which will provide satisfactory weight and balance control. Loading schedules may be applied to individual aircraft or to a complete fleet. When an operator utilizes several types or models of aircraft, the loading schedule should be identified with the type or model of aircraft for which it is designed.
CENTER OF GRAVITY TRAVEL DURING FLIGHT The operator's flight manual should show procedures which fully account for the extreme variations in c.g. travel during flight caused by all or any combination of the following variables:
1. The movement of passengers and cabin attendants from their normal seat position in the aircraft cabin to the lounge or lavatory.
2. Possible change in c.g. position due to landing gear retraction.
3. The effect of the c.g. travel during flight due to fuel used.
RECORDS The operator's weight and balance system should include metho ds by workable. Several systems have been devised and many variations of the required documents are in use. All the systems strive for a rapid method of determining if the aircraft's weight and balance is within the stated tolerances. The systems are more sophisticated than those used for general aviation aircraft, however, they are subject to some of the same errors. Simple arithmetic errors and errors in updating necessary records after equipment changes are common sources of trouble. The latest systems are designed to eliminate the human error factor while speeding up the process of getting weight and balance information to the pilot and others who are Weight and balance control systems are primarily based upon information contained in official sources, such as the Airplane Flight Manual, Type Certificate Data Sheets, etc. Ultimately, all systems are desigred to provide values for a load manifest which in turn shows that the weight and balance condition is within limits for the flight.
AIRPLANE FLIGHT MANUAL The airplane flight manual may be found in several forms-variations of the manuals are the result of the slight differences in operations by the various aircraft operators. Some manuals contain all the essential weight and balance information together with flight performance information in one volume, others utilize a separate volume for loading information.
A typical manual contains an explanation of the approved weight and balance system. It also proconcerned.
WEIGHT AND BALANCE SYSTEMS The large aircraft operator's weight and balance control system may be in any form that proves used ın me load mannest.
Title Weight Arm Moment Lb. In. 1000 Captain 170 229 39 First Officer 170 229 39 Flight Engineer 170 263 45 First Observer 170 263 45 Second Observer 170 290 49 Fwd. Cabin Attendant - Female 130 311 40 Fwd, Cabin Attendant - Male 150 311 47 Art Cabin Attendant - Female 130 1169 152 Aft Cabin Attendant - Male 150 1169 175 FIGURE 50. Crewmember index table.
LOAD MANIFEST The load manifest (fig. 51) is completed by use of information from the manual as it pertains to the particular flight. Basic opcrating weight is either calculated or carried forward from previous records.
Payload and fuel-load indexes are obtained from load tables. When the weight and index items are totaled on the load manifest, such factors as zero.
fuel weight, taxi gross weight, and c.g. in % MAC are indicated. The load manifest makes provisions for last minute corrections such as would be necessary when cargo or additional passengers are added just before takeoff. Weights on the load manifest may be indicated in kilograms (kilo or kg.), or pounds, or both. Forms used for international operations will usually have weights indicated in
TYPICAL SYSTEMS Loading summary chart. A typical approach to the problem of finding c.g. quickly is found in the use of a loading summary chart. Representative loading summary charts are shown in figures 52 and 53. These charts provide a means for determining c.g. position with some of the arithmetic steps omitted. Generally, the charts are entered at the top with basic operating weight and its index. Then a line is drawn downward and corrections are made to the right or left as appropriate for loads in each compartment. When all the compartment loads are considered, the line will indicate the zero fuel weight index. Continuing the line downward, a right or left adjustment is made for fuel load. The line is then terminated in the grid section of the chart at a horizontal line which represents the total weight.
54 The terminal point of the line is an indication of
c.g. in % MAC or index. Many turbojet aircraft load summary charts will provide an answer directly in stabilizer setting increments.
Load adjusters. Military aircraft have for many years made use of load adjusters for weight and balance computations. The load adjuster is a balance computer similar in form to the conventional slide rule. It consists of a base, a slide and a transparent, movable indicator. A representative load adjuster is illustrated in figure 54.
Load adjusters should never be interchanged between aircraft of different series or models. Although the method of using all load adjusters is generally the same, the scales that appear on a load adjuster are designed for use with one specific type of aircraft.
Generally, the load adjuster is used in a manner similar to the procedure explained for the load summary chart. The process begins with the basic operating weight and index. The index is always placed under the cursor or hairline of the load adjuster. Then the cursor is moved to the right or left a distance determined by the weight and index units for each load item added to the basic operating weight. As each load item is considered, the cursor is moved until all load items, including fuel, have been accounted for. After the final movement of the cursor, the total weight index will appear under the cursor hairline.
The load adjuster also has a c.g. grid which permits quick conversion of the answer from total weight index to c.g. in % MAC. Inasmuch as the load adjuster is designed for one model airplane.
the fore and aft limits are indicated on special scales. After determining total weight index, the
FLIGHT LOADING MANIFEST MODEL AIRPLANE NO. FLIGHT NO
WEIGHT INDEX
ITEM POUNDS UNITS
REMARKS INDEX UNITS WEIOHT (BAL ARM-463) (FROM WT. • BAL. LOG ) BASIC WEIGHT LB c.0. % MAC 10,000 OIL GALI CREW INO.
CREW BAGGAGE
WASH & DRINK WATER GAL)
PASSENGER SERVICE EQUIPMENT
EMERGENCY EQUIPMENT
SPECIAL EQUIPMENT BASIC OPERATING WEIGHT LB c. 0 % MAC
PASSENGERS BAQGAGE - FWD. COMPT.
BAGGAGE -AFT COMPT.
CARGO-FWD, COMPT
CARGO - A COPT ZERO FUEL WEIGHT LB c.C % NAC TANK DRIP STICK UN DRIPSTICK GALLONS DRIPSTICK POUNDS GAGE L8 GAGE DIFF. OR - UNITS INDEX RESERVES NO. 164 OUTBO, MAINS NO. 164 INBD. MAINS NO.2€3
CENTER WING TOTALS
LB / GAL TOTALIZER
CORRECTIONS TEM WEIGHT -LB INDEX UNITS
CHANGES TOTAL GAL LB / GAL ITEM WT. INDEX (UNCORRECTED) TAXI GROSS WEIGHT LB C.G. %MAC
• CORRECTIONS (IF REQUIRED) (CORRECTED) TAXI GROSS WEIGHT LB c.o.
COMPUTED- DATE
TOTAL ADDED CHECKED DATE
TOTAL REMOVED -
NET PILOT DATE
DIFFERENCE FIcURE 51. Flight loading manifest form.
Dispatch Airport Flight
• Destination A/C LOADING SUMMARY - DOUGLAS DC-6B Date (FIRST CLASS - 66 PASSENGER - CONFIGURATION) Compart. Comport. Compart.| Compart. compare comp.
Forward Cargo H AFT Corgo G WEIGHT-LBS ITEM 100 20 240
DASIE INDEX INOE A ALLOW WTS FEEL WI 1000LB3 1S - TANNE NDEX -HING W NOTES 110,000 (I) INDEXES FOLLOWING EQUA HINED BY THE INDEX-100 + EW! (ARM 101] 105.000
(2)BASIC
DISPATCHING CG BASIC 90,000 PROCEED DOWNWARD THROUG VEL = 83.00 .9021
LEFT WI TO ENTER FROM EF DISPATCH WEIGHT AND .000c
WHERE DISPATCH WEIGHT & VERTICAL INDEX MEET. READ CG. IN % MAC REVERSE ARROW INDICATION IN THE ROCCO VE FOR LUNANO HE FUEL.
AMOUNT TO OC USEL. GIVE 70.000
NEW INDEX (LESS) THEN PROCEED
DOWNWARD TO INTERSECTION WEIGHT AND NEW INDEX. THIS
63.000 LANDING C.G. IN A M.A.C C G. WILL ALWAYS TRAVEL FOR- WARD AS FUEL USED.)
60,000 53,000 kma 155.000 FIcURE 52. Loading summary chart-DC-6B.
100T 50% FICURE 53. Loading summary chart-C:V-880M.
OPERATING WEIGHT VEL WEIONT NO. I MAIN наз MAIN HO.A MAIN CENTER SECTION GROSS TAKE-OFF WEIGHT TAKE-OFF C. 0.
s†z 58
BALANCE COMPUTER BALAÁICE COMPUTER OVERLAY
FWD AFT FIGURE 55. Balance computer and overlay.
location of the c.g. relative to its limits can easily be seen.
A diagram of the aircraft fuselage is normally included on the load adjuster. This diagram is used to help identify various compartment locations.
Balance computer. A slide rule can be circular as well as linear in construction-the aeronautical computer is an example of the circular type. Circular slide rules or computers have been adapted to the solution of weight and balance problems.
Essentially, these balance computers are circular load adjusters, and like the linear type, can be used only for an aircraft of one make, model, and configuration. The identification markings of a balance computer should be carefully checked to insure its correct use.
The circular balance computer consists of a card on which are printed curved scales for load items and a curved c.g. grid. A different card is provided for each configuration aircraft and can be included in the weight and balance section of the aircraft flight manual. A transparent plastic overlay sheet with a simple straight line similar to the cursor on the load adjuster is used on top of the balance computer card (fig. 55).
The procedure for use of the circular balance computer is similar to that used on the slide rule type load adjuster. Starting with basic index units, progressive movements of the overlay are made in clockwise or counterclockwise directions. A pencil mark is made on the overlay before making each adjustment for a load item. After the final fuel item adjustment is accounted for, the line on the plastic overlay indicates the c.g. location where it crosses 59
GRID
TEMPLATE FUEL
PASSENGERS
AR CARGO FWD FIGURE 56. Template and grid.
the gross weight line on the c.g. grid. The c.g. is indicated in % MAC on the grid and the grid itself is a limit envelope (fig. 55).
The design of the circular balance computer takes into account several general assumptions pertaining to the normal operation of the aircraft. Among these is the assumption that passengers will have a preference for empty seats next to the windows and that the fuel will be loaded and consumed according to standard schedules.
If standard practices are followed, the computer allows omission of the intermediate steps of calculating moments and indexes for the load items.
Template and grid. A similar system makes use of a large weight and balance grid upon which the weight items are directly plotted. The grid indicates the weight and balance limits of the aircraft as 60 expressed in % MAC. The grid can be printed on a hard plastic material from which the plot is erased after use or on a paper form which is kept as a record for each flight. The values for the load items are plotted progressively by the use of a plastic template (fig. 56). The final plot of the fuel load terminates at the intersection of the total weight and c.g. in % MAC.
As in all other systems, this system relies upon getting off to a good start with a reliable basic operating weight and basic operating c.g. in % MAC. Since the final plot represents the fuel load, the plotted fuel line can be followed down the chart as•fuel is consumed in flight to get a continuous graphic indication of c.g. location during flight (fig.
57).
Advanced systems. New systems of weight and
BALANCE LIMITATIONS CENTER OF GRAVITY - % MAC 44 40 36 32 28 24 20 16 12 MAXIMUM TAXI WEIGHT 182,000 180,000 MAXIMUM INFLIGHT WEIGHT 180,000 TAXI WT. AND C.G.
170,000 160,000 MAXIMUM LANDING AIRPLANE GROSS WEIGHT - LB. WEIGHT
• FUEL 150,000 AFT C.G. LIMIT TAKEOFF -FORWARD C.G
FLIGHT AND LANDING LIMIT INFLIGHT 140,000
MAXIMUM ZERO
FUEL WEIGHT
ZERO FUEL WT, 130,000
• PASSENGERS REAR
• FORWARD C.G. LIMIT
TAKEOFF AND LANDING
FORWARD 120,000
REAR - CARGO
FORWARD
- BASIC WT. AND C.G.
100,000 44 40 36 32 28 24 20 16 12 FIGURE 57. Balance limitations grid.
WEIGHT AND BALANCE MANUAL 5-10-61 Equipment List N-113.
Balance Chk Description and Identification Quantity Weight Arm Compressor-Air Fuel Starter 50.0 875.6 ABC Co. 4056728 Pressure Regulating Shutoff Valve 1 7.5 835.4 Jones Inc. 1726001-10 Jones Inc. 1726001- 9 (Optional) Boost Pump, Fuel, High Pressure 2 7.8 756.3 Smith Co. HD 309721-1 2 7.8 779.2 2 7.8 801.5 2 7.8 835.7 Boost Pump, Fuel, High Pressure 1 10.2 753.0 Lotco Inc. XX45678-9 FIGURE 58. Large aircraft equipment list.
balance control are being devised and will undoubtedly be adopted in the future by the large aircraft operators. Electronic computers can be used to calculate and print out the weight and balance answers; the computer input possibly being based upon passenger and cargo reservation information.
Other systems have been investigated utilizing devices which measure the weight applied to each landing gear when the airplane is on the ground.
These devices are installed in the landing gear system and produce a numerical read out of gross weight and c.g. position. The read out could be located in a convenient location in the flight com-
LARGE AIRCRAFT WEIGHT AND BALANCE
RECORDS It is apparent when a study is made of the weight and balance control systems introduced in this chapter, that the use of a valid Basic Operating Weight (BOW) is essential for accurate results. Operating personnel must rely upon BOW information in the aircraft records. Maintenance personnel must assure that the recorded BOW is correct.
BOW is defined as the weight of the aircraft as loaded ready for payload and fuel. The BOW, there- 62 fore, includes the empty aircraft with all permanently installed equipment, normal oil and fluids (except fuel), crew and crew baggage, passenger service equipment, emergency equipment, and special equipment.
The aircraft is weighed to establish the empty weight and c.g. before it is put into service. When a record is made of this weighing, an equipment list is established which shows each item of installed equipment included in the empty weight. From then on, the condition for empty weight can be duplicated by assuring that this same equipment is installed An excerpt from the equipment list of an FAA aircraft is shown in figure 58.
When equipment changes take place, an appropriate entry is made on a weight and balance log or the equipment list itself is amended so that the empty weight and c.g. are properly corrected. It is essential that any change in structure or equipment be entered in the records, otherwise all other calculations will be inaccurate. Part of a weight and balance log for an FAA aircraft is shown in figure The use of "empty fleet weights" and "basic operating fleet weights" are explained in FAA Advisory Circular 120-27. When feet weights are used,
ACTUAL WEIGHT AND BALANCE LOG Serial: 18066 Registration: N 113 Balance Index Item and Description Weight Arm Moment CG %MAC Units
SUMMARY Pre-flight Weighing 98,320 847.3 83355696 25•5 +3,783 Additions +978 +795556 Deductions -429 -338838 BASIC WEIGHT - 98,869 (847•7) 83812414 25.4 +3,803 FIGURE 59. Weight and balance log.
weight and balance procedures can be standardized and periodic weighings reduced; these advantages are possible when a large number of similar aircraft are used by a particular operator.
The term "zero fuel weight" indicates the maximum authorized weight of an aircraft without fuelthis weight is the sum of BOW and payload. It should be understood that passengers or cargo are included in zero fuel weight. When the zero fuel weight is high because of a large payload, the fuel load must be proportionately low to prevent exceeding maximum takeoff or landing weights. On the other hand, if a large fuel load is needed for a long-range flight or for low-altitude operation, IFR holding, or traffic delays, a reduction of payload and zero fuel weight may be required.
Average weights of adult passengers are assumed to be 160 pounds in summer (May 1-Oct. 31) and 165 pounds in winter (Nov. 1-Apr. 30). Children under 2 are considered "babes-in-arm" and children 2 through 12 are averaged at 80 pounds each. Passenger carry-on baggage is calculated at 5 pounds each. Most weight and balance control systems assume that passengers will select the window seats first, the aisle seats second, and the center of threeabreast seating last. With these assumptions, passenger index tables are calculated. Allowances are made for those loading situations where passengers happen to group in extreme forward or aft locations.
In flight, movement of passengers or crewmembers is also considered and load adjustments made. Any such allowances have the effect of reducing the load-carrying flexibility of the aircraft.
A typical passenger load index chart is shown in figure 60. It should be noted that this chart assumes that passengers are seated in the normal distribution around the center (centroid) of the forward and aft passenger compartments. A separate table in figure 60 provides information about cargo loads. The assumption is again made that the cargo is loaded evenly around the centroid of the cargo hold.
Fuel is loaded in large aircraft according to a schedule presented in the FAA approved manuals.
Such a procedure distributes the fuel among the fuel tanks in a manner which will cause a minimum of difficulty with weight and balance (fig. 61).
Personnel involved with weight and balance are, therefore, able to determine the fuel moments or index from standard tables or by calculating the moment of the fuel in each tank.
Fuel is used according to procedures given in the flight manual. Besides ensuring structural integ.
rity, an important reason for following a standard sequence of fuel tank selection is to control the c.g.
location. The flight crew has a much less complex 63
PASSENGER LOADING TABLE CARGO LOADING TABLE Number Weight Moment Moment 1000 1000 Pass. Lb. Forward Hold Aft Hola FWD. COMP. CENTROID 486. 3 Weight Lo. Arm 581 1066 Arm 5 850 413 10 1,700 827 15 2,550 1,240 20 3,400 1,653 25 4,250 2,067 29 4,930 2,397 AFT. COMP. CENTROID 928.8 5 850 789 10 1,700 1,579 15 2,550 2,368 20 3,400 3,158 25 4,250 3,947 30 5,100 4,736 58 35 5,950 5,526 40 6,800 6,315 45 7,650 7,105 50 8,500 7,894 54 9,180 8,526
FUEL LOADING TABLE Weight Tank 1 and 3 Tank 2 Weight . (3 Cell) Moment Moment 1000 Arm 1000 Lb.
7,583 817.5 6,949 8,500 8,037 817.2 7,355 9,000 8,492 817.0 7,762 9,500 8,947 816.8 8,168 10,000 9,402 816.6 8,574 10,500 9,857 816.5 9,32 11,000 10,313 816.3 11,500 10,770 816.1 9,793 12,000 18,500 906.8 16,776 815.1 15,079 18,500 19,000 907.8 17,248 815.0 15,485 19,000 19,500 908.9 17,724 814.9 15,891 19,500 20,000 910.1 18,202 814.9 16,298 20,000 20,500 911.7 18,690 814.8 16,703 20,500 21,000 913.4 19,181 814.7 17,109 21,000 21,500 915.5 19,683 814.6 17,514 21,500 FIGURE 60. Loading tables.