Patent Publication Number: US-2018029707-A1

Title: Cargo handling system, method and apparatus

Description:
TECHNOLOGICAL FIELD 
     The presently disclosed subject matter relates to cargo handling systems, methods and apparatuses, particularly for freight aircraft. 
     BACKGROUND 
     Cargo aircraft routinely transport cargo (also referred to herein as air freight) over national and international routes. Such cargo is often containerized and secured on standardized pallets, which can be loaded, secured and unloaded from the aircraft freight deck using respective cargo handling systems (CHS). 
     Conventional aircraft CHS can be classified into two general categories: manual handling systems; powered handling systems. 
     Manual CHS often include a plurality of rollers and/or castors and/or ball transfer units (BTU) set on the floor of the freight deck, and pallets supporting the cargo are manually moved over the rollers and/or castors, and secured in place with ropes, belts, or other locking devices. 
     Powered CHS conventionally include a conveyor system that is built into the floor of the freight deck of the aircraft and which move the standardized cargo pallets over the floor of the freight deck. For example, powered drive units (PDU) statically located on the freight deck provide a series of longitudinally spaced powered drive wheels on the floor that in turn engage the underside of the standardized pallets and horizontally move the standardized pallet in a variety of horizontal directions on the freight deck. When at the desired locations, the cargo pallets are secured thereat via a plurality of locking devices that lock onto a peripheral lip of the pallet. 
     By way of non-limiting examples, the following publications disclose cargo handling systems or components related thereto: U.S. Pat. No. 3,741,504, U.S. Pat. No. 3,978,975, U.S. Pat. No. 6,557,800, U.S. Pat. No. 3,906,870. 
     GENERAL DESCRIPTION 
     According to a first aspect of the presently disclosed subject matter, there is provided a cargo handling system for a freight deck of an aircraft, comprising:
         support structure configured for at least partially supporting at least one cargo unit thereon;   at least one mobile transport apparatus configured for selectively moving over the freight deck to at least one or to a plurality of locations thereon, for selectively engaging to the at least one cargo unit, for selectively propelling said at least one cargo unit over said freight deck while the apparatus is engaged to the at least one cargo unit, for enabling said at least one cargo unit to be deposited at a desired said location supported on said support structure, and for selectively disengaging from the at least one cargo unit;   a plurality of locking devices configured for selectively releasably locking the at least one cargo unit with respect to the freight deck at said desired location.       

     The cargo handling system according to the aforesaid first aspect of the presently disclosed subject matter can comprise one or more of the following elements or features. 
     For example, each said mobile transport apparatus can comprise a releasable engagement system for selectively engaging with and disengaging from said at least one cargo unit, and a powered drive unit configured for selectively propelling the respective said mobile transport apparatus over the freight deck. For example, said powered drive unit comprises a plurality of wheels rotatably mounted thereto and configured for rolling over the freight deck. For example, said wheels are operatively connected to powered drive for turning said wheels. 
     Optionally, said wheels are mounted to a chassis member such that the rotational axes of said wheels are in parallel relationship with one another, and further optionally, said wheels comprise any one of omni wheels, poly wheels and Mecanum wheels. 
     Alternatively, said wheels are mounted to a chassis member such that the rotational axes of said wheels are not all in parallel relationship with one another, and further optionally, said wheels comprise any one of omni wheels, poly wheels and Mecanum wheels. For example, said wheels are mounted to a chassis member such that the rotational axes of said wheels are in non-parallel relationship with one another. For example, the mobile transport system comprises at least one set of wheels, each set comprising four said wheels mounted to a chassis member such that the rotational axes of two said wheels are in orthogonal relationship with the rotational axes of the other two said wheels. Alternatively, the mobile transport system comprises at least one set of wheels, each set comprising three said wheels mounted to a chassis member in triangular arrangement. 
     Additionally or alternatively to the above, in at least one example of the cargo handling system, said wheels are rotatably mounted with respect to the apparatus in fixed orientation with respect thereto, and wherein a rotational direction and turning velocity of each wheel are each independently controllable to enable the mobile transport apparatus to move in any desired direction over the freight deck. 
     Additionally or alternatively to the above, in at least one example of the cargo handling system, said support structure comprises at least one pair of parallel spaced support rails configured for at least partially supporting said at least one cargo unit thereon while allowing said at least one cargo unit to move over said spaced support rails. For example, said support rails comprise rollers rotatably mounted to an upper part thereof, such as to allow said at least one cargo unit to move over said spaced support rails with said rollers in rolling contact with said at least one cargo unit. 
     Additionally or alternatively to the above, in at least one example of the cargo handling system, said mobile transport apparatus is configured for propelling the said at least one cargo unit when said at least one cargo unit is in overlying relationship therewith. For example, parts of said mobile transport apparatus in overlying relationship with said at least one cargo unit have a height dimension from the freight deck not exceeding a datum height dimension defined by said support structure. 
     Additionally or alternatively to the above, in at least one example of the cargo handling system, said releasable engagement system is configured for releasably engaging with an underside of said at least one cargo unit. For example, said releasable engagement system comprises an apparatus height changing system, configured for selectively changing the height of said mobile transport apparatus from a first height, less than said datum height dimension, to a second height, not less than said datum height dimension. Additionally or alternatively, said releasable engagement system comprises a cam arrangement pivotably mounted to the chassis member and operatively connected to a vertically displaceable upper cargo unit contact plate, and wherein said cam arrangement comprises a plurality of cams that are selectively are reversibly pivotable while in urging contact with said contact plate to thereby vary the height of the contact plate. Additionally or alternatively, said releasable engagement system is configured for selectively changing the height dimension of said mobile transport apparatus via any one of a jack arrangement, an inflatable arrangement a scissor lift mechanism, and a pivotable arrangement for said wheels. 
     Additionally or alternatively to the above, in at least one example of the cargo handling system, said mobile transport apparatus is configured having a height between 2 inches and 5 inches. 
     Additionally or alternatively to the above, in at least one example of the cargo handling system, said mobile transport apparatus is configured for propelling the said at least one cargo unit when said at least one cargo unit is in at least partially juxtaposed relationship therewith. 
     Additionally or alternatively to the above, in at least one example of the cargo handling system, said releasable engagement system is configured for selectively clamping with respect to a peripheral lip of the cargo unit. 
     Additionally or alternatively to the above, in at least one example of the cargo handling system, the respective cargo handling system further comprises a controller configured for remotely controlling operation of at least said mobile transport apparatus. 
     Additionally or alternatively to the above, in at least one example of the cargo handling system, the respective cargo handling system further comprises a guiding system configured for guiding said at least one mobile transport apparatus with respect to the freight deck. For example, said guiding system comprises guiding rails configured for constraining movement of said wheels to said guiding rails. Additionally or alternatively, said guiding system comprises a sensor arrangement configured for providing control signals to said mobile transport apparatus for controlling movement thereof along a predetermined path over the freight deck. 
     Additionally or alternatively to the above, in at least one example of the cargo handling system, said mobile transport apparatus comprises at least one of:
         a battery, the system further comprising a recharging system, including a recharger docking station provided in the freight deck and connected to a power supply and a docking head provided in the mobile transport apparatus, the docking head and docking station being configured for establishing electrical connection with one another when said docking head docks with said docking station; and   electrical cables reversibly wound on a spool, the spool being mounted to one of the mobile transport apparatus and the freight deck, and wherein electrical power is provided to the mobile transport apparatus by a power source in the aircraft or outside of the aircraft via said electrical cables, and wherein the electrical cables are spooled in or out according to the relative location of the mobile transport apparatus with respect to the freight deck.       

     Additionally or alternatively to the above, in at least one example of the cargo handling system, the aircraft has a side freight entrance to the freight deck, and the respective cargo handling system further comprises a plurality of BTU&#39;s and/or a plurality of pivotable PDU&#39;s on a portion of the freight deck facing the side freight entrance. 
     Additionally or alternatively to the above, in at least one example of the cargo handling system, said cargo unit is in the form of, or comprises, a pallet. 
     Additionally or alternatively, the cargo handling system comprises a wireless control system for wirelessly controlling operation of said transport apparatus. 
     For example, the wireless control system according to the first aspect of the presently disclosed subject matter can comprise one or more of the elements or features as disclosed herein with respect to the wireless control system according to the second aspect of the presently disclosed subject matter, mutatis mutandis. 
     Additionally or alternatively, said cargo handling system comprises a sensor system configured for outputting an alignment signal representative of an alignment of the cargo unit with respect to the support structure. For example the sensor system according to the first aspect of the presently disclosed subject matter can comprise one or more of the elements or features as disclosed herein with respect to the sensor system according to the third aspect of the presently disclosed subject matter, mutatis mutandis. 
     According to the aforesaid first aspect of the presently disclosed subject matter, there is also provided a mobile transport apparatus for use with a cargo handling system for a freight deck of an aircraft, the mobile transport apparatus configured for selectively moving over the freight deck to a plurality of locations thereon, for selectively engaging to at least one cargo unit, for propelling said at least one cargo unit over said freight deck when the apparatus is engaged to the at least one cargo unit, for depositing said at least one cargo unit on a desired said location supported on a support structure provided on the freight deck, and for selectively disengaging from the at least one cargo unit. 
     The mobile transport apparatus according to the aforesaid first aspect of the presently disclosed subject matter can comprise one or more of the following elements or features. 
     For example, the mobile transport apparatus comprises a releasable engagement system for selectively engaging with and disengaging from said at least one cargo unit, and a powered drive unit configured for selectively propelling the respective said mobile transport apparatus over the freight deck. 
     Additionally or alternatively to the above, said mobile transport apparatus is configured for propelling the said at least one cargo unit when said at least one cargo unit is in overlying relationship therewith or in at least partially juxtaposed relationship therewith. For example, parts of said mobile transport apparatus in overlying relationship with said at least one cargo unit have a height dimension from the freight deck not exceeding a datum height dimension defined by the support structure. 
     Additionally or alternatively to the above, said mobile transport apparatus is configured having a height between 2 inches and 5 inches. 
     Additionally or alternatively to the above, said mobile transport apparatus further comprises a controller configured for enabling remotely controlling operation thereof. 
     Additionally or alternatively to the above, the mobile transport apparatus can further optionally comprise a guiding system configured for guiding said mobile transport apparatus with respect to the freight deck. 
     Additionally or alternatively to the above, said mobile transport apparatus can comprise at least one of:
         a battery, and further comprising a recharging system, including a recharger docking station provided in the freight deck and connected to a power supply and a docking head provided in the mobile transport apparatus, the docking head and docking station being configured for establishing electrical connection with one another when said docking head docks with said docking station; and   electrical cables reversibly wound on a spool, the spool being mounted to one of the mobile transport apparatus and the freight deck, and wherein electrical power is provided to the mobile transport apparatus by a power source in the aircraft or outside of the aircraft via said electrical cables, and wherein the electrical cables are spooled in or out according to the relative location of the mobile transport apparatus with respect to the freight deck.       

     Additionally or alternatively to the above, said cargo unit is in the form of, or comprises, a pallet. 
     Additionally or alternatively, said mobile transport apparatus comprises a wireless control system for wirelessly controlling operation of said transport apparatus. 
     For example, the wireless control system according to the first aspect of the presently disclosed subject matter can comprise one or more of the elements or features as disclosed herein with respect to the wireless control system according to the second aspect of the presently disclosed subject matter, mutatis mutandis. 
     Additionally or alternatively, said mobile transport apparatus comprises a sensor system configured for outputting an alignment signal representative of an alignment of the cargo unit with respect to the support structure. For example the sensor system according to the first aspect of the presently disclosed subject matter can comprise one or more of the elements or features as disclosed herein with respect to the sensor system according to the third aspect of the presently disclosed subject matter, mutatis mutandis. 
     According to the aforesaid first aspect of the presently disclosed subject matter, there is also provided a method for handling cargo units on a freight deck of an aircraft, comprising:
         causing at least one mobile transport apparatus to move over the freight deck to at least one of a plurality of locations thereon;   selectively engaging the at least one mobile transport apparatus to the at least one cargo unit at one said location;   propelling said at least one cargo unit over said freight deck to a second said location while the at least one mobile transport apparatus is engaged to the at least one cargo unit;   selectively disengaging the mobile transport apparatus from the at least one cargo unit; and   depositing said at least one cargo unit at said second location on the freight deck.       

     The method according to the aforesaid first aspect of the presently disclosed subject matter can comprise one or more of the following elements or features. 
     For example, the method can comprise:
         providing a support structure on the flight deck and comprising the step of depositing said at least one cargo unit at said second location on said support structure on the freight deck; and   selectively releasably locking the at least one cargo unit with respect to the freight deck at said second location.       

     Additionally or alternatively, the method can comprise controlling the motion of the mobile transport apparatus over the freight deck in any one of a manual manner, an automatic manner, an autonomous manner and via remote control. 
     Additionally or alternatively, the method can comprise at least one of:
         inserting a said cargo unit into the freight deck via a side entrance of the aircraft, steering said mobile transport apparatus towards said cargo unit, engaging said cargo unit and steering the mobile transport apparatus to a desired location along a desired cargo path defined on the freight deck, depositing said cargo unit thereat, and disengaging said mobile transport apparatus from said cargo unit;   inserting a said cargo unit into the freight deck via a side entrance of the aircraft, aligning and directing said cargo unit, towards a desired rectilinear cargo path defined on the freight deck, engaging said cargo unit and to said mobile transport apparatus on said cargo path, propelling said mobile transport apparatus to a desired location along a desired cargo path while engaged to the cargo unit, depositing said cargo unit thereat, and disengaging said mobile transport apparatus from said cargo unit;   inserting a said cargo unit into the freight deck via a nose or tail entrance of the aircraft, steering said mobile transport apparatus towards said cargo unit, engaging said cargo unit and steering the mobile transport apparatus to a desired location along a desired cargo path defined on the freight deck, depositing said cargo unit thereat, and disengaging said mobile transport apparatus from said cargo unit.       

     Additionally or alternatively, the method can comprise the step in which said mobile transport apparatus propels the said at least one cargo unit when said at least one cargo unit is in overlying relationship therewith or in at least partially juxtaposed relationship therewith. 
     Additionally or alternatively, the method can comprise selectively changing the height of said mobile transport apparatus from a first height, less than a spacing of a space between the cargo unit and the freight deck, introducing the mobile transport apparatus into said space so that said cargo unit is overlying said mobile transport apparatus, to a second height, greater than said first height, wherein to engage with an underside of the cargo unit. 
     Additionally or alternatively, in the method said cargo unit is in the form, of or comprises a pallet. 
     According to a second aspect of the presently disclosed subject matter, there is also provided a cargo handling system for a freight deck of an aircraft, comprising:
         support structure configured for at least partially supporting at least one cargo unit thereon over the freight deck;   transport apparatus configured for selectively transporting the at least one cargo unit over said support structure;   wireless control system for wirelessly controlling operation of said transport apparatus.       

     The cargo handling system according to the aforesaid second aspect of the presently disclosed subject matter can comprise one or more of the following elements or features. 
     For example, the cargo handling system can further comprise a plurality of locking devices configured for selectively releasably locking the at least one cargo unit with respect to the freight deck at a desired location. 
     Additionally or alternatively, said transport apparatus comprises a mobile transport apparatus configured for selectively moving over the freight deck to a plurality of locations thereon, for selectively engaging to said at least one cargo unit, for propelling said at least one cargo unit over said freight deck when the mobile transport apparatus is engaged to the at least one cargo unit, for depositing said at least one cargo unit on a desired said location supported on said support structure, and for selectively disengaging from the at least one cargo unit. For example the mobile transport apparatus according to the second aspect of the presently disclosed subject matter can comprise one or more of the elements or features as disclosed herein with respect to the mobile transport apparatus according to the first aspect of the presently disclosed subject matter, mutatis mutandis. Alternatively, said transport apparatus comprises a plurality of powered drive units (PDU&#39;s) statically located on the freight deck and longitudinally spaced parallel to said support structure, each PDU comprising a powered drive wheel configured for selectively engaging an underside of the at least one cargo unit for moving the at least one cargo unit over said support structure. 
     Additionally or alternatively, said wireless control system comprises a transmitter unit remote from a receiver unit, said receiver unit being operatively coupled to the transport apparatus and configured for controlling operation of the transport apparatus responsive to receiving control signals transmitted from said transmitter unit. For example, said control signals include electromagnetic signals, for example radio signals, infra-red signals, microwave signals, and so on. 
     Additionally or alternatively, said cargo handling system comprises a sensor system configured for outputting an alignment signal representative of an alignment of the cargo unit with respect to the support structure. For example the sensor system according to the second aspect of the presently disclosed subject matter can comprise one or more of the elements or features as disclosed herein with respect to the sensor system according to the third aspect of the presently disclosed subject matter, mutatis mutandis. 
     According to a third aspect of the presently disclosed subject matter, there is also provided a cargo handling system for a freight deck of an aircraft, comprising:
         support structure configured for at least partially supporting at least one cargo unit thereon over the freight deck;   sensor system configured for outputting an alignment signal representative of an alignment of the cargo unit with respect to the support structure.       

     The cargo handling system according to the aforesaid third aspect of the presently disclosed subject matter can comprise one or more of the following elements or features. 
     For example, said alignment comprises a degree of alignment between cargo unit and the support structure compared with an ideal alignment, and said alignment signal is representative of said degree of alignment. For example, said ideal alignment occurs where the cargo unit is sufficiently aligned with respect to the support structure to enable the cargo unit to be moved over and supported by the support structure. 
     Additionally or alternatively, said sensor system comprises a first component coupled to the at least one cargo unit and a second component coupled to the support structure, wherein said first component interacts with said second component to generate said alignment signal. For example:
         one of said first component and second component comprises a transmitter and wherein the other one of said first component and second component comprises a receiver, and wherein said receiver transmits energy to said receiver, and wherein a parameter of said energy varies as a function of said degree of alignment wherein to generate said alignment signal;       

     or:
         said first component comprises an image acquisition system and second component comprises a visual marker representative of said ideal alignment, and wherein said image acquisition system obtains and processes images of said visual marker wherein to generate said alignment signal.       

     Additionally or alternatively, said alignment signal is at least one of an audio signal and a visual signal to guide manual manipulation of the cargo unit into alignment with the support structure. 
     Additionally or alternatively, the cargo handling system further comprises a mobile transport apparatus configured for selectively moving over the freight deck to a plurality of locations thereon, for selectively engaging to the at least one cargo unit, for propelling the at least one cargo unit over said freight deck when the mobile transport apparatus is engaged to the at least one cargo unit, for depositing the at least one cargo unit on a desired said location supported on said support structure, and for selectively disengaging from the at least one cargo unit, wherein said alignment signal is at least one of a digital signal and an electromagnetic signal to, and wherein said mobile transport apparatus is further configured for controlling movement of the cargo unit into alignment with the support structure responsive to said alignment signal. For example the mobile transport apparatus according to the third aspect of the presently disclosed subject matter can comprise one or more of the elements or features as disclosed herein with respect to the mobile transport apparatus according to the first aspect of the presently disclosed subject matter, mutatis mutandis. 
     Additionally or alternatively, the cargo handling system comprises
         transport apparatus configured for selectively transporting the at least one cargo unit over said support structure;   wireless control system for wirelessly controlling operation of said transport apparatus.       

     For example the transport apparatus according to the third aspect of the presently disclosed subject matter can comprise one or more of the elements or features as disclosed herein with respect to the transport apparatus according to the second aspect of the presently disclosed subject matter, mutatis mutandis. 
     Additionally or alternatively, for example, the wireless control system according to the third aspect of the presently disclosed subject matter can comprise one or more of the elements or features as disclosed herein with respect to the wireless control system according to the second aspect of the presently disclosed subject matter, mutatis mutandis. 
     A feature of at least some examples of the presently disclosed subject matter is that the respective cargo handling system can shorten the time and/or the manpower required for loading and/or for unloading cargo with respect to an aircraft, as compared with conventional CHS installed in the same type of aircraft. 
     Another feature of at least some examples of the presently disclosed subject matter is that in the case of malfunction, servicing, or maintenance of the respective mobile transport apparatus, this can be replaced with another mobile transport apparatus, and thus enable the aircraft to proceed with loading/unloading in a relatively short time. 
     Another feature of at least some examples of the presently disclosed subject matter is that the weight of the respective cargo handling system can be significantly less than the weight of a conventional cargo handling system. 
     Another feature of at least some examples of the presently disclosed subject matter is that the respective mobile transport apparatus can be controlled remotely by an operator, and can have its own power unit, and thus requires little if any of the infrastructure that is specifically required with conventional CHS. This enables these examples of the cargo transport system to be installed in the cargo deck of an aircraft with a minimum of modification of the cargo deck, not requiring (or at least minimizing the need for) conventional CHS ducting, cables, wiring, control panels, PDU&#39;s, etc. to be installed in the cargo deck itself. Less installation tasks are thus required during manufacture of a cargo aircraft or when converting a passenger aircraft to a cargo aircraft, than are required with conventional CHS. This considerably simplifies the installation of the respective cargo handling system in the aircraft, which can be accomplished in much faster manner and at less cost than with conventional CHS. 
     Another feature of at least some examples of the presently disclosed subject matter is that the respective cargo handling system provides an improvement in reliability as compared with conventional CHS installed in the same type of aircraft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to understand the disclosure and to see how it may be carried out in practice, examples will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is an isometric view of a pallet or cargo unit, for use with examples of the cargo handling system of the presently disclosed subject matter. 
         FIG. 2  is a plan view of a cargo handling system according to a first example of the presently disclosed subject matter;  FIG. 2( a )  is a plan view of a cargo handling system according to a variation of the example of  FIG. 2 ;  FIG. 2( b )  is a partial isometric view of the example of  FIG. 2  used with two cargo units in side-by-side relationship;  FIG. 2( c )  is a partial isometric view of the example of  FIG. 2  used with one wide cargo unit using two mobile transport apparatuses in side-by-side relationship, shown without the wide cargo unit in  FIG. 2( d ) . 
         FIG. 3( a )  illustrates in isometric top view a first example of the mobile transport apparatus of the system of  FIG. 2 ;  FIG. 3( b )  illustrates in isometric bottom view the mobile transport apparatus of  FIG. 3( a )  engaged to a cargo unit;  FIG. 3( c )  illustrates in bottom view the mobile transport apparatus of  FIG. 3( a )  engaged to a cargo unit;  FIG. 3( d )  illustrates in cross-sectional side view of an example of a releasable engagement system of the mobile transport apparatus of  FIG. 3( a ) . 
         FIG. 4  illustrates in front view the example of  FIG. 2 , wherein the respective deployable mechanical abutment member is in its retracted position. 
         FIG. 5  illustrates in front view the example of  FIG. 2 , wherein the respective deployable mechanical abutment member is in its deployed position. 
         FIGS. 6( a ) and 6( b )  illustrate in side view an alternative variation of the example of a releasable engagement system of  FIG. 3( d ) . 
         FIG. 7  illustrates in side view an alternative variation of the example of a releasable engagement system of  FIG. 3( d ) . 
         FIG. 8  illustrates in side view another alternative variation of the example of a releasable engagement system of  FIG. 3( d ) . 
         FIG. 9  illustrates in side view another alternative variation of the example of a releasable engagement system of  FIG. 3( d ) . 
         FIGS. 10( a ) and 10( b )  illustrate in side view another alternative variation of the example of a releasable engagement system of  FIG. 3( d ) . 
         FIGS. 11( a ) and 11( b )  illustrate in side view another alternative variation of the example of a releasable engagement system of  FIG. 3( d ) . 
         FIG. 12  is a partial plan view of a cargo handling system according to a second example of the presently disclosed subject matter. 
         FIG. 13  is a side view of an example of a transport apparatus comprised in the cargo handling system example of  FIG. 12 ;  FIG. 13( a )  is a side view of an alternative example of a transport apparatus comprised in the cargo handling system example of  FIG. 12 ;  FIG. 13( b )  is a side view of another alternative example of a transport apparatus comprised in the cargo handling system example of  FIG. 12 . 
         FIG. 14  is a partial plan view of a cargo handling system according to a third example of the presently disclosed subject matter. 
         FIG. 15  is a side view of an example of a transport apparatus comprised in the cargo handling system example of  FIG. 14   
         FIG. 16  is a bottom view of transport apparatus example of  FIG. 15 . 
         FIGS. 17( a ) to 17( f )  schematically illustrate various translational and rotational movements of the transport apparatus example of  FIG. 15  obtained with combinations of motions of the wheels thereof;  FIG. 17( g )  schematically illustrates the direction of motion of a wheel of transport apparatus example of  FIG. 15 . 
         FIG. 18( a )  is a side view of an alternative example of a transport apparatus comprised in the cargo handling system example of  FIG. 14 ;  FIG. 18( b )  is a side view of another alternative example of a transport apparatus comprised in the cargo handling system example of  FIG. 14 . 
         FIG. 19  is a partial plan view of a cargo handling system according to a fourth example of the presently disclosed subject matter. 
         FIG. 20  is a top isometric view of an alternative example of the guiding system of the cargo handling system example of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a particular type of standardized cargo pallet (interchangeably referred to herein as a loading platform), generally designated with the reference character P, is illustrated in  FIG. 1 . Such a pallet P is in the form of a rectangular plate member, having width W, length L, nominal thickness t, and peripheral edge E. The pallet P defines a cargo-loading area A on its upper face UF, and, cargo C can be affixed in place on area A. Area A is spaced from edge E by a peripheral lip Q, which circumscribes the area A. The peripheral lip Q is configured for being engaged with locking devices on the freight deck of an aircraft, as is known in the art. In some cases, standardized cargo containers (e.g. unit load devices (ULD)) have an integral pallet formed therewith, and each standardized cargo container comprises a respective peripheral lip configured for engaging with the aforesaid locking devices. In some commonly used pallets, the plan area of the pallet (W×L) can be any one of: 125 inch×96 inch, or 125 inch×88 inch, or 156.2 cm×153.4 cm. 
     While the following disclosure refers to cargo units in the form of the aforesaid pallet P (with or without cargo affixed thereto), it is to be noted that the disclosure applies, mutatis mutandis, to other types of pallets, and also to other types of cargo units, that can be handled by at least some examples of the system, method and apparatus of the presently disclosed subject matter. 
     Referring to  FIG. 2 , a cargo handling system  10  for handling each of a plurality of cargo units, according to a first example of the first aspect of the presently disclosed subject matter, comprises one (or more) mobile transport apparatus  100  (also interchangeably referred to herein as “apparatus” or as “transport apparatus”), a cargo support system  200 , a guiding system  300 , and a plurality of locking devices  400  located on the freight deck D. Each cargo unit comprises or is securely carried on a respective pallet P, with respect to a cargo storage path CS defined on the freight deck D of an aircraft AC. 
     In this example, the aircraft AC comprises a cargo door CD on one side of the aircraft for loading and unloading the cargo (via pallets P) with respect to the fright deck D, and there are four cargo storage paths CS defined on the freight deck D, designated CS 1 , CS 2 , CS 3 , CS 4 , originating from a pallet turning and alignment area S located on the freight deck D in the vicinity of the side cargo door CD of the aircraft. Two cargo storage paths CS 1 , CS 2  are generally parallel to one another and to the centerline CL of the aircraft, and extend forward of the pallet turning and alignment area S, and the other two cargo storage paths CS 3 , CS 4  are generally parallel to one another and to the centerline CL of the aircraft, and extend aft of the pallet turning and alignment area S. Such cargo storage paths CS are configured for pallets P that are of a suitable size to fit within less than a half-width of the freight deck D, so that two rows of pallets P are loadable onto the juxtaposed pairs of cargo storage paths CS 1 , CS 2  (or the juxtaposed pairs of cargo storage paths CS 3 , CS 4 ), in side-by-side configuration, as illustrated in  FIG. 2( b )  for example. In alternative variations of this example other configurations for one or more cargo storage paths can be defined instead. 
     Referring also to  FIG. 4 , the cargo support system  200  comprises at least one pair of parallel support rails  220 , arranged along each respective cargo storage path CS. Each rail  220  comprises a plurality of rollers  230  rotatably mounted thereto such that an upper part of the rollers  230  project above the rails  220 . The rollers  230  are spaced longitudinally along the length of the rails  220  and having their respective rolling axes orthogonal to the longitudinal direction of the rails  220 . The rails  220  are spaced apart by spacing R, and are configured for supporting all, or at least a majority of, the weight of each pallet P (together with its cargo) as the pallet P is being transported over the rails  220  via contact with the rollers  230 , and at a spacing T above the freight deck D, during operation of the system  10 . The rails  220  are also configured for supporting all of the weight of all the pallets P (each, together with its cargo) when all the pallets P have been deposited, each at its final position, along the respective cargo storage path CS, as well as additional g-forces according to specifications. 
     Accordingly, each rail  220  is on, or close to, a respective load bearing beam B of the freight deck D so that the weight of the pallet and cargo is supported by the respective load bearing beam B without damaging the floor of the freight deck D, and thus minimizing any moment arm of the aforesaid load with respect to the respective bearing beam B. 
     In this example and in other examples, spacing T, and thus the maximum height of the apparatus  100 , is or can be adjusted to be in the range between about 2 inches (about 5.1 cm) and 4 inches (about 10.2 cm), or between about 2 inches (about 5.1 cm) and 5 inches (about 12.7 cm), for example about 3 inches (about 7.6 cm). 
     Referring also to  FIGS. 3( a ) to 3( d ) , the apparatus  100  is configured for transporting in turn each pallet P (together with its cargo) with respect to the respective cargo path CS on freight deck D, for depositing the pallet P at its final position in the respective cargo storage path CS, and for disengaging from the pallet P. The apparatus  100  is guided along the respective cargo storage path CS via guiding system  300 . 
     The apparatus  100  is mobile and comprises a releasable engagement system  110 , a powered drive unit  140  and a controller  160 . In at least this example, the apparatus  100  is configured for selectively transporting each pallet P, one at a time, while each respective pallet P is in overlying relationship therewith, and is thus accommodated in the space M between the underside, i.e. lower face LF, of the pallet P and the freight deck D. 
     The releasable engagement system  110  is configured for selectively engaging to, and for selectively disengaging from, the apparatus  100  with respect to each pallet P in operation of the system  10 . The powered drive unit  140  is configured for selectively moving the apparatus  100  over the freight deck D to any one of a plurality of locations thereon along the respective cargo path CS, and for concurrently propelling the respective pallet P to at least one such location when the apparatus  100  is engaged to the cargo unit via the engagement system  110  and pallet P. The controller  160  is configured for controlling movement of the apparatus  100  with respect to the freight deck D, in particular with respect to the respective cargo path CS. 
     The powered drive unit  140  comprises a chassis member  141  having a generally parallelepiped shape, with two lateral sides  142 , a front end  144 , and a rear end  146 , and a top  148 . Each lateral side  142  is inboard of and facing the respective rails  220 . The apparatus  100  comprises a plurality of wheels  150  rotatably mounted at each lateral side  142 , and at least some of these wheels are operatively connected to motors  151  housed in the chassis member  141  to provide motive power to the wheels  150 , which in operation roll over the flight deck D to displace the powered drive unit  140  with respect thereto. 
     In this example, releasable engagement system  110  operates to selectively provide a clearance between the top  148  and the lower face LF of the pallet P to enable the pallet P and the apparatus  100  to move with respect to one another between a position in which pallet P and the apparatus  100  are not in overlying relationship and a position in which pallet P and the apparatus  100  are in overlying relationship. The releasable engagement system  110  further operates to selectively remove this clearance between the top  148  and the lower face LF of the pallet P, in particular when the pallet P and the apparatus  100  are in overlying relationship, so that the apparatus  100  engages with the lower face LF of the pallet P, engaging the same thereby enabling both the apparatus  100  and the pallet P to move together propelled by the powered drive unit  140 . 
     In other words, the releasable engagement system  110  is configured for releasably engaging with the underside or lower face LF of the pallet P. Furthermore, the releasable engagement system  110  comprises or is in the form of an apparatus height changing system, configured for selectively effectively changing the height of the mobile transport apparatus  100  from a first height, less than a datum height dimension defined by spacing T, to a second height, not less than this datum height dimension. 
     Thus, in this example, and referring to  FIG. 3( a ) , the releasable engagement system  110  comprises four retractable powered engagement units  170  (though in alternative variations of this example the releasable engagement system  110  can instead comprise one, two, three or more than four retractable powered engagement units  170 , mutatis mutandis). 
     Referring to  FIG. 3( d ) , each retractable powered engagement unit  170  comprises at least one roller or wheel  171  mounted on a horizontal axle  173 , and comprising a motor for selectively rotating the wheel  171  in clockwise and/or anticlockwise directions. The wheel  171  is pivotably mounted to a housing member  172  via a strut member  174  that is pivoted to the housing member  172  at pivot axis  175 . The strut member  174  comprises a powered actuator to enable the wheel  171  to be selectively positioned between at least a first (deployed) position p 1  and a second (retracted) position p 2 . The first position p 1  is an upper position for maximum frictional engagement between the wheel  171  and the underside of the pallet P. The second position p 2  is a lowermost position in which the wheel  171  is fully disengaged with respect to the underside of the pallet P. 
     The retractable powered engagement units  170  are mounted in wells  179  provided on the top  148  of the chassis member  141 , such that in said first position p 1  the respective wheels  171  do not protrude above the top  148 , and thus maintain the effective height of the apparatus  100  at less than T. In the second position, the wheels  171  protrude above top  148 , thereby increasing the effective height of the apparatus  100 , and enabling frictional engagement with the underside of a pallet P. 
     The chassis member  141  has a longitudinal length that is the same or slightly greater than the longitudinal length of the pallet P, and comprises selectively deployable mechanical abutment members  178  at each one of the front end  144 , and the rear end  146 . Referring in particular to  FIGS. 4 and 5 , each abutment member  178  comprises a horizontal primary strut member  177  pivotably mounted to the respective front end  144  or rear end  146  via a pair of spaced, parallel secondary strut members  176 . The secondary strut members  176  can be pivoted from a first (retracted) position illustrated in  FIG. 4  (and optionally prevented from pivoting further via mechanical stop  183 ), in which the primary strut member  177  is at a height at or below the top  148 , to a second (deployed) position illustrated in  FIG. 5 , in which the primary strut member  177  is at a height well above the top  148 . In fact, in the second position the primary strut members  177  are at a height to prevent relative forward and aft movement between the pallet P and the apparatus  100  when in superposed relationship. 
     In one mode of operation, the apparatus  100 , with the wheels  171  in their respective second positions p 2 , and the abutment member  178  in their respective first positions, is inserted under the pallet P (or conversely, the pallet P is moved over the apparatus  100 ), the effective height of the apparatus  100  being less than height T. When the pallet P is in full overlying relationship with the apparatus  10 , such that the front abutment member  178  is in front of the pallet P and the aft abutment member  178  is aft of the pallet P, the two abutment members  178  are actuated (or alternatively manually manipulated) to move to an lock at their respective second positions, thereby effectively longitudinally trapping the pallet P over the apparatus  10 . Then, the powered engagement units  170  are actuated to pivot the respective wheels  171  to their first positions p 1 , frictionally engaging the underside of the pallet P. The powered drive unit  140  can now drive the apparatus  100  together with the pallet P along the cargo path CS to its required position. Optionally, the abutment member  178  that is furthest away from the apparatus  100  prior to commencing the overlying process can be in its second position throughout. In any case, it is to be noted that for this mode of operation, the wheels  171  are not required to rotate per se, and thus in corresponding alternative variations of this example, the wheels  171  can be replaced with friction pads that are selectively deployable and retractable between two positions corresponding to the aforesaid first position p 1  and second position p 2  of the wheel  171 , mutatis mutandis, and operate to selectively provide a frictional engagement with the underside of the pallet P. 
     In another mode of operation, the apparatus  100 , with the wheels  171  in their respective second positions p 2 , and the abutment member  178  in their respective first positions, is partially inserted under the pallet P (or conversely, the pallet P is moved over the apparatus  100 ), the effective height of the apparatus  100  being less than height T. When the pallet P is in partial overlying relationship with the apparatus  100 , such that the pallet only overlies the nearest part of the apparatus  100  thereto including at least the nearest powered engagement units  170 , the powered engagement units  170  are actuated to pivot the respective wheels  171  to their first positions p 1 , and the wheels  171  of the nearest units  170  frictionally engage the underside of the pallet P. The wheels  171  are also powered to rotate, thereby moving the pallet P in a horizontal direction over the apparatus  100  until the pallet P is in full overlying relationship with the apparatus  10 , such that the front abutment member  178  is in front of the pallet P and the aft abutment member  178  is aft of the pallet P. The wheels  171  stop rotation to maintain this relative position between the pallet P and the apparatus  100 . The two abutment members  178  are actuated to move to their respective second positions, thereby effectively longitudinally trapping the pallet P over the apparatus  10 . Then, with the wheels  171  still at their first positions p 1  frictionally engaging the underside of the pallet P, the powered drive unit  140  can drive the apparatus  100  together with the pallet P along the cargo path CS to its required position. Optionally, the abutment member  178  that is furthest away from the apparatus  100  prior to commencing the overlying process can be in its second position throughout. 
     Examples of such a powered engagement unit  170  can include a 3-inch self-lifting powered drive unit (PDU) and the 2-inch spring loaded PDU provided by Ancra International LLC of the USA 
     In an alternative variation of this example, and referring to  FIGS. 6( a ) and 6( b ) , the releasable engagement system  110  comprises a cam arrangement  119  including a plurality of generally identical cams  118  that are pivotable between a first position and a second position about respective pivot axes by means of a suitable controllable actuator (not shown). The cams  118  each comprise a curved slot  117  in which a pin  116  is engaged, the pins  116  being fixed to a pallet engagement plate  115  which is vertically displaceable with respect to the upper part of the apparatus  100  or the chassis member  141 . In the second position, and referring to  FIG. 6( b ) , the cams  118  are rotated to their maximum clockwise position (as seen in this figure) so that the pallet engagement plate  115  is at its lowest position, defining a height for the apparatus less than spacing T. In the first position, and referring to  FIG. 6( a ) , the cams  118  are rotated in an anticlockwise direction (as seen in this figure) so that the pallet engagement plate  115  is raised, increasing the height for the apparatus  100  to at least spacing T, thereby enabling engagement of the underside of the pallet P. 
     In an alternative variation of this example, and referring to  FIG. 7 , the releasable engagement system  110  comprises a jack arrangement including one or more piston members  121  each telescopically displaceable with respect to a respective jack sleeve  122  between a first position and a second position by means of a suitable controllable actuator (not shown), for example hydraulic, pneumatic or mechanical actuators. The free end of the piston members  122  are fixed to a pallet engagement plate  115  which is displaceable with respect to the upper part of the apparatus  100 , while the respective jack sleeves  122  are fixed to the chassis member  141 . In the second position, the piston members are fully retracted in their respective jack sleeves  122  so that the pallet engagement plate  115  is at its lowest position, defining a height for the apparatus less than spacing T. In the first position, and referring to  FIG. 7 , the piston members are extended with respect to their respective jack sleeves  122  so that the pallet engagement plate  115  is raised, increasing the height for the apparatus  100  to at least spacing T, thereby enabling engagement of the underside of the pallet P. 
     In an alternative variation of this example, and referring to  FIG. 8 , the releasable engagement system  110  comprises an inflatable arrangement including one or more bellows-like members  161 , each being inflatable between a first height and a second height hydraulically or pneumatically. The upper end of the bellows-like members  161  are fixed to a pallet engagement plate  115  which is displaceable with respect to the upper part of the apparatus  100 , while the lower ends of the respective bellows-like members  161  are fixed to the chassis member  141 . In the second height, the bellows-like members  161  are fully deflated, or at least sufficiently deflated so that the pallet engagement plate  115  is at its lowest position, defining a height for the apparatus less than spacing T. In the first height, and referring to  FIG. 8 , the bellows-like members  161  are sufficiently inflated so that the pallet engagement plate  115  is raised, increasing the height for the apparatus  100  to at least spacing T, thereby enabling engagement of the underside of the pallet P. 
     In an alternative variation of this example, and referring to  FIG. 9 , the releasable engagement system  110  comprises a scissor lift mechanism  181  controllably movable between a first position and a second position by means of a suitable controllable actuator  182 , for example a hydraulic, pneumatic or mechanical actuator. The upper end of the scissor lift mechanism  181  is fixed to a pallet engagement plate  115  which is displaceable with respect to the upper part of the apparatus  100 , while the lower end of the scissor lift mechanism  181  is fixed to the chassis member  141 . In the second position, the scissor lift mechanism  181  is sufficiently retracted so that the pallet engagement plate  115  is at its lowest position, defining a height for the apparatus less than spacing T. In the first position, and referring to  FIG. 9 , the scissor lift mechanism  181  is sufficiently extended with so that the pallet engagement plate  115  is raised, increasing the height for the apparatus  100  to at least spacing T, thereby enabling engagement of the underside of the pallet P. 
     In an alternative variation of this example, and referring to  FIG. 10( a )  and  FIG. 10( b ) , the releasable engagement system  110  comprises a mechanical lift arrangement in which the wheels  150  are pivotably mounted to the chassis member  141  via struts  152  that are pivoted to the chassis member  141  at respective pivot axes  153 . The struts  152  are controllably movable between a first position and a second position by means of a suitable controllable actuator (not shown). In the second position, and referring to  FIG. 10( b ) , the struts  152  are pivoted at a relatively shallow angle with respect to the ground surface (such as the deck D) so that the apparatus  100  is at its lowest position, defining a height for the apparatus less than spacing T. In the first position, and referring to  FIG. 10( a ) , the struts  152  are pivoted at a relatively less shallow angle with respect to the ground surface (such as the deck D) so that the apparatus  100  is raised, increasing the height for the apparatus  100  to at least spacing T, thereby enabling engagement of the underside of the pallet P. 
     Thus, in the examples illustrated in  FIGS. 3( a )  to  5 , and  6 ( a ) to  10 ( b ), the respective releasable engagement system operate by selectively providing the apparatus with an effective height that is less than spacing T to allow the apparatus  100  to assume a position underneath the pallet P, and by selectively enabling the apparatus to increase its effective height to at least spacing T so that the apparatus becomes partially loaded with the pallet and thus engages the same by friction. In an alternative variation of these examples, and referring to  FIG. 11( a )  the releasable engagement system  110  operates to selectively engage to and disengage from the pallet P via the peripheral lip Q thereof. Thus, in this example, the height of the apparatus  100  remains the same prior to and after engagement with the pallet P, and is less than spacing T to allow the apparatus  100  to assume a position underneath the pallet P. the engagement system in this example is in the form of a clamp  192  at the front end or at the back end of the chassis member  141 . The clamp comprises jaws  191  that are pivotable between a first position and a second position by means of a suitable controllable actuator (not shown). In the first position, the clamp is open, and each jaw  191  is pivoted to its lowest position so that no part of the clamp  192  is at a height greater than spacing T. In the second position, and referring to  FIG. 11( a ) , the jaws  191  are pivoted over the peripheral lip Q so as to clamp the peripheral lip Q thereby engaging the pallet P. Optionally, two such clamps  192  can be provided, one each at the front end and at the back end of the chassis member  141 , as illustrated in  FIG. 11 ( b ) . 
     Referring again to  FIGS. 3( a ) to 3( c ) , the wheels  150  on one side  142  of the chassis member  141  are parallel to the wheels  150  on the other side  142  of the chassis member  141 . Thus the wheels  150  rotate together in one direction or the other direction to move the apparatus  100  forwards or backwards along the respective cargo path CS. 
     In this example, the guiding system  300  is passive, and comprises a pair of laterally spaced guide rails  310  which are configured for passively guiding the path of the apparatus  100  forwards and backwards along the respective cargo path CS. The apparatus  100  is thus restricted to rectilinear movement constrained by rails along the respective cargo path CS. 
     As best seen in  FIGS. 4 and 5 , each guide rail  310  has a U-shaped cross-section for accommodating parts of the rims of wheels  150  (on the respective side  142  of the chassis member  141 ) that are in contact therewith as the wheels roll on the guide rails  310 , and for constraining the rolling motion of the wheels with respect thereto. The guide rails  310  are located inboard of the rails  220 . The guide rails  310  are configured for supporting the weight of the apparatus  100 , and in some examples also are configured for supporting part of (not including a majority of) the weight of the pallet P plus its cargo, when the pallet P is propelled by the apparatus  100  along the respective cargo storage path CS. Accordingly, each guide rail  310  is on or close to the respective load bearing beam B of the freight deck D so that the weight of the apparatus  100  (and optionally part of the weight of the pallet and cargo) is supported by the respective load bearing beam B without damaging the floor of the freight deck D. 
     In alternative variations of this example, the guide rails  310  are configured for supporting the majority of the weight of the apparatus  100 , and the weight of the pallet P plus its cargo, when the pallet P is propelled by the apparatus  100  along the respective cargo storage path CS. 
     In alternative variations of this example, the guide rails  310  are configured for supporting all of the weight of the apparatus  100  plus the weight of the pallet P and its cargo, when the pallet P is propelled by the apparatus  100  along the respective cargo storage path CS. In such cases, the support system  200  can optionally be omitted from the system  10 . 
     In alternative variations of this example, two sets of separate load bearing beams (not shown) are provided in the freight deck for each cargo storage path CS. One set of load bearing beams are for carrying the load from each set of rails  220 , and the other set of load bearing beams are for carrying the load from guide rails  310 , both of which can in close proximity to one another. 
     In any case, the powered drive unit  140  is electrically powered to enable the apparatus  100  to be selectively moved up and down the respective cargo storage path CS to any desired position thereon. In this example, and referring again to  FIG. 2 , the electrical power is provided by a battery carried by the apparatus  100 , and the battery is configured for being recharged in one or more of an automated, automatic and manual manner, via recharging system  500 . Recharging system  500  comprises a recharger docking station  550 , provided near the area S at the rear end of the guiding system  300  of the respective cargo storage path CS, and a docking head  580  provided at rear end  146  of the apparatus  100 , facing the area S. A first set of electrical terminals are provided at docking head  580 , and electrically connected to the battery. A second set of electrical terminals are provided at docking station  550 , and electrically connected to a power supply of the aircraft AC, or to an external power supply, routed via the aircraft AC. The docking head  580 , docking station  550 , and the first and second sets of electrical connections have mating structures such as to ensure that when the apparatus  100  approaches the area S and docking head  580  docks with the docking station  550 , the first set of electrical terminals establish electrical connection with the second set of electrical terminals, enabling the battery to be recharged. 
     The apparatus  100  can be docked to the docking station  550  manually, i.e., by manually controlling the apparatus  100  via controller  160  to approach and dock with the docking station  550  whenever desired. Alternatively, the apparatus  100  can be docked to the docking station  550  automatically, i.e., by controlling the apparatus via controller  160  to approach and dock with the docking station  550  at the beginning of each loading or unloading cycle. Alternatively, the apparatus  100  can be docked to the docking station  550  autonomously, i.e., wherein the controller  160  controls the apparatus  100  to approach and dock with the docking station  550  according to pre-established criteria, for example where the power levels in the battery have reached a minimum acceptable level. 
     Additionally or alternatively, the electrical power is provided by a battery carried by the chassis member  141 , but the battery is connected to a power source in the aircraft or outside of the aircraft via electrical cables that are wound on a spool and carried either by the apparatus  100  or located on the freight deck, and the cable is spooled in or out according to the location of the apparatus  100  in the respective cargo path CS and thus the respective spacing between the apparatus  100  and the power connection in the freight deck. This set up allows the battery to be recharged continuously or as required, and independently of the position of the apparatus  100 . Alternatively, no battery is carried by the apparatus  100 . Rather, power is routed directly to the apparatus  100  from a power source in the aircraft or outside of the aircraft via electrical cables that are wound on a spool and carried either by the apparatus  100  or located on the freight deck, and the cable is spooled in or out according to the location of the apparatus  100  in the respective cargo path CS and thus the respective spacing between the apparatus  100  and the power connection in the freight deck. 
     In alternative variations of this example, and referring to  FIG. 20 , the guiding system  300  is an active guidance system, and comprises an optical guidance system  310 ′, and does not require the guiding rails  310 , which can thus be optionally omitted. The optical guidance system  310 ′ comprises optical sensors  311 ′, mounted on the left and right sides of the front end  144  of the mobile transport apparatus  100  that faces the end of rails  220 . The optical guidance system  310 ′ further comprises optical emitters  312 ′, located at the end of the rails  220  facing the area S. The optical emitters  312 ′ at each end of the two rails  220  emit light at the same intensity towards area S, and when the optical sensors  311 ′ are at least partially facing the optical emitters  312 ′, each sensor receives light emitted from one or both emitters  312 ′. However, the intensity of light received by each of the optical sensors  311 ′ will be the same only when the mobile transport apparatus  100  is aligned with the rails  220 . Prior to such alignment, and depending on the degree of misalignment, each optical sensor  311 ′ will detect different intensities of light. The controller  315 ′ is configured for analyzing the difference in intensities and controls movement of the mobile transport apparatus  100  in response thereto in an effort to equalize the intensities, and thereby align the mobile transport apparatus  100 . Such optical guidance systems  310 ′ are known in the art. Controller  160  can act as controller  315 ′, or can be different from controller  315 ′. 
     As already mentioned, the controller  160  is configured for controlling movement of the apparatus  100  with respect to the freight deck D, in particular with respect to the respective cargo path CS. In this example, the controller  160  comprises computer control for controlling the movement of the apparatus  100  in an automated or semi-automated manner. For this purpose, the system  10  further optionally comprises sensors (not shown) to determine the position of the apparatus  100  within its respective cargo path CS, and the location of any pallets P already secured in their desired positions on the cargo path CS. 
     In alternative variations of this example, the controller  160  is a manual control for controlling the movement of the apparatus, and thus an operator manually operates the apparatus, using suitable control switches/devices in a control box, operatively connected to the apparatus  100  via wires. 
     In alternative variations of this example, the controller  160  operates as manual control for controlling the movement of the apparatus, and thus an operator manually operates the apparatus, using suitable control switches/devices in a control box, operatively connected to the apparatus  100  via wireless remote control, and thus controller  160  comprises a wireless remote control system including a suitable signal receiver (and optionally signal transmitter) system for receiving signals from the operator (and optionally transmitting signals to the operator, for example relating to operation of the apparatus  100 ). The operator can be in the aircraft itself, or in a completely remote location, and can monitor operation of the system  10  via cameras installed in the aircraft, for example. 
     The locking devices  400  are located on the freight deck D and are configured for selectively releasably locking each pallet P with respect to the freight deck D. Such locking devices are well known in the art and will not be described in further detail herein. In the example illustrated in  FIG. 2 , there is an outboard set of locking devices  400  for each of the cargo storage paths CS 1 , CS 2 , CS 3 , CS 4 , for laterally locking the pallets P on the outboard sides thereof, a set of locking devices  400  located between cargo storage paths CS 1 , CS 2 , and also located between cargo storage paths CS 3 , CS 4 , for laterally locking the pallets P on the inboard sides thereof, plus additional locking devices  400  on the freight deck D and/or comprised on the cargo support system  200 , for locking the pallets P in a forward and aft direction for each respective cargo path CS. 
     The pallet turning and alignment area S in this example is similar to such arrangements in conventional CHS, and comprises turning/alignment devices, for example a plurality of ball transfer units (BTU) set on the floor of the freight deck, together with PDU&#39;s that are also pivotable about respective vertical axes. This arrangement enables any pallet entering area S via the cargo door CD to be autonomously and/or automatically manipulated over the area S, adjusting its position and orientation thereon, until the pallet is aligned with the desired cargo path CS. In alternative variations of this example, the turning and alignment area S in this example comprises a plurality BTU&#39;s set on the floor of the freight deck, but without PDU&#39;s, and the pallets P can be manually manipulated over the BTU&#39;s and into alignment with the desired cargo path CS. 
     In any case, it is to be noted that top of the rollers  230  of the cargo support systems  200  are at the same height as the tops of the BTU&#39;s (and PDU&#39;s) of the area S, with respect to the freight deck D. This enables the pallets P to be transferred between cargo support system  200  and the area S smoothly and with the pallets P being maintained level. 
     One mode of operation of system  10  for loading a plurality of pallets P in the freight deck D is as follows. 
     First, a pallet P supporting a cargo unit is loaded from outside of the aircraft AC into the area S via the cargo door CD in a conventional manner. Then, the pallet P is manipulated on area S also in a conventional manner to align the pallet P with a particular cargo path CS, for example cargo storage path CS 1 , and the pallet P is moved onto the respective rails  220  of the cargo support system  200  at a portion thereof abutting the area S. If the respective apparatus  100  is not already in position beneath the pallet P, it is selectively moved into such a position by moving apparatus  100  towards this position along the guide rails  310 . 
     Next, the apparatus  100  engages the pallet P via the respective releasable engagement system  110 , and then the powered drive unit  140  drives the apparatus  100  together with the pallet P along the cargo path CS to its required position. In other words, in operation the apparatus  100  effectively carries the pallet P over the freight deck to a desired location thereon, though while the pallet P is being thus transported on the rails  220 , most or all of the weight of the pallet P, and of course the cargo thereon, is being supported by the respective cargo support system  200 . 
     If this is the first pallet P that is being processed along cargo path CS 1 , then its position is typically chosen to be at the far, forward end of the cargo path CS 1 , closest to the nose of the aircraft AC (alternatively any other position can be chosen along the cargo path CS 1 ), and the pallet P is locked in place via the respective locking devices  400 . If there is another pallet at this position already, the current pallet P is moved to a position immediately aft thereof via the apparatus  100  (alternatively to any other position along the cargo path CS 1  between the prior pallet and the area S), and then locked in place via the respective locking devices  400 . 
     Once the pallet P is locked in place, the apparatus  100  is disengaged from the pallet P by disengaging the releasable engagement system  110 , and the apparatus is then moved back towards area S to engage with and transport the next pallet P to the next position along the storage path CS 1 , in a similar manner to the first pallet, mutatis mutandis, after which the pallet is locked in position. 
     This procedure can be repeated until the storage path CS 1  has been filled with the desired number of pallets P, up to its full capacity. The other storage paths CS 2 , CS 3 , CS 4 , can be provided with pallets P in a similar manner to that described for storage path CS 1 , mutatis mutandis, each concurrently therewith (using additional apparatuses  100 ), or in any desired sequence (for example using the same apparatus  100  or using separate apparatuses  100 , one for each cargo path CS). 
     Unloading the pallets from the freight deck D comprises the same steps as loading, but in reverse. 
     Such cargo storage paths CS as illustrated in  FIG. 2  assume that the pallets P are of a suitable size to fit within less than a half-width of the freight deck D. However, the system  10  can also be used with pallets P that are configured having a width that is greater than a half-width of the freight deck D. For example, and referring to  FIGS. 2( c ) and 2( d ) , pallets P′ having a width that overlies the width of two juxtaposed cargo storage paths CS 1 , CS 3  (or alternatively one or both of cargo storage paths CS 2 , CS 4 , mutatis mutandis) can be transported by concurrently using two apparatuses  100 , one in each of the respective cargo storage paths CS 1 , CS 3  also in juxtaposed configuration. The two apparatuses  100  together transport the wide pallet P′ (with its cargo load) while this is being partially or fully supported over the two respective cargo support systems  200 , and the apparatuses  100  are being guided each by its respective guiding system  300 . 
     In alternative variations of this example, and referring to  FIG. 2( a ) , one or both of cargo storage paths CS 1 , CS 3  (or alternatively one or both of cargo storage paths CS 2 , CS 4 ) can deviate from parallel to the aircraft centerline CL where the cross-section of the aircraft begins to significantly decrease towards the nose and tail of the aircraft, respectively, allowing one or more single pallets P to be accommodated in these regions one behind the other, where pairs of such pallets in side-by-side arrangement could not fit. In such examples, at least some of the wheels  150  are rotatably mounted to the sides  142  via mountings that are pivotable about a vertical axis, allowing the apparatus  100  to travel along the curved portions  390  of the guiding system  300  corresponding to these deviations. Alternatively, the top  148  is pivotable about a vertical axis with respect to the chassis member  141 . 
     In yet other alternative variations of this example, the aircraft AC is configured for receiving the pallets P via the nose or tail of the aircraft, and thus the respective cargo handling system does not require the aforesaid pallet turning and alignment area S located on the respective freight deck D. Furthermore, cargo storage paths CS 1 , CS 3  can be contiguous, and cargo storage paths CS 2 , CS 4  can also be continuous. In such an example, the pallets P are loaded from the nose opening or tail opening of the aircraft, and the first pallet is transported by the apparatus to the other end of the respective cargo storage path CS, and after the pallet has been locked in place the apparatus  100  returns to the nose opening or tail opening to then transport another pallet along the respective cargo storage paths CS, and so on for the other pallets. 
     In yet other alternative variations of this example, the apparatus  100  can be configured for providing a rotational displacement to the cargo unit with respect to the chassis member  141  about a vertical axis. For example, the releasable engagement system  110  can be in the form of PDU&#39;s that are pivotable about a vertical axis. Alternatively, a turntable is mounted onto the top  148  of the chassis member  141 , and the cargo unit is supported over the turntable. This feature allows for the orientation of the cargo unit to be controlled independently of the direction of motion of the apparatus  100 , and can facilitate alignment of the cargo unit on the support structure, for example. 
     Referring to  FIG. 13 , a second example of the apparatus, designated  800 , has the elements and functions of the apparatus  100  as described herein, mutatis mutandis, with some differences as will become clearer herein. In this example the apparatus  800  is mobile and has a maximum height that is not restricted to spacing T. Thus, the apparatus  800  cannot fit under a pallet P i.e., the apparatus  800  is not configured for being accommodated in the space M between the lower face LF of the pallet P and the freight deck D, although parts of the apparatus  800  can indeed enter the space M during operation thereof. 
     Rather, apparatus  800  is configured for being selectively affixed to a pallet P and for assuming a position forward or aft of the pallet P, enabling the apparatus  800  to push and/or pull the pallet P along the desired cargo storage path CS, to its position thereon, after which the pallet P can be deposited and affixed in place, and the apparatus  800  can then disengage from the pallet P and move away therefrom. 
     Apparatus  800  thus comprises a releasable engagement system  810 , a powered drive unit  840  and a controller  860 , similar to releasable engagement system  110 , a powered drive unit  140  and a controller  160  of the first example, mutatis mutandis. In this example, the apparatus  800  is configured for selectively transporting each pallet P, one at a time, while each respective pallet P is in juxtaposed forward-aft relationship therewith. 
     The releasable engagement system  810  is configured for selectively engaging and for selectively disengaging the apparatus  800  with respect to each pallet P, in operation of the respective cargo handling system  10 ′. The powered drive unit  840  is configured for selectively moving the apparatus  800  over the freight deck D to a plurality of locations thereon along the respective cargo path CS, and for concurrently propelling the respective pallet P to at least one such location when the apparatus  800  is engaged to the pallet P via the engagement system  810 . The controller  860  is configured for controlling movement of the apparatus  800  with respect to the freight deck D, in particular with respect to the respective cargo path CS. 
     The powered drive unit  840  is similar to powered drive unit  140 , except that it can be relatively taller, not being constrained by the height limitation of height T, facilitating accommodation in the drive unit  840  of relatively larger motors, gears, and other equipment for operation thereof. As with the first example, the powered drive unit  840  has a chassis member  841  and comprises two lateral sides  842 , each inboard of and facing the respective rails  820 , and comprises a plurality of wheels  850  rotatably mounted to each lateral side  842 . The wheels  850  are operatively connected to one or a plurality of motors (not shown) housed in the chassis member  841  to provide motive power to the wheels  850 , which in operation roll over the flight deck D to displace the powered drive unit  840  and thus the apparatus  800  with respect thereto, while being guided by the laterally spaced guide rails  310  of guiding system  300  forwards and backwards along the respective cargo path CS. 
     In this example, releasable engagement system  810  does not require to provide a clearance between the top  848  thereof and the lower face LF of the pallet P. Rather, the engagement system  810  is configured to enable the apparatus  800  to selectively engage to and disengage from the pallet P when the apparatus  800  is in juxtaposed relationship therewith, and, when engaged, for both the apparatus  800  and the pallet P to move together propelled by the powered drive unit  840 . In other words, in operation the apparatus  800  tows the pallet P over the freight deck to a desired location thereon. 
     In this example, the engagement system  810  comprises a clamping system  811  configured for selectively clamping the lip Q of the pallet P. For example, clamping system  811  comprises upper and lower clamping members or jaws  811   a ,  811   b  pivotable about axis  811   c  to selectively clamp the jaws  811   a ,  811   b  to the lip Q of the pallet P. Alternatively, and referring to  FIG. 13( a ) , the engagement system  810  can be in the form of a fork-lift arrangement, comprising forks  812  that are vertically movable by means of mast  814  between a disengaged position and an engaged position. In the disengaged position, the forks  812  are spaced from the freight deck D by a spacing less than spacing T, allowing the forks  812  to be inserted into space M so that the pallet P is in overlying relationship therewith. In the engaged position the forks  812  are spaced from the freight deck D by a spacing equal to or just greater than spacing T to enable the forks  812  to abut against the underside LF of the pallet and become partially load-bearing, thereby engaging the pallet P. 
     In the second example the transport apparatus  800  essentially replaces the transport apparatus  100  in a second example of the cargo handling system  10 ′. Thus, and referring to  FIG. 12 , cargo handling system  10 ′ comprises one or more transport apparatus  800 , the cargo support system  200 , the guiding system  300  (active or passive), and the plurality of locking devices  400  located on the freight deck D, and as with the first example, each cargo unit comprises or is carried on a respective pallet P, with respect to a cargo storage path CS defined on the freight deck D of an aircraft AC. 
     System  10 ′ can be operated in a similar manner to the first example of system  10 , with some differences, mutatis mutandis. 
     Thus, in one mode of operation, a pallet P supporting a cargo unit is loaded from outside of the aircraft AC into the area S via the cargo door CD and is manipulated on area S to align the pallet P with a particular cargo path CS, for example cargo storage path CS 1 , for example as disclosed above for the first example, mutatis mutandis. The pallet P is moved onto the rails  220  of the respective cargo support system  200  at a portion thereof abutting the area S. Until this point, the respective apparatus  800  is in a parked position spaced away from the pallet P, for example at a location in area S or another part of the flight deck D, for example the cargo path CS that is on the other side of area S and longitudinally aligned therewith. For this purpose, the guide rails  310  can extend into area S and optionally be contiguous with the guide rails  310  of the longitudinally aligned cargo path CS. For example, the guide rails  310  of cargo path CS 1 , CS 3  are contiguous and span the area S, and/or the guide rails  310  of cargo path CS 2 , CS 4  are contiguous and span the area S. Once the pallet P is supported on the rails  220  and is abutting the area S, the respective apparatus  800  is moved into position behind the pallet P in area S, guided thereto by the extended guide rails  310 . 
     Next, the apparatus  800  engages the pallet P via the respective releasable engagement system  810 , and then the powered drive unit  840  drives the apparatus  800  together with the pallet P along the cargo path CS in a direction radiating away from the area S to its required position, while the apparatus  800  is guided along the desired path via guiding system  300 . While the pallet P is being thus transported, most or all of the weight of the pallet P, and of course the cargo thereon, is being supported by the respective cargo support system  200 . The pallet P is then deposited at the desired position and locked in place via the respective locking devices  400 . The apparatus  800  is then disengaged from the pallet P by disengaging the releasable engagement system  810 , and the apparatus  800  is then moved back to its parking position in area S to engage with and transport the next pallet P to the next position along the respective storage path CS, after which the pallet is locked in position. This procedure can be repeated until the storage path CS has been filled with the desired number of pallets P up to its full capacity. Each one of storage paths CS 1 , CS 2 , CS 3 , CS 4 , can be provided with pallets P in a similar manner, mutatis mutandis, each concurrently with one another, or in any desired sequence. 
     Unloading the pallets from the freight deck D comprises the same steps as loading, but in reverse. 
     In an alternative variation of the second example, and referring to  FIG. 13( b ) , the apparatus  800  comprises a releasable engagement system  810  at each one of its forward and aft ends. Thus one such apparatus  800  can be used for transporting pallets P for one or another of each pair of longitudinally aligned storage paths—for example storage paths CS 1 , CS 3 , or storage paths CS 2 , CS 4 . The forward-located engagement system  810  selectively engages with pallets P that are to be transported along and retained in storage path CS 1  (or storage path CS 2 ), being moved in a direction towards the nose of the aircraft during loading, and in a direction towards the area S during unloading. Similarly, the aft-located engagement system  810  selectively engages with pallets P that are to be transported along and retained in storage paths CS 3  (or storage paths CS 4 ) being moved in a direction towards the tail of the aircraft during loading, and in a direction towards the area S during unloading. In such an example, a recharging system can be provided, comprising a recharger docking station and a docking head, similar to the aforesaid recharging system  500 , recharger docking station  550 , and docking head  580 , mutatis mutandis. For example, the recharger docking station can be at or near the front and/or rear of the aircraft, close to respective end(s) of the guiding system  300  of one or more cargo storage path CS, and can be reached by the apparatus  800  when there are no pallets P in the respective storage path CS. In another example, the recharger docking station can be provided anywhere on the freight deck, and is retractable with respect to the floor of area S to enable the apparatus  800  to move over the retract recharger docking station when the latter is not being used. The docking head can be provided at rear end and/or at the front end of the apparatus  800 , for example. 
     The cargo handling system according to the first and second examples can optionally be provided as a retrofit in at least some existing freight aircraft that already incorporate a conventional powered CHS. For example, such retrofit can proceed as follows. All the PDU&#39;s of the conventional powered CHS that are located in the straight track, forward and aft of the respective area S are removed. However, the current rails onto which the pallets are supported while being moved into their respective final positions are used as the support system  200 , and the existing locking devices are retained and are used as the locking devices  400 . This leaves a spacing between the lower face LF of the pallet P and the freight deck D, corresponding to space M. One or another of the apparatuses  100  or  800  can then be provided for shuttling between the area S and the final desired positions of the pallets P along the respective storage paths, and the respective guiding system  300  is installed on the freight deck D, for example between the aforesaid rails. The guide rails  310  can have a pitch (corresponding to the pitch of the wheels of the apparatus  100  or  800 ) that places them close to the aforesaid rails and thus close to the respective underfloor support beams. However, if necessary, additional support can be provided for the guiding system  300 , for example via additional load bearing beams provided under the floor of the freight deck D. However, particularly where the second example of the apparatus  800  is being used, the weight of the pallet P (plus cargo) is still mainly supported by the aforesaid rails, so the fright deck between the rails only requires to be able to support the weight of the apparatus  800 . In such a retrofit, the BTU&#39;s and/or rotatable PDU on the respective area S, i.e. the pallet turning section next to the aircraft side door (cargo door) operate conventionally, and then each apparatus  800  only transports the pallets along the respective longitudinal track along the aforesaid rails. 
     In alternative variations of this example, the controller  860  operates as manual control for controlling the movement of the apparatus  800 , and thus an operator manually operates the apparatus, using suitable control switches/devices in a control box, operatively connected to the apparatus  800  via wireless remote control, and thus controller  860  comprises a wireless remote control system including a suitable signal receiver (and optionally signal transmitter) system for receiving signals from the operator (and optionally transmitting signals to the operator, for example relating to operation of the apparatus  800 ). The operator can be in the aircraft itself, or in a completely remote location, and can monitor operation of the system  10 ′ via cameras installed in the aircraft, for example. 
     Referring to  FIGS. 15 and 16 , a third example of the apparatus, designated with the reference numeral  700 , is mobile and comprises the elements and functions of the apparatus  100  as disclosed herein, mutatis mutandis, with some differences as will become clearer herein. In this example the apparatus  700  has a maximum height that is similarly restricted to spacing T, and the apparatus  700  is thus configured to fit under a pallet P, i.e., the apparatus  700  is accommodated in the space M between the lower face LF of the pallet P and the freight deck D. 
     The apparatus  700  differs from apparatus  100  mainly in that apparatus  700  is configured for being controllably steered over the freight deck D with respect to more than one translational degrees of freedom and/or one or more rotational degrees or freedom over the freight deck, and is not restricted to rectilinear movement constrained by rails. Referring to  FIG. 14 , the corresponding cargo handling system  20  thus comprises one or more transport apparatus  700 , as well as a cargo support system  1200 , a guiding system  1300 , and a plurality of locking devices  1400  located on the freight deck D. As with the first example, each cargo unit comprises or is carried on a respective pallet P, with respect to a cargo storage path CS defined on the freight deck D of an aircraft AC. In particular, it is to be noted that the system  20  does not require to have, but nevertheless can optionally have, the turning/aligning devices (for example BTU&#39;s and/or pivotable PDU&#39;s) in the pallet turning and alignment area S, and thus such turning/aligning devices can optionally be omitted. On the other hand, area S is provided with spacer blocks  770 , having rollers thereon at the same height from the freight deck D as the rollers of the support rails  1220 , and in spaced relationship. The spacer blocks  770  are located just inside of the cargo door CD, and allow an apparatus  700  to be parked in-between the spacer blocks  770 , while a pallet P is supported on the spacer blocks  770  just inside the area S when the pallet P is first introduced into the freight deck D via the cargo door. 
     Apparatus  700  thus comprises a releasable engagement system  710 , a powered drive unit  730  and a controller  760 . The releasable engagement system  710  and the controller  760  are respectively similar to releasable engagement system  110  and controller  160  of the first example and/or alternative variations thereof, mutatis mutandis, and will not be described further. In this example, the apparatus  700  is configured for selectively transporting each pallet P, one at a time, while each respective pallet P is in overlaying relationship with the apparatus  700 . According to the third example of the presently disclosed subject matter, two transport apparatuses  700  can be used together in side-by-side spaced relationship to transport a very wide pallet, for example of the kind illustrated in  FIG. 2( c ) . 
     In this example, and referring again to  FIGS. 15 and 16 , the powered drive unit  730  comprises one set of four omni wheels  731  (also referred to interchangeably herein as poly wheels) rotatably mounted to a chassis member  735 , two wheels  731  on each lateral side thereof, and provide the ability for the apparatus  700  to move, and thus to be steered, in all directions over the freight deck D. In alternative variations of this example, the powered drive unit  730  comprises a plurality of sets of four omni wheels  731 , the sets being serially or otherwise spaced longitudinally along the length of chassis member  735 . 
     Each omni wheel  731  comprises discs or rollers  732 , of much smaller diameter than the diameter of the omni wheel  731 , and the discs or rollers  732  are rotatably mounted to the omni wheel  731  around its circumference, perpendicular to the rolling direction or rolling axis of the omni wheel  731 . In other words, the rotational axes of the discs or rollers  732  are parallel to respective tangential directions on the circumference of the omni wheel  731 . Each omni wheel  731  can thus turn about its rolling axis  799  with full force over a surface, but can also slide laterally with ease. 
     Such omni wheels are well known in the art. 
     In this example, all the wheels  731  are not in parallel relationship one to another, but rather the wheels  731  are rotatably mounted to the chassis member  735  at different angles with respect to the chassis member  735 , with the respective axes  732  of adjacent wheels  731  being angularly displaced one from the other at about 90°. The drive unit  730  further comprises a plurality of motors to turn each of the wheels  731  independently from one another, and controllable to selectively provide a desired rotational velocity and rolling direction (clockwise or anticlockwise) in each wheel  731  independently of the other wheels  731 . 
     For ease of reference, the four wheels are separately designated with the reference numerals  731 A (forward, right),  731 B (aft, right),  731 C (aft, left),  731 D (forward, left), and four directions of motion for the apparatus can also be defined as forward (FWD), aft (AFT), right (RHT) and left (LFT). Also for ease of reference, and referring to  FIG. 17( g ) , by the respective “direction of motion” V of each wheel  731  is meant the direction along which the wheel moves over a surface (such as the freight deck D, for example) when the wheel is turned around its respective axis  700 . This direction of motion V can be resolved into a forwards/aft component V FA  and a lateral, right/left component V RL , with respect to the apparatus  700 , since all the wheels  731  are inclined (or have their turning axes inclined) with respect to the forwards/aft directions and the lateral, right/left directions. 
     As can be seen from  FIGS. 17( a ) to 17( f ) , the drive unit  730  can be steered as follows:
         To move the apparatus  700  in a forward direction (FWD), all the wheels  731  are rotated so that they all move in a direction having a direction component V FA  in the forward direction (FWD) ( FIG. 17( a ) ).   To move the apparatus  700  in a aft direction (AFT), all the wheels  731  are rotated so that they all move in a direction having a direction component V FA  in the aft direction (AFT) ( FIG. 17( c ) ).   To move the apparatus  700  in a left direction (LFT), all the wheels  731  are rotated so that they all move in a direction having a direction component V RL  in the left direction (LFT) ( FIG. 17( b ) ).   To move the apparatus  700  in a right direction (RHT), all the wheels  731  are rotated so that they all move in a direction having a direction component V RL  in the right direction (RHT) ( FIG. 17( d ) ).   Thus, to move the apparatus  700  in any one of the major directions forward, aft, right or left, all the wheels  731  are rotated so that they all move in a direction having a direction component V RL  or V FA  parallel to the desired major direction.   To move the apparatus  700  in any diagonal direction with respect to the major directions forward, aft, right or left, the two wheels  731  having their axes parallel to the desired diagonal direction are not rotated, while the other two wheels  731  having their axes orthogonal to the desired direction are rotated so that they all move in a direction V parallel to the desired diagonal direction ( FIG. 17 ( e ) ).   To rotate the apparatus  700  in an anticlockwise direction with respect to a vertical axis (viewed from above), all the wheels  731  are turned clockwise so that for each opposed pair of wheels (first pair—wheels  731 A,  731 C; second pair  731 B,  731 D) the two wheels move in opposite directions to form a couple in the anticlockwise direction ( FIG. 17 ( e ) ).   Conversely, to rotate the apparatus  700  in a clockwise direction with respect to a vertical axis (viewed from above), all the wheels  731  are turned anticlockwise so that for each opposed pair of wheels the two wheels move in opposite direction to form a couple in the clockwise direction.       

     Thus, the drive unit  730  is configured for providing the apparatus  700  with at least two translational degrees of freedom over the freight deck D and one rotational degree of freedom about an axis orthogonal to the freight deck D. It is evident that the drive unit  730  (and thus the apparatus  700 ) can be steered by combining these translational and rotational motions in any desired manner to provide any desired translational and rotational motion over a surface such as the freight deck D. Such steering is controlled by the controller  760 , to operate the apparatus  700  manually, automatically and/or autonomously. 
     In alternative variations of this example, the omni wheels of the third example of the presently disclosed subject matter can be replaced with Mecanum wheels, which are similar to the omni wheels, but the respective peripheral rollers are mounted to the circumference of the wheel with the roller axes each being obliquely positioned (e.g. at) 45° to the rolling axis of the wheel. In such an example, one front wheel has left-handed rollers with the respective rear wheel on the same side of the chassis member  735  having right-handed rollers, while the other front wheel has right-handed rollers and the other rear wheel has left-handed rollers. Thus each wheel applies a force generally orthogonally to the diagonal that the wheel is on, and the apparatus can thus steered along any desired direction. When all four wheels are moved in the same direction with respect to a ground surface, the apparatus is moved forward or backwards; when the wheels on one side of the chassis member  735  are moved in the opposite direction to those on the other side, the apparatus is rotated about a vertical axis; when wheels on one diagonal are rolled in the opposite direction to those on the other diagonal (with respect to the ground), the apparatus is moved laterally. Thus, these combinations of these movements allow steering of the apparatus on the freight deck in any direction and/or rotation. 
     Such Mecanum wheels are well known in the art. 
     In alternative variations of this example, the drive unit  730  can instead comprise any other plurality of omni wheels or Mecanum wheels—for example three omni wheels or more than four omni wheels, to provide the aforesaid two degrees of freedom in translation and one degree of freedom in rotation. In such examples in which the drive unit comprises three omni wheels, these can be in triangular configuration, with the wheels angularly displaced from one another about the center of the chassis by 120° for example, and commonly known as a Kiwi Drive. 
     In other alternative variations of this example, the wheels of the drive unit  730  are rotatably mounted to the chassis member  735  in parallel relationship to one another, two wheels  731  on each side thereof, and steered using differential steering (also referred to as skid steering), in which by varying the speed or rolling direction of the wheels the apparatus  700  can be turned in any desired direction. 
     The cargo support system  1200  and the locking devices  1400  are respectively similar to the cargo support system  200  and locking devices  400  as described for the first example, mutatis mutandis, and will not be described in any further detail herein. 
     The guiding system  1300  is an active guiding system, and is configured for enabling the apparatus  700  to be guided into alignment with the pair of parallel support rails  220  of the cargo support system  200  provided in the respective cargo path CS, and so that the apparatus  700  can move between the support rails  1220  of the cargo support system  1200  to any desired position along the respective cargo path CS. 
     The guiding system  1300  in this example comprises a plurality of sensors  1320  strategically located on the apparatus  700 , and which are operatively connected to the controller  760 . For example, two such sensors  1320  are provided on the forward end of the apparatus  700 . The sensors  1320  detect laser light emitted from a plurality of emitters  1330  provided along the nominal path of the apparatus from the cargo door CD. The emitters  1330  are located at positions such that the intensity of the laser light detected by the sensors is at a maximum when the apparatus  700  is aligned with the desired path, and less than maximum when the apparatus deviates from this path. The various laser emitters can operate concurrently, or in any desired sequence along the path. Accordingly, the controller  760  steers the apparatus  700  by attempting to maximize the detected laser light at the detectors. 
     In alternative variations of this example, the guiding system  1300  can operate in a similar manner to optical guidance system  310 ′, mutatis mutandis. 
     In alternative variations of this example, the active guidance system  1300  can comprise visual markings on the freight deck, for example retro-reflective lines that mark the desired path of the apparatus  700  from the parked position between the spacer blocks  770  to each of the cargo paths CS. The guidance system can further comprise illumination devices and optical sensors on the underside of the apparatus  700  that respectively illuminate the floor and record the reflected light, which is at highest intensity when the reflected light originates from the visual markings. The controller  760  steers the apparatus  700  by attempting to maximize the detected reflected light at the detectors. 
     In alternative variations of this example, the guiding system  1300  can be in the form of the passive version of guiding system  300  of the first example comprising guide rails  310 , as described above mutatis mutandis. In operation, the controller  760  steers the apparatus  700  into alignment with the laterally spaced guide rails  310  and such that the wheels  731  are guided on the guide rails  310  when the apparatus  700  is moved forward or backwards. 
     In alternative variations of this example, the cargo handling system  20  can omit the guiding system  1300 , and the apparatus  700  can be guided to the desired locations over the freight deck by manual control, wherein a human controller manually guides the apparatus  700  via remote control, using cables for example. 
     In alternative variations of this example, the controller  760  operates as manual control for controlling the movement of the apparatus, and thus an operator manually operates the apparatus, using suitable control switches/devices in a control box, operatively connected to the apparatus  700  via wireless remote control, and thus controller  760  comprises a wireless remote control system including a suitable signal receiver (and optionally signal transmitter) system for receiving signals from the operator (and optionally transmitting signals to the operator, for example relating to operation of the apparatus  700 ). The operator can be in the aircraft itself, or in a completely remote location, and can monitor operation of the system  20  via cameras installed in the aircraft, for example. 
     In any case, the powered drive unit  730  is electrically powered to enable the apparatus  700  to be selectively and controllably steered within the respective cargo storage path CS to any desired position thereon. In this example, the electrical power is provided by a battery carried by the chassis member  735 , which is configured for being recharged in one or more of an automated, automatic and manual manner, via recharging system  750 . Recharging system  750  is similar to recharging system  500  as described above for the first example or second example, mutatis mutandis, and comprises a recharger docking station  752 , provided wherever convenient, for example in the area S, and a docking head  754  provided on the apparatus  700 . A first set of electrical terminals are provided at docking head  754 , and electrically connected to the battery, and a second set of electrical terminals are provided at docking station  752 , and electrically connected to a power supply of the aircraft AC, or to an external power supply, routed via the aircraft AC. The docking head  754 , docking station  752 , and the first and second sets of electrical connections have mating structures such that to ensure that when the apparatus  700  approaches the docking station  752 , and docking head  754  docks with the docking station  752 , the first set of electrical terminals establish electrical connection with the second set of electrical terminals, enabling the battery to be recharged. The apparatus  700  can be docked to the docking station  752  manually, automatically, or autonomously, for example as described above for the first example, mutatis mutandis. 
     Additionally or alternatively, the electrical power is provided by a battery carried by the chassis member  735 , but this is connected to a power source in the aircraft or outside of the aircraft via electrical cables that are wound on a spool and carried either by the apparatus  700  or located on the freight deck, and the cable is spooled in or out according to the location of the apparatus  700  in the respective cargo path CS, and allows the battery to be recharged continuously or as required, and independent of the position of the apparatus  700 . Alternatively, no battery is carried by the apparatus  700 , and power is routed directly to the apparatus  700  from a power source in the aircraft or outside of the aircraft via electrical cables, for example as described above for the first example, mutatis mutandis. 
     One mode of operation of system  20  for loading a plurality of pallets P in the freight deck D is as follows. 
     First, a pallet P supporting a cargo unit is loaded from outside of the aircraft AC into the area S via the cargo door CD in a conventional manner, and is deposited on spacer blocks  770 . If the apparatus  700  is not already in its initial position between the spacer blocks  770 , the apparatus  700  is controllably steered to this position, manually, automatically or autonomously. For this purpose, the area S does not require any BTU&#39;s or pivotable PDU&#39;s therein, and thus the deck D at area S can be flat, for example 
     Next, the apparatus  700  engages the pallet P via the respective releasable engagement system  710 . 
     Then, the pallet P is manipulated on area S by steering the apparatus  700  to align the pallet P with a particular desired cargo path CS, for example cargo storage path CS 1 , and the pallet P is moved onto the rails  220  of the respective cargo support system  200  at a portion thereof abutting the area S. The powered drive unit  730  continues to drive the apparatus  700  together with the pallet P along the cargo path CS to its required position. 
     In other words, in operation the apparatus  700  effectively carries the pallet P over the freight deck to a desired location thereon, though while the pallet P is being thus transported on the rails  220 , most or all of the weight of the pallet P, and of course the cargo thereon, is being supported by the respective cargo support system  200 . 
     If this is the first pallet P that is being processed along cargo path CS 1 , then its position is typically chosen to be at the far, forward end of the cargo path CS 1 , closest to the nose of the aircraft AC, and the pallet P is locked in place via the respective locking devices  400 . If there is another pallet at this position already, the current pallet P is moved to a position immediately aft thereof via the apparatus  700 , and then locked in place via the respective locking devices  400 . 
     Once the pallet P is locked in place, the apparatus  700  is disengaged from the pallet P by disengaging the releasable engagement system  710 , and the apparatus  700  is then moved back towards area S, in particular to its initial position between the spacer blocks  770  to engage with and transport the next pallet P to the next position along the storage path CS 1 , after which the pallet is locked in position. 
     This procedure can be repeated until the storage path CS 1  has been filled with the desired number of pallets P up to its full capacity. The other storage paths CS 2 , CS 3 , CS 4 , can be provided with pallets P in a similar manner to that described for storage path CS 1 , mutatis mutandis, each concurrently therewith (using a plurality of apparatuses  700 ), or in any desired sequence (using one or more apparatuses  700  in turn). Thus, the same apparatus  700  can be used for each storage path CS in turn, or several apparatuses  700  can be employed, one for each or several storage paths CS, allowing for concurrent operation. 
     Unloading the pallets from the freight deck D comprises the same steps as loading, but in reverse. 
     It is to be noted that one or more of cargo storage paths CS can deviate from being parallel to the aircraft centerline CL where the cross-section of the aircraft begins to significantly decrease towards the nose and tail of the aircraft, for example as illustrated in  FIG. 2( a ) , and the apparatus  700  can be steered along each respective cargo path CS via the controller  760  and guiding system  1300 . In yet other alternative variations of this example, the aircraft AC is configured for receiving the pallets P via the nose or tail of the aircraft, and thus in the respective cargo handling system each pallet P is transported by the apparatus  700  along the respective cargo storage path CS, and after the pallet has been locked in place the apparatus  700  returns to the nose or tail opening to then transport another pallet along the respective cargo storage paths CS, and so on for the other pallets. The spacer blocks are in such a case placed near the nose or tail opening. 
     Referring to  FIGS. 18( a ) and 18( b ) , a fourth example of the apparatus, designated  900 , has all the elements and functions of the apparatus  700 , mutatis mutandis, with some differences as will become clearer herein. In this example the apparatus  900  has a maximum height that is not restricted to spacing T, and the apparatus  900  cannot fit under a pallet P i.e., the apparatus  900  is not configured for being accommodated in the space M between the lower face LF of the pallet P and the freight deck D, although parts of the apparatus  900  can indeed enter the space M during operation thereof. 
     Rather, apparatus  900  is configured for being selectively affixed to a pallet P and for assuming a position forward or aft of the pallet P in a similar manner to apparatus  800  according to the second example of the presently discoed subject matter. This enables the apparatus  900  to be steered while pushing or pulling the pallet P over area S and along the desired cargo storage path CS, to its position thereon, after which the pallet P can be deposited and affixed in place, and the apparatus  900  can then disengage from the pallet P and move away therefrom. In other words, in operation the apparatus  900  tows the pallet P over the freight deck to a desired location thereon. In this example, the apparatus  900  is configured for selectively transporting each pallet P, one at a time, while each respective pallet P is in juxtaposed forward-aft relationship therewith. 
     Apparatus  900  thus comprises, a powered drive unit  930  and a controller  960 , similar to the powered drive unit  730  and a controller  760  of the third example, mutatis mutandis. 
     Apparatus  900  also comprises a releasable engagement system  910  similar to the releasable engagement system  810  of the second example, mutatis mutandis, and is thus configured for selectively engaging and for selectively disengaging the apparatus  800  with respect to each pallet P, in operation of the respective cargo handling system. Thus, and referring to  FIG. 18( a )  in particular, the releasable engagement system  910  comprises a clamping system  911  configured for selectively clamping the lip Q of the pallet P, for example similar to the clamping system,  811  of the second example, mutatis mutandis. Alternatively, and referring to  FIG. 18( b )  in particular, the engagement system  910  can be in the form of a fork-lift arrangement, for example similar to the fork lift arrangement of the second example, mutatis mutandis. 
     In the fourth example the transport apparatus  900  essentially replaces the transport apparatus  700  in a fourth example of the cargo handling system  20 ′. Thus, and referring to  FIG. 19 , cargo handling system  20 ′ according to the fourth example thereof comprises one or more transport apparatus  900 , the cargo support system  1200 , the guiding system  1300 , and the plurality of locking devices  1400  located on the freight deck D, as disclosed herein for the third example, mutatis mutandis. Each cargo unit comprises or is carried on a respective pallet P, with respect to a cargo storage path CS defined on the freight deck D of an aircraft AC. 
     System  20 ′ can be operated in a similar manner to the third example of system  20 , mutatis mutandis, with the main difference being that the apparatus  900  engages with each pallet via the respective releasable engagement system  910  and moves each pallet thus engaged in juxtaposed relationship rather than the overlying relationship of the third example Unloading the pallets from the freight deck D comprises the same steps as loading, but in reverse. 
     In alternative variations of this example, the controller  960  operates as manual control for controlling the movement of the apparatus  900 , and thus an operator manually operates the apparatus, using suitable control switches/devices in a control box, operatively connected to the apparatus  900  via wireless remote control, and thus controller  960  comprises a wireless remote control system including a suitable signal receiver (and optionally signal transmitter) system for receiving signals from the operator (and optionally transmitting signals to the operator, for example relating to operation of the apparatus  900 ). The operator can be in the aircraft itself, or in a completely remote location, and can monitor operation of the system  20 ′ via cameras installed in the aircraft, for example. 
     It is to be noted that the feature of wireless remote control system for the cargo handling system according to the first aspect of the presently disclosed subject matter (for example as disclosed above for the first, second, third or fourth examples or alternative variations thereof) is novel per se, and is applicable also to conventional cargo handling systems, mutatis mutandis. 
     Thus, according to a second aspect of the presently disclosed subject matter, there is also provided a cargo handling system for a freight deck of an aircraft, comprising:
         support structure configured for at least partially supporting at least one cargo unit thereon over the freight deck;   transport apparatus configured for selectively transporting the at least one cargo unit over said support structure;   wireless control system for wirelessly controlling operation of said transport apparatus.       

     In at least one example according to the second aspect of the presently disclosed subject matter, the support structure, the transport apparatus and the wireless control system can comprise the support structure, the mobile transport apparatus and the wireless remote control system, respectively, as disclosed above for the first, second, third or fourth examples or alternative variations thereof, according to the first aspect of the presently disclosed subject matter, mutatis mutandis. 
     In at least one other example according to the second aspect of the presently disclosed subject matter, the support structure and the transport apparatus can comprise the support structure and the transport apparatus used in conventional cargo transport systems. For example, the transport apparatus comprises a plurality of powered drive units (PDU&#39;s) statically located on the freight deck and longitudinally spaced parallel to the support structure, which is conventionally in the form of rails comprising rollers on an upper part thereof. Each PDU includes a powered drive wheel configured for selectively engaging an underside of the respective cargo unit for moving the respective cargo unit over the support structure. The wireless control system can comprise the wireless remote control system as disclosed above for the first, second, third or fourth examples or alternative variations thereof, according to the first aspect of the presently disclosed subject matter, mutatis mutandis. 
     In any case, the wireless control system according to the second aspect of the presently disclosed subject matter comprises a transmitter unit remote from a receiver unit, the receiver unit being operatively coupled to the respective transport apparatus and configured for controlling operation of the transport apparatus responsive to receiving control signals transmitted from the transmitter unit, which is remotely operated by the user. For example, the control signals include electromagnetic signals, for example radio signals, infra-red signals, microwave signals, and so on. 
     It is to be noted that the feature of the active guiding system for the cargo handling system according to the first aspect of the presently disclosed subject matter (for example as disclosed above for the first, second, third or fourth examples or alternative variations thereof) is one example of a sensor system that is novel per se, and is applicable also to conventional cargo handling systems, mutatis mutandis. 
     Thus, according to a third aspect of the presently disclosed subject matter, there is also provided a cargo handling system for a freight deck of an aircraft, comprising:
         support structure configured for at least partially supporting at least one cargo unit thereon over the freight deck;   sensor system configured for outputting an alignment signal representative of an alignment of the cargo unit with respect to the support structure.       

     In at least one example according to the third aspect of the presently disclosed subject matter, the support structure and the sensor system can comprise the support structure and the active guiding system, respectively, as disclosed above for the first, second, third or fourth examples or alternative variations thereof, according to the first aspect of the presently disclosed subject matter, mutatis mutandis. 
     In at least one other example according to the third aspect of the presently disclosed subject matter, the support structure can comprise the support structure of conventional cargo transport systems, and the sensor system is configured for guiding the manual manipulation of the cargo units into alignment with the support structure. Thereafter, once the cargo unit is aligned on the support structure, the cargo unit can be moved along using a conventional PDU or the mobile transport apparatus according to the first aspect of the presently disclosed subject matter. 
     In at least some examples, the aforesaid alignment refers to (and thus comprises) the degree of actual alignment between cargo unit and the support structure compared with an ideal alignment, and can include an angular and/or a translational deviation from the ideal alignment. The alignment signal generated by the sensor system is representative of this degree of alignment. For example, this ideal alignment occurs where the cargo unit is sufficiently aligned with respect to the support structure to enable the cargo unit to be moved over the support structure while supported by the support structure. 
     In at least one such example, the sensor system comprises a first component coupled to the cargo unit and a second component coupled to the support structure, and the first component interacts with the second component to generate the alignment signal. For example one of said first component and second component comprises a transmitter and the other one of said first component and second component comprises a receiver. The receiver transmits energy to the receiver (for example infra-red, radio waves, ultrasound, microwaves, and so on), and a parameter of this energy (for example the intensity thereof) varies as a function of the degree of alignment, enabling the sensor system to generate the alignment signal, which can have a signal strength, for example, that is related to this degree of alignment. 
     In another example, the first component comprises an image acquisition system and second component comprises a visual marker representative of the aforesaid ideal alignment. For example the first component can be a digital camera with optical recognition software for example, and the second component can be a strip running along the direction towards the support structure, the strip being reflective or of a different color to the rest of the floor, and is thus easily recognizable visually. The image acquisition system obtains and processes images of the visual marker, enabling the sensor system to generate the alignment signal, which can have a signal strength, for example, that is related to this degree of alignment. 
     In any case, such an alignment signal can be provided in the form of an audio signal and/or a visual signal to guide manual manipulation of the cargo unit into alignment with the support structure. For example, one or more persons pushing the cargo unit into alignment with the support structure can maneuver the cargo unit on the BTU&#39;s by listening to the audio signal and/or observing the visual signals. For example, the audio signals can be provided via one or more speakers, and can be in the form of beeps for example, in which the loudness thereof and/or the frequency thereof increase the closer the cargo unit is in ideal alignment with the support structure (culminating in a constant tone when alignment is reached, for example), and vice versa. For example, the visual signals can comprise a series of LED&#39;s or other light sources in prominent display, for example on the cargo unit itself or in the freight deck, and the number of LED&#39;s that are lit increases the closer the cargo unit is in ideal alignment with the support structure (culminating in all the LED&#39;s being lit when alignment is reached, for example), and vice versa. 
     In examples where the cargo unit is supported and transported over the flight deck on a mobile transport apparatus (for example, as disclosed above for the first, second, third or fourth examples or alternative variations thereof, according to the first aspect of the presently disclosed subject matter, mutatis mutandis), the alignment signal can be a digital signal or any other control signal for controlling the operation, and in particular the motion, of the mobile transport unit. 
     In the method claims that follow, alphanumeric characters and Roman numerals used to designate claim steps are provided for convenience only and do not imply any particular order of performing the steps. 
     Finally, it should be noted that the word “comprising” as used throughout the appended claims is to be interpreted to mean “including but not limited to”. 
     While there has been shown and disclosed examples in accordance with the presently disclosed subject matter, it will be appreciated that many changes may be made therein without departing from the spirit of the presently disclosed subject matter.