There are many critical aspects of an aircraft taking flight, which a commercial airline must resolve when determining if a departing aircraft is safe for take-off. Two of these factors are identifying the proper Weight and Center of Gravity for the aircraft. Hereinafter, aircraft “Center of Gravity” will be referred to as aircraft “CG.”
The Federal Aviation Administration (“FAA”) has published FAA-Advisory Circular AC20-161 defining requirements for onboard aircraft weight and balance systems used to “measure” the aircraft weight. Variations of onboard aircraft weighing systems basically convert the aircraft landing gear struts into scales. Prior art methods for converting aircraft landing gear struts into scales are well documented and reference may be made to United States patents:
The FAA has also published Advisory Circular AC120-27E defining requirements for an approved method to determine the aircraft weight by “calculations” which are independent of any requirement to measure of the aircraft total weight. The fully loaded weight of the aircraft is calculated by a process of compiling the weights of various payload items based upon FAA approved “designated” average weights, for the varying elements such as passengers, carry-on baggage, checked baggage, crew weight, cargo weight and the weight of fuel loaded; onto a previously measured empty aircraft weight. This method of calculating the aircraft weight based on the summing of the various elements loaded on to a pre-measured empty aircraft weight is often referred to as the Load Build-Up Method, hereinafter referred to as “LBUM”.
In spite of the prior art patents, no U.S. airlines currently use OnBoard aircraft Weight and Balance Systems (OBWBS), but instead all typically use the UBUM to deternnine aircraft weight.
A determination of the aircraft CG can be made from the calculations for the weight of each element of payload to an assigned and known location within the aircraft. Aircraft CG is a critical factor within an airline's Flight Operations Department. If the aircraft CG is too far aft and outside the aircraft's certified CG limits, the aircraft nose can rise uncontrollably during take-off, where the aircraft will become unstable, resulting in a stall and possible crash. Furthermore, fuel is the most costly item in an airline's annual expenses. Airline profit margins are slim at best, so any and all efforts must be used to reduce fuel consumption. The aircraft CG location affects the amount of engine power required to keep the aircraft aloft, and how much fuel the engines require to do so. If an aircraft is loaded with the CG positioned towards the forward limit of the aircraft's CG envelope, the pilot must add rear stabilizer trim for the nose-heavy aircraft. This additional rear stabilizer trim will increase the aerodynamic drag on the aircraft, thus consume more fuel. If an aircraft can be loaded with the aircraft CG positioned near the aft limit of the aircraft CG envelope, the aircraft will require less trim and be more fuel efficient.
Typical aircraft used in day-to-day airline operations are commonly supported by a plurality of compressible, telescopic landing gear struts. These landing gear struts contain pressurized hydraulic fluid and nitrogen gas. The weight of the aircraft rests upon and is supported by “pockets” of compressed nitrogen gas, within the landing gear struts. Aircraft weight supported by these pockets of gas is called the “sprung” weight. There is additional aircraft weight which is not identified by changes in landing gear strut pressure. This additional weight is associated with various landing gear components located below the pockets of compressed gas including such items as the landing gear wheels, tires, brakes, strut piston, and other lower landing gear components. Aircraft weight associated with these lower landing gear components located below the pockets of compressed gas is called the “unsprung” weight. Unsprung weight remains a relatively constant weight. Aircraft brake wear and tire wear result in a minimal and virtually insignificant amount of weight loss to the unsprung weight. The unsprung weight is added to the sprung weight, to identify a total weight supported by each landing gear strut.
The methods of prior art aircraft weighing systems, determine the “sprung” weight of the aircraft by measuring the pressure within the landing gear struts and multiplying strut pressure by the load supporting surface area of the strut piston; or as an alternative method, monitoring landing gear strut axle deflection as additional weight is added to the aircraft. Among the disadvantages of the prior art onboard aircraft weight measuring systems are that airlines can suffer severe schedule disruptions by using a “measured” aircraft weight value, as opposed to methods of “calculating” aircraft weight based upon the LBUM.
Aircraft load planning is a crucial part of keeping an airline running on schedule. A scheduled aircraft departure will commence its load planning process up to one year prior to the actual flight. Airlines do not offer ticket sales for a flight, more than twelve months prior to the flight. As each ticket for a scheduled flight is purchased, the average passenger and average checked bag weights are assigned into a computer program, continually updating throughout the year the planned load for that flight. Aircraft have a Maximum design Take-Off Weight “MTOW” limitation, where airline operations use assumptions as to the weight of passengers and baggage loaded onto the aircraft, to stay below the aircraft MTOW limitation.
AC 120-27E designates the approved weight assumptions/assignments for airline passengers and baggage:
Historical weather events regarding wind velocity and direction, combined with storm patterns along scheduled airline routes are also considered when planning the amount of fuel that will be consumed for a potential flight. On the actual day of a flight, typically two hours prior to the departure of that flight, the flight's automated load planning program will be transferred to the desktop computer display of one of the airline's Flight Dispatchers. It is the responsibility of the Flight Dispatcher to then monitor the planned load of that flight as passengers check-in at the gate. The passengers and number of checked bags are input to the load planning program. Typically this process goes without interruption and the aircraft will dispatch on schedule, as planned. As the door of the aircraft is closed and the load-plan is closed-out by the Flight Dispatcher, the “planned load” will always match the “departure load” as submitted to the FAA; because both are based on the same compilation of weight assumptions used in determining the LBUM. Using a means to measure the actual aircraft weight, just as the aircraft door closes, and the possibility of the measured weight not matching the calculated weight of the LBUM, would have the airline facing a potential departure delay to resolve any difference in the two separate but parallel weight determinations. This potential for delay in the flight departure, on as many as 2,200 daily flights for a single airline, results in the various airlines not willing to take the risk of hundreds of flight delays each day. Many if not most airlines currently dispatch their aircraft under FAA approved LBUM procedures; a method which helps to keep the airlines on schedule. This creates an incentive for airlines to continue to use the FAA approved assumed weights, irregardless to whether the assumed aircraft weight determination is accurate. The FAA has expressed concerns regarding any airline which might measure total aircraft weight, but chose to not disclose such measured total aircraft weight on the aircraft flight manifest.
Airlines would appreciate an opportunity to use the CG tracking capabilities of today's aircraft weight and balance systems, to more efficiently place baggage and cargo below decks, and take advantage of the reduced fuel consumption benefits; but are not willing to take the risk of scheduled departure delays when the aircraft's planned weight as determined by weight assumptions does not match an actual measured total aircraft weight.
The methods described herein are applicable as alternatives to existing prior art aircraft weight and balance measuring systems for determining aircraft CG, independent of measuring the entire weight of the aircraft, but rather measuring only the weight supported by the nose landing gear, to further determine the remaining weight supported by the main landing gear, to further determine the aircraft CG.
It is an object of the present invention to provide a method to determine aircraft CG, without the requirement to measure the entire weight of the aircraft.
A method determines a Center of Gravity of an aircraft on the ground and having plural main landing gear struts and a nose landing gear strut. Each of the main and nose landing gear struts supporting a respective amount of aircraft weight when the aircraft is on the ground. The method determines a total weight of the aircraft, independent of measuring the aircraft weight. A weight supported by the nose landing gear strut is measured. The measured nose strut weight is compared to the total aircraft weight as a percentage. The aircraft Center of Gravity is identified as a percentage of the distance between the nose and main landing gear struts.
In accordance with one aspect, the step of measuring a weight supported by the nose landing gear strut further comprises the step of measuring an internal pressure within the nose landing gear strut.
In accordance with another aspect, the nose landing gear strut has an axle. The step of measuring a weight supported by the nose landing gear strut further comprises the step of measuring a deflection in the nose landing gear strut axle.
In accordance with another aspect, the step of measuring a weight supported by the nose landing gear strut further comprises the step of measuring rotation of a linkage on the nose landing gear strut.
In accordance with another aspect, the step of measuring a weight supported by the nose landing gear strut further comprises the step of placing a scale beneath the nose landing gear strut tires.
In accordance with another aspect, the step of determining the total weight of the aircraft further comprises the step of using a load build-up process of applying assumed weight values for items such as fuel, passengers and baggage, to the empty measured weight of the aircraft.
In accordance with another aspect, the aircraft is flown under a Regulatory Authority and the load build-up weight values for the passengers and baggage are approved by the Regulatory Authority.
In accordance with another aspect, further comprising the step of dispatching the aircraft for a flight using the determined aircraft Center of Gravity and the independently determined aircraft weight.
In accordance with another aspect, the step of determining the aircraft Center of Gravity further comprises the step of determining the aircraft Center of Gravity as a distance measured from the aircraft datum line.
In accordance with another aspect, the step of determining the aircraft Center of Gravity further comprises the step of determining the aircraft Center of Gravity as a % MAC.
In accordance with another aspect, the step of determining the aircraft Center of Gravity further comprises the step of determining the aircraft Center of Gravity as a distance relative to an aircraft station number.
A method determines a Center of Gravity of an aircraft on the ground and having plural main landing gear struts and a nose landing gear strut. Each of the main and nose landing gear struts supporting a respective amount of aircraft weight when the aircraft is on the ground. A total weight of the aircraft is determined, independent of measuring the aircraft weight. The aircraft weight comprises the operating empty weight of the aircraft, the weight of fuel on board, the weight of payload items on board including the weight of passengers on board, and the weight of baggage on board. The weights of the passengers and the baggage being determined by Regulatory Authority approved designated weights. A weight supported by the nose landing gear strut is measured. The weight determined by the combined main landing gear struts is determined by removing the measured nose strut weight from the independently determined total aircraft weight. The determined combined main landing gear strut weight is compared to the total aircraft weight to identify the aircraft Center of Gravity as a percentage of the distance between the nose and main landing gear struts.
In accordance with one aspect, the step of measuring a weight supported by the nose landing gear strut further comprises the step of measuring an internal pressure within the nose landing gear strut.
In accordance with another aspect, the nose landing gear strut has an axle. The step of measuring a weight supported by the nose landing gear strut further comprises the step of measuring a deflection in the nose landing gear strut axle.
In accordance with another aspect, the step of measuring a weight supported by the nose landing gear strut further comprises the step of measuring rotation of a linkage on the nose landing gear strut.
In accordance with another aspect, the step of measuring a weight supported by the nose landing gear strut further comprises the step of placing a scale beneath the nose landing gear strut tires.
In accordance with another aspect, step of determining the total weight of the aircraft further comprises the step of using a load build-up process of applying designated weight values for items such as fuel, passengers and baggage, to the empty measured weight of the aircraft.
In accordance with another aspect, the aircraft is flown under a Regulatory Authority. The load build-up weight values for the passengers and baggage are approved by the Regulatory Authority.
In accordance with another aspect, the step of dispatching the aircraft for a flight using the determined aircraft Center of Gravity and the independently determined aircraft weight.
In accordance with another aspect, the step of determining the aircraft Center of Gravity further comprises the step of determining the aircraft Center of Gravity as a distance measured from an aircraft datum line.
In accordance with another aspect, the step of determining the aircraft Center of Gravity further comprises the step of determining the aircraft Center of Gravity as a % MAC.
In accordance with another aspect, the step of determining the aircraft Center of Gravity further comprises the step of determining the aircraft Center of Gravity as a distance relative to an aircraft station number.
A method determines a Center of Gravity of an aircraft on the ground and having plural main landing gear struts and a nose landing gear strut. Each of the main and nose landing gear struts supporting a respective aircraft weight when the aircraft is on the ground. A total weight of the aircraft is determined independent of measuring the weight supported by the nose landing gear strut. A combined weight supported by the plural main landing gear struts is measured. The measured weight supported by the plural main landing gear struts is compared to the total weight of the aircraft to determine the aircraft Center of Gravity.
Although the features of this invention, which are considered to be novel, are expressed in the appended claims; further details as to preferred practices and as to the further objects and features thereof may be most readily comprehended through reference to the following description when taken in connection with the accompanying drawings, wherein:
An aircraft is typically supported by plural landing gear struts. In many if not most cases, the aircraft is supported by three landing gear struts. Each landing gear strut is designed much like and incorporates many of the features of a telescopic shock absorber. The shock absorber of the landing gear strut comprises internal fluids of both hydraulic oil and compressed nitrogen gas. More simply said the weight of an aircraft rests on three pockets of compressed nitrogen gas. Pressure contained within the landing gear struts is measured in “psi”. With any object that has a “known total weight” which is resting on three independent points, and one of the three points has a measured weight, the combined weight supported by the remaining two points can be determined by subtracting the one measured weight from the known total weight.
The present invention offers a new method to determine aircraft CG. Total aircraft weight is determined independently of measuring the weight supported at all of the landing gear struts. In the preferred embodiment, the total aircraft weight determination incorporates LBUM calculations. The weight supported by the nose landing gear strut is measured. This measured weight allows for the computation of the weight supported by the combined main landing gear struts, to further determine aircraft CO without a need to measure the weight supported by the combined main landing gear struts. This new method for determining aircraft CG is independent of using a measured total weight of the aircraft, or a measured weight supported by the combined main landing gear struts.
Typically the nose landing gear supports 8%-16% of the total aircraft weight, depending upon the location of aircraft CG; where the remainder of the weight is supported by the combined main landing gear. As aircraft CG moves either forward or aft, the relationship or ratio of nose landing gear weight as related to combined main landing gear weight will change in direct relation to the change in aircraft CG. The weight supported by the combined main landing gear struts, divided by the total weight of the aircraft as a percentage, will determine the location of the aircraft CG as a percentage of the distance between the nose landing gear and the main landing gear, measured aft from the location of the nose landing gear, or as a percentage of the wheel-base distance.
Measuring internal gas pressure within the nose landing gear strut, and applying adjustments to the nose gear pressure, which adjustments are made to correct for landing gear strut seal friction (reference is made to U.S. Pat. No. 5,214,586 and No. 5,548,517), allows for the measured calculation of the weight supported by the nose landing gear.
With the entire weight of the aircraft distributed between the nose landing gear and the combined man landing gear, then subtracting the measured weight supported by the nose gear from the total aircraft weight calculation made by the LBUM, determines a computed weight supported by the combined main landing gear struts. A further comparison of the determined or computed weight supported by the combined main landing gear to that of the total weight, the aircraft CG can be identified without the need to measure the total aircraft weight.
Alternative measurements of strut supported weights may be used. For example, the present invention additionally offers a method to measure weight supported by the nose landing gear strut by measuring landing gear strut component yielding bending on such components as the landing gear axle or mounting trunion pins which attach the landing gear to the airframe, by strain gauge sensors bonded to these yielding components. As another alternative, the aircraft weight on the combined main landing gear struts can be measured and then subtracted from the total aircraft weight to determine nose landing gear weight; then such determined nose landing gear weight further compared to the total aircraft weight to determine aircraft CG.
Referring now to the drawings, wherein like reference numerals designate corresponding parts throughout the several views and more particularly to
The MAC is the average (Mean) width of the wing's lifting surface (Aerodynamic Chord). In the case of a swept-wing aircraft 1, the leading edge of the MAC is locative just aft of the leading edge of the wing where it attaches to the aircraft 1. The trailing edge of the MAC is located just forward of the aft wing-tip. Airline operations often reference the aircraft CG 5 location as a point some percentage aft of the forward edge of the mean aerodynamic chord, or as % MAC.
Aircraft 1 has a tricycle landing gear configuration consisting of a nose landing gear 9, and also shown two identical main landing gears including a right main landing gear 11 and a left main landing gear 13. Main landing gears 11 and 13 are located at the same point along the aircraft's horizontal axis 7, but for convenience in this illustration, are shown in a perspective view for this
Continuing with the example, 100% of aircraft 1 weight totals 163,800 lb. The distribution of the total aircraft weight has 86.50% of aircraft weight supported by the combined main landing gears 11 and 13 at 141,687 lb. and the remaining 13.50% of aircraft weight supported by nose landing gear 9 at 22,113 lb.
Landing gear 9, 11 and 13 incorporate one or more tires 15 to distribute the weight of aircraft 1 which is resting on the ground 17. Electronic elements which together are used in this invention, and are attached to aircraft 1, are an aircraft center of gravity measurement computer 19; and aircraft inclinometer 25, landing gear strut pressure sensors 27 with embedded temperature probes (shown in
Although the aircraft shown in
Referring now to
The items listed in this LBUM example, represent some but not all items a specific airline may choose to build their individual FAA approved weight and balance control system, but different items may be selected as elements categorized in other airlines' FAA approved LBUM method. Examples of other items which are not listed above can be standardized cargo articles which maintain a constant weight. Some airlines carry various maintenance tools and spare aircraft components for which these weights do not vary, but are separately noted within that airline's particular LBUM.
In the United States of America, the FAA is the Regulatory Authority that approves the designated weights. In other countries or regions, other Regulatory Authorities may have jurisdiction.
The LBUM weight determination is transmitted to the pilot of aircraft 1, and the pilot will manually input the LBUM total aircraft weight determination into computer 19 via keypad 20 (see
Referring now to
As discussed in the “background” section above, many airlines determine aircraft weight using designated weight values based on historical weight data for various elements such as passengers, baggage and small cargo loaded onto the aircraft. A pre-measured empty aircraft weight is associated with the sum of the designated weights of the accumulated items loaded onto the aircraft, without the need to physically place the aircraft on weighing scales prior to each departure.
Shown initially on this chart as a 1u example, the horizontal double-arrow 31 illustrates the forward and aft CG limitations of an aircraft having a weight of 140,000 lb. The forward CG limitation for take-off and landing is 6.4% MAC, illustrated by the “Forward Takeoff and Landing Limit” line 33. The aft CG limit for the 140,000 lb. aircraft is 29.5% MAC illustrated by vertical dashed line 35, in this example, dashed line 35 intersecting at the higher engine thrust setting of 26,000 pounds.
When using this size of chart, typically on 8½×11″ paper, it is very difficult in making a distinction between the forward CG limit of an aircraft weighing 163,700 lb. to that of an aircraft weighing 163,800 lb. This is widely understood within the airline industry, thus when determining the CG limitation for a loaded aircraft, the pilots often will use a weight that has been rounded up to the nearest 1,000 lb.
By way of this 2nd heavier example, the aircraft weight has been established within an acceptable 2,000 lb. range (±1,000 lb.) for the further determination of acceptable CO limitations within FAA Regulatory requirements. Though the ±1,000 lb. weight range may be acceptable for the CG determination, such weight conclusion would not be accurate enough, thus unacceptable to FAA Regulatory requirements as a means to determine aircraft “dispatch weight” being the official aircraft weight used prior to the take-off for a flight. For this 2nd example a LBUM calculated weight of the aircraft is 163,800 lbs., falling within the 2,000 lb. weight range between 162,800 lb. and 164,800 lb.; where box 37 illustrates the 2,000 lb. range representing a possibility for potential weight determination error of ±1,000 lb. The forward and aft CG limitations are illustrated by the bold “diagonal” double-arrow 39 pointing to a forward CG limit of 10.7% MAC illustrated by vertical dashed-line 41, with the opposing end of double arrow 39 pointing to an aft CG limit of 32.5% MAC illustrated by vertical dashed-line 43. Double-arrow 39 is shown as diagonal due to an “implied curtailment” applied to both forward and aft CG limits associated with the ±1.000 lb. range of the weight determination. Vertical dotted-line 45 (which is slightly forward of dashed-line 41) illustrates the forward CG limit for the aircraft with a weight determination at “precisely” 163,800 lb. Vertical dotted-line 47 (which is slightly aft of dashed-line 43) illustrates the aft CG limit for the aircraft with a weight determination at “precisely” 163,800 lb. There is negligible difference between the locations of dotted-line 45 representing the forward CG limit using an accurate aircraft weight, to that of dashed-line 41 using an assumed aircraft weight range of ±1,000 lb. There is negligible difference between the locations of dotted-line 47 representing the aft CG limit using an accurate aircraft weight, to that of dashed-line 43 using an assumed aircraft weight range of ±1,000 lb. The negligible difference in the forward and aft aircraft CG limitations, based upon a ±1,000 lb. range in the determination of the aircraft weight, allows fir aircraft weight determinations to be made within a pre-defined acceptable range of accuracy (in this example ±1,000 lb.) resulting in forward and aft CG limitation curtailments which are negligible but still more conservative than the limitations associated with the “precise” weight of 163,800 lb.
Referring now to
Referring now to
Axle deflection sensor 29 will transmit a signal representing the weight applied to the nose landing gear strut 9, to the system computer 19 (shown in
Referring now to
Located directly above nose landing gear 9 is a black circle 59 (shown in this perspective view as an oval) which represents the location for which nose landing gear strut 9 supports weight. Located directly above right main landing gear 11 is a black circle 61 (shown as an oval) which represents the location for which right main landing gear strut 11 supports weight. Located directly above left main landing gear 13 is a black circle 63 (shown as an oval) which represents the location for which left main landing gear strut 13 supports weight. Located directly above nose landing gear black circle 59 and located along vertical dotted-line 65 is reference point 73 which represents the center of the weight supporting area for the nose landing gear strut 9, located along aircraft longitudinal axis line 7. Located directly above right main landing gear black circle 61 and located at the opposing end of vertical dotted-line 67 is reference point 75 which represents the center of the weight supporting area for right main landing gear strut 11. Located directly above left main landing gear black circle 63 and located at the opposing end of vertical dotted-line 69 is reference point 77 which represents the center of the weight supporting area for left main landing gear strut 13. Line 79 is perpendicular to aircraft longitudinal axis line 7 and connects right main gear reference point 75 and left main gear reference point 77, passing through reference point 81 which is located on line 79 at the intersection of line 79 with aircraft longitudinal axis line 7. Reference point 81 is an equal-distance between reference points 75 for the right main landing gear and reference point 77 for the left main landing gear. Reference point 81 is the location along aircraft longitudinal axis 7 corresponding to the point at which the supported weight by the combined right and left main landing gear would be assigned, in the calculation of aircraft CG 5. Any weight supported by the combined right and left main landing gear struts will be apportioned to this reference point 81 location along longitudinal axis line 7. The position of point 73, is located aft from the datum line 3 (also shown in
As shown in
In the preferred embodiment, the method for determining aircraft CG includes the following steps:
As illustrated in
As illustrated in
In this example, the aircraft CG 5 is located 86.50% aft of point 73. Point 73 is the forward edge of the aircraft wheel-base, and aircraft CG 5 is located 86.50% along the measured length of line 83 being equivalent to the aircraft wheel-base. Nose landing gear strut pressure is measured at 1,156 psi, which relates to 22,113 lb. supported by the nose landing gear strut. The total weight of the aircraft as calculated by LBUM is 163,800 lb. The 22,113 lb. supported by the nose landing gear strut is equivalent to 13.50% of the total aircraft weight. The remaining 86.50% of the aircraft weight can only be supported by the remaining combined main landing gear struts, thus must be computed to equal 141,687 lb.
Point 73 represents the center of nose gear 9. The length of line 83, from point 73 to point 81, does not change. The distance from point 73 to the datum line 3 is known and does not change, thus the location of CG 5 is relative to the datum line, and can be determined.
Determination of aircraft CG can be accomplished by identifying the computed weight of the combined main landing gear by subtracting the measured weight supported by the nose landing gear from the LBUM calculated total weight of the aircraft, to further determine the percentage of the combined main landing gear weight as a percentage of the total aircraft weight, where:
This determined CG location is a percentage of the distance aft from the location of nose landing gear, to the location of the main landing gear.
An alternate method for the determination of aircraft CG can be accomplished by measuring the weight supported by the nose landing gear and determining that percentage of weight supported by the nose gear to the total aircraft weight as determined by the LBUM. The percentage of weight supported by nose landing gear is applied as an equivalent percentage of the distance between the nose landing gear and the main landing gear to determine the location of the aircraft CG, where:
To make this CG determination, which is based on aircraft wheel-base dimension more practical for use by an airline operator the CG determination may be converted into a value of % MAC which is a corresponding value in reference to a point associated a percentage value located aft of the leading edge of the aircraft's Mean Aerodynamic Chord. A simple look-up table is created which relates % wheel-base to that of % MAC. Additionally a simple look-up table is created which relates % wheel-base to that of a corresponding value in relation to an aircraft station number. An additional look-up table is obtained from a range of pressure measurements taken from the nose landing gear in relation to measured aircraft CO, during an optional and initial calibration of the system, while the aircraft is resting on weighing measuring scales. The scales are used in the initial calibration process, but are not needed in subsequent aircraft CG determinations by reference to the created look-up table. The look-up table can be updated while the aircraft is in operation, by extrapolating from initial calibration data to the weight distribution ratios experienced at the time a CG determination is desired. There are multiple variations of using different combinations of measured landing gear supported weight in relation to a calculated total aircraft weight, to identify aircraft CG. For example, the weight supported by each main landing gear can be measured and combined, then subtracted from the calculated total aircraft weight to determine the remainder weight supported by the single nose landing gear, as an alternate method to determine the aircraft CG.
Referring now to
In operation, the aircraft is at a location at the airport preparing for its next flight. Typically if the aircraft is taking on passengers and baggage, the aircraft is located at a gate. The aircraft takes on weight in the form of passengers, baggage, cargo and/or fuel.
When the aircraft is ready, it departs the gate, taxis to the runway and then takes off down the runway and begins flight. Most, if not all, commercial aircraft are approved for flight by way of being dispatched. To be approved or dispatched for flight, the takeoff weight of the aircraft is determined to ensure the weight is within the operational limits of the aircraft. To determine aircraft CG the methods herein described above are used. However, to determine the total aircraft weight, another method independent of physically weighing the aircraft is used. An example of a method to determine total aircraft weight (the LBUM process) is to use approved weight assumptions assigned for passengers and their baggage. In addition to the assumptions regarding passenger weight and baggage weight, the empty weight of the aircraft is known from past measurements on scales. The weight of fuel is determined from measuring the volume of fuel added to the aircraft during refueling and converting that volume into pounds. The CG of the aircraft just before being dispatched and for takeoff can be monitored and determined using the techniques described above. Once the total weight and aircraft CG determinations are made, the aircraft is then dispatched, and approved for flight.
Additionally, as an exemplary embodiment of the invention has been disclosed and discussed, it will be understood that other applications of the invention are possible and that the embodiment disclosed may be subject to various changes, modifications, and substitutions without necessarily departing from the spirit and scope of the invention.