
U.S. Pat. No. 5,521,584
This known method is intended for recording that ice has been formed or is during formation, in particular on airfoils when the aircraft stands on the ground. The purpose is to save time-consuming inspection in order to decide whether or not the aircraft has to be deiced, before take off.
The functioning of the method is based upon the fact that ice has an insulating effect: After having been high in the air aircraft and the contents of fuel tanks, being often localized in the airfoils, may have been cooled to below the freezing point of ice. If there is mild air with a high moisture content at the place where the aircraft has landed, the moisture can condense and freeze to ice on the airfoil at the regions concerned. At selected places where there can be a risk of icing, special sensors are attached to be able to measure the heat flow from the moist, warm air to the cooled aircraft part. As the aircraft part is covered by an increasingly thick ice layer, the heat flow will decrease because of the insulation effect of the ice. Heat flow and temperature picture make it possible to calculate the tickness of the ice being possibly formed. Thus, the pilot on the background of the measurements can decide in a simple manner whether or not deicing is required.
This form of icing is not of interest with respect to an aircraft during flight, and accordingly this known method in the form shown can not be employed for recording ice formation as a result of collision with undercooled rain in the air during flight, and still less be able to warn about any risk of such icing.
The patent specification and claims do not contain any indication to the effect that the inventor has contemplated this possibility.
Thus, methods being known hitherto have not been directed to providing a pre-warning regarding risk of icing being present. When an ice layer has started to be deposited, there can already exist risk factors which aircraft pilots are to a highest degree interested in avoiding. Accordingly, there is a great need for means for detecting conditions involving a risk of ice formation, before such ice formation is initiated. This invention therefore is directed to this task, and is based on temperature measurements as are also known methods for detecting an ice coating having actually been deposited.
SUMMARY OF THE INVENTION
In their broadest aspect the novel and specific features of the invention in the first place consist in that the surface temperature is measured with temperature measuring elements disposed in at least two surface points having different air pressures, that a recording of the change of the temperature difference with time between the points, is taken as a basis for the detection and a corresponding indication being presented to the pilot or crew of the aircraft, and that at least one temperature measuring element gives a measure of absolute temperature, that provides a check of the validity of the detection and the indication when the absolute temperature is between 0° C. and −55° C.
In addition to the main features just recited regarding the method according to the invention, there are stated further and subordinate method features in the claims. Moreover the invention comprises an apparatus for detection of conditions involving a risk of ice formation on the surface of the aircraft in movement, based on temperature measurement, as also stated in the claims.
In technical terms it is clear that the above recording of temperature difference/time changes, will be performed by means of a computer and that this after a suitable signal processing will deliver control or output signals to for example an instrument panel that can be observed by the aircraft crew, for indications, alarm or warning to the effect that the conditions at one or more surface portions of the aircraft involve risk of ice formation. Accordingly, necessary action can be taken in due time, for example by adequate maneuvering or activation of deicing equipment.
By means of the invention it is possible for example for a passenger airplane pilot to follow the development of the relevant temperature relationships through several minutes before the instant when icing will start. For aircraft with a velocity of several hundred kilometers per hour this means that warning about risk of ice formation can be indicated several tens of kilometers beforehand. The significance of this can not be over-estimated.
The invention is based in part on a new understanding regarding the mechanisms or processes that occur immediately adjacent to the surfaces of aircraft in movement, and in the following description these relationships will be discussed further. In general regarding meterological relationships of interest in this connection, reference is here made to the book “Vær og klima i farger” (title in English: Weather and climat in colours) by Petter Dannevig and Svante Bodin, H. Aschehoug & Co., Oslo 1978, see in particular page 105 pp in the book.
When an aircraft moves through the air, there will be local variations in the relative velocity between the air molecules and the various parts of the surface of the aircraft—depending on the shape and the manner of its movement. In particular the leading edge of the airfoil and tail rudder profiles as well as the propeller, and on helicopters: the main rotor and the tail rotor, are regions of in
Dinh Tien
Futuris AS.
Jordan Charles T.
LandOfFree
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