阅读说明：本技术 用于减缓枢转主起落架上的结构载荷的系统和方法 (System and method for mitigating structural loads on pivoting main landing gear ) 是由 N·佛格哈尼 D·T·山本 L·A·马尔基 于 2020-09-25 设计创作，主要内容包括：本发明涉及用于减缓枢转主起落架上的结构载荷的系统和方法。一种枢转转弯载荷减缓(PTLA)制动系统,用于在枢转转弯操纵中减缓飞行器的枢转主起落架上的结构载荷。PTLA制动系统包括制动控制系统,该制动控制系统可操作地联接到至少两个主起落架,每个主起落架具有两个或更多个轮轮。PTLA制动系统还包括联接到制动控制系统的PTLA制动抑制子系统。在枢转转弯操纵中,子系统抑制枢转主起落架的两个或更多个轮中的一个或多个轮的制动,使得两个或更多个轮中的至少一个轮处于未制动状态,并且其余数量的两个或更多个轮处于制动状态。PTLA制动系统减缓了结构载荷,并减少了对处于未制动状态的至少一个轮的磨损。(The invention relates to a system and a method for mitigating structural loads on a pivoting main landing gear. A pivot turn load mitigation (PTLA) braking system for mitigating structural loads on a pivoting main landing gear of an aircraft during a pivot turn maneuver. The PTLA brake system includes a brake control system operably coupled to at least two main landing gears, each main landing gear having two or more wheel wheels. The PTLA brake system also includes a PTLA brake suppression subsystem coupled to the brake control system. In a pivot turn maneuver, the subsystem inhibits braking of one or more of the two or more wheels of the pivoting main landing gear such that at least one of the two or more wheels is in an unbraked state and the remaining number of the two or more wheels is in a braked state. The PTLA braking system mitigates structural loads and reduces wear on at least one wheel in an unbraked state.)

1. A pivot turn load mitigation (PTLA) brake system (12), the PTLA brake system (12) for mitigating structural loads (28a) on a pivoting main landing gear (32) of an aircraft (10) in a pivot turn maneuver (30), the PTLA brake system (12) comprising:

a brake control system (14), the brake control system (14) operably coupled to at least two main landing gears (24), each of the at least two main landing gears (24) having two or more wheels (46), wherein the brake control system (14) controls braking of the at least two main landing gears (24); and

a Pivot turn load mitigation (PTLA) brake suppression subsystem (16), the PTLA brake suppression subsystem (16) coupled to the brake control system (14), wherein the PTLA brake suppression subsystem (16) suppresses braking of one or more of the two or more wheels (46) of a main landing gear (24) including the pivoting main landing gear (32) in the pivot turn maneuver (30) such that at least one wheel (46) of the two or more wheels (46) is in an unbraked state (52) and a remaining number (54) of the two or more wheels (46) are in a braked state (56),

wherein the PTLA braking system (12) mitigates the structural load (28a) on the pivoting main landing gear (32) of the aircraft (10) in the pivot turning maneuver (30) and reduces wear (136) to the at least one wheel (46) in the unbraked state (52).

2. A PTLA brake system (12) according to claim 1, wherein the at least two main landing gears (24) include a left main landing gear (24a) and a right main landing gear (24b), each main landing gear having two pairs (48) of wheels (46), each pair (48) of wheels (46) being disposed on an axle (49).

3. A PTLA brake system (12) according to claim 1 or 2, wherein the at least two main landing gears (24) include one of a 2-main landing gear configuration (36), a 3-main landing gear configuration (38), or a 4-main landing gear configuration (40).

4. A PTLA braking system (12) according to claim 1 or 2, wherein the pivoting main landing gear (32) has four wheels (46) and the PTLA braking suppression subsystem (16) suppresses braking of one wheel (46), two wheels (46), or three wheels (46) in the pivot turn maneuver (30) of the aircraft (10).

5. A PTLA brake system (12) as set forth in claim 1 or 2 wherein said PTLA brake inhibit subsystem (16) inhibits braking via activation (92) of a pivot turn load mitigation (PTLA) brake inhibit command (90) to one or more brake control units (74) of said brake control system (14) upon satisfaction of one or more brake inhibit conditions (94).

6. The PTLA braking system (12) of claim 5, wherein the one or more brake inhibit conditions (94) include one or more of:

(a) an on-ground state of the aircraft (96) when the aircraft (10) is in an on-ground position (98);

(b) an acceptable aircraft ground speed (100) when an aircraft ground speed (101) of the aircraft (10) is less than a pivot turn load mitigation, PTLA, speed threshold (104); or

(c) A pivot turn load mitigation, PTLA active flag command indication (106), the PTLA active flag command indication (106) generated by monitoring logic (108) of the PTLA brake inhibit subsystem (16) to monitor a brake pedal position (110) to detect a start (31) of the pivot turn maneuver (30) according to one of a plurality of pivot turn brake pedal profiles (112).

7. A PTLA braking system (12) as claimed in claim 5 or 6 wherein the PTLA brake inhibit command (90) is deactivated upon satisfaction of one or more brake inhibit deactivation conditions (118) including one or more of:

(a) an aircraft ground speed (101) of the aircraft (10) exceeding a pivot turn load mitigation (PTLA) speed threshold (104);

(b) both the left brake pedal command (120a) and the right brake pedal command (120b) exceed a pivot turn load mitigation, PTLA, trigger brake pedal command threshold (122) for at least a predetermined period of time (124); or

(c) The aircraft (10) enters an active parking brake state (126).

8. PTLA brake system (12) according to claim 5 or 6 wherein the PTLA brake inhibit command (90) is initiated to inhibit braking of a wheel selection (50) of one axle pair (48a) of wheels (46) on the pivoting main landing gear (32) once one or more of the brake inhibit conditions (94) is met and the wheel selection (50) of the one axle pair (48a) of wheels (46) is changed to a different axle pair (48b) of wheels (46) in a sequential order (51) upon initiation (31) of a subsequent pivot turn maneuver (30 a).

9. PTLA brake system (12) as claimed in claim 5 or 6, wherein the aircraft (10) comprises a taxi brake release function (130) and the PTLA brake inhibit subsystem (16) is integrated with the taxi brake release function (130),

wherein the taxi brake release function (130) selects a wheel select (50) for the PTLA brake inhibit command (90) to inhibit braking of one or more but not all of the wheels (46) of the pivoting main landing gear (32).

10. A method (250) for mitigating structural loads (28a) on a pivoting main landing gear (32) of an aircraft (10) in a pivot turn maneuver (30), the method (250) comprising the steps of:

(252) initiating the pivot turn maneuver (30) with the aircraft (10), the aircraft (10) having a pivot turn load mitigation (PTLA) braking system (12), the PTLA braking system (12) comprising: a brake control system (14), the brake control system (14) operably coupled to at least two main landing gears (24), each of the at least two main landing gears (24) having two or more wheels (46), wherein the brake control system (14) controls braking of the at least two main landing gears (24); and a pivot turn load mitigation (PTLA) brake inhibit subsystem (16), the PTLA brake inhibit subsystem (16) coupled to the brake control system (14);

(254) initiating a PTLA brake inhibit command (90) for pivot turn load alleviation of the PTLA brake inhibit subsystem (16) to one or more brake control units (74) of the brake control system (14) upon satisfaction of one or more brake inhibit conditions (94); and

(256) in the pivot turn maneuver (30), inhibiting braking of one or more of the two or more wheels (46) of the pivoting main landing gear (32) such that at least one wheel (46) of the two or more wheels (46) is in an unbraked state (52) and a remaining number (54) of the two or more wheels (46) are in a braked state (56),

wherein the PTLA braking system (12) mitigates the structural load (28a) on the pivoting main landing gear (32) of the aircraft (10) in the pivot turning maneuver (30) and reduces wear (136) to the at least one wheel (46) in the unbraked state (52).

11. The method (250) according to claim 10, wherein initiating (254) the PTLA brake inhibit command (90) of the PTLA brake inhibit subsystem (16) further comprises: initiating the PTLA brake inhibit command (90) of the PTLA brake inhibit subsystem (16) upon satisfaction of one or more of the brake inhibit conditions (94), the brake inhibit conditions (94) including one or more of:

(a) an on-ground state of the aircraft (96) when the aircraft (10) is in an on-ground position (98);

(b) an acceptable aircraft ground speed (100) when an aircraft ground speed (101) of the aircraft (10) is less than a pivot turn load mitigation, PTLA, speed threshold (104); or

(c) A pivot turn load mitigation, PTLA active flag command indication (106), the PTLA active flag command indication (106) generated by monitoring logic (108) of the PTLA brake inhibit subsystem (16) to monitor a brake pedal position (110) to detect a start (31) of the pivot turn maneuver (30) according to one of a plurality of pivot turn brake pedal profiles (112).

12. The method (250) of claim 10 or 11, further comprising: after inhibiting braking (256), deactivating (258) the PTLA brake inhibit command (90) upon satisfaction of one or more brake inhibit deactivation conditions (118), the one or more brake inhibit deactivation conditions (118) including one or more of:

(a) an aircraft ground speed (101) of the aircraft (10) exceeding a pivot turn load mitigation (PTLA) speed threshold (104);

(b) both the left brake pedal command (120a) and the right brake pedal command (120b) exceed a pivot turn load mitigation, PTLA, trigger brake pedal command threshold (122) for at least a predetermined period of time (124); or

(c) The aircraft (10) enters an active parking brake state (126).

13. The method (250) of claim 10 or 11, further comprising: initiating (252) the pivot turn maneuver (30) with the aircraft (10), wherein the aircraft (10) has a taxi brake release function (130); and integrating (260) the PTLA brake inhibit subsystem (16) with the taxi brake release function (130) such that the taxi brake release function (130) selects a wheel selection (50) for the PTLA brake inhibit command (90) to inhibit braking of one or more but not all of the wheels (46) of the pivoting main landing gear (32).

14. The method (250) according to claim 10 or 11, wherein inhibiting braking (256) further comprises inhibiting braking (256) of one wheel (46), two wheels (46), or three wheels (46) in the pivot turn maneuver (30) of the aircraft (10).

15. A method (250) according to claim 10 or 11 wherein inhibiting braking (256) further comprises inhibiting braking (256) of a wheel selection (50) of one axle pair (48a) of wheels (46) on the pivoting main landing gear (32), and in the event of initiating (31) a subsequent pivot turn maneuver (30a), the inhibited wheel selection (50) of said one axle pair (48a) of wheels (46) is changed to a different axle pair (48b) of wheels (46) in a sequential order (51).

Technical Field

The present disclosure relates generally to systems and methods for braking aircraft, and more particularly to systems and methods for braking a pivoting main landing gear of an aircraft in and during a pivot turn maneuver.

Background

Large transport aircraft, whether commercial or military, typically include a main landing gear arrangement that supports most of the weight of the aircraft, along with nose landing gear for stability and steering. The main landing gear typically includes left and right main landing gears, each main landing gear having a plurality of wheels, and each wheel including one or more brakes.

The wheel brakes on the main landing gear are controlled by the pilot after landing to assist in ground deceleration of the aircraft. The driver may also control the wheel brakes during ground coasting maneuvers, as well as during pivot turning maneuvers or 2-point turning maneuvers performed on the ground. The large mass and high landing speed of the aircraft result in very high momentum, which can translate into very high structural loads during braking maneuvers, such as when a brake is suddenly applied.

There are known systems and methods for braking the main landing gear during a pivot turn maneuver. However, this known system and method brakes all of the wheels on the pivoting main landing gear. Braking all of the wheels on the pivoting main landing gear during a pivot turn maneuver may result in excessive wear on the wheels and tires, as well as increased structural and braking loads on the pivoting main landing gear. Further, known systems and methods may require the use of heavy and bulky main landing gear assemblies and components to withstand the high structural and braking loads experienced during a pivot turn maneuver.

Accordingly, there is a need in the art for systems and methods that: avoiding braking all wheels on the pivoting main landing gear and allowing certain wheels on the pivoting main landing gear to roll freely during a pivot turn maneuver, reducing structural loads on the pivoting main landing gear during the pivot turn maneuver, reducing the weight of the main landing gear assembly and components designed to withstand high loads during the pivot turn maneuver, and providing significant advantages over known systems and methods.

Disclosure of Invention

Exemplary implementations of the present disclosure provide systems and methods for braking a pivoting main landing gear of an aircraft in and during a pivot turn maneuver. As discussed in the detailed description below, versions of the systems and methods may provide significant advantages over existing systems and methods.

In one exemplary version, a pivot turn load mitigation (PTLA) braking system is provided for mitigating structural loads on a pivoting main landing gear of an aircraft during a pivot turn maneuver. The PTLA brake system includes a brake control system operatively coupled to at least two main landing gears. Each of the at least two main landing gears has two or more wheels. The brake control system controls braking of at least two main landing gears.

The PTLA braking system also includes a pivot turn load mitigation (PTLA) brake inhibit subsystem coupled to the brake control system. In a pivot turn maneuver, the PTLA brake inhibit subsystem inhibits braking of one or more of the two or more wheels of one main landing gear, including the pivoting main landing gear, such that at least one of the two or more wheels is in an unbraked state and the remaining number of the two or more wheels are in a braked state. The PTLA braking system mitigates structural loads on a pivoting main landing gear of the aircraft during a pivot turn maneuver and reduces wear on at least one wheel in an unbraked state.

In another version, an aircraft is provided. The aircraft includes a fuselage, one or more wings attached to the fuselage, and a plurality of landing gears attached to the fuselage. The plurality of landing gears includes a nose gear and at least two main landing gears. Each of the at least two main landing gears has two or more wheels. During a pivot turn maneuver of the aircraft, one of the at least two main gear includes a pivoting main gear.

The aircraft also includes a pivot cornering load mitigation (PTLA) braking system. The PTLA brake system includes a brake control system operatively coupled to at least two main landing gears. The brake control system controls braking of at least two main landing gears.

The PTLA braking system also includes a pivot turn load mitigation (PTLA) brake inhibit subsystem coupled to the brake control system. During a pivot turning maneuver, the PTLA brake inhibit subsystem inhibits braking of one or more of the two or more wheels of one main landing gear, including the pivoting main landing gear, such that at least one of the two or more wheels is in an unbraked state and the remaining number of the two or more wheels are in a braked state. The PTLA braking system mitigates structural loads on the pivoting main landing gear during a pivot turn maneuver of the aircraft and reduces wear on the at least one wheel in an unbraked state.

In another version, a method for mitigating structural loads on a pivoting main landing gear of an aircraft during a pivot turn maneuver is provided. The method includes the step of initiating a pivot turn maneuver with the aircraft. The aircraft has a pivot cornering load mitigation (PTLA) braking system. The PTLA brake system includes a brake control system operatively coupled to at least two main landing gears. Each of the at least two main landing gears has two or more wheels. The brake control system controls braking of at least two main landing gears. The PTLA braking system also includes a pivot turn load mitigation (PTLA) brake inhibit subsystem coupled to the brake control system.

The method also includes the steps of: once the one or more brake suppression conditions are satisfied, a Pivot Turn Load Alleviation (PTLA) brake suppression command of the PTLA brake suppression subsystem is initiated to one or more brake control units of the brake control system. The method also includes the steps of: braking of one or more of the two or more wheels of the pivoting main landing gear is inhibited in a pivot turn maneuver such that at least one of the two or more wheels is in an unbraked state while the remaining number of the two or more wheels are in a braked state. The PTLA braking system mitigates structural loads on a pivoting main landing gear of the aircraft during a pivot turn maneuver and reduces wear on at least one wheel in an unbraked state.

The features, functions, and advantages that have been discussed can be achieved independently in various versions of the present disclosure or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings.

Drawings

The disclosure may be better understood by reference to the following detailed description taken in conjunction with the accompanying drawings, which illustrate preferred and exemplary versions, but are not necessarily drawn to scale, wherein:

FIG. 1A is an illustration of a perspective view of an aircraft having a pivot turn load mitigation (PTLA) brake system according to a version of the present disclosure;

FIG. 1B is an illustration of a top plan view of the aircraft and PTLA braking system of FIG. 1A;

FIG. 2A is a diagram illustrating a functional block diagram of an aircraft having an exemplary PTLA braking system of the present disclosure;

FIG. 2B is a diagram illustrating a functional block diagram of the aircraft and PTLA braking mitigation subsystem of FIG. 2A with a PTLA entry scenario and a PTLA exit scenario;

FIG. 3A is an illustration of a schematic diagram of one version of a PTLA brake system command logic diagram;

FIG. 3B is an illustration of a schematic diagram of another version of a PTLA brake system command logic diagram;

FIG. 3C is an illustration of a schematic diagram of yet another version of a PTLA brake system command logic diagram;

FIG. 4 is a graphical illustration showing a first pivot turn brake pedal curve;

FIG. 5 is a graphical illustration showing a second pivot turn brake pedal curve;

FIG. 6 is a graphical illustration showing a third pivot turn brake pedal curve;

FIG. 7 is a graphical illustration showing a fourth pivot turn brake pedal curve;

FIG. 8 is an illustration of a flow chart showing an exemplary version of the method of the present disclosure;

FIG. 9 is a flow chart of a version of an aircraft manufacturing and service method; and

FIG. 10 is an illustration of a functional block diagram of a version of an aircraft.

The drawings shown in this disclosure represent various aspects of the presented versions, and only the differences will be discussed in detail.

Detailed Description

The disclosed versions or embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all of the disclosed versions are shown. Indeed, several different versions may be provided and should not be construed as limited to the versions set forth herein. Rather, these versions are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

Referring now to the drawings, FIG. 1A is an illustration of a perspective view of an aircraft 10 having a pivot turn load mitigation (PTLA) brake system 12 constructed in accordance with a version of the present disclosure, and FIG. 1B is an illustration of a top plan view of the aircraft 10 and the PTLA brake system 12 of FIG. 1A. Fig. 2A is a diagram illustrating a functional block diagram of an aircraft 10 having an exemplary PTLA brake system 12 of the present disclosure.

The blocks in fig. 2A represent elements, and the lines connecting the various blocks do not imply any particular dependency of the elements. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and/or physical couplings between the various elements, although it is noted that other alternative or additional functional relationships or physical connections may exist in the versions disclosed herein.

As shown in fig. 1A-1B and 2A, the PTLA brake system 12 includes a brake control system 14 and a pivot cornering load alleviation (PTLA) brake inhibit subsystem 16 coupled to the brake control system 14. As shown in fig. 1A-1B, the aircraft 10 includes a fuselage 18, with one or more wings 20 coupled to the fuselage 18, and a tail 21. The aircraft 10 may be supported at a number of points via landing gear 22 (see fig. 1A, 1B, 2A), including Main Landing Gear (MLG)24 (see fig. 1A-1B, 2A) and nose landing gear 26 (see fig. 1A-1B). As shown in fig. 1A-1B, the main landing gear 24 is positioned rearward of the nose landing gear 26, and the main landing gear 24 includes a left main landing gear 24a and a right main landing gear 24B.

In one version disclosed herein, a PTLA braking system 12 is provided for mitigating loads 28 (see fig. 2A), such as structural loads 28a (see fig. 2A), on at least one main landing gear 24, including a pivoting main landing gear 32 (see fig. 2A) of the aircraft 10, in a pivot turn maneuver 30 (see fig. 2A) or during a pivot turn maneuver 30 performed or conducted by the aircraft 10. During a pivot turn maneuver 30, for example, if the aircraft 10 has two main gear landing gears 24, one main gear landing gear 24 includes a pivoting main gear 32 (see fig. 2A) and the other main gear landing gear 24 (see fig. 2A) includes a non-pivoting main gear 34. The pivoting main gear 32 is closer to the pivot turn maneuver 30 or the center of turn 33 of the pivot turn than the non-pivoting main gear 34 (see fig. 2A). The pivoting main landing gear 32 is closest to or closest to the pivot turn maneuver 30 or the turn center 33 of the pivot turn. The torque is high when pivoting near the center of the pivoting main landing gear 32. During the pivot turning maneuver 30, one main landing gear 24 is braking and pivots about the braked main landing gear 24, while the other main landing gear 24 moves circumferentially about the braked main landing gear 24. There are typically two brake pedals 64 (see fig. 2A), such as a left brake pedal 64a (see fig. 2A) and a right brake pedal 64B (see fig. 2A), each brake pedal 64 commanding a different main landing gear 24, and each brake pedal 64 being operable by a different pilot 154 (see fig. 2B).

As shown in fig. 1A, the main landing gear 24 is a 2-main landing gear configuration 36 (see also fig. 2A). Although the main landing gear 24 shown in fig. 1A is a 2-main landing gear configuration 36, the PTLA braking system 12 may also be used with a 3-main landing gear configuration 38 (see fig. 2A), a 4-main landing gear configuration 40 (see fig. 2A), or other suitable main landing gear configurations.

As shown in fig. 1A-1B, each main landing gear 24 may include a strut 42 carrying a wheel carriage 44. The wheel carriage 44 may include a plurality of wheels 46 (see fig. 1A-1B, 2A), the plurality of wheels 46 being selectively or collectively braked to reduce the speed of the aircraft 10 during taxiing maneuvers and after landing rollout. The aircraft 10 has at least two main landing gears 24, and each of the at least two main landing gears 24 has two or more wheels 46. For example, each main landing gear 24 may have two wheels, four wheels, six wheels, or another suitable number of wheels. Where the at least two main landing gears 24 include a left main landing gear 24a and a right main landing gear 24b, each of the left and right main landing gears 24a, 24b may have two pairs 48 (see fig. 2A) of wheels 46. Each pair 48 of wheels 46 is disposed on an axle 49 (see fig. 2A), such as a common axle or a single axle. As discussed in more detail below, during the pivot turning maneuver 30, one or more wheels 46, e.g., one or more of the two or more wheels 46, may be in the form of one or more unbraked wheels 46a (see fig. 2A) in an unbraked state 52 (see fig. 2A), and the remaining number 54 (see fig. 2A) of wheels 46, e.g., two or more wheels 46, may be in the form of braked wheels 46b (see fig. 2A) in a braked state 56 (see fig. 2A). In one version, as shown in fig. 3A-3C, each main landing gear 24, including left and right main landing gears 24a, 24b, may include two front wheels 46C and two rear wheels 46d, and also include two inboard wheels 46e and two outboard wheels 46 f.

Each wheel 46 has one or more brakes 58 (see fig. 1A-1B, 2A), the one or more brakes 58 being coupled to the wheel 46 or located at the wheel 46. As shown in fig. 1A-1B, the brake control system 14 is operatively coupled to at least two main landing gears 24 and to a brake 58. The brake control system 14 is configured to control braking of at least two main landing gears 24. Brake control system 14 may direct the application of various combinations of brakes 58 based on one or more aircraft characteristics or parameters, as will be discussed in more detail below. The brake control system 14 may also inhibit braking of the selected brakes 58 based on these characteristics or parameters.

Thus, the brake control system 14 may receive pilot inputs 60 (see fig. 1A-1B, 2A) (e.g., command signals 62 (see fig. 2A) received via brake pedals 64 (see fig. 2A) at a flight deck 66 (see fig. 2A) of the aircraft 10), thresholds 68 (see fig. 1A-1B, 2A), and aircraft data 70 (see fig. 1A-1B, 2A). In particular, with the version of the ptl brake system 12 of the present disclosure, the aircraft data 70 and thresholds 68 may be used to determine which brakes 58 to apply and which brakes 58 to inhibit, as will also be described in greater detail below.

As shown in FIG. 2A, the brake control system 14 includes a brake controller 72 having a plurality of brake control units 74. The brake control unit 74 includes an electronic control unit that controls the command signal 62 representing a brake command 76. The brake control unit 74 may be implemented with a brake controller 72, for example in the form of a processor, microprocessor or other suitable controller device. The brake control unit 74 may be used with suitable hardware components, suitable software or programmable logic, memory elements, etc., and the brake control unit 74 may perform various functions under the control of the brake controller 72 or other suitable control device. In one version, one or more of the brake control units 74 may be implemented with a computer processor that houses software and provides an external interface for the software.

The brake control system 14 may also include a plurality of controls 78 (see fig. 2A), such as one or more of wheel speed control, fluid temperature control, wheel temperature control, valve control, brake control, parking brake control, wheel power control, anti-skid control, skid brake release control, or other suitable control. The brake control system 14 may be powered by a power source 80 (see FIG. 2A), such as an electric power source or other suitable power source.

As further shown in fig. 2A, the brake control system 14 includes a plurality of brake control valves 82. Each of the brake control valves 82 has a first end 84a (see fig. 3A to 3C) and a second end 84b (see fig. 3A to 3C). The first end 84a of the brake control valve 82 is coupled to one or more brake control units 74 via an electrical connector element 86 (see fig. 3A-3C) such as a wire or other suitable connector element. The second end 84b of each brake control valve 82 is coupled to one or more brakes 58 on each wheel 46 via a hydraulic connector element 88, such as a hydraulic line or other suitable connector element. One or more of the plurality of brake control units 74 generates one or more brake commands 76 (see fig. 2A) to one or more of the plurality of brake control valves 82. Those skilled in the art will appreciate that different aircraft brake control systems and aircraft configurations may be used to implement versions of the PTLA brake system 12, and that the brake control system 14 described herein is merely one exemplary version.

As further shown in fig. 1A-1B and 2A, the PTLA brake system 12 includes a PTLA brake inhibitor subsystem 16 coupled to the PTLA brake system 12. The PTLA brake suppression subsystem 16 is configured to suppress braking during and during a pivot turn maneuver 30 of the aircraft 10, and to suppress braking 58 of one or more of the two or more wheels 46 of one main landing gear 24, including the pivoting main landing gear 32, such that at least one wheel 46 of the two or more wheels 46 is in an unbraked state 52 (see fig. 2A), e.g., a rolling state 53 (see fig. 2A) or a suppressed state 57 (see fig. 2A), and a remaining number 54 of the two or more wheels 46 (see fig. 2A) is in a braked state 56 (see fig. 2A).

The PTLA brake inhibit subsystem 16 is configured to generate a pivot turn load mitigation (PTLA) brake inhibit command 90 (see FIG. 2A). During and during the pivot turn maneuver 30, once the one or more brake inhibit conditions 94 are met, the PTLA brake inhibit subsystem 16 inhibits braking of one or more of the two or more wheels 46 of the pivoting main landing gear 32 and inhibits the brake 58 via activation 92 of a pivot turn load retard (PTLA) brake inhibit command 90 to the one or more brake control units 74 of the brake control system 14.

As shown in fig. 2A, the one or more brake inhibit conditions 94 may include an on-ground status 96 of the aircraft, which is indicated when the aircraft 10 is at an on-ground location 98 (i.e., the aircraft 10 is positioned in a ground location rather than in the air, and is moving in a ground location). If the aircraft 10 is in the on-ground position 98, the brake inhibit condition 94 is met or met. If the aircraft 10 is airborne, the brake inhibit condition 94 is not met or met. The on-ground state 96 of the aircraft may be determined with the aircraft 10 in the on-ground position 98, may be determined with an on-ground indication or sensor input of the aircraft, may be determined with an indication or sensor input of full extension of the main landing gear, may be determined with an indication or sensor input of tilting of the trucks 44 of the main landing gear 24, may be determined with a shock strut squat switch or an oil pressure indication or sensor input, or may be determined with another suitable indication or sensor input.

As shown in FIG. 2A, the one or more brake inhibit conditions 94 may also include an acceptable aircraft ground speed 100 that is indicated when an aircraft ground speed 101 of the aircraft 10 is less than a Pivot Turn Load Alleviation (PTLA) speed threshold 104. In one exemplary version, the PTLA speed threshold 104 is 10 (ten) knots or less than 10 knots, and if the aircraft ground speed 101 is 11 (eleven) knots and the aircraft ground speed 101 exceeds the PTLA speed threshold 104 of 10 knots, then the brake inhibit condition 94 is not met or met. If the aircraft ground speed 101 is 9 (nine) knots, the aircraft ground speed 101 is less than the PTLA speed threshold 104 of 10 knots and the brake inhibit condition 94 is met or met. The acceptable aircraft ground speed 100 is preferably less than 2 knots. The aircraft ground speed 101 used to determine the acceptable aircraft ground speed 100 may be estimated or determined from an average wheel speed 102 (see fig. 2A), where average wheel speed means averaging all aircraft wheel speeds, may be estimated or determined from an Inertial Reference System (IRS) ground speed or acceleration, or may be estimated or determined using another suitable system or device.

As shown in fig. 2A, the one or more brake inhibit conditions 94 may also include a Pivot Turn Load Alleviation (PTLA) active flag command indication 106 generated by monitoring logic 108 of the PTLA brake inhibit subsystem 16 to monitor a brake pedal position 110 according to one of a plurality of pivot turn brake pedal curves 112 to detect the onset 31 of the pivot turn maneuver 30. For example, the monitoring logic 108 monitors both the left and right brake pedals 64a and 64b to detect and determine whether one or more pilots are initiating or attempting the pivot turn maneuver 30. The monitoring logic output 108a (see fig. 2A) is determined based on a plurality of pivot turn brake pedal curves 112, as discussed below with respect to fig. 4-7. The brake inhibit condition 94 is met or met if the monitoring logic 108 of the PTLA brake inhibit subsystem 16 detects the beginning 31 of the pivot turn maneuver 30 based on one of the plurality of pivot turn brake pedal profiles 112.

In one version, one or more of the brake inhibit conditions 94 includes one brake inhibit condition 94 being met or met, where the one brake inhibit condition 94 includes an on-ground state 96 of the aircraft or an equivalent indication or sensor input, or an acceptable aircraft ground speed 100 or an equivalent determination or estimation, or a PTLA active flag command indication 106. In another version, the brake inhibit conditions 94 may include two brake inhibit conditions 94 being met or met, where the two brake inhibit conditions 94 include a combination of the on-ground status 96 of the aircraft and the PTLA active flag command indication 106, or a combination of the acceptable aircraft ground speed 100 and the PTLA active flag command indication 106, or a combination of the on-ground status 96 of the aircraft and the acceptable aircraft ground speed 100, or another suitable combination. In another version, the brake inhibit conditions 94 may include three brake inhibit conditions 94 being met or met, where the three brake inhibit conditions 94 include an on-ground state 96 of the aircraft or an equivalent indication or sensor input, and an acceptable aircraft ground speed 100 or an equivalent determination or estimation, and a PTLA active flag command indication 106.

Thus, when one or more of the brake inhibit conditions 94 are met or detected, the PTLA brake inhibit subsystem 16 generates and initiates a PTLA brake inhibit command 90 (see fig. 2A) to the one or more brake control units 74 of the brake control system 14, and the one or more brake control units 74 enable the PTLA brake inhibit command 90 to send the PTLA brake inhibit command 90 to the wheel selection 50 (see fig. 2A) for determining which of the two or more wheels 46 of the pivoting main landing gear 32 is to be inhibited and inhibiting braking of the wheel 46 in the wheel selection 50. Preferably, the PTLA brake inhibit command 90 is initiated very quickly after one or more of the brake inhibit conditions 94 are met or met, such as within 100ms (one hundred milliseconds) of the meeting or detection of one or more brake inhibit conditions 94. The plurality of brake control units 74 receive the PTLA brake inhibit command 90 from the PTLA brake inhibit subsystem 16 and inhibit generation of at least one brake command 76 (see FIG. 2A) corresponding to at least one of the plurality of brake control valves 82 coupled to the at least one wheel 46 in the unbraked state 52. Preferably, the selection of one or more wheels 46 to be inhibited (see FIG. 2A) is sequentially changed to the next wheel 46 whenever the left or right commanded brake pedal effort transitions from greater than 12% (twelve percent) to 8% (eight percent) of full brake pedal travel.

In one version, the wheel select 50 may include one axle pair 48a of the wheels 46 on the pivoting main landing gear 32, for example, one axle pair 48a of the front wheels 46C (see fig. 3A-3C) or one axle pair 48a of the rear wheels 46d (see fig. 3A-3C) on the left main landing gear 24a (when the left main landing gear 24a is the pivoting main landing gear 32) or on the right main landing gear 24b (when the right main landing gear 24b is the pivoting main landing gear 32). In this version, one axle pair 48a of the wheel 46 will be restrained once.

Preferably, the wheel select 50 includes a pair 48 of wheels 46, namely a front wheel 46C (see fig. 3A-3C) or a rear wheel 46d (see fig. 3A-3C) that share an axle 49 (see fig. 2A), that are located on the four-wheel 46, two-axle 49 pivoting main landing gear 32 and are in an unbraked state 52 (see fig. 2A) during the pivoting turn maneuver 30, and the other pair 48 of the four-wheel 46, two-axle 49 pivoting main landing gear 32 is in a braked state 56 (see fig. 2A) during the pivoting turn maneuver 30. In this version, for each subsequent pivot turn maneuver 30a (see FIG. 2A), the wheel select 50 of one axle pair 48a of the wheels 46 is changed in a sequential order 51 (see FIG. 2A) to a different axle pair 48b (see FIG. 2A) of the wheels 46, such as the other axle pair 48a of the wheels 46. Preferably, the selection of the inhibited axle pair 48c (see FIG. 2A) is sequentially changed to the next axle pair 48a of the wheel 46 whenever the left or right commanded brake pedal effort transitions from greater than 12% (twelve percent) to 8% (eight percent) of full brake pedal travel. This percentage value corresponds to a normalized full brake pedal travel, e.g., 0% being full brake pedal release and 100% being full brake pedal depression.

In another version, where the pivoting main landing gear 32 has four wheels 46, the PTLA brake inhibit command 90 of the PTLA brake inhibit subsystem 16 may inhibit braking of one wheel 46, i.e., one wheel 46 on the pivoting main landing gear 32 is in the unbraked state 52 and three wheels 46 are in the braked state 56 during and during the pivot turn maneuver 30 of the aircraft 10. In yet another version, where the pivoting main landing gear 32 has four wheels 46, the PTLA brake inhibit command 90 of the PTLA brake inhibit subsystem 16 may inhibit braking of three wheels 46, i.e., three wheels 46 on the pivoting main landing gear 32 are in the unbraked state 52 and one wheel 46 is in the braked state 56 during and during the pivot turn maneuver 30 of the aircraft 10. In yet another version, in the case of a pivoting main landing gear 32 having four wheels 46, the PTLA brake inhibit command 90 of the PTLA brake inhibit subsystem 16 may inhibit braking of two wheels 46 other than the axle pair 48a wheels 46, such as one front wheel 46c and one rear wheel 46d, or an inboard wheel 46e (see fig. 2A) or an outboard wheel 46f (see fig. 2A), or two diagonal wheels 46i (see fig. 2A), such as two opposing corner wheels, during a pivoting turning maneuver 30 of the aircraft 10.

For a combination of axle pairs 48a of wheels 46 of two diagonal wheels 46i, such as two opposing diagonal wheels, where one pair of two diagonal wheels 46i is in a braking state 56 and the other pair of two diagonal wheels 46i is in a rolling state 53 (see fig. 2A), the estimated reduction in torsional load reaction force 28b or torque load is about 9%. For a combination of axle pairs 48a of wheels 46, with one front wheel 46c (see FIG. 2A) and one rear wheel 46d (see FIG. 2A) in a braking state 56 and the other front wheel 46c and the other rear wheel 46d in a rolling state 53, the estimated torsional load reaction force 28b or torque load reduction is about 18%. For a combination of axle pairs 48a of wheels 46, with two front wheels 46c (see FIG. 2A) in the braking state 56 and the other two rear wheels 46d (see FIG. 2A) in the rolling state 53, the estimated torsional load reaction force 28b or torque load reduction is about 13%. This alternate wheel pairing enables integration with the taxi brake release function 130 (see fig. 2A).

The PTLA brake inhibit command 90 serves as a pivot turn assist function 114 (see FIG. 2A) and may be implemented in one brake control unit 74 (see FIG. 2A) or more than one brake control unit 74.

Furthermore, the PTLA brake suppression subsystem 16 may be configured such that no single loss of function results in false brake suppression on both trucks 44, i.e., on the left and right trucks. Furthermore, no single loss of function other than the loss of power to the brake control unit 74 of the brake control system 14 results in a loss of function on one main landing gear 24.

As shown in fig. 2A, PTLA brake inhibit command 90 may undergo deactivation 116 and be removed when one or more brake inhibit deactivation conditions 118 are met or met. As shown in FIG. 2A, the one or more brake inhibit deactivation conditions 118 may include the aircraft ground speed 101 of the aircraft 10 exceeding the Pivot Turn Load Alleviation (PTLA) speed threshold 104, e.g., the aircraft ground speed 101 exceeding or being greater than 10 (ten) knots. As shown in fig. 2A, the one or more brake inhibit deactivation conditions 118 may also include two brake pedal commands 120, including a left brake pedal command 120a and a right brake pedal command 120b, exceeding a Pivot Turn Load Alleviation (PTLA) trigger brake pedal command threshold 122 for at least a predetermined period of time 124. In one version, predetermined period of time 124 may be one (1) second, e.g., above the 50% command threshold, after both left and right brake pedal commands 120a and 120b exceed the PTLA trigger brake pedal command threshold 122. The predetermined period of time 124, e.g., a one (1) second delay, is to ensure that both brake pedal commands 120 (see FIG. 2A) are consistently above the PTLA trigger brake pedal command threshold 122, e.g., above the 50% command threshold, indicating that the pilot 154 (see FIG. 2B) needs to quickly stop the aircraft 10 or become completely stopped. Once a predetermined period of time 124 (e.g., one (1) second timing) has expired and both brake pedal commands 120 are above or exceed the PTLA trigger brake pedal command threshold 122, e.g., above the 50% command threshold, the remaining two brakes 58 that are inhibited will return to the commanded braking level.

As shown in FIG. 2A, the one or more brake inhibit disabled conditions 118 may also include the aircraft 10 entering an active parking brake state 126, i.e., parking brake 128 of the aircraft 10 is engaged, or becomes active.

In one version, one or more of the brake inhibit disable conditions 118 includes one brake inhibit disable condition 118 being met or met, where one brake inhibit disable condition 118 includes the aircraft ground speed 101 of the aircraft 10 exceeding a Pivot Turn Load Alleviation (PTLA) speed threshold 104, or two brake pedal commands 120 including a left brake pedal command 120a and a right brake pedal command 120b exceeding a PTLA trigger brake pedal command threshold 122 for at least a predetermined period of time 124, or the aircraft 10 entering an active park brake state 126. In another version, the brake inhibit deactivation condition 118 may include two brake inhibit deactivation conditions 118 being met or met, where the two brake inhibit deactivation conditions 118 include a combination of: aircraft ground speed 101 of aircraft 10 exceeds pivot turn load retard (PTLA) speed threshold 104, and two brake pedal commands 120, including left brake pedal command 120a and right brake pedal command 120b, exceed PTLA trigger brake pedal command threshold 122 for at least predetermined period of time 124; or a combination comprising: aircraft 10 exceeds PTLA speed threshold 104 and aircraft 10 enters an active park brake state 126; or a combination comprising: two brake pedal commands 120, including a left brake pedal command 120a and a right brake pedal command 120b, exceed the PTLA trigger brake pedal command threshold 122 for at least a predetermined period of time 124, and the aircraft 10 enters an active park brake state 126. In another version, brake inhibit deactivation condition 118 may include three brake inhibit deactivation conditions 118 being met or met, where the three brake inhibit deactivation conditions 118 include that aircraft ground speed 101 of aircraft 10 exceeds Pivot Turn Load Alleviation (PTLA) speed threshold 104, and that both brake pedal commands 120, including left brake pedal command 120a and right brake pedal command 120b, exceed PTLA trigger brake pedal command threshold 122 for at least a predetermined period of time 124, and that aircraft 10 enters active park braking state 126.

As further shown in fig. 2A, the aircraft 10 may optionally include a taxi brake release function 130. In the event that aircraft 10 already includes taxi brake release function 130, ptl brake suppression subsystem 16 may be integrated with taxi brake release function 130 to obtain taxi brake release function integration 132. The taxi brake release function 130 may limit the brakes 58 to one or more, but not all, of the wheels 46. In one embodiment, the taxi brake release function 130 may limit the brakes 58 to a pair 48 (see FIG. 2A) of wheels 46. The taxi brake release function 130 selects a wheel select 50 (see fig. 3A-3C) for the ptia brake inhibit command 90 (see fig. 2A, 3A-3C) to inhibit braking of one or more, but not all, of the wheels 46 of the pivoting main landing gear 32. In one embodiment, one or more, but not all, of the wheels 46 may be selected, such as a wheel pair, as shown in the left main landing gear 24a in fig. 3A-3C, and discussed in further detail below, as it optionally enables integration of an existing taxi brake release function 130, also referred to as a taxi brake selection function, and a PTLA brake inhibit command 90 function under the same PTLA brake inhibit subsystem 16 algorithm or programmed logic.

The ptl brake system 12 mitigates loads 28 (see fig. 2A), such as structural loads 28a (see fig. 2A), on the pivoting main landing gear 32 during a pivot turning maneuver 30 of the aircraft 10 and reduces wear 136 (see fig. 2A) to the at least one wheel 46 in the unbraked state 52 (i.e., with at least one unbraked wheel 46a (see fig. 2A) inhibiting braking) and reduces wear 136 to the tires of the wheel 46. In addition, the PTLA braking system 12 inhibits braking on one or more brakes 58 on the pivoting main landing gear 32 to reduce the torsional load reaction force 28b (see fig. 2A) exerted on the pivoting main landing gear 32. The PTLA braking system 12 may also reduce steering forces 134 (see FIG. 2A), which in turn reduces wear 136. The PTLA braking system 12 may also provide U-turn optimization 138 (see fig. 2A) when the inboard wheel 46e is released. The PTLA braking system 12 may also reduce the overall weight of the main landing gear 24 because various components and materials on the main landing gear 24 may be reduced or eliminated with reduced structural loads 28a and reduced steering forces 134, such as a smaller reduced weight scissor link, a smaller reduced weight torque link, or another small size structure on the main landing gear 24, such as the pivoting main landing gear 32. The possibility of reducing the weight of the main landing gear 24 of the aircraft 10 may save at least twenty-five pounds (25lbs) of weight or more.

Referring now to fig. 2B, fig. 2B is an illustration of a functional block diagram showing the aircraft 10 and the PTLA brake suppression subsystem 16 of fig. 2A having a plurality of PTLA entry scenarios 140 and a plurality of PTLA exit scenarios 142. As further shown in fig. 2B, PTLA brake system 12 includes brake control system 14 and PTLA brake inhibit subsystem 16 that monitors for a PTLA entry scenario 140 and a PTLA exit scenario 142. As shown in fig. 4-7, and discussed in further detail below, various pivot turn brake pedal profiles 112 (see fig. 2B) that are monitored and sensed by the monitoring logic 108 (see fig. 2A), each representing one of the PTLA entry scenarios 140 and one of the PTLA exit scenarios 142, are detected and determined by the beginning 31 (see fig. 2A) of the pivot turn maneuver 30 (see fig. 2B). Each of the PTLA entry scenarios 140 and each of the PTLA exit scenarios 142 include an initial state 144 (see fig. 2B), a state change 146 (see fig. 2B), and a result 148 (see fig. 2B).

Three (3) exemplary PTLA access scenarios 140 are described below using the a-side 150 (see fig. 2B) and the B-side 152 (see fig. 2B) of one main landing gear 24 (see fig. 2B) entering the pivot turn maneuver 30 (see fig. 2B) or pivot turn to become the pivoting main landing gear 32 (see fig. 2B), with the brake pedal 64 (see fig. 2B) connected to one main landing gear 24, and four wheels 46 (see fig. 2B) of one main landing gear 24 having brakes 58 (see fig. 2B). These three (3) exemplary PTLA entry scenarios 140 are summarized as follows:

(1) the first PTLA entry scenario 140a (see fig. 2B) includes: (a) an initial state 144 in which no brakes 58 are applied/applied on side a and no brakes 58 are applied/applied on side B, wherein aircraft ground speed 101 (see fig. 2B) is below PTLA speed threshold 104 (see fig. 2B), e.g., as determined using average wheel speed 102 (see fig. 2B); (b) a state change 146 in which pilot 154 (see fig. 2B) applies brake pedal 64 on side a and does not apply brake pedal 64 on side B, wherein aircraft ground speed 101 (see fig. 2B) is below ptl speed threshold 104, e.g., as determined using average wheel speed 102; and (c) one or more brakes 58 on side a are applied and one or more brakes 58 on side B are the result 148 of holding brake 58a (see fig. 2B) in a hold-down state 57 (see fig. 2B) and no brakes 58 are applied on side B, and wherein the aircraft ground speed 101 (see fig. 2B) is below the PTLA speed threshold 104, e.g., as determined using the average wheel speed 102.

(2) The second PTLA entry scenario 140B (see fig. 2B) includes: (a) an initial state 144 in which brake 58 is applied/applied on side a and brake 58 is applied/applied on side B, wherein aircraft ground speed 101 (see fig. 2B) is below PTLA speed threshold 104, e.g., as determined using average wheel speed 102; (b) the pilot releases the brake pedal 64 on side B and the brake pedal 64 on side B is still applied and remains depressed state change 146, wherein the aircraft ground speed 101 (see fig. 2B) is below the PTLA speed threshold 104, e.g., as determined using the average wheel speed 102; and (c) the result 148 that one or more brakes 58 on side a are still applied, and all brakes 58 on side B and one or more brakes 58 on side a are released, such that the one or more brakes 58 on side a that are released are the hold brakes 58a in the hold state 57, and wherein the aircraft ground speed 101 (see fig. 2B) is below the PTLA speed threshold 104, e.g., as determined using the average wheel speed 102.

(3) The third PTLA entry scenario 140c (see fig. 2B) includes: (a) an initial state 144 in which brake 58 is applied/applied on side a and no brake 58 is applied/applied on side B, wherein aircraft ground speed 101 (see fig. 2B) is above PTLA speed threshold 104, e.g., as determined using average wheel speed 102; (b) a state change 146 in which aircraft 10 decelerates such that aircraft ground speed 101 (see fig. 2B) is below PTLA speed threshold 104, e.g., as determined using average wheel speed 102, and brake pedal 64 on side B is still applied/applied and remains depressed, while brake pedal 64 on side B is not applied; and (c) a result 148 of no brakes 58 being applied on side B and one or more brakes 58 on side a being released such that the one or more brakes 58 on side a that are released are the hold brakes 58a in the hold state 57, and wherein the aircraft ground speed 101 (see fig. 2B) is below the ptl speed threshold 104, e.g., as determined using the average wheel speed 102.

Three (3) exemplary ptl exit scenarios 142 (see fig. 2B) are described below using the a-side 150 and B-side 152 of one main landing gear 24 entering the pivot turn maneuver 30 or pivot turn to become the pivoting main landing gear 32 (see fig. 2B), with brake pedals 64 connected to one main landing gear 24, and two or more wheels 46, e.g., four wheels 46, of one main landing gear 24 having brakes 58. These three (3) exemplary PTLA exit scenarios 142 are summarized as follows:

(1) the first PTLA exit scenario 142a (see fig. 2B) includes: (a) one or more brakes 58 on side a are applied and are hold brakes 58a in hold state 57, and no brakes 58 on side B are applied/initial state 144, where aircraft ground speed 101 (see fig. 2B) is below PTLA speed threshold 104, e.g., as determined using average wheel speed 102; (b) a state change 146 where the pilot releases the brake pedal 64 on side a, but the brake pedal 64 on side B is not applied, wherein the aircraft ground speed 101 (see fig. 2B) is below the PTLA speed threshold 104, e.g., as determined using the average wheel speed 102; and (c) a result 148 of no brakes 58 being applied on the a-side and no brakes 58 being applied on the B-side, where the aircraft ground speed 101 (see fig. 2B) is below the PTLA speed threshold 104, e.g., as determined using the average wheel speed 102.

(2) The second PTLA exit scenario 142B (see fig. 2B) includes: (a) one or more brakes 58 on side a are applied and are hold brakes 58a in hold state 57, and an initial state 144 where no brakes 58 are applied on side B, where aircraft ground speed 101 (see fig. 2B) is below PTLA speed threshold 104, e.g., as determined using average wheel speed 102; (b) the pilot applies the brake pedal 64 on side B, and the state change 146 where the brake pedal 64 on side a remains depressed, wherein the aircraft ground speed 101 (see fig. 2B) is below the PTLA speed threshold 104, e.g., as determined using the average wheel speed 102; and (c) all (all) brakes 58 are applied/applied on side a and all (all) brakes 58 are applied/applied on side B, wherein the aircraft ground speed 101 (see fig. 2B) is below the PTLA speed threshold 104, e.g., as determined using the average wheel speed 102.

(3) The third PTLA exit scenario 142c (see fig. 2B) includes: (a) one or more brakes 58 on side a are applied and are hold brakes 58a in hold state 57, and an initial state 144 where no brakes 58 are applied on side B, where aircraft ground speed 101 (see fig. 2B) is below PTLA speed threshold 104, e.g., as determined using average wheel speed 102; (b) a state change 146 in the acceleration of the aircraft 10 such that the aircraft ground speed 101 (see fig. 2B) is above the PTLA speed threshold 104, e.g., as determined using the average wheel speed 102, and the brake pedal 64 on side B is still applied/applied and held depressed, while the brake pedal 64 on side B is not applied; and (c) a result 148 of all (all) brakes 58 being applied on side a and no brakes 58 being applied on side B, wherein the aircraft ground speed 101 (see fig. 2B) is above the PTLA speed threshold 104, e.g., as determined using the average wheel speed 102.

With multiple ptl entry scenarios 140 and multiple ptl exit scenarios 142 discussed above, the brakes 46 may be limited to one or more, but not all, of the brakes 46 based on the taxi brake release function 130 (see fig. 2A), and no brakes applied may mean that the brakes are below a certain pedal threshold, e.g., a minimum ptl triggers a brake pedal command threshold 122A (see fig. 4), e.g., 25% pilot brake pedal effort (see fig. 4-7). Additionally, using the multiple PTLA entry scenario 140 and the multiple PTLA exit scenario 142 discussed above, applying or applied pedals may mean that the brake 58 exceeds a certain pedal threshold, such as a maximum PTLA trigger brake pedal command threshold 122b (see FIG. 4), for example 27% pilot brake pedal effort (see FIG. 4-7), and releasing the pedals may mean that the brake 58 is below a minimum PTLA trigger brake pedal command threshold 122a (see FIG. 4), for example 25% pilot brake pedal effort (see FIG. 4-7). Further, the differential wheel speeds between the left and right main landing gears 24a, 24b may be considered to achieve a more accurate starting criterion. Further, a second threshold may be used to ensure that the pivot turn command is intended or not intended, and a delay function may be used to ensure that the brake pedal command 120 is intended to execute a scenario, i.e., pivot turn. The percentage value corresponds to a normalized full brake pedal travel, e.g., 0% is full brake pedal release and 100% is full brake pedal depression.

As shown in fig. 1A-1B and 2A, in another version of the present disclosure, an aircraft 10 is provided that includes a fuselage 18 (see fig. 1A-1B), one or more wings 20 (see fig. 1A-1B) attached to the fuselage 18, and a plurality of landing gears 22 (see fig. 1A-1B) attached to the fuselage 18. The plurality of landing gears 22 includes a nose gear 26 (see fig. 1A-1B) and at least two main landing gears 24 (see fig. 1A-1B, 2A), each of the at least two main landing gears 24 having two or more wheels 46 (see fig. 1A-1B, 2A), wherein during a pivot turn maneuver 30 (see fig. 2A) of the aircraft 10, one of the at least two main landing gears 24 includes a pivot main landing gear 32 (see fig. 2A). Each main landing gear 24 may have, for example, two wheels, four wheels, six wheels, or another suitable number of wheels.

The aircraft 10 also includes a PTLA brake system 12, the PTLA brake system 12 including a brake control system 14 operably coupled to at least two main landing gears 24, wherein the brake control system 14 controls braking of the at least two main landing gears 24. The PTLA system also includes a PTLA brake inhibit subsystem 16 coupled to the brake control system 14, wherein the PTLA brake inhibit subsystem 16 inhibits braking of one or more of the two or more wheels 46 of the one main landing gear 24 including the pivoting main landing gear 32 during the pivot turning maneuver 30 such that at least one wheel 46 of the two or more wheels 46 is in an unbraked state 52 and a remaining number 54 of the two or more wheels 46 is in a braked state 56. As described above, the PTLA brake system 12 mitigates structural loads 28a on the pivoting main landing gear 32 during the pivot turn maneuver 30 of the aircraft 10 and reduces wear 136 to the at least one wheel 46 in the unbraked state 52.

Upon detection of one or more of the brake inhibit conditions 94 (see fig. 2A), the PTLA brake inhibit subsystem 16 inhibits braking via initiation 92 of a PTLA brake inhibit command 90 (see fig. 2A) to one or more brake control units 74 (see fig. 2A) of the brake control system 14. As described above, the one or more brake inhibit conditions 94 include one or more of: (a) an on-ground state 96 (see FIG. 2A) of the aircraft, which is indicated when the aircraft 10 is in an on-ground position 98; (b) an acceptable aircraft ground speed 100 (see FIG. 2A) that is indicated when aircraft ground speed 101 (see FIG. 2A) of aircraft 10 is less than PTLA speed threshold 104; or (c) a pta active flag command indication 106 (see fig. 2A) generated by monitoring logic 108 (see fig. 2A) of the pta brake suppression subsystem 16 to monitor a brake pedal position 110 (see fig. 2A) to detect the onset 31 of the pivot turn maneuver 30 based on one of a plurality of pivot turn brake pedal profiles 112 (see fig. 2A).

The PTLA brake inhibit command 90 is deactivated when one or more of the brake inhibit deactivation conditions 118 (see FIG. 2A) are met or met. The brake inhibit deactivation condition 118 may include one or more of the following: (a) aircraft ground speed 101 of aircraft 10 exceeds PTLA speed threshold 104; (b) both left brake pedal command 120a (see fig. 2A) and right brake pedal command 120b (see fig. 2A) exceed the PTLA trigger brake pedal command threshold 122 (see fig. 2A) for at least a predetermined period of time 124 (see fig. 2A); or (c) the aircraft 10 enters the active parking brake state 126 (see fig. 2A).

In one version, the aircraft 10 may also include a taxi brake release function 130, and the PTLA brake suppression subsystem 16 is integrated with the taxi brake release function 130, the taxi brake release function 130 executing a PTLA brake suppression command 90 on behalf of the PTLA brake suppression subsystem 16 to suppress braking of one or more, but not all, of the wheels 46 of the pivoting main landing gear 32.

Referring now to fig. 3A-3C, fig. 3A is an illustration of a schematic view of a PTLA brake system command logic diagram 156a in a pivot turn maneuver 30 of the aircraft 10, fig. 3B is an illustration of a schematic view of another version of the PTLA brake system command logic diagram 156B, and fig. 3C is an illustration of a schematic view of yet another version of the PTLA brake system command logic diagram 156C.

Fig. 3A shows a PTLA brake system command logic diagram 156a wherein the brake inhibit condition 94 includes one brake inhibit condition 94, the one brake inhibit condition 94 including a PTLA active flag Command (CMD) indication 106 that activates the PTLA brake inhibit command 90 to cause the PTLA brake inhibit Command (CMD) enable function 158 wherein the brake control unit 74 (see fig. 2A) of the brake control system 14 enables the PTLA brake inhibit command 90. The ptl active flag command indication 106 is generated by the monitoring logic 108 (see fig. 2A), the monitoring logic 108 determining whether the pilot 154 (see fig. 2B) is attempting the pivot turn maneuver 30, and determining the monitoring logic output 108a (see fig. 2A) based on one of the pivot turn brake pedal curves 112 (see fig. 2A-2B, 4-7).

Fig. 3B shows a PTLA brake system command logic diagram 156B, where the brake inhibit conditions 94 include two brake inhibit conditions 94, the two brake inhibit conditions 94 including either: (a) an on-ground status 96 of the aircraft and a PTLA active flag Command (CMD) indication 106, or (b) an acceptable aircraft ground speed 100 and a PTLA active flag Command (CMD) indication 106, either combination of which initiates the PTLA brake inhibit command 90. This results in the PTLA brake inhibit Command (CMD) enabling function 158, wherein the brake control unit 74 (see fig. 2A) of the brake control system 14 enables the PTLA brake inhibit command 90. The ptl active flag command indication 106 is generated by the monitoring logic 108 (see fig. 2A), the monitoring logic 108 determining whether the pilot 154 (see fig. 2B) is attempting the pivot turn maneuver 30, and determining the monitoring logic output 108a (see fig. 2A) based on one of the pivot turn brake pedal curves 112 (see fig. 2A-2B, 4-7).

Fig. 3C shows a PTLA brake system command logic diagram 156b, where brake inhibit conditions 94 include all of the following: (a) an on-ground state 96 of the aircraft, (b) an acceptable aircraft ground speed 100, and (c) a PTLA active flag Command (CMD) indication 106 to initiate or generate a PTLA brake inhibit command 90. This results in the PTLA brake inhibit Command (CMD) enabling function 158, wherein the brake control unit 74 of the brake control system 14 (see fig. 2A) enables the PTLA brake inhibit command 90. The ptl active flag command indication 106 is generated by the monitoring logic 108 (see fig. 2A), the monitoring logic 108 determining whether the pilot 154 (see fig. 2B) is attempting the pivot turn maneuver 30, and determining the monitoring logic output 108a (see fig. 2A) based on one of the pivot turn brake pedal curves 112 (see fig. 2A-2B, 4-7).

As shown in fig. 3A-3C, a PTLA brake inhibit Command (CMD) enable function 158 is executed wherein the brake control unit 74 (see fig. 2A) of the brake control system 14 enables the PTLA brake inhibit command 90 to cause the PTLA brake inhibit Command (CMD) sent to the wheel select function 162 to be enabled 160. As further shown in fig. 3A-3C, if a PTLA brake inhibit command 90 is present and present on the aircraft 10 (see fig. 1A-1B, 2A), the PTLA brake inhibit command 90 may optionally be integrated with a taxi brake release function 130 to obtain a taxi brake release function integration 132. As shown in fig. 3A-3C, when the current taxi brake release selection 164 is already present and present on the aircraft 10, the current taxi brake release selection 164 may be optionally selected to select wheel X166 in the number 1 position 168 corresponding to the outboard and forward wheel position number 1168 a of the wheel 46 of the left main landing gear 24a, which in this case is the pivoting main landing gear 32. As shown in fig. 3A-3C, the current taxi brake release selection 164 further selects wheel Y170 in number 2 position 172, which corresponds to forward outboard wheel position number 2172 a of wheel 46 of the left main landing gear 24 a. Fig. 3A-3C show a left main landing gear 24a having four wheels 46 and a right main landing gear 24b having four wheels 46. Wheel X166 and wheel Y170 are the pair of axles 48a of wheel 46 (see fig. 3A-3C). The PTLA brake inhibit command 90 inhibits braking of wheel X166 and wheel Y170, and wheel X, Y inhibits Command (CMD)174 (see fig. 3A-3C) from being sent to brake control unit Command (CMD) generation 176. As shown in fig. 3A-3C, the brake control unit command generation 176 also receives a pilot pedal Command (CMD)178 and a Hardware (HW) enable Command (CMD) 180.

As shown in fig. 3A-3C, the brake control unit command generation 176 then sends a wheel X inhibit Command (CMD)182 and a wheel Y inhibit Command (CMD)184 to the brake control valve 82. One brake control valve 82 is coupled or connected to wheel X166 via a first hydraulic connector element 88a to inhibit braking of wheel X166 on the left main landing gear 24a, while the other brake control valve 82 is coupled or connected to wheel Y170 via a second hydraulic connector element 88b to inhibit braking of wheel Y170 on the left main landing gear 24 a. As shown in fig. 3A-3C, the PTLA brake inhibit command 90, along with the brake control unit 74 and the brake control valve 82, causes the pair of wheels 46h on the pivoting main landing gear 32 to be inhibited. As shown in fig. 3A-3C, no wheels are inhibited on the right main landing gear 24b as the non-pivoting main landing gear 34.

Referring now to fig. 4, fig. 4 is a diagram illustrating a graph 186 of the pivot turn brake pedal curve 112 in the form of an exemplary first pivot turn brake pedal curve 112a, wherein for entering a left pivot turn maneuver 188, both initially and with an end scenario where both pedals are depressed 190, entering a pivot turn maneuver 30 in the form of a left pivot turn maneuver 30b is performed. As shown in FIG. 4, graph 186 includes a first portion 192 where on the y-axis is pilot brake pedal effort 193 in percent (%) and on the x-axis is time 194 in seconds(s). This percentage value corresponds to a normalized full brake pedal travel, e.g., 0% being full brake pedal release and 100% being full brake pedal depression. As further shown in fig. 4, the graph 186 includes a second portion 196 having a pivot turn flag 198 on the y-axis and also having a time 194 in seconds(s) on the x-axis, and a first inactive portion 200, an active portion 202, and a second inactive portion 204 along the x-axis. As further shown in fig. 4, the graph 186 includes a third portion 206, the third portion 206 illustrating a braking state 208 of the wheels 46 on the left and right main landing gears 24a, 24 b. As further shown in FIG. 4, the braking state 208 includes no brake 210, brake apply 212, and holding brake-no brake 214.

As shown in fig. 4, the first portion 192 shows a left pedal plot 216 of the left pedal 218 and a right pedal plot 220 of the right pedal 222 through the first inactive portion 200, the active portion 202, and the second inactive portion 204 when the entering left pivot turn maneuver 188 transitions to entering and disengaging the braked pivot turn. The first portion 192 also shows a hysteresis 224, the hysteresis 224 having a minimum PTLA trigger brake pedal command threshold 122a and a maximum PTLA trigger brake pedal command threshold 122 b. As used herein, "hysteresis" refers to output selection in which the output command changes by different thresholds depending on the direction in which the input command is traveling. This hysteresis is used in the control function to avoid limit cycle effects in the output command if the input signal, e.g., brake pedal command, oscillates from one fixed threshold to another.

As shown in fig. 4, during the first inactive portion 200, both the left pedal 218 and the right pedal 220 are initially depressed and the wheels 46 of the left and right main landing gears 24a and 24b are in the brake applied 212 braking state 208. As further shown in fig. 4, during the active portion 202, the left pedal 218 is held depressed and the right pedal 222 is released and the wheels 46 of the right main landing gear 24b are in the no brake 210 braking state 208. As shown in fig. 4, when right pedal profile 220 falls below the minimum PTLA trigger brake pedal command threshold 122A (and average wheel speed 102 (see fig. 2A) is less than PTLA speed threshold 104 (see fig. 2A)) transitioning from first inactive portion 200 to active portion 202, PTLA brake inhibit command 90 is initiated and enters PTLA, and PTLA brake inhibit command 90 (see fig. 2A, 3A-3C) is sent to brake control unit 74 (see fig. 3A-3C) and wheel select 50 (see fig. 3A-3C) to inhibit brakes 58 (see fig. 2A) on a pair of 48 wheels 46 on left main landing gear 24 a. As shown in fig. 4, during the active portion 202, the pair 48 of front wheels 46c on the left main landing gear 24a is in a brake-inhibited, no-brake 214 braking state 208, while the pair 48 of rear wheels 46d on the left main landing gear 24a is in a brake-applied 212 braking state 208. Note that the pair 48 of rear wheels 46d may be suppressed instead of the pair 48 of front wheels 46c on the left main landing gear 24a, or other combinations of wheels 46 may be suppressed, such as diagonal wheels 46i (see fig. 2A), one wheel 46, three wheels 46, or other suitable number of wheels.

As shown in fig. 4, when the right pedal profile 220 exceeds the maximum PTLA trigger brake pedal command threshold 122b transitioning from the active portion 202 to the second inactive portion 204, the PTLA brake inhibit command 90 is deactivated, and in the second inactive portion 204, the left pedal 218 remains depressed and applied, and the right pedal 222 is applied, resulting in an all-brake applied state 226 upon exit of the PTLA. As shown in fig. 4, during the second inactive portion 204, all of the wheels 46 on the left and right main landing gears 24a, 24b are in a brake applied 212 braking state 208.

Referring now to fig. 5, fig. 5 is a diagram illustrating a graph 228 of the pivot turn brake pedal curve 112 in the form of an exemplary second pivot turn brake pedal curve 112b, wherein for both pedals initially depressed and entering the left pivot turn maneuver 188 with the end scenario released 230, entering the pivot turn maneuver 30 in the form of the left pivot turn maneuver 30b is undertaken. As shown in FIG. 5, graph 228 includes a first portion 192 where on the y-axis is pilot brake pedal effort 193 in percent (%) and on the x-axis is time 194 in seconds(s). This percentage value corresponds to a normalized full brake pedal travel, e.g., 0% being full brake pedal release and 100% being full brake pedal depression. As further shown in FIG. 5, the graph 228 includes a second portion 196 in which the pivot turn flag 198 is on the y-axis and the time 194 in seconds(s) is on the x-axis, as well as a first inactive portion 200, an active portion 202, and a second inactive portion 204 along the x-axis. As further shown in fig. 5, the graph 228 includes a third portion 206, the third portion 206 illustrating the braking state 208 of the wheels 46 on the left and right main landing gears 24a, 24 b. As further shown in FIG. 5, the braking state 208 includes no brake 210, brake apply 212, and holding brake-no brake 214.

As shown in fig. 5, the first portion 192 shows a left pedal plot 216a of the left pedal 218 and a right pedal plot 220a of the right pedal 222 through the first inactive portion 200, the active portion 202, and the second inactive portion 204 when the entering left pivot turn maneuver 188 transitions to entering and disengaging the braked pivot turn. The first portion 192 also shows a hysteresis 224, the hysteresis 224 having a minimum PTLA trigger brake pedal command threshold 122a and a maximum PTLA trigger brake pedal command threshold 122 b.

As shown in fig. 5, during the first inactive portion 200, both the left pedal 218 and the right pedal 220 are initially depressed and the wheels 46 of the left and right main landing gears 24a and 24b are in the brake applied 212 braking state 208. As further shown in fig. 5, during the active portion 202, the left pedal 218 is depressed and the right pedal 222 is released and the wheels 46 of the right main landing gear 24b are in the no brake 210 braking state 208. As shown in fig. 5, when the right pedal profile 220a falls below the minimum PTLA trigger brake pedal command threshold 122A (and the average wheel speed 102 (see fig. 2A) is less than the PTLA speed threshold 104 (see fig. 2A)) transitioning from the first inactive portion 200 to the active portion 202, the PTLA brake inhibit command 90 is initiated and enters PTLA, and the PTLA brake inhibit command 90 (see fig. 2A, 3A-3C) is sent to the brake control unit 74 (see fig. 3A-3C) and the wheel select 50 (see fig. 3A-3C) to inhibit the brakes 58 (see fig. 2A) on the pair of 48 wheels 46 on the left main landing gear 24 a. As shown in fig. 5, during the active portion 202, the pair 48 of rear wheels 46d on the left main landing gear 24a is in a brake inhibited-no brake 214 braking state 208, while the pair 48 of front wheels 46c on the left main landing gear 24a is in a brake applied 212 braking state 208. Note that the pair 48 of front wheels 46c may be suppressed instead of the pair 48 of rear wheels 46d on the left main landing gear 24a, or other combinations of wheels 46 may be suppressed, such as diagonal wheels 46i (see fig. 2A), one wheel 46, three wheels 46, or other suitable number of wheels.

As shown in fig. 5, when the left pedal curve 216a is below the minimum PTLA trigger brake pedal command threshold 122a for transitioning from the active portion 202 to the second inactive portion 204, the PTLA brake inhibit command 90 is deactivated, and in the second inactive portion 204, the left pedal 218 is released and the right pedal 222 remains released such that all of the wheels 46 on the left and right main landing gears 24a and 24b are in the no-brake 210 braking state 208 when the PTLA exits.

Referring now to fig. 6, fig. 6 is a diagram illustrating a graph 232 of the pivot turn brake pedal curve 112 in the form of an exemplary third pivot turn brake pedal curve 112c, wherein entering the pivot turn maneuver 30 in the form of the left pivot turn maneuver 30b is performed for entering the left pivot turn maneuver 188 without the pedal initially depressed and with both pedals depressed 234 at the end scenario. As shown in FIG. 6, graph 232 includes a first portion 192 where on the y-axis is pilot brake pedal effort 193 in percent (%) and on the x-axis is time 194 in seconds(s). This percentage value corresponds to a normalized full brake pedal travel, e.g., 0% being full brake pedal release and 100% being full brake pedal depression. As further shown in fig. 6, the graph 232 includes a second portion 196 with a pivot turn flag 198 on the y-axis and a time 194 in seconds(s) on the x-axis, and a first inactive portion 200, an active portion 202, and a second inactive portion 204 along the x-axis. As further shown in fig. 6, the graph 228 includes a third portion 206, the third portion 206 illustrating the braking state 208 of the wheels 46 on the left and right main landing gears 24a, 24 b. As further shown in fig. 6, the braking state 208 includes no brake 210, brake apply 212, and hold-down brake-no brake 214.

As shown in fig. 6, the first portion 192 shows a left pedal plot 216b of the left pedal 218 and a right pedal plot 220b of the right pedal 222 through the first inactive portion 200, the active portion 202, and the second inactive portion 204 when the entering left pivot turn maneuver 188 transitions to entering and disengaging the braked pivot turn. The first portion 192 also shows a hysteresis 224, the hysteresis 224 having a minimum PTLA trigger brake pedal command threshold 122a and a maximum PTLA trigger brake pedal command threshold 122 b.

As shown in fig. 6, during the first inactive portion 200, both the left pedal 218 and the right pedal 216 are initially not depressed, and the wheels 46 of the left and right main landing gears 24a and 24b are in the no-brake 210 braking state 208. As further shown in fig. 6, during the active portion 202, the left pedal 218 is applied and depressed and the right pedal 222 is not applied and depressed and the wheels 46 of the right main landing gear 24b are in the no brake 210 braking state 208. As shown in fig. 6, when left pedal curve 216b exceeds the maximum PTLA trigger brake pedal command threshold 122b that transitions from the first inactive portion 200 to the active portion 202 (and the average wheel speed 102 (see fig. 2A) is less than the PTLA speed threshold 104 (see fig. 2A)), the PTLA brake inhibit command 90 is initiated and enters the PTLA, and the PTLA brake inhibit command 90 (see fig. 2A, 3A-3C) is sent to the brake control unit 74 (see fig. 3A-3C) and the wheel select 50 (see fig. 3A-3C) to inhibit the brakes 58 (see fig. 2A) on the pair of 48 wheels 46 on the left main landing gear 24 a. As shown in fig. 6, during the active portion 202, the pair 48 of front wheels 46c on the left main landing gear 24a is in a brake-inhibited, no-brake 214 braking state 208, while the pair 48 of rear wheels 46d on the left main landing gear 24a is in a brake-applied 212 braking state 208. Note that the pair 48 of rear wheels 46d may be suppressed instead of the pair 48 of front wheels 46c on the left main landing gear 24a, or other combinations of wheels 46 may be suppressed, such as diagonal wheels 46i (see fig. 2A), one wheel 46, three wheels 46, or other suitable number of wheels.

As shown in fig. 6, the PTLA brake inhibit command 90 is deactivated when the right pedal plot 220b exceeds the maximum PTLA trigger brake pedal command threshold 122b transitioning from the active portion 202 to the second inactive portion 204, and in the second inactive portion 204 the left pedal 218 remains depressed and applied and the right pedal 222 is depressed and applied such that an all-brake applied state 226 results upon exit of the PTLA. As shown in fig. 6, during the second inactive portion 204, all of the wheels 46 on the left and right main landing gears 24a, 24b are in a brake applied 212 braking state 208.

Referring now to fig. 7, fig. 7 is a diagram illustrating a graph 236 of the pivot turn brake pedal curve 112 in the form of an exemplary fourth pivot turn brake pedal curve 112d, wherein entering the pivot turn maneuver 30 in the form of the left pivot turn maneuver 30b is performed for entering the left pivot turn maneuver 188 without the pedals initially being depressed and then both pedals being released 238 at the end scenario. As shown in FIG. 7, graph 232 includes a first portion 192 where on the y-axis is pilot brake pedal effort 193 in percent (%) and on the x-axis is time 194 in seconds(s). This percentage value corresponds to a normalized full brake pedal travel, e.g., 0% being full brake pedal release and 100% being full brake pedal depression. As further shown in fig. 7, the graph 232 includes a second portion 196 with a pivot turn flag 198 on the y-axis and a time 194 in seconds(s) on the x-axis, and a first inactive portion 200, an active portion 202, and a second inactive portion 204 along the x-axis. As further shown in fig. 7, the graph 228 includes a third portion 206, the third portion 206 illustrating the braking state 208 of the wheels 46 on the left and right main landing gears 24a, 24 b. As further shown in FIG. 7, the braking state 208 includes no brake 210, brake apply 212, and holding brake-no brake 214.

As shown in fig. 7, the first portion 192 illustrates a left pedal plot 216c of the left pedal 218 and a right pedal plot 220c of the right pedal 222 through the first inactive portion 200, the active portion 202, and the second inactive portion 204 when the entering left pivot turn maneuver 188 transitions to entering and disengaging the braked pivot turn. The first portion 192 also shows a hysteresis 224, the hysteresis 224 having a minimum PTLA trigger brake pedal command threshold 122a and a maximum PTLA trigger brake pedal command threshold 122 b.

As shown in fig. 7, during the first inactive portion 200, neither the left pedal 218 nor the right pedal 220 is initially depressed, and the wheels 46 of the left and right main landing gears 24a and 24b are in the no-brake 210 braking state 208. As further shown in fig. 7, during the active portion 202, the left pedal 218 is applied and depressed and the right pedal 222 is not applied and depressed and the wheels 46 of the right main landing gear 24b are in the no brake 210 braking state 208. As shown in fig. 7, when left pedal curve 216C exceeds the maximum PTLA trigger brake pedal command threshold 122b that transitions from the first inactive portion 200 to the active portion 202 (and the average wheel speed 102 (see fig. 2A) is less than the PTLA speed threshold 104 (see fig. 2A)), the PTLA brake inhibit command 90 is initiated and enters PTLA, and the PTLA brake inhibit command 90 (see fig. 2A, 3A-3C) is sent to the brake control unit 74 (see fig. 3A-3C) and the wheel select 50 (see fig. 3A-3C) to inhibit the brakes 58 (see fig. 2A) on one or more, but not all, of the wheels 46, for example, to inhibit the brakes 58 on a pair 48 of wheels 46 on the left main landing gear 24 a. As shown in fig. 7, during active portion 202, one or more but not all of the wheels 46 on left main landing gear 24a, such as the pair 48 of rear wheels 46d, are in a brake inhibited-brake no brake 214 braking state 208, and one or more but not all of the wheels 46 on left main landing gear 24a, such as the pair 48 of front wheels 46c, are in a brake applied 212 braking state 208. It should be noted that one or more, but not all, of the wheels 46 may be suppressed, such as the pair 48 of front wheels 46c, instead of one or more, but not all, of the wheels 46 on the left main landing gear 24a, such as the pair 48 of rear wheels 46d, or other combinations of suppression wheels 46, such as diagonal wheels 46i (see fig. 2A), one wheel 46, three wheels 46, or other suitable number of wheels.

As shown in fig. 7, when the left pedal curve 216c is below the minimum PTLA trigger brake pedal command threshold 122a for transitioning from the active portion 202 to the second inactive portion 204, the PTLA brake inhibit command 90 is deactivated, and in the second inactive portion 204, the left pedal 218 is released and the right pedal 222 remains released such that all of the wheels 46 on the left and right main landing gears 24a and 24b are in the no-brake 210 braking state 208.

Referring now to fig. 8, fig. 8 is an illustration of a flowchart showing an exemplary version of a method 250 of the present disclosure. In another version of the present disclosure, a method 250 (see fig. 8) for mitigating structural loads 28a (see fig. 2A) on a pivoting main landing gear 32 (see fig. 2A) of an aircraft 10 (see fig. 1A-1B, 2A) during and during a pivot turn maneuver 30 (see fig. 2A) is provided.

The blocks in fig. 8 represent operations and/or portions thereof, and the lines connecting the various blocks do not imply any particular order or dependency of the operations or portions thereof. The disclosure of fig. 8 and the steps of method 250 set forth herein should not be construed as necessarily determining the order in which the steps are to be performed. Rather, although an illustrative order is indicated, it should be understood that the order of the steps may be modified as appropriate. Thus, certain operations may be performed in a different order or concurrently.

As shown in FIG. 8, the method 250 includes the step of initiating 252 a pivot turn maneuver 30 of the aircraft 10. The aircraft 10 has a pivot cornering load mitigation (PTLA) brake system 12 (see fig. 1A-1B, 2A). As described in detail above, the PTLA brake system 12 includes a brake control system 14 (see fig. 1A-1B, 2A), the brake control system 14 being operably coupled to at least two main landing gears 24 (see fig. 1A-1B, 2A). Each of the at least two main landing gears 24 has two or more wheels 46 (see fig. 1A-1B, 2A). For example, each main landing gear 24 may have two wheels, four wheels, six wheels, or another suitable number of wheels. The brake control system 14 controls the braking of at least two main landing gears 24. The PTLA brake system 12 also includes a pivot cornering load alleviation (PTLA) brake inhibit subsystem 16 (see fig. 1A-1B, 2A) coupled to the brake control system 14.

The step of initiating 252 (see fig. 8) a pivot turn maneuver 30 of the aircraft 10 may further include initiating 252A pivot turn maneuver 30 of the aircraft 10 having the PTLA brake system 12, wherein the brake control system 14 includes a plurality of brake control units 74 (see fig. 2A) and a plurality of brake control valves 82 (see fig. 2A), wherein one of the plurality of brake control units 74 receives the PTLA brake inhibit command 90 (see fig. 2A) from the PTLA brake inhibit subsystem 16 to inhibit generation of at least one brake command 76 (see fig. 2A) to at least one wheel 46.

As shown in fig. 8, the method 250 further includes the step of initiating 254 a pivot turn load retard (PTLA) brake inhibit command 90 (see fig. 2A) of the PTLA brake inhibit subsystem 16 to one or more brake control units 74 (see fig. 2A) of the brake control system 14 once the one or more brake inhibit conditions 94 (see fig. 2A) are satisfied. The step of initiating 254 (see fig. 8) further includes initiating a PTLA brake inhibit command 90 upon satisfaction of one or more brake inhibit conditions 94 including one or more of: (a) an on-ground indication 96 (see FIG. 2A) of the aircraft when the aircraft 10 is in an on-ground position 98 (see FIG. 2A); (b) acceptable aircraft ground speed 100 (see FIG. 2A) when aircraft ground speed 101 (see FIG. 2A) of aircraft 10 is less than pivot turn load retard (PTLA) speed threshold 104 (see FIG. 2A); or (c) a Pivot Turn Load Alleviation (PTLA) active flag command indication 106 (see fig. 2A) generated by monitoring logic 108 (see fig. 2A) of the PTLA brake suppression subsystem 16 to monitor a brake pedal position 110 (see fig. 2A) to detect a beginning 31 (see fig. 2A) of a pivot turn maneuver 30 (see fig. 2A) based on one of a plurality of pivot turn brake pedal profiles 112 (see fig. 2A, 4-7).

As shown in fig. 8, the method 250 also includes the step of inhibiting braking 256 of one or more of the two or more wheels 46 (see fig. 1A-1B, 2A) of the pivoting main landing gear 32 during the pivot turn maneuver 30 such that at least one wheel 46 of the two or more wheels 46 is in the unbraked state 52 (see fig. 2A) and the remaining number 54 of the two or more wheels 46 (see fig. 2A) is in the braked state 56 (see fig. 2A). The PTLA braking system 12 mitigates structural loads 28a on the pivoting main landing gear 32 of the aircraft 10 in the pivot turn maneuver 30 and reduces wear 136 to the at least one wheel 46 in the unbraked state 52 (see fig. 2A).

The step of inhibiting braking 256 (see fig. 8) may also include inhibiting braking 256 of one of the wheels 46, two of the wheels 46, or three of the wheels 46 in the pivot turn maneuver 30 of the aircraft 10. The step of inhibiting braking 256 may also include inhibiting braking 256 of one or more, but not all, of the inhibited wheel selections 50 (see fig. 2A) on the pivoting main landing gear 32, such as one axle pair 48a (see fig. 2A) of the wheels 46, and in the event of a beginning 31 of a subsequent pivot turn maneuver 30a (see fig. 2A), changing the inhibited wheel selection 50 of one or more, but not all, of the wheels 46, such as one axle pair 48a of the wheels 46, to a different one or more, but not all, of the wheels 46, such as a different axle pair 48b (see fig. 2A) of the wheels 46, in a sequential order 51 (see fig. 2A).

As shown in fig. 8, after the step of inhibiting braking 256, the method 250 may also optionally include a step 258 of deactivating the PTLA brake inhibit command 90 once one or more brake inhibit deactivation conditions 118 (see fig. 2A) are met. As described above, the one or more brake inhibit deactivation conditions 118 include one or more of: (a) an aircraft ground speed 101 (see FIG. 2A) of the aircraft 10 exceeding a Pivot Turn Load Alleviation (PTLA) speed threshold 104 (see FIG. 2A); or (b) both left brake pedal command 120a (see fig. 2A) and right brake pedal command 120b (see fig. 2A) exceed a Pivot Turn Load Alleviation (PTLA) trigger brake pedal command threshold 122 (see fig. 2A) for at least a predetermined period of time 124 (see fig. 2A); or (c) the aircraft 10 enters the active parking brake state 126 (see fig. 2A).

As shown in fig. 8, the method 250 may also optionally include initiating 252A pivot turn maneuver 30 in the event that the aircraft 10 has a taxi brake release function 130 (see fig. 2A), and integrating 260 the PTLA brake suppression subsystem 16 with the taxi brake release function 130 already present and existing in the aircraft 10, such that the taxi brake release function 130 selects a wheel selection 50 (see fig. 3A-3C) for a PTLA brake suppression command 90 (see fig. 2A, 3A-3C) to suppress braking of one or more, but not all, of the wheels 46 of the pivoting main gear 32.

Referring now to fig. 9 and 10, fig. 9 is a flow diagram of an embodiment of an aircraft manufacturing and service method 300, and fig. 10 is an illustration of a functional block diagram of an embodiment of an aircraft 316. Referring to fig. 9-10, versions of the present disclosure may be described in the context of an aircraft manufacturing and service method 300 as shown in fig. 9 and an aircraft 316 as shown in fig. 10. During pre-production, exemplary aircraft manufacturing and service method 300 (see FIG. 9) may include specification and design 302 (see FIG. 9) of aircraft 316 (see FIG. 10) and material procurement 304 (see FIG. 9). During manufacturing, component and subassembly manufacturing 306 (see FIG. 9) and system integration 308 (see FIG. 9) of an aircraft 316 (see FIG. 10) is performed. Thereafter, aircraft 316 (see FIG. 10) may undergo certification and delivery 310 (see FIG. 9) in order to be placed in service 312 (see FIG. 9). While in service 312 (see FIG. 9), aircraft 316 (see FIG. 10) may be scheduled for routine maintenance and repair 314 (see FIG. 9), which routine maintenance and repair 314 may also include modification, reconfiguration, refurbishment, and other suitable repairs.

Each of the processes of aircraft manufacturing and service method 300 (see fig. 9) may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For purposes of this description, a system integrator may include, but is not limited to, any number of aircraft manufacturers and major-system subcontractors; the third party may include, but is not limited to, any number of suppliers, subcontractors, and suppliers; and the operators may include airlines, leasing companies, military entities, maintenance organizations, and other suitable operators.

As shown in FIG. 10, an aircraft 316 produced by exemplary aircraft manufacturing and service method 300 may include a fuselage 318 having a plurality of systems 320 and interior trim 322. As further shown in fig. 10, embodiments of system 320 may include one or more of a propulsion system 324, an electrical system 326, a hydraulic system 328, and an environmental system 330. Any number of other systems may be included. Although an aerospace embodiment is shown, the principles of the disclosure may be applied to other industries, such as the automotive industry, including motor vehicles, the marine industry, including boats, ships, and submarines, and other suitable industries.

The methods and systems embodied herein may be used during any one or more stages of aircraft manufacturing and service method 300 (see FIG. 9). For example, components or subassemblies corresponding to component and subassembly manufacturing 306 (see FIG. 9) may be manufactured or processed in a manner similar to components or subassemblies produced while aircraft 316 (see FIG. 10) is in service 312 (see FIG. 9). Moreover, one or more method embodiments, system embodiments, or a combination thereof may be utilized during component and subassembly manufacturing 306 (see FIG. 9) and system integration 308 (see FIG. 9), for example, by substantially expediting assembly or reducing costs of aircraft 316 (see FIG. 10). Similarly, when the aircraft 316 (see FIG. 10) is in service 312 (see FIG. 9), for example, but not limiting of, maintenance and repair 314 (see FIG. 9) may be performed using one or more of a method version, a system version, or a combination thereof.

The disclosed version of the PTLA brake system 12 (see fig. 1A-1B, 2A) and method 250 (see fig. 8) mitigates loads 28 (see fig. 2A) or torque loads, such as structural loads 28a (see fig. 2A) and torsional load reaction forces 28B (see fig. 2A), on the pivoting main landing gear 32 (see fig. 2A) of the aircraft 10 during and during the pivot turn maneuver 30 (see fig. 2A) of the aircraft 10 and reduces wear 136 on one or more wheels 46 of the pivoting main landing gear 32 having brakes 58 inhibited by the PTLA brake system 12 and reduces wear 136 on the tires of that wheel 46. In addition, the PTLA braking system 12 inhibits braking on one or more brakes 58 on the pivoting main landing gear 32 to reduce the torsional load reaction force 28b (see fig. 2A) exerted on the pivoting main landing gear 32. Loads 28 (see fig. 2A) or torque loads, such as structural loads 28a (see fig. 2A) and torsional load reactions 28b (see fig. 2A), on the pivoting main landing gear 32 (see fig. 2A) are reduced because only a portion of the brakes 58, such as half of the brakes 58, are applied, while the other portion of the brakes 58 or the other half of the brakes 58 are inhibited or unbraked. The PTLA brake system 12 provides load mitigation for a 2-point turn maneuver or a pivot turn maneuver 30.

Furthermore, the disclosed version of the PTLA brake system 12 (see fig. 1A-1B, 2A) and method 250 (see fig. 8) may also reduce the steering force 134 (see fig. 2A), which in turn reduces the wear 136. The PTLA braking system 12 may also provide U-turn optimization 138 (see fig. 2A) when the inboard wheel 46e (see fig. 2A) is released. An additional advantage of the PTLA braking system 12 is that the overall weight of the main landing gear 24 may also be reduced because various components and materials on the main landing gear 24 may be reduced or eliminated with reduced structural loads 28a and reduced steering forces 134, such as a smaller, reduced weight scissor link, a smaller, reduced weight torque link, or another small size structure on the main landing gear 24, such as pivoting the main landing gear 32. Further, the PTLA brake system 12 reduces braking loads during braking pivot maneuvers or pivot turn maneuvers 30 by the aircraft 10 having the 2-main landing gear configuration 36 (see fig. 1A) to take advantage of individual wheel brake control.

Additionally, the disclosed versions of the ptl brake system 12 (see fig. 1A-1B, 2A) and method 250 (see fig. 8) provide for integration with a taxi brake release function 130 (see fig. 2A) that may already be present or present on the aircraft 10 to obtain a taxi brake release function integration 132 (see fig. 2A). The taxi brake release function 130 selects a predetermined one or more, but not all, of the wheels 46, such as a pair of wheels 46, when making the wheel selection 50 (see fig. 3A-3C), and the PTLA brake inhibit command 90 uses the wheel selection 50 to assist the brake control unit 74 to inhibit braking of one or more, but not all, of the wheels 46, such as the pair 48 of wheels 46, of the pivoting main landing gear 32.

Further, one disclosed version of the ptl brake system 12 (see fig. 1A-1B, 2A) and method 250 (see fig. 8) provides axle pairs 48a of wheels 46 that are side-by-side and share a common axle 49 (see fig. 2A) therebetween. The paired axle release approach with two wheels 46 sharing an axle 49 on the main landing gear 24 on two axles 49 of four wheels 46 is an exemplary scheme or arrangement where half of the wheels 46 are unbraked and restrained by the PTLA brake system 12 and the other half of the wheels 46 are braked during the pivot turn maneuver 30. The PTLA brake system 12 logic may alternate between the pair 48 of front wheels 46c being inhibited and the pair 48 of rear wheels 46d being inhibited on the pivoting main landing gear 32 (see fig. 2A). It should be noted that the PTLA brake system 12 may also inhibit braking of one wheel 46, two wheels 46, three wheels 46, or other suitable number of wheels 46 in the pivot turn maneuver 30 performed by the aircraft 10.

Further, the present disclosure includes embodiments according to the following clauses:

clause 1. an aircraft, comprising:

a body;

one or more wings attached to the fuselage;

a plurality of landing gears attached to the fuselage, the plurality of landing gears including a nose gear and at least two main landing gears, each of the at least two main landing gears having two or more wheels, wherein, during a pivot turn maneuver of the aircraft, one of the at least two main landing gears includes a pivoting main landing gear; and

a pivot turn load mitigation (PTLA) braking system, comprising:

a brake control system operably coupled to the at least two main landing gears, wherein the brake control system controls braking of the at least two main landing gears; and

a pivot turn load mitigation (PTLA) brake inhibit subsystem coupled to the brake control system, wherein the PTLA brake inhibit subsystem inhibits braking of one or more of the two or more wheels of a main landing gear including the pivot main landing gear during the pivot turning maneuver such that at least one of the two or more wheels is in an unbraked state and a remaining number of the two or more wheels are in a braked state,

wherein the PTLA braking system mitigates structural loads on the pivoting main landing gear and reduces wear on the at least one wheel in the unbraked state during a pivot turn maneuver of the aircraft.

Clause 2. the PTLA brake system 12 of clause 1, wherein the at least two main landing gears 24 include a left main landing gear 24a and a right main landing gear 24b, each main landing gear having two pairs 48 of wheels 46, each pair 48 of wheels 46 being disposed on an axle 49.

Clause 3. the PTLA brake system 12 of clause 1, wherein the at least two main landing gears 24 include one of a 2-main landing gear configuration 36, a 3-main landing gear configuration 38, or a 4-main landing gear configuration 40.

Clause 4. the aircraft of clause 3, wherein the PTLA brake inhibit command is disabled upon satisfaction of one or more brake inhibit disable conditions, the one or more brake inhibit disable conditions comprising one or more of:

(a) the aircraft ground speed of the aircraft exceeding the pivot turn load mitigation (PTLA) speed threshold;

(b) both the left and right brake pedal commands exceed a pivot turn load mitigation (PTLA) trigger brake pedal command threshold for at least a predetermined period of time; or

(c) The aircraft enters an active parking brake state.

Many modifications and other embodiments of the disclosure will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. The embodiments described herein are intended to be illustrative and are not intended to be limiting or exhaustive. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Any claimed embodiment of the present disclosure need not necessarily include all embodiments of the present disclosure.