AIRCRAFT HYDRAULIC SYSTEM

Abstract

An aircraft hydraulic system utilizes a hydraulic fluid that includes a heat transfer fluid and a friction modifier additive.

Claims

1. An aircraft hydraulic system comprising: a hydraulic fluid including a heat transfer fluid and a friction modifier.

2. The aircraft hydraulic system set forth in claim 1, wherein the heat transfer fluid is hydrocarbon-based.

3. The aircraft hydraulic system set forth in claim 2, wherein the aircraft hydraulic system is a friction plate brake system.

4. The aircraft hydraulic system set forth in claim 2, wherein the aircraft hydraulic system is a clutch system.

5. The aircraft hydraulic system set forth in claim 3 further comprising: a friction plate exposed to the hydraulic fluid.

6. The aircraft hydraulic system set forth in claim 5, wherein the friction modifier includes a long chain molecule having a polar end associated with the friction plate and a non-polar end associated with the hydrocarbon based heat transfer fluid.

7. The aircraft hydraulic system set forth in claim 2, wherein the friction modifier is a fatty acid.

8. The aircraft hydraulic system set forth in claim 2, wherein the friction modifier is a carboxylic acid.

9. The aircraft hydraulic system set forth in claim 2, wherein the hydrocarbon-based heat transfer fluid is a synthetic hydrocarbon-based heat transfer fluid.

10. The aircraft hydraulic system set forth in claim 9, wherein the synthetic hydrocarbon-based heat transfer fluid is polyalphaolefin.

11. The aircraft hydraulic system set forth in claim 2, wherein the hydrocarbon-based heat transfer fluid is mineral-based.

12. The aircraft hydraulic system set forth in claim 2, wherein the heat transfer fluid has a viscosity of about 1100 centistokes or less at negative sixty-five degrees Fahrenheit.

13. The aircraft hydraulic system set forth in claim 12, wherein the heat transfer fluid has a viscosity within a range of about 500 to 1100 centistokes at negative sixty-five degrees Fahrenheit.

14. An aircraft hydraulic fluid comprising: a heat transfer fluid; and a friction modifier.

15. The aircraft hydraulic fluid set forth in claim 14, wherein the heat transfer fluid is hydrocarbon-based.

16. The aircraft hydraulic fluid set forth in claim 15, wherein the friction modifier is a fatty acid.

17. The aircraft hydraulic fluid set forth in claim 15, wherein the friction modifier is a carboxylic acid.

18. The aircraft hydraulic fluid set forth in claim 14, wherein the heat transfer fluid is polyalphaolefin.

19. The aircraft hydraulic fluid set forth in claim 14, wherein the heat transfer fluid has a viscosity of about 1100 centistokes or less at negative sixty-five degrees Fahrenheit.

20. The aircraft hydraulic fluid set forth in claim 19, wherein the heat transfer fluid has a viscosity within a range of about 500 to 1100 centistokes at negative sixty-five degrees Fahrenheit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiments. The drawings that accompany the detailed description can be briefly described as follows:

[0025] FIG. 1 is a schematic of an aircraft utilizing an aircraft hydraulic system as one exemplary embodiment.

DETAILED DESCRIPTION

[0026] Referring to FIG. 1, an aircraft 20 is illustrated having an aircraft hydraulic system 22 that utilizes a hydraulic fluid (i.e., see arrow 24). Examples of the hydraulic system 22 may include a friction plate brake system, a clutch system, a flight control actuation system, a helicopter hoist, and others. The aircraft hydraulic system 22 may include at least one friction plate 26 as is commonly known to one having skill in the art of hydraulic systems. It is contemplated and understood that the aircraft system may further include systems that utilize gear arrangement requiring lubrication.

[0027] Known hydraulic fluids that may be hydrocarbon-based, are commonly used in known aircraft hydraulic systems. Such hydraulic fluids may exhibit undesirably high viscosities at low temperatures of, for example, about negative sixty-five degrees Fahrenheit (65 F.). One example of a traditional hydraulic fluid used in the aviation industry is Castrol Brayco 795 (manufactured by the BP Corporation headquartered in the UK) having a viscosity of about 2400 centistokes at about negative sixty-five degrees Fahrenheit (65 F.). For aviation applications, the low temperature requirement (i.e., 65 F.) may be a government aviation regulation (e.g., Federal Aviation Authority regulation).

[0028] Hydraulic fluid 24 of the present disclosure includes a low temperature heat transfer fluid and a friction modifier. The low temperature heat transfer fluid may be hydrocarbon-based and traditionally is not used as a hydraulic fluid. For example, the low temperature heat transfer fluid is known to be used as an electrical coolant fluid. The heat transfer fluid may have a viscosity of about 1100 centistokes, or less, at temperatures of about 65 F., or less. Preferably, the viscosity at 65 F. may be within a range of about 500 to 1100 centistokes. In one embodiment, a preferred viscosity of the heat transfer fluid may be about 500 centistokes at about 65 F. Examples of the heat transfer fluid may include a synthetic polyalphaolefin (e.g., Castrol Brayco Micronic 889), a mineral-based hydrocarbon, and others. Castrol Brayco Micronic 889 has a viscosity of about 800 centistokes at about negative sixty-five degrees Fahrenheit (65 F.). In yet another example, the heat transfer fluid may be Royco 602 (manufactured by the Univar Company headquartered in Redmond, Wash.) having a viscosity of about 1087 centistokes at about negative sixty-five degrees Fahrenheit (65 F.).

[0029] The friction modifier provides a uniform friction upon the friction plate(s) 26. The friction modifier may be, or may include, long chain molecules with a polar end associated with, for example, the friction plate 26 of the aircraft hydraulic system 22, and a non-polar end associated with the aircraft hydraulic fluid 24. Examples of a friction modifier may be a fatty acid, a carboxylic acid, and others.

[0030] Advantages and benefits of the present disclosure include aviation friction plate and clutch systems that incorporate hydrocarbon-based heat transfer fluids with improved low temperature fluidity and containing friction modifiers, which results in improved performance at lower temperatures.

[0031] The term about is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, about can include a range of 8% or 5%, or 2% of a given value.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms a, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms comprises and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.

[0033] While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.