Method and system for loading and balancing an aircraft

Abstract

Method and system for loading and balancing an aircraft. The system comprises a balance acquiring device for measuring and / or calculating that a center of gravity of the aircraft is positioned within safe predetermined limits. An empty space and a goods space are arranged adjacent each other in a longitudinal direction of a cargo space. Displacement means moves the empty space and / or the goods space in the longitudinal direction to influence upon the center of gravity. Determining means are arranged for determining safe longitudinal positions of the goods space and / or the empty space in which the center of gravity is within said safe predetermined limit. The goods space and / or the empty space are adjusted during flight for adjustment of the center of gravity in dependence of the flight conditions, for saving fuel (aft position) and for stable operation (forward position).

Description

[0001] TITLE: METHOD AND SYSTEM FOR LOADING AND BALANCING AN AIRCRAFT

[0002] FIELD OF INVENTION

[0003] The present invention relates to a device and method for measuring weight of an aircraft and for balancing the aircraft for adjustment of center of gravity.

[0004] BACKGROUND ART

[0005] A passenger aircraft may be provided with a longitudinal floor / ceiling dividing the aircraft into an upper passenger space and a lower cargo space comprising cargo compartments. The cargo space additionally comprises other equipment required for the aircraft.

[0006] The present invention may be used on any aircraft. However, below, Boeing 737 is discussed as an example. Boeing 737 has a forward cargo compartment accessible via a forward cargo door and an aft cargo compartment accessible via an aft cargo door. The aircraft is supported by three wheel assemblies, two wheel assemblies under the wings and one nose wheel assembly.

[0007] One or both of the cargo compartments may be provided with a transport device for moving goods from an entrance of the cargo compartment to an inner end of the cargo compartment. Such transport device may be a transport band or belt, which is powered by an electric motor. Goods are loaded in the two cargo compartments for balancing the aircraft so that a center of gravity is positioned within an allowed range.

[0008] The wheel assemblies may be provided with load transducers, which measures the load exerted on the wheels. In this manner, the total weight may be measured. In addition, the center of gravity may be measured. The wheels may be arranged on weight scales arranged on the ground of the airport for measuring the weight on each wheel. Alternatively, or additionally, the wheel struts may be provided with strain gauges that measures the weight on each wheel. Other devices may measure the distance between the fuselage and the ground, as an indication of a compression of springs of the wheel assemblies.

[0009] By these measures, the total weight of the aircraft and the balancing of the aircraft can be measured at ground before take-off. The aircraft is balanced so that the center of gravity is always forward of a center of lift of the wings. This will ensure that the aircraft is always tipped forward if the aircraft looses speed, which will result in that the aircraft gain speed again.

[0010] If the balancing is performed so that the center of gravity is close to the aft limit of the allowable range, the aircraft may be difficult to control during take-off and harsh flight conditions. On the other hand, if the center of gravity is close to the forward limit of the allowable range, the aircraft may need extra long distance for take-off and may also have an increased fuel consumption. Therefore, the balancing may be a trade-off between these two limits.

[0011] When the aircraft is cruising at a high altitude, it may be desired to have the center of gravity close to the aft end of the range, since the fuel consumption then becomes small. However, the possibility to influence upon the balance during flight is limited essentially only to pump fuel between tanks.

[0012] There is a need in the art for a balancing feature that enables the aircraft to balance the center of gravity during flight that is safe and decreases the fuel consumption.

[0013] SUMMARY OF THE INVENTION

[0014] Accordingly, an object of the present invention is to mitigate, alleviate or eliminate one or more of the above-identified and other deficiencies and disadvantages singly or in any combination.

[0015] In an aspect, there is provided a method for loading and balancing an aircraft, comprising: loading the aircraft with goods for balancing the aircraft so that a center of gravity is positioned within safe predetermined limits at ground; loading at least a portion of said goods for arranging empty spaces and goods spaces adjacent each other in a longitudinal direction of the aircraft at ground; moving or simulating moving said empty spaces and / or goods spaces in the longitudinal direction for adjustment of the center of gravity; determining safe longitudinal positions of said empty spaces and / or said goods spaces, in which safe longitudinal positions the center of gravity is within said safe predetermined limits. The method may further comprise: measuring and / or calculating the total weight of the aircraft to determine that the total weight is below a predetermined maximum weight.

[0016] In an embodiment, the method may further comprise: adjusting, during flight, the center of gravity within said safe predetermined limits by moving said empty spaces and / or said goods spaces within said safe longitudinal positions.

[0017] In a further embodiment, the method may further comprise: adjusting, during flight, the center of gravity to an aft position for reducing fuel consumption, and / or adjusting, during flight, the center of gravity to a forward position for increasing manoeverability.

[0018] In a still further embodiment, the method may further comprise: locking the goods spaces from movement in between said adjustment during flight. In addition, the method may further comprise: measuring a position of the center of gravity of the aircraft during flight.

[0019] In another aspect, there is provided a system for loading and balancing an aircraft, comprising: a balance acquiring device for measuring and / or calculating that a center of gravity of the aircraft is positioned within safe predetermined limits; an empty space and a goods space arranged adjacent each other in a longitudinal direction of a cargo space of the aircraft; displacement means for moving said empty space and / or said goods space in the longitudinal direction of the cargo space to influence upon the center of gravity; determining means for determining safe longitudinal positions of said goods space and / or said empty space in which the center of gravity is within said safe predetermined limit. The system may further comprise: a weight acquiring device for measuring and / or calculating the total weight for determining that the total weight is below a predetermined maximum weight.

[0020] In an embodiment, the system may further comprise: a control device for adjusting the position of the loading member for adjusting the center of gravity during flight. Stop means may be arranged for preventing said goods space and / or said empty space from moving out of said safe longitudinal positions.

[0021] In a further embodiment, the system may further comprise: a loading member comprising said goods space and at least a portion of said empty space, wherein the loading member is arranged to at least partly move said goods space into said empty space in the longitudinal direction between an aft longitudinal position and a forward longitudinal position of the goods space and vice versa. The loading member may comprise a belt which is moveable in a longitudinal direction of the cargo space; a first partition wall and a second partition wall between which the goods space is arranged; a drive arrangement for engagement with the belt; and a motor and a worm gear for self-locking movement of the belt.

[0022] BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Further objects, features and advantages of the invention will become apparent from the following detailed description of embodiments of the invention with reference to the drawings, in which:

[0024] Fig. l is a schematic side view of an aircraft in which an embodiment of the present invention can be installed.

[0025] Fig. 2 is a diagram showing limits for the center of gravity and maximum load of an aircraft.

[0026] Fig. 3 is a schematic side view of an embodiment of the present invention.

[0027] Fig. 4 is a schematic side view of another embodiment of the present invention.

[0028] Fig. 5 is a schematic side view or a portion of the embodiment of Fig. 4.

[0029] DETAILED DESCRIPTION OF EMBODIMENTS

[0030] Below, several embodiments of the invention will be described. These embodiments are described in illustrating purpose in order to disclose the best mode and to enable a skilled person to carry out the invention. However, such embodiments do not limit the scope of the invention, which is only limited by the patent claims. Moreover, certain combinations of features are shown and discussed. However, other combinations of the features described are possible within the scope of the invention. There are many factors that lead to efficient and safe operation of an aircraft. Among these factors is proper weight and balance control. The weight and balance system commonly employed among aircraft consists of three elements: the weighing of the aircraft, the maintaining of the weight and balance range or limits, and the proper loading of the aircraft. Improper loading and balancing may be the cause of failure to complete the flight, or failure to start or end the flight.

[0031] The responsibility for proper weight and balance control begins with the engineers and designers, and extends to the aircraft mechanics that maintain the aircraft and the pilots who operate them. The designers of an aircraft have set the maximum weight, based on the amount of lift the wings can provide under the operation conditions for which the aircraft is designed. The structural strength of the aircraft also limits the maximum weight the aircraft can safely carry.

[0032] An ideal location or position of the center of gravity (CG) is very carefully determined by the designers, and a maximum deviation allowed from this specific location is defined.

[0033] The manufacturer provides the aircraft operator with the empty weight of the aircraft and the location of its empty weight center of gravity (EWCG) at the time the certified aircraft leaves the factory. The pilot in command of the aircraft has the responsibility on every flight to know the maximum allowable weight of the aircraft and its CG limits. This allows the pilot to determine on the preflight inspection that the aircraft is loaded in such a way that the CG is within the allowable limits before flight.

[0034] Severe uncoordinated maneuvers or flight into turbulence can impose dynamic loads on the structure great enough to cause failure. In accordance with Title 14 of the Code of Federal Regulations (14 CFR) part 23, the structure of a normal category aircraft must be strong enough to sustain a load factor of 3.8 times its weight.

[0035] Most modern aircraft are so designed that if all seats are occupied, all luggage allowed by the luggage compartment is carried, and all of the fuel tanks are full, the aircraft will be grossly overloaded. This type of design requires the pilot to give great consideration to the requirements of the flight. If maximum range is required, occupants or luggage must be left behind, or if the maximum load must be carried, the range, dictated by the amount of fuel on board, must be reduced.

[0036] One important preflight consideration is the distribution of the load in the aircraft. Loading the aircraft so the gross weight is less than the maximum allowable is not enough. This weight must be distributed to keep the CG within the limits specified before flight.

[0037] The fuel load should also be balanced longitudinally as well as laterally.

[0038] Balance control refers to the location of the CG of an aircraft. This is of primary importance to aircraft stability, which determines safety in flight. The CG is the point at which the total weight of the aircraft is assumed to be concentrated, and the CG must be located within specific limits for safe flight. Both lateral and longitudinal balance are important, but the prime concern is longitudinal balance; that is, the location of the CG along the longitudinal or lengthwise axis of the aircraft. An aircraft is designed to have stability that allows it to be trimmed so it will maintain straight and level flight with hands off the controls. Longitudinal stability is maintained by ensuring the CG is slightly ahead or forward of the center of lift. This produces a nose-down force independent of the airspeed. This is balanced by a variable nose-up force, which is produced by a downward aerodynamic force on the horizontal tail surfaces or stabilizers that varies directly with the airspeed.

[0039] If a rising air current should cause the nose to pitch up, the aircraft will slow down and the downward force on the tail will decrease. The weight concentrated at the CG will pull the nose back down. If the nose should drop in flight, the airspeed will increase and the increased downward tail load will bring the nose back up to level flight.

[0040] As long as the CG is maintained within the allowable limits for its weight, the aircraft will have adequate longitudinal stability and control. If the CG is too far aft, it will be too near the center of lift and the aircraft may be unstable, and may be difficult to recover from a stall. If the CG is too far forward, the downward tail load will have to be increased to maintain level flight. This increased tail load has the same effect as carrying additional weight; the aircraft will have to fly at a higher angle of attack, and drag will increase as will fuel consumption. A more serious problem caused by the CG being too far forward is the lack of sufficient elevator authority. At slow takeoff speeds, the elevator might not produce enough nose-up force to rotate the aircraft and on landing there may not be enough elevator force to flare the aircraft. Both takeoff and landing runs will be lengthened if the CG is too far forward.

[0041] Consequently, the aircraft is loaded with goods and passengers in a carefully determined manner. Normally, the goods is weighted and entered into a computer system that can distribute the goods in a manner resulting in a proper position of the CG. Often the weight of the passengers is not weighted, but a statistical approach is used. All passenger is assigned a weight which is constant. The passengers are assigned to seats in the aircraft, so that the aircraft is balanced. Since often people from Japan has a mean weight which is smaller than people from United States, such deviations may be taken care of by the computer system.

[0042] Anyhow, the true weight and distribution of the weight of the passengers in the aircraft cannot be assessed without measuring the weight of each passenger and the luggage. In certain airports it is implemented that each passenger including hand luggage is weighted before entering the aircraft and the measured weight is attributed to a corresponding seat. In this manner, the weight distribution can be known in advance and be taken care of by the computer system. Many aircrafts are equipped with a CG range chart indicating the allowed CG position in relation to the aircraft total weight. The range chart may indicate a CG range in relation to a stationary position or datum of the aircraft, such as a fuselage station.

[0043] Such a CG range chart is shown in Fig. 2 in relation to a small aircraft that can have a maximum aircraft weight of 1100 kg and wherein a CG range is between 208 - 236 cm behind or aft of a fuselage station.

[0044] As indicated, the CG may not be too far from the aft end of the CG range if the aircraft is heavily loaded above 900 kg.

[0045] The chart also shows that the aircraft weight is limited to below 820 kg and the CG range is limited to between 208 - 220 cm if the aircraft is going to be used in Utility category. In Utility category, the aircraft is approved for limited acrobatics such as spins, lazy eights, chandelles, and steep turns in which the bank angle exceeds 60°. When operated in the Normal category, the aircraft is restricted from these maneuvers.

[0046] Fig. 2 also shows a wing cross section 21 with the lifting force point 22 and leading edge 23 (LE) indicated.

[0047] In larger aircrafts it is common to use another measure, namely in percent of a mean aerodynamic chord (MAC) of the aircraft wings. It is important for longitudinal stability that the CG be located ahead of the center of lift of a wing. Since the center of lift is expressed as a percentage of the MAC, the location of the CG is expressed in the same terms. The CG limits are indicated in relation to a leading edge (LE) of the mean aerodynamic chord, i.e. LEM AC. When constructing the aircraft, the design is made so that the air foils have a predetermined center of lift. In addition, a length of the mean aerodynamic chord (MAC) and a position of the leading edge (LE) in relation to a datum are indicated. Knowing these parameters, the percentage of the position of CG in relation to MAC can be calculated. If the aircraft mentioned above with reference to Fig. 2 has a MAC of 75 cm and a position of LE of 200 cm forward of the fuselage station, the CG limits will be 10% - 47% MAC. Normally, an aircraft will have acceptable flight characteristics if the CG is located somewhere near 25% MAC.

[0048] The empty weight of the aircraft (EW) is known in advance as well as the empty weight center of gravity (EWCG). If the loaded goods is weighted and also the passengers are weighted, and the amount of fuel and oil loaded is known, the total weight of the aircraft and the center of gravity can be calculated before take-off.

[0049] However, the entire loaded aircraft may alternatively or additionally be weighted to determine its total loaded weight and the center of gravity CG. This can be performed by measuring the loads of the wheels by one or several scales or other means.

[0050] In an embodiment, the wheels may be entered on mechanical scales, such as of a low-profile type. Large aircraft may be weighed by rolling them onto weighing platforms with electronic weighing cells that accurately measure the force applied on the wheels by the weight of the aircraft.

[0051] Electronic load cells may be used when the aircraft is weighed by raising it on jacks. The load cells are placed between the jacks and jack pads on the aircraft, and the aircraft is raised on the jacks until the wheels are off the ground and the aircraft is in a level flight attitude. The weight measured by each load cell is indicated on the control panel.

[0052] Mechanical scales should be protected when they are not in use, and they must be periodically checked for accuracy by measuring a known weight.

[0053] Electronic scales normally have a built-in calibration that allows them to be accurately zeroed before any load is applied.

[0054] Fig. 1 is a side view of an aircraft 1 of the type Boeing 737, comprising a passenger space 2 and a forward cargo compartment 3 having a forward cargo door 5 and an aft cargo compartment 4 having an aft cargo door 6. A lifting force 7 is lifting the aircraft during flight. The lifting force normally operates from a lifting force point 7a adjacent the middle of the wings 7b. A load force 8 is concentrated in a center of gravity 8a (CG) and operates at a point slightly forward of the lifting force point 7a. A balancing force 9 is exerted by stabilizers 9b and operates at a stabilizer force point 9a aft of the lifting force point 7a, normally as aft as possible from the lifting force point 7a. At ground, the aircraft is supported by two wing wheels 2a arranged aft of the lifting force point 7a and a nose wheel 2b arranged close to the nose or front portion of the aircraft. Other aircrafts may have other layout of the corresponding parts.

[0055] With reference to Fig. 1, during flight, the wings exert a lifting force 7. The total weight 8 of the aircraft including passengers and luggage and fuel etc is concentrated to a Center of Gravity (CG) point 8a forward of the lifting force point 7a. In order to balance the aircraft during flight, the stabilizers 9b exerts a downward stabilizer force 9. The lifting force 7 is the sum of the total load force 8 and the stabilizer force 9.

[0056] If the center of gravity is arranged closer to the lifting force point 7a as shown by dotted arrow 8’, the stabilizer force is decreased as shown by arrow 9’ for keeping the balance. The lifting force 7 is decreased by the same amount as the stabilizer force as shown by arrow 7’. A decrease of the wing lifting force (from arrow 7 to arrow 7’) as well as a decrease of the stabilizer force (from arrow 9 to arrow 9’) result in a decrease of fuel consumption. However, an aft arrangement of the center of gravity (close to the lifting force point 7a) results in that the manoeverabilty of the aircraft may be compromised.

[0057] A consideration is that most aircrafts are constructed so that if both the passenger space and the luggage space are filled, the aircraft will be heavily overloaded. Thus, there inevitably becomes spaces within the passenger space and / or the luggage space which are empty. Intelligent arrangement of such empty spaces, would be desired. It is not a good idea to adjust passenger empty space because passenger tends to move uncontrolled. However, empty spaces in the luggage space may be used intelligently.

[0058] According to embodiments of the invention, the center of gravity may be influenced upon or shifted, not only during preflight conditions, but also during flight. Such shifting may reduce fuel consumption without compromising safety.

[0059] In an embodiment shown in Fig. 3, the aft cargo compartment is provided with a loading member. In the embodiment shown in Fig. 3, the loading member comprises a moveable longitudinal transport belt 31 which is returned by an aft roller 32 adjacent the aft cargo door 6 and a forward roller 33. The forward roller 33 is driven by an electric motor 34 and a worm gear 35. The aft roller 32 is idling (free rolling). The worm gear 35 has the property that it is self-locking. If the electric motor 34 is not running, the worm gear will effectively prevent the corresponding roller 33 from rotation, and the belt 31 will be locked in its position.

[0060] The belt 31 is provided with a forward partition wall 36 and an aft partition wall 37 delimiting a goods space 15. The aft partition wall 37 may be removable for facilitating loading of goods 38 between the partition walls 36, 37. When the goods have been loaded, the aft partition wall 37 is secured in place, so that the goods are entrapped between the partition walls 36, 37 in the goods space 15.

[0061] Forward of partition wall 36, there is an empty space 10. The empty space 10 and the goods space 15 influence upon the center of gravity. If the empty space 10 is moved aft by moving the transport belt 31 forward, the center of gravity will move forward and vice versa. The empty space 10 will be divided in a decreasing forward empty space forward of partition wall 36 and an increasing aft empty space aft of the partition wall 37. If the forward empty space is decreased, the center of gravity will move forward. This is because the luggage 38 between the partition walls 36 and partition wall 37 in the goods space 15 moves forward. The partition walls 36, 37 and the belt 31 together form the loading member. The loading member 31, 36, 37 is moveable as a unit between an aft position shown in Fig. 3 and a forward position shown by broken lines 39 in Fig. 3.

[0062] Further movements beyond the forward position is prevented by a forward stop device 40 and further movements beyond the aft position is prevented by an aft stop device 41.

[0063] The aft stop device 41 may be removable together with the aft partition wall 37 when loading the goods and then replaced.

[0064] The forward and aft stop devices 40, 41 are adjustable and are adjusted in dependence of the measurement of the center of gravity at ground before take off.

[0065] Consequently,, the movement of the goods space and / or the empty space is confined to safe longitudinal positions. If the aircraft is heavily loaded, there is a restricted position for the forward position of the goods space 15. This is shown by a second forward stop device 40a, which is adjustable and is determined at ground before flight. The normal forward stop device 40 may additionally be measured together with the restricted second forward stop device 41a.

[0066] This is of interest for the pilot if the flight includes an intermediate stop in which some passengers will leave the aircraft and thereby the total weight will decrease. In this case, the pilot may deactive the second forward stop device 40a after said passengers have left the aircraft and use the full dynamic range of CG positions including the normal stop device 40, see the chart of Fig. 2.

[0067] There may be arranged a scale, which indicates the position of the goods space between its two extreme positions. The scale may give a measure between 0 % and 100%. Thus, the pilot may know where the center of gravity is positioned at any time by reading the scale.

[0068] There may be arranged locking devices which locks the loading member in an adjusted position, which may be at the end of the safe longitudinal positions or between such safe longitudinal positions

[0069] Such locking devices may be electromagnets which when activated locks the belt and / or the goods space in its position. Another type of locking device may be hooks which cooperate with lugs in the cargo space or cogs or cog wheels cooperating with cog racks.

[0070] When the loading member should be adjusted, such locking device is deactivated and the loading member is free to be adjusted. When, the adjustment is finalized, the locking device is activated. Such locking device can be in addition to the self-locking feature of a worm-gear or be instead of such self-locking feature of the worm-gear.

[0071] The loading member 31, 36, 37 may be moveable over a safe distance shown by arrow 42.

[0072] The goods is loaded in a cargo space of the aircraft by placing the belt in the aft position. All goods may have been weighted in advance. The total number of passengers is also known in advance and the seats occupied by the passengers. The total weight of the passengers including hand-luggage can be estimated. Alternatively or additionally the passengers and the hand-luggage can be weighted.

[0073] The goods is loaded both in the forward cargo compartment and in the rear cargo compartment (if applicable) and on the loading member in the goods space. After loading, the loading member may be positioned in a middle position between its extreme positions. Thereafter, a center of gravity is measured to be at a desired position, for example at 25% MAC. Finally, the loading member is positioned in its two end positions and the center of gravity is measured in both positions and it is determined that both positions results in that the center of gravity is within the allowed range, for example between 10% and 47% MAC. If the CG position is outside its allowable range, the stop devices are adjusted so as to limit the movement of the goods space accordingly.

[0074] If the loading member is close or adjacent to the cargo door, for example the aft cargo door, the loading member may not occupy the entire cargo space and there will be a space forward of the loading member, which may be loaded with goods in a normal manner.

[0075] The end or extreme positions of the loading member may not result in that the end positions in the range of center of gravity is reached. For example, when the loading member is in its maximum forward position, the center of gravity may be 17% MAC and when the loading member is in its maximum aft position, the center of gravity may be 40% MAC, which both are within the safe predetermined limits of the center of gravity.

[0076] The position of the goods space and / or the empty space can be adjusted by the pilot or by a control computer of the aircraft both at the ground and during flight.

[0077] Adjustment of the position of the goods space and / or the empty space may be prevented or restricted during take off and landing.

[0078] A possible scenario may be that the pilot wants to initiate a take-off at 25% MAC, whereby the load member is adjusted to a corresponding position. This gives the pilot adequate control during start. The position is maintained during the entire take-off. When cruising altitude has been reached, the pilot activates the worm gear motor 34, 35 to move the load member aft as long as desired, for example to the position shown at 37 in Fig. 3 corresponding to 17% MAC. This will result in that the drive computer of the aircraft reduces the attack angle of the stabilizers and reduce the drag thereof according to arrow 9’, thereby decreasing the fuel consumptions. In addition, the aircraft only needs to produce a smaller lifting force according to arrow 7’ counteracting weight of the aircraft and the downward force 9’ of the stabilizers, which means that the energy for producing the lifting force will decrease and thereby further decrease the fuel consumption.

[0079] If the aircraft reaches an area of turbulence, the pilot may want better command and stability of the aircraft, whereby the load member is moved forwards as much as requested by the pilot or the aircraft command system, for example 35 % MAC.

[0080] During landing, better command is desired, whereupon the load member may be adjusted to provide 25% MAC.

[0081] During flight, the fuel is burned and the center of gravity is influenced by such decrease of fuel. The center of gravity is normally moved forward when fuel is consumed. This may be compensated automatically by moving the loading member appropriately aft as determined by the aircraft control computer. If several persons move aft in the aircraft in unison, the center of gravity may be influenced and this can be compensated automatically by moving the loading member forwards.

[0082] Since it most often is desired to move the loading member towards the aft, it may be advantageous to adjust the position mentioned above so that the loading member is 25% from its forward position when the aircraft center of gravity is 25% MAC. This will give better adjustment possibilities during flight.

[0083] It is noted that the center of gravity should not be too far forward if the aircraft is heavily loaded close to its maximum weight. This is clear from a study of the diagram of Fig. 2, which indicates that the maximum forward position of the center of gravity is 220 cm behind a fuselage station at maximum load of 1100 kg but can be up to 208 cm behind the fuselage station when the load is below 880 kg.

[0084] On the other hand, if manoeverability is desired, such as during utility flight, the center of gravity should be more forward.

[0085] Many of the adjustment can be performed automatically by a flight computer. Other adjustments can be under full control of the pilot or a combination.

[0086] The considerations in the eight previous paragraphs may apply to all embodiments described in the present specification.

[0087] In order to make appropriate adjustments, it may be desired to measure the center of gravity during flight. The stabilizer downward force 9 is an indication of the position of the center of gravity, the smaller the force 9 is, the more aft is the center of gravity, but still forward of the lifting force point 7a.

[0088] The inclination or attack angle of the stabilizers is a measure of the force 9. Strain gauges may be arranged at the stabilizers to measure the inclination of the stabilizers.

[0089] Another indication of the center of gravity is fuel consumption per minute or per km.

[0090] A further manner to determine if the aircraft is properly balanced is to move the loading member or goods space slightly back and forward. If the center of gravity is close to its aft position, such small movements will cause a large correcting response from the flight computer compared to if the center of gravity is close to its forward position, since the aircraft is more sensitive to stabilizer action when the center of gravity is close to its aft position.

[0091] All these measuring methods may be combined in order to control the aircraft and the goods space and / or empty space to optimize the aircraft during take-off, flight and landing.

[0092] The loading member may be arranged as far aft in the aircraft as possible, since the lever arm will be large. Alternatively or additionally, the loading member may be arranged as forward as possible, which will also give a large lever arm. It is desired to arrange the loading member in the last fourth and / or the first fourth of the aircraft.

[0093] Arrangement of the goods space and / or the empty space aft of the aft cargo door or forward of the forward door is advantageous.

[0094] It is also possible to arrange the loading member in the main cargo compartment beneath the wings, and in this case, the loading member may be larger and perhaps comprise almost all goods loaded in the aircraft. It is important to ensure that the center of gravity under no circumstances will arrive outside the range allowed for the aircraft. A computer can calculate the appropriate goods distribution in each circumstance. As a second safety measure, the aircraft may be weighted by scales before take-off, with the loading member in its extreme positions.

[0095] The amount of goods required at the loading member or goods space for appropriate control is calculated by the computer. If there is too heavy goods at the goods space, it may be difficult to fine-tune the aircraft during flight, when it is desired to have the center of gravity close to its aft end. If there is too little goods at the goods space, the range of adjustment of the center of gravity may be too small.

[0096] Another embodiment of the loading member is shown in Fig. 4. The aircraft comprises an aft cargo compartment 44a having an aft cargo door 46. The aft cargo compartment includes an extra aft cargo compartment 44b extending aft of the aft cargo door 46. There is also a forward cargo compartment 43a having a forward cargo door 45. The forward cargo compartment includes an extra forward cargo compartment 43b extending forward of the forward cargo door 46.

[0097] A lifting force 47 operates from a lifting force point 47a. A center of gravity force 48 operates from a center of gravity that can be adjusted between a forward center of gravity 48a and an aft center of gravity 48b. A balancing force 49 is exerted by stabilizers 49b. At ground, the aircraft is supported by wheels 42a and 42b.

[0098] In the embodiment of Fig. 4, four arrangements of loading members are shown which can be used separately or in any combination.

[0099] A first aft loading member 51 is arranged in the extra aft cargo compartment 44b, which is narrowing towards the aft as shown. A container 51a (forming the goods space) is arranged at a transport belt 51b similar to transport belt 31 shown in Fig. 3. The container 51a is moveable between an aft position shown in Fig. 4 and a forward position, as shown by arrow 51c. Since the container 51a is arranged at a long distance from the lifting force point 47a, a small movement of the container 51a results in a large movement or shift of the center of gravity force 48.

[0100] A second aft loading member 52 is arranged forward of the aft cargo door 46. The second aft loading member comprises one or several containers 52a (three are shown) arranged on a transport belt 52b. The plurality of containers 52a are moveable from the shown forward position to an aft position as shown by arrow 52c. The containers may be moved in unison or in sequence. If moved in sequence, the aft container is first moved as far aft as possible, whereupon the second container is moved until close to the first moved container and so forth, until proper balance has been achieved. Since the most forward container is relatively close to the lifting force point 47a, it will have small influence on the position of the center of gravity. A third forward loading member 53 is arranged forward of the center of gravity in the forward cargo compartment 43a. One or several containers 53a (four are shown) are arranged on a transport belt 53b. The plurality of containers 53a are moveable from the shown forward position to an aft position as shown by arrow 53c. The containers may be moved in unison or in sequence.

[0101] A fourth forward loading member 54 is arranged in the extra forward cargo compartment 43b. A container 54a is arranged on a transport belt 54b and is moveable between the shown forward position and an aft position as shown by arrow 54c. Since the container 54a is arranged at a long distance from the lifting force point 47a, a small movement of the container 54a results in a large movement of the center of gravity 48. It is noted that the container 54a may be at least partly moved into the empty space used by the cargo door 45. This is only temporary during flight. When the aircraft is on ground, the container can be moved back to the position shown in Fig. 4.

[0102] The container may be the loading member 36, 37, 38 described in Fig. 3 or the goods space. Alternatively or additionally, the container may be preloaded in a standard format at the airport as is known.

[0103] The transport belt may be replaced by any means that may move the loading member as described above, such as chains, wires, rollers, cog wheels or magnetic movement devices. This applies to all the described embodiments. The transport belt may be an endless belt arranged over the rollers.

[0104] When loading containers, driven rollers may be used for moving the containers to the intended position, and for moving the containers during flight. After movement, the containers are securely locked in place, for example with electromagnets or mechanical measures.

[0105] The embodiment in which the container is located forward of or adjacent the forward cargo door and in which the container is located aft of or adjacent the aft cargo door are advantageous since they will have a large impact on the position of the center of gravity. Thus a smaller cargo load may be used, which means that the loading member may be easier to lock in position after adjustments during flight, which improves the security.

[0106] It is possible to arranged the loading member in the area of the cargo door, after the rest of the cargo has been loaded. In this embodiment, the aircraft need not be reconstructed for housing specialized transport facilities for the goods, but a freestanding prebuilt unit comprising a goods space and an empty space may be inserted in the door space opposite the door or any other convenient place.

[0107] Fig. 4 shows the third forward loading member 53 in which all four containers are arranged at a forward position. An empty space is shown at the aft side of the containers.

[0108] Fig. 5 shows the third forward loading member 53 in three consecutive positions. In the first position, the aft container has been moved into the empty space and a new empty space 11 is formed between the first and the second aft containers. In the second position, the second container has been moved into the empty space 11 and a new empty space 12 has been formed between the second and third container. In the third position, the third container has been moved into the empty space 12 and a new empty space 13 has been formed between the third and fourth container. In this sequence, it can be seen that the empty space is moved for influencing upon the center of gravity.

[0109] The measurement may determine that the positions shown in Fig. 5 results in that the center of gravity is within predetermined limits. Thus, the positions of the empty space indicated in Fig. 5 are safe longitudinal positions. The containers may be arranged at any position within these safe longitudinal positions.

[0110] The empty spaces do not need to have the same size as the goods space, but may be smaller or larger. There may be several empty spaces. For example, if the second left container in Fig. 5 is moved only half the distance, two empty spaces are formed, which are small.

[0111] Since security is of outmost importance, the system may be arranged so that the loading members cannot be moved if there is turbulence or other disorder in the aircraft. In addition, restrictions may apply during take-off and landing.

[0112] Although the safe longitudinal positions of the goods space and the empty space may be determined at ground before take-off, further determination of the safe longitudinal positions may be required or desired during flight. Such adjustment can be made in dependence of consumption of fuel and can be pre-calculated by a flight computer. Other adjustment may be performed after an intermediary stop for leaving or adding passengers and / or goods or for adding new fuel for a long trip. Such adjustment may result in new limits for the movement of the goods space and empty space.

[0113] It is also conceivable that the balancing can be dynamically controlled during flight by observing the movement of the aircraft.

[0114] The safe longitudinal positions can be determined by simulating movement of the goods space and empty space and calculating the resultant impact on the center of gravity. The simulation can be performed by estimating the weight of the goods space and the weight of the entire aircraft. In addition, the longitudinal position of the goods space is estimated or determined in advance.

[0115] It is also conceivable that the take-off is performed by an adjustment of the goods space and empty space controlled by the computer data without actual measurement. After take-off, when it is desired to adjust the center of gravity, such adjustment may be preceded by measurement of the safe longitudinal positions up in the air during flight, by measurements as indicated above.

[0116] In the claims, the term "comprises / comprising" does not exclude the presence of other elements or steps. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit. Additionally, although individual features may be included in different claims or embodiments, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and / or advantageous. In addition, singular references do not exclude a plurality. The terms "a", "an", “first”, “second” etc. do not preclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

[0117] Although the present invention has been described above with reference to specific embodiment, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and other embodiments than those specified above are equally possible within the scope of these appended claims.

Claims

CLAIMS1. A method for loading and balancing an aircraft, comprising: loading the aircraft with goods for balancing the aircraft so that a center of gravity is positioned within safe predetermined limits at ground; loading at least a portion of said goods for arranging empty spaces and goods spaces adjacent each other in a longitudinal direction of the aircraft at ground; moving or simulating moving of said empty spaces and / or goods spaces in the longitudinal direction for adjustment of the center of gravity; determining safe longitudinal positions of said empty spaces and / or said goods spaces, in which safe longitudinal positions the center of gravity is within said safe predetermined limits.

2. The method according to claim 1, further comprising: measuring and / or calculating the total weight of the aircraft to determine that the total weight is below a predetermined maximum weight.

3. The method according to claim 1 or 2, further comprising: adjusting, during flight, the center of gravity within said safe predetermined limits by moving said empty spaces and / or said goods spaces within said safe longitudinal positions.

4. The method as claimed in claim 3, further comprising: adjusting, during flight, the center of gravity to an aft position for reducing fuel consumption.

5. The method as claimed in claim 3, further comprising: adjusting, during flight, the center of gravity to a forward position for increasing manoeverability.

6. The method according to claim 3, 4 or 5, further comprising: locking the goods spaces from movement in between said adjustment during flight.

7. The method according to any one of the previous claims, further comprising: measuring a position of the center of gravity of the aircraft during flight.

8. A system for loading and balancing an aircraft, comprising: a balance acquiring device for measuring and / or calculating that a center of gravity of the aircraft is positioned within safe predetermined limits;an empty space and a goods space arranged adjacent each other in a longitudinal direction of a cargo space of the aircraft; displacement means for moving said empty space and / or said goods space in the longitudinal direction of the cargo space to influence upon the center of gravity; determining means for determining safe longitudinal positions of said goods space and / or said empty space in which the center of gravity is within said safe predetermined limit.

9. The system according to claim 8, further comprising: a weight acquiring device for measuring and / or calculating the total weight for determining that the total weight is below a predetermined maximum weight.

10. The system according to claim 8 or 9, further comprising: a control device for adjusting the position of the loading member for adjusting the center of gravity during flight.

11. The system according to claim 8, 9 or 10, further comprising: stop means for preventing said goods space and / or said empty space from moving out of said safe longitudinal positions.

12. The system according to any one of claims 8 to 11, further comprising: a loading member comprising said goods space and at least a portion of said empty space, wherein the loading member is arranged to at least partly move said goods space into said empty space in the longitudinal direction between an aft longitudinal position and a forward longitudinal position of the goods space and vice versa.

13. The system according any one of claims 8 to 12, wherein the loading member comprises: a belt which is moveable in a longitudinal direction of the cargo space; a first partition wall and a second partition wall between which the goods space is arranged; a drive arrangement for engagement with the belt; and a motor and a worm gear for self-locking movement of the belt.

Images