Patent Application
20180290727
The present disclosure relates generally to aircraft flight controls for managing aerodynamic wing lift characteristics, and more specifically to engine nacelle chine systems for achieving improved stall performance while maintaining pitch control at high angles of attack.
Aerodynamic landing configurations of swept-wing transport aircraft are often a compromise between two competing objectives: 1) minimizing aircraft stall speed, and 2) maintaining an acceptable nose-down pitching moment capability at high angles of attack. Aircraft certification requirements specify both minimum landing speed safety margins relative to aircraft stall speed, and sufficient nose-down pitch control at high angles of attack to ensure safe recovery from wing stalls. A given certified stall speed is based upon a particular maximum lift coefficient (CLMAX) that the aircraft can achieve. Higher CLMAX values correspond to lower stall speeds, which are directly translatable into slower landing speeds. Slower landing speeds, in turn, permit shorter runway operations and/or greater payload capabilities. For aft-swept wings, a design change that causes an inboard wing, the most forward portion of the wing, to generate more lift near CLMAX may, however, result in greater nose-up pitching moment, rather than the required nose-down pitching moment. A greater nose-up pitching moment will degrade stall recovery capability, and thus works against a design that balances performance efficiencies with required stall recovery capability.
For aft-swept wings on transport aircraft having their engines mounted below the wing, a nacelle chine is often used as design feature to increase CLMAX. Each chine is attached to an engine nacelle, and generates a vortex that favorably influences inboard wing aerodynamics to delay air flow separation from an upper surface of the wing, which occurs at the onset of a wing stall. The chine results in an increased CLMAX, but produces an undesirable incremental nose-up pitching moment. The nose-up pitching moment can become a constraint that in some cases prevents implementing other design features that would generate even greater CLMAX values, such as use of larger nacelle chines or more effective inboard leading edge high lift devices. Thus, there is a need in the art for inventions that provide additional nose-down pitching moment control, particularly at post-CLMAX or “post-stall” angles of attack, without compromising “pre-stall” CLMAX performance.
In accordance with one form of the present disclosure, a chine spoiler system manages airflow over an aircraft wing that includes an engine nacelle suspended below the wing. The system includes a chine mounted to an inboard surface of the nacelle; the chine is configured to generate a vortex that passes over an inboard upper surface of the wing. The vortex influences inboard wing aerodynamics in a manner to increase maximum coefficient of lift of the wing. The system includes a chine spoiler control module for disabling effectiveness of the chine during recovery from an aerodynamic stall of the wing.
In accordance with another form of the present disclosure, an aircraft having an aft-swept wing, including an engine nacelle suspended below the wing, includes a chine spoiler system for managing airflow over the aircraft wing. The chine spoiler system includes a chine positioned on an inboard surface of the aircraft engine nacelle, and a chine spoiler control module configured to selectively enable and disable the chine as a function of angle of attack of the wing, and to disable the chine immediately following a stall of the wing.
In accordance with yet another form of the present disclosure, a method of making a chine spoiler system to enable and disable a chine to selectively control aerodynamic airflow over an upper surface of an aft-swept aircraft wing having an engine nacelle suspended below the wing includes steps of providing a chine on an inboard surface of an aircraft engine nacelle. The method further includes configuring a chine spoiler control module to have signal inputs of aircraft wing flap configuration and angle of attack, and configuring the chine spoiler control module to disable the chine upon a wing stall.
The features, functions, and advantages disclosed herein can be achieved independently in various embodiments or may be combined in yet other embodiments, the details of which may be better appreciated with reference to the following description and drawings.
It should be understood that referenced drawings are not necessarily to scale, and that disclosed embodiments are illustrated only schematically. Aspects of the disclosed embodiments may be combined with or substituted by one another, and within various systems and environments that are neither shown nor described herein. As such, it should be understood that the following detailed description is merely exemplary, and not intended to be limiting in either application or use.
The following detailed description addresses both apparatus and methods for carrying out the present disclosure. Actual scope of the disclosure is as defined in the appended claims.
Referring initially to
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The vortex 36 generated by the chine 30 is designed to favorably influence aerodynamics of the inboard wing portion 38. The vortex 36, configured to pass over the wing 14, intensifies as the angle of attack of the wing 14 increases. As the wing approaches a maximum lift coefficient (CLMAX), which occurs just prior to an aerodynamic stall of the wing, the vortex acts to delay airflow separation from the upper wing surface 23. This effectively delays a stall by increasing the CLMAX of the wing. However, once a stall occurs, it is desirable that the effect of the chine be disabled to enhance stall recovery characteristics.
As will be explained herein, the chine 30 may be selectively disabled by a chine spoiler system 40 that, in addition to the chine 30, includes a chine spoiler control module 60 situated onboard the aircraft 10, as also shown in
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In the disclosed embodiment, the chine spoiler door is depicted as being positioned forwardly, and orthogonally oriented with respect to, the chine 30′. Alternative embodiments may permit the chine spoiler door to have other positional relationships and orientations sufficient to influence airflow over the chine. For example, the chine spoiler door could be angled with respect to orientation of the fixed chine 30′ and/or be situated to either side of the chine, if and as determined to be aerodynamically effective to disable the chine 30′.
As will be appreciated by those skilled in the art, it is envisioned that the chine spoiler control module 60 of the chine spoiler door embodiment may also be similarly programmed relative to wing flap configuration and angle of attack to selectively influence aerodynamic airflow over the chine 30′.
Referring now to
As configured, the chine spoiler system 40 may operate as a function of both wing flap configuration and angle of attack, but, for purposes of this disclosure, at least as a function of angle of attack. As angle of attack of the wing 14 is reduced during a stall recovery, the chine 30 will be re-extended by the chine spoiler system 40 at an angle of attack indicated as Chine Re-extend Threshold #2, and will remain extended until the angle of attack is reduced below an angle of attack indicated as Chine Retract Threshold #1. Of course, at lower angles of attack, such as during typical flight routines including cruise, the chine spoiler module 60 will keep the chine 30 retracted.
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Finally, a method of making a chine spoiler system for an aircraft, to enable and disable a chine to selectively control aerodynamic airflow over an upper surface of an aft-swept aircraft wing having an engine nacelle suspended below the wing, may include steps of providing a chine on an inboard surface of an aircraft engine nacelle, and installing a chine spoiler control module in the aircraft to have signal inputs of aircraft wing flap configuration and angle of attack. Further steps may include configuring the chine spoiler control module to disable the chine upon a wing stall event.
Additional steps may include configuring the chine spoiler control module to maintain the chine in a normally disabled position at low angles of attack, including a cruise phase of flight, and configuring the chine spoiler control module to enable and disable the chine as a function of angle of attack. Further steps may include configuring the chine to be retractable on the inboard surface of the nacelle, and configuring the chine spoiler control module to disable the chine at a predetermined angle of attack threshold by retracting the chine.
An alternate method may include steps of fixing the chine to the nacelle, affixing a deployable chine spoiler door on the nacelle forwardly of the chine, and orienting the chine spoiler door to deploy to a position that influences airflow over the chine, and disabling the chine by deploying the chine spoiler door.
Numerous iterations of logic programs may be installed into the chine spoiler control module 60. For example, the active enabling and disabling of the chine may only be required for some flap configurations. In various other flap configurations, the chine may remain enabled or disabled at all angles of attack.
The disclosed embodiments and features may have additional variations and alternative constructions neither described nor suggested herein. For example, choice of whether to utilize a retractable chine or whether to implement a chine spoiler door to disable a chine may be dependent on constraints of particular engine nacelle designs, and/or may be different for new, as opposed to retrofit, implementations. Similarly, whether the nacelle chine or spoiler door retracts into a recess of the nacelle or retracts directly against the nacelle will depend upon particular constraints for a given aircraft. Moreover, specific retrofit arrangements may call for different chine enablement and disablement points in the curves 70 and 80 for optimization of stall recovery characteristics, as may be appreciated by those skilled in the art.
In addition, the chine spoiler control module 60 may be a separate system on an airplane, and/or its functions may be integrated into other systems that perform other functions. Moreover, although the module 60 has been described as configured to retract a chine immediately following or during a stall of an aircraft wing, this disclosure is broad enough to cover the disablement of a chine at the onset of a stall, or even within the CLMAX threshold portions of curves 70 and 80, for example. Finally, although the disclosure presents structures in specific shapes and sizes depicted, numerous variations of structures displayed herein may be envisioned for use in alternative embodiments, as may be appreciated by those skilled in the art.
