Aeronautics and astronautics – Aircraft structure – Ice prevention
Reexamination Certificate
1999-08-06
2001-05-08
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft structure
Ice prevention
Reexamination Certificate
active
06227492
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to electrical heating systems for the prevention or removal of ice accumulation on the surface of aircraft structural members and, more particularly, to a redundant ice management system for aircraft.
BACKGROUND OF THE INVENTION
The accumulation of ice on aircraft proprotors, wings and other structural members in flight is a well known danger during low temperature conditions. As used herein, the terms “aircraft members” or “structural members” are intended to refer to any aircraft surface susceptible to icing during flight, including proprotors, wings, stabilizers, engine inlets and the like. Attempts have been made since the earliest days of flight to overcome the problem of ice accumulation. While a variety of techniques have been proposed for removing ice from aircraft before or during flight, many prior systems or techniques experience various drawbacks or possess certain limitations.
One approach to ice management that has been used is so-called thermal de-icing. In thermal de-icing, the leading edges, that is, the portions of the aircraft that meet and break the airstream impinging on the aircraft, are heated to prevent the formation of ice or to loosen accumulated ice. The loosened ice is then blown from the structural members by the airstream passing over the aircraft.
In one form of thermal de-icing, heating is accomplished by placing an electrothermal pad, including heating elements, over the leading edges of the aircraft, or by incorporating the heating elements into the structural members of the aircraft. Electrical energy for each heating element is typically derived from a generating source driven by one or more of the aircraft engines or transmissions. The electrical energy is intermittently or continuously supplied to provide heat sufficient to prevent the formation of ice or to loosen accumulating ice.
With some commonly employed thermal de-icers, the heating elements are configured as ribbons, e.g. interconnected conductive segments, that are mounted on a flexible backing. The conductive segments are separated from each other by gaps, e.g. intersegmental gaps, and each ribbon is electrically energized by a pair of contact strips. When applied to a wing or other airfoil surface, the segments are arranged in strips or zones extending spanwise or chordwise of the aircraft wing, rotor or airfoil. One of these strips, known as a spanwise parting strip, is disposed along a spanwise axis which commonly coincides with a stagnation line that develops during flight in which icing is encountered. Other strips, known as chordwise parting strips, are disposed at the ends of the spanwise parting strip and are aligned along chordwise axes. Other zones, known as spanwise shedding zones, are typically positioned above and below the spanwise parting strip at a location intermediate the chordwise parting strips. Between adjacent zones, a gap, known as an interheater gap, sometimes exists.
One known method for de-icing causes electrical current to be transmitted continuously through parting strips so that the strips are heated continuously to a temperature above 32° F. In the spanwise shedding zones, on the other hand, current is transmitted intermittently so that the spanwise shedding zones are heated intermittently to a temperature above about 32° F.
While this technique of heating the various zones generally is effective to melt ice (or prevent its formation) without the consumption of excessive current, a problem exists in that melting of ice in the inter-segmental and interheater gaps can be difficult or impossible. Moreover melting of ice on or around the contact strips can also be difficult or impossible. Accumulation of ice in the gaps and on the contact stripe is particularly undesirable because the unmelted ice can serve as “anchors” for ice that would be melted but for the ice accumulated in the gaps or on the contact strips.
Another problem with prior thermal-based systems is their lack of reliability. Aircraft members, such as rotors of a helicopter or proprotors of tiltrotor aircraft, undergo much strain and stress associated with aircraft operation. Ongoing use of aircraft inevitably results in some damage to aircraft components. With respect to heating elements integrated within an aircraft member, breaks in blanket circuitry can cause thermal de-icing systems to fail, posing serious risk to aircraft crew and equipment during cold weather operations. And yet another concern with heating element circuitry is the potential for inconsistency, e.g. hot spot or cold spot generation, and larger than acceptable power consumption.
Problems may also be encountered where strips are run along the entire length of the aircraft. The size of the ice being shed by the aircraft member can cause a hazard to the aircraft's fuselage. If the particle of ice is too large, it could hit and may even penetrate the fuselage.
SUMMARY OF THE INVENTION
In response to the foregoing concerns, the present invention provides a new and improved thermal ice management system for aircraft structural members. Specifically, the present invention provides a secondary section having secondary anti-ice elements and secondary de-ice zones which provide thermal ice management to aircraft structural members.
The redundant ice management system of the present invention, includes a primary ice management sub-system that provides thermal ice management to aircraft structural members and a secondary ice management sub-system that provides back-up thermal ice management to aircraft structural members in the event of a failure by the primary ice management sub-system.
Further novel aspects of the present invention are found with the incorporation and use of separate zones within the primary and secondary sub-systems, integration of the redundant ice management systems with a controller and the integration of the controller with atmospheric, structural and system monitoring capabilities.
The present invention also provides a method for managing the formation of ice on aircraft structural members with an ice management system having primary and secondary ice management sub-systems that includes monitoring aircraft structural members and atmospheric conditions for ice formation on the aircraft's structural members, activating primary ice management systems in response to an indication of ice formation on the aircraft's structural members, monitoring the primary ice management systems to determine its operational readiness and efficiency and activating the secondary ice management system in response to monitoring of the primary ice management if the primary ice management system fails operational readiness and efficiency requirements.
One advantage of the present invention is that it provides for a backup ice management scheme in the event of a failure by the primary system. By providing primary and secondary sub-system elements, heat is effectively and efficiently generated throughout the aircraft member regardless of primary system failure. Sections of the primary and secondary sub-system elements are oriented spanwise and chordwise along the aircraft's structural member in a manner that can provide adequate surface coverage for thermal management operations.
Another advantage of the present invention is that it optimizes element dimensions, such that primary and secondary sub-system sections promote efficient heating along the entire targeted area and minimizes the amount of overlapping that is required to gain desired heat distribution for thermal ice management.
Yet another advantage of the present invention is that it eliminates cold spots which can arise on and around aircraft structural member through selective activation of heating elements disposed along a structural member.
Another advantage of the present invention is that it affords highly desirable levels of heating while using a minimum amount of power. More specifically, by sequentially heating spanwise shedding areas, power consumption is minimized by the controller witho
Aubert Roger Jacques Michel
Eisenhauer Mark P.
Froman Gary Scott
Miller Richard Dean
Pappas John Peter
Barefoot Galen L.
Bell Helicopter Textron Inc.
Gardere Wynne & Sewell LLP
Warren, Jr. Sanford E.
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