Patent Publication Number: US-2011073706-A1

Title: Aircraft tug

Description:
BACKGROUND 
     The present disclosure relates to ground movement of aircraft, and more particularly to an aircraft tug which moves an aircraft to a desired location without use of aircraft engine power. 
     Aircraft engine power is almost exclusively used to taxi aircraft, typically to or from a runway. Operation of the aircraft engines in a ground environment may be relatively loud and, when used to provide aircraft ground movement, may burn relatively large quantities of fuel. 
     Vehicles often referred to as a tug are typically utilized to facilitate the ground movement of aircraft. The tug is a small manned vehicle which couples to the aircraft nose gear such that the vehicle may push or tow the aircraft. The tug commonly utilizes a separate tow bar system for attachment to the aircraft nose gear. The most typical use for aircraft tugs is pushback from the terminal gate and to tow an aircraft for maintenance operations. 
     SUMMARY 
     An aircraft tug according to an exemplary aspect of the present disclosure includes a tow bar which extends from a chassis, the tow bar operable to autonomously selectively attach with an aircraft main landing gear assembly. 
     A method of taxiing an aircraft according to an exemplary aspect of the present disclosure includes: autonomously selectively attaching a multiple of aircraft tugs to a respective multiple of aircraft main landing gear assemblies; and remotely controlling the multiple of aircraft tugs to taxi the aircraft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
         FIG. 1  is indicative of a aircraft within a typical airport layout by which an aircraft tug may provide the motive force to taxi the aircraft; 
         FIG. 2  is a schematic view of an aircraft tug; 
         FIG. 3  is indicative of an airport layout and designated area for autonomous aircraft tug operations; 
         FIG. 4  is a perspective view of the aircraft tug of  FIG. 2 ; 
         FIG. 5  is a schematic view of another embodiment of an aircraft tug; 
         FIG. 6  is a perspective view of the aircraft tug of  FIG. 5 ; 
         FIG. 7  is a schematic view of one embodiment of an engagement system for the aircraft tug; 
         FIG. 8  is a schematic view of another embodiment of an engagement system for the aircraft tug; 
         FIG. 9  is a flow chart which represents aircraft tug operation for an aircraft arrival; and 
         FIG. 10  is a flow chart which represents aircraft tug operation for an aircraft departure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a general arrangement for remote controlled aircraft movement. The aircraft  10  generally includes a fuselage  12  with a tail  14  and a set a wings  16 . The aircraft also includes a landing gear system  18  which generally includes a nose gear assembly  18 A, and main gear assemblies  18 B. Although a pair of main gear assemblies  18 B is illustrated in the disclosed non-limiting embodiment, it should be understood that aircraft with any number of main gear assemblies  18 B may benefit herefrom. 
     A remotely operated aircraft tug  30 A is coupled to each main gear assembly  18 B in a push arrangement. That is, the remotely operated aircraft tug  30 A may attach aft of the main gear  18 B to essentially push the aircraft  10  and provide the motive force therefore when not under aircraft engine power. Alternatively, the remotely operated aircraft tug  30 A may attach forward of the main gear  18 B to essentially pull the aircraft  10  and provide the motive force therefore when not under aircraft engine power. 
     The aircraft tug  30 A generally includes a power source  32  and a control module  34  ( FIG. 2 ). The power source  32  may include an on-board source such as an internal combustion engine or battery system. The power source  32  may be recharged while docked at the airport gate or between aircraft service events at a docking station within a designated aircraft tug staging area TS ( FIG. 3 ) near an active runway. Alternatively or in addition thereto, the power source  32  may receive power from an off-board source such as an aircraft electrical system E typically generated by an aircraft auxiliary power unit (APU). 
     The control module  34  generally includes a processor, a memory, and an interface. The processor may be any type of known microprocessor having desired performance characteristics. The memory may be any computer readable medium which stores the data and control algorithms described herein. The interface facilitates communication with other tug systems such as a wireless communication system. The functions of the control module  34  are disclosed in terms of functional block diagrams, and it should be understood by those skilled in the art with the benefit of this disclosure that these functions may be enacted in either dedicated hardware circuitry or programmed software routines capable of execution in a microprocessor based electronics control embodiment. 
     The control module  34  provides for operation of the aircraft tug  30 A through wireless communication with a remote control source  20 . The remote control source  20  may be integrated into the aircraft  10  for use by an aircrew  22 , integrated into a fixed airport installation  24  for automated taxi operations, or may be a hand held system for use by a ground crew  26 . The aircraft  10  may be steered by the aircrew  22  through the aircraft flight controls  28 , autonomously through the fixed airport installation  24 , by the off-board ground crew  26  or combinations thereof. For example, the aircraft tugs  30 A may be autonomously positioned for attachment to each main gear assembly  18 B within a taxiway area A, controlled by the aircrew  22  within a designated area B, then positioned within an embark/disembark area C by the groundcrew  26  ( FIG. 3 ). It should be understood that various methodologies for control and operations may alternatively or additionally be provided. 
     The aircraft flight controls  28 , such as rudder pedal system  28 A or nose gear steering tiller  28 B, steers the nose gear  18 A to control the direction of the aircraft  10  with the motive force provided by the aircraft tugs  30 A. In this example, the remote control source  20  need only provide speed control for each aircraft tug  30 A as steering control is achieved directly through the steerable nose gear  18 A under conventional flight controls  28  such as the rudder pedal system  28 A or nose gear steering tiller  28 B. Since an individual aircraft tug  30 A attaches to each of the main gear  18 B, differential traction therebetween may also be utilized to maneuver the aircraft  30 A. Moreover, each aircraft tug  30 A may move independently such that a differential speed of each individual aircraft tug  30 A provides additional aircraft maneuverability than that heretofor achieved. For example, one aircraft tug  30 A may push forward while the other aircraft tug  30 A remains stationary or pulls backward so that the aircraft  10  may be essentially pivoted in place. 
     Movement of the aircraft tugs  30 A may be controlled directly through the aircraft flight controls  28  such as the rudder pedal system  28 A and the throttle quadrant  28 B which communicate through the remote control source  20 . Since multi-engine aircraft include a multiple of throttles, operation of particular throttles, for example, the throttle associated with the port engine may be operable to control the aircraft tug  30 A connected to the port main gear assembly  18 B while the throttle associated with the starboard engine may be operable to control the aircraft tug  30 A connected to the starboard main gear assembly  18 B. Such an arrangement facilitates intuitive aircrew control similar to that utilized when the aircraft is taxied under engine power. 
     Alternatively or in addition thereto, the remote control source  20  provides aircraft tug control independent of the aircraft flight controls  28 . The remote control source  20 , in one non-limiting embodiment, may be a control panel within the cockpit. 
     Referring to  FIG. 2 , the aircraft tug  30 A generally includes the power source  32  and the control module  34  within a chassis  36  which rides upon an undercarriage  38 . The chassis  36  may be a relatively low slung arrangement to readily fit underneath the aircraft  10 . It should be understood that various shapes of chassis may alternatively be provided. The undercarriage  38  may include at least one set of steerable wheels  40  and one set of driven wheels  42  powered by the power source  32 . 
     A tow bar  44  extends from the chassis  36  to engage the respective main gear assemblies  18 B. The tow bar  44  includes a first arm  46 A and a second arm  46 B with a drive drum  48  therebetween. The first arm  46 A and the second arm  46 B may be spaced a fixed distance apart to receive the main gear wheels  18 W therebetween. Alternatively, the first arm  46 A is movable relative to the second arm  46 B such that the tow bar  44  is engageable with various gear systems  18 . 
     The first arm  46 A and the second arm  46 B in the disclosed non-limiting embodiment each include a first arm section  50 A and a second arm section  50 B, the second arm section  50 B angled relative to the first arm section  50 A at an obtuse angle ( FIG. 4 ). The first arm section  50 A may be generally parallel to ground with the second arm section  50 B angled toward the ground. The second arm section  50 B on either or both the first arm  46 A and the second arm  46 B includes an engagement system  52  operable to engage the main gear assembly  18 B. The engagement system  52  selectively engages and disengages with the respective main gear assembly  18 B generally around the landing gear tires  18 T. The engagement system  52  may selectively engage and disengage with a hollowed end section of an axle  18 WA or other portion of the main gear assembly  18 B. The engagement system  52  may be of various forms, such as a link, connector, clevis or other attachment. Such an arrangement may be advantageous for main gear assemblies with single or double wheels typical of relatively smaller aircraft. 
     The drive drum  48  is powered by the power source  32  to rotate about an axis of rotation D. When the engagement system  52  is engaged with the main gear assembly  18 B, the drive drum  48  is operable to transfer rotation to the main gear tires  18 T of the main gear wheels  18 W and thereby move the aircraft  10 . The drive drum  48  may include a resilient material such as rubber or a machined surface such as serrations or knurling so as to provide significant traction to the main gear tires  18 T without damage thereto. 
     Whereas the tow bar  44  is attached to the main gear assembly  18 B, the motive force may alternatively or additionally be communicated directly through the drive drum  48 . The steerable wheels  40  and the driven wheels  42  permit controlled independent movement of the aircraft tug  30 A when not attached to the main gear assemblies  18 B. When attached to the main gear assembly  18 B, the drive drum  48  may alternatively or additionally be rotated to rotate the main gear tires  18 T and thus move the aircraft  10 . The extended tow bar  44  and chassis  36  readily operate as a counterbalance for power transfer to the drive drum  48 . 
     Referring to  FIG. 5 , an alternative non-limiting embodiment the aircraft tug  30  includes a tow bar  44 ′ with a drive drum  48 ′ which extends from at least one side. In this non-limiting embodiment, the tow bar  44 ′ include an engagement system  52 ′ operable to engage the respective main gear assembly  18 B. The engagement system  52 ′ selectively engages and disengages with the main gear assembly  18 B generally between the landing gear tires  18 T (also illustrated in  FIG. 6 ). The engagement system  52 ′ may selectively engage and disengage with a landing gear component  18 S such as a strut, bogie beam or other portion of the main gear assembly  18 B. Such an arrangement may be advantageous for main gear assemblies with a multiple of wheels typical of larger aircraft. 
     The aircraft tug  30  may additionally provide all or some aircraft ground electric power for a more electric aircraft while attached to the aircraft tug  30 . A tug power connector  54  on the tow bar  44 ′ may be utilized to connect the power source  32  with the aircraft electrical system E. An aircraft ground electric power connection  18 E may be located on the main gear assembly  18 B in a position accessible by the tug power connector  54  such that power is communicated between the aircraft tug  30  and the aircraft electrical system E when engagement with the main gear assembly  18 B is established. The tug power connector  54 , in one non-limiting embodiment, may be integrated with the engagement system  52 ′ 
     Power for ground operation of aircraft environmental control system, lighting, hydraulic electric motor pumps, communication, navigation, lavatory operation, engine start and other requirements may thus be provided by the aircraft tug  30 . The aircraft APU thus need not be operated at airports where such aircraft tugs  30  are provided—typically the busiest and thus the highest emission airports. Minimal additional aircraft weight is required for the aircraft ground electric power connection  18 E. Maintenance of the aircraft tug and ground power system is on a per aircraft tug basis and will thereby not impact aircraft availability. 
     Referring to  FIG. 7 , one non-limiting embodiment of the engagement system  52 A is operable to engage the landing gear component  18 S of the respective main gear assembly  18 B through a receiver  18 R on the main landing gear bogie beam  18 Bb. The engagement system  52 A may be used with or without the drive drum  48 . 
     The engagement system  52 A extends from the tow bar  44 ′ for insertion at least partially into the receiver  18 R as the aircraft tug  30  tug approaches the main gear assembly  18 B. In addition, a latch system  54  includes a latch actuator  56  and a receiver latch  58 . The latch actuator  56 , such as a pneumatic, hydraulic, electric or mechanical actuator drives the receiver latch  58  at least partially around the receiver  18 R. The receiver latch  58  may at least partially surround the receiver  18 R opposite the area within which the engagement system  52 A extends into the receiver  18 R to provide for fore and aft force transfer from the aircraft tug  30  to the main gear assembly  18 B. 
     After the tow bar  44 ′ is latched to the main gear assembly  18 B, a weight transfer system  60  is actuated to raise the tow bar  44 ′ relative to the chassis  36 . A weight transfer actuator  62  actuator such as a pneumatic, hydraulic, electric or mechanical actuator drives displaces the tow bar  44 ′ on the chassis  36  with respect to the undercarriage  38  along a vertical guide system  64  such as a roller system which may include a vertical guide  66  on the chassis  36  an a roller system  68  on the tow bar  44 ′ which engages the vertical guide. The weight transfer actuator  62  effectively transfers a vertical load from the main gear assembly  18 B to the aircraft tug  30  to increase traction on the undercarriage  38  to reduce the deadweight requirements for the aircraft tug  30  yet provide sufficient normal force for traction. Should slip be detected, the vertical force from the weight transfer system  60  may be adjusted to maintain a desired balance. 
     The weight transfer system  60  may be further adjusted so that the aircraft tug  30  rotates about the axle closest to the main gear assembly  18 B after engagement to increase force on the driven wheels  42  and lift the far, steerable wheels  40  to reduce a yaw force from potential transfer to the main gear assembly  18 B. When disengaged from the main gear assembly  18 B, the aircraft tug  30  rests on both sets of wheels  40 ,  42 . 
     Referring to  FIG. 8 , another non-limiting embodiment of an engagement system  52 B is operable to engage the landing gear component  18 S of the respective main gear assembly  18 B through a receiver  18 R on the main landing gear bogie beam  18 Bb. The engagement system  52 B may be used with or without the drive drum  48 . 
     The receiver  18 R in this non-limiting embodiment includes a set of pins  18 P which are displaced vertically relative to the main landing gear bogie beam  18 Bb. The tow bar  44  includes a first tow bar section  44 A and a second tow bar section  44 B. 
     The first tow bar section  44 A and the second tow bar section  44 B are respectively actuated by a respective actuator  70 A,  70 B such as a pneumatic, hydraulic, electric or mechanical actuator in an upward direction to engage the pins  18 P from below relative to ground to thereby provide for fore and aft force transfer from the aircraft tug  30  to the main gear assembly  18 B. The engagement arrangement provided by the first tow bar section  44 A and the second tow bar section  44 B integrates the weight transfer discussed above to effectively transfer a vertical load from the main gear assembly  18 B to the aircraft tug  30  to increase traction on the undercarriage  38  to reduce the deadweight requirements for the aircraft tug  30  yet provide sufficient normal force for traction. The first tow bar section  44 A and the second tow bar section  44 B also permits independent adjustment as discussed above so that the aircraft tug  30  rotates about the axle closest to the main gear assembly  18 B after engagement to increase force on the driven wheels  42  and lift the far, steerable wheels  40  and to reduce a yaw force from potential transfer to the main gear assembly  18 B. 
     Referring to  FIG. 9 , when the aircraft  10  lands and reaches the taxiway area A, the aircraft tugs  30 A assigned by the fixed airport installation  24  or other system are autonomously positioned and attach to each main gear assembly  18 B. The aircraft tugs then signal that control is transferred to the aircrew  22  to provide the motive force to move the aircraft  10  within the designated area B. The aircrew may then shut down the aircraft engines. When the aircraft  10  reaches an embark/disembark area C, the aircraft  10  may be finally positioned by the groundcrew  26 , the aircrew  22 , or autonomously through the fixed airport installation  24 . That is, control of the aircraft tugs may be handed off from the aircrew  22  to the ground crew  26  or another local system to autonomously position the aircraft  10 . 
     Referring to  FIG. 10 , from the embark/disembark area C, the procedure is essentially reversed so that once pushback occurs, control of the aircraft tugs may be handed off from the ground crew  26  or the local system to the aircrew  22  to permit the aircrew  22  to taxi out to the designated departure runway. When the aircrew  22  reaches a desired location off the departure runway such as the taxiway area A, the aircrew  22  may start engines and perform a preflight check. Once complete, the aircrew  22  will then signal for the aircraft tugs to detach. The aircraft tugs may then autonomously return to the designated aircraft tug staging area TS ( FIG. 3 ) at which the aircraft tug may recharge if need be. It should be understood that various methodologies for control and operations may alternatively or additionally be provided to include for example, that the tug  30  is driven manually under some circumstances. 
     As it may not be appropriate for the aircraft tugs to be placed on an active runway; and aircraft typically require a warm-up and preflight check period, the taxiway area A may be remote from the active runway which still requires aircraft to taxi under their own power. However, such operations as those described herein significantly reduces aircraft idle and taxi time when under their own power. 
     It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting. 
     It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
     Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure. 
     The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.