Weight added fwd. of old c.g. Je.g. moves fwd. new c.g. will be exactly on the aft limit; if the Weight removed aft of old c.g. weight is located any further to the rear, the aft Weight added aft of old c.g. Weight removed fwd. of old c.g. / c.g. moves aft c.g. limit will be exceeded.
Example 20. Example 21. Given:
Given: Aircraft total weight-6,400 lb.
Aircraft total weight-7,000 lb. c.g. -Sta. 80.0 Cog. -Sta. 79.0 Aft c.g. limit -Sta. 80.5 Find: How far aft can additional baggage weigh- ing 200 Ib. be placed without exceeding the Rear c.g. limit -Sta. 80.5 Find: How much baggage can be located in the aft baggage compartment at station 150 with- out exceeding the aft c.g. limit?
rear c.g. limit?
Solution: Solution:
1. Use the added weight formula: Use the added weight formula.
Added weight Ac.g. NoTE.—In this problem, the new total weight New total weight - Dist. between wt. and old c.g. is not given, therefore, it is more convenient
1.5 to use the version of. the formula which makes 7,200 Dist. between wt. and old c.g. use of the old total weight.
2. Add to old c.g.: Distance between wt. and old c.g. =54 in. 79 in. +54 in.= 133 in. aft of datum Old total weight Added weight Added weight - 150-80.5- = Dist. between wt. and new c.g. Ac.g.
When the 200 Ib. is located at Sta. 133, the Added weight = 46 lb. 6,400 34
Chapter 6
CONTROL OF LOADING-
GENERAL AVIATION Before any flight, the pilot should determine the weight and balance condition of the aircraft. In the early days of flying, aircraft were loaded by guess and intuition. On occasion, the results were grim. Through trial and error the early pilots learned about weight and balance. Today there is no excuse for following this method. Simple and orderly procedures based on sound principles have been devised by aircraft manufacturers for the determination of loading conditions. The pilot, however, must use these procedures and exercise good judgment. In many modern aircraft, it is not possible to fill all seats, baggage compartments, and fuel tanks and still remain within the approved weight and balance limits. If the maximum passenger load is carried, the pilot must often reduce the fuel load or reduce the baggage.
USEFUL LOAD CHECK A simple and fundamental weight check should always be made by general aviation pilots before flight. This check should determine if the useful load is exceeded. The check may be a mental calculation if the pilot is familiar with the aircraft's limits and knows that unusually heavy loads are not aboard.
But when all seats are being occupied, fuel tanks are full, and some baggage is aboard, the pilot should do some careful calculations.
The pilot needs to know the useful load limit of the particular aircraft. This information may be
EMPTY AIRCRAFT PILOT AGGAGE
PSGR PSGR FIGURE 30. Empty weight + useful load = takeoff weight.
WEIGHT & BALANCE DATA AIRCRAFT SERIAL NO. 15556480 FAA REGISTRATION NO. N3248X
ITEM WEIGHT ARM MOMENT STANDARD AIRPLANE 975.0 32.0 31200. 0 OPTIONAL EQUIPMENT 89.0 26.1 2322.9 PAINT 15.5 85.3 1322.2 UNUSABLE FUEL 20.0 43.0 860.0 LICENSED EMPTY WEIGHT 1099.5 32.5 35705.1 (GROSS WT) - (LICENSED EMPTY WT) = USEFUL LOAD (1800 LB) -( 1099.5 LB) = 700.5 LBS
IT IS THE RESPONSIBILITY OF THE OWNER AND PILOT TO ENSURE THAT THE AIRPLANE IS PROPERLY LOADED. THE DATA ABOVE INDICATES THE EMPTY WEIGHT, C.G., AND USE-
FUL LOAD WHEN THE AIRPLANE WAS RELEASED FROM THE FACTORY. REFER TO THE LATEST WEIGHT AND BALANCE RECORD WHEN ALTERATIONS HAVE BEEN MADE.
SAMPLE LOADING PROBLEM
ITEM WEIGHT ARM MOMENT (LBS) (IN) (LB-IN/1000) LICENSED EMPTY WEIGHT 1099.5 35.7 OIL 12 - 15.0 -0.2 PILOT & PASSENGER 340 40.0 13. 6 FUEL 188.5 43.0 8.1 BAGGAGE 160 65.0 10. 4 TOTAL LOADED AIRPLANE 1800 67. 6 FIGURE 31. Weight and balance data.
found in the latest weight and balance report, in a log book, or on a major repair and alteration form, located in the aircraft. If useful load is not stated directly, simply subtract empty weight from maximum takeoff weight. Be especially weight conscious of aircraft which have a limited useful load because 36 they are the ones which cause weight and balance troubles.
• The check is simple enough-just be sure to include all the load items included in the useful load--then check the total against the limit. The calculations might look like this:
Example 22.
Pounds Mr. Jones (instructor) • 175 Pilot .. 180 Fuel-30 gallons 180 Oil-8 quarts 15 Baggage 5 Total . 555 Useful Joad limit is 575 Ibs.
The calculations indicate that the useful load is not exceeded and the flight can take place.
Now suppose that Mr. Jones, in the example, is replaced by a new instructor who weighs 210 lb. A useful load check will show that the aircraft is too heavy. The pilot in our example must reduce the load to the specified useful load limit. There is no alternative in this small aircraft but to reduce the fuel load, even if all the baggage has been removed.
Pilots should be aware of, and on the alert for, unusual loadings. They should remember that the manufacturer's initial weight and balance calculations and some examples in the owner's manual make the assumption that the pilot and passengers weigh a standard 170 Ib. each. Heavyweight passengers can overload a small aircraft seriously. A student and instructor may easily weigh 220 Ib. each in winter clothing; this represents a potential overload of 100 lb. The baggage compartment is another place where pilot vigilance should be directed-the maximum compartment load placard must be obeyed. Frequently, a restriction is placed on rear seat occupancy with the maximum baggage aboard.
WEIGHT AND BALANCE RESTRICTIONS Be sure to follow your aircraft's weight and balance restrictions. The loading conditions and empty weight of your particular aircraft (fig. 31) may differ from those in the owner's manual due to modifications or equipment changes. Sample loading problems in the owner's manual are intended for guidance only; each aircraft must be treated separately for weight and balance. The pilot should understand that although the aircraft is certified for a specified maximum gross weight, it will not safely take off with this load under all conditions. Conditions which affect takeoff and climb performance such as high elevations, high temperatures, and high humidity (high-density altitudes), may require operation at reduced weight. Other factors to consider are runway length, runway surface, runway slope, surface wind, and the presence of obstacles.
Pilot experience and proficiency should always be considered-if in doubt, reduce the load.
Some small aircraft are designed so that it is not possible to load them in a condition which will place the c.g. outside the fore or aft limits if standard load schedules are observed. These aircraft have the seats, fuel, and baggage accommodations located very near the c.g. limits. They also have special empty weight c.g. limits listed in their specifications. Loads can be added to or removed from any location within the c.g. range with complete freedom from concern about c.g. movement.
Such action cannot cause the c.g. to move beyond the c.g. limits of these aircraft (see fig. 32), but maximum weight limits can still be exceeded.
ADDING OR REMOVING THIS WEIGHT CANNOT MOVE THE C.G. BEYOND LIMITS
FORWARD LIMIT AFT LIMIT FIGURE 32. Changing weight between c.g. limits.
Most aircraft, however, can be loaded in a manner which will place the c.g. beyond limits. Even though the useful load is not exceeded, an out-of-balance condition is serious from a stability and control standpoint. The pilot can quickly determine if the load is within limits, if the aircraft is simple enough to make use of a loading schedule. This schedule may be found in the weight and balance report, the aircraft log book, the owner's manual, or may be posted in the form of a placard. A typical placard may appear similar to the one shown in figure 33.
LOADING SCHEDULE
FUEL PASSENGERS BAGGAGE FULL 2 REAR 100 LBS 39 GAL 1 FRONT AND NONE 2 REAR FULL 1 FRONT AND FULL 1 REAR
INCLUDES PILOT AND FULL OIL FIGURE 33. Loading schedule placard.
The loading schedule should be treated as a suggested loading plan only. The pilot should make a check by means of weight and balance calculations to see if limitations are not being exceeded. The assumption in the use of the loading schedule is that each passenger weighs approximately the standard weight of 170 lb. It is obvious that passenger weights could vary widely from the assumed standard.
AIRPLANE FLIGHT MANUAL Each airplane of over 6,000 lbs. maximum weight is furnished with an airplane flight manual. An airplane of less than 6,000 Ibs, may have information furnished in the form of placards, markings, or manuals. When an airplane flight manual is furnished, the following is included:
a. Limitations and data:
(1) The maximum weight.
(2) The empty weight and c.g. location.
(3) The useful load.
(4) The composition of the useful load, including the total weight of fuel and oil with full tanks.
b. Load distribution:
The established c.g. limits are furnished in the airplane flight manual. If the available loading space is adequately placarded or arranged so that no reasonable distribution of the useful load will result in a c.g. outside of the stated limits, the airplane flight manual may not include any information other than the statement of c.g. limits. In other cases, the manual includes enough information to indicate loading combinations that will keep the c.g. within established limits.
LIGHT SINGLE-ENGINE AIRCRAFT
LOADING PROBLEMS Aircraft manufacturers use one of several available systems to provide the aircraft loading information. The following weight and balance problems will show how the pilot can determine if the maximum weight limit is exceeded or the c.g. is located beyond limits.
Assume you are a pilot planning a flight in a light single-engine, four-place aircraft. Your load consists of yourself, one front seat passenger and two rear seat passengers, full fuel and oil, and 60 lb. of baggage (fig. 34). Here is how the critical weight and balance problems are solved for this case by two different methods (examples 23 and 24).
Example 23.
Solution by index table:
1. From the manual or weight and balance report, determine the empty weight and empty weight c.g. (arm) of the aircraft.
2. Determine the arms for all useful load items.
3. Determine the maximum weight and c.g.
range. (For this case-Max. TOGW= 2,400 lb., c.g. range - Sta. 35.6 to 45.8.)
4. Calculate the actual weights for the useful load items.
5. Construct a table as follows (pg. 39), and enter the appropriate values. Multiply each individual weight and arm to obtain moments.
OIL PILOT & FRONT PASS TWO REAR PASS BAGGAGE -20" + 35" +72" + 92" C.G. LIMITS NEGATIVE ARMS POSITIVE ARMS FUEL +35.6" to +45.8" +48" DATUM EMPTY WEIGHT 1340 LBS MAX T.O. WEIGHT 2400 LBS EMPTY WEIGHT C.G. +38.5" FIcURE 34. General aviation aircraft-weight and balance diagram.
Weight X Arm = Moment (lb.-in.) Weight and balance computations are greatly Aircraft simplified by two graphic aids the loading graph Oil ......... (empty) .. 1,340 15 - 20.0 38.5 51,590 - 300 and the center of gravity moment envelope. The Pilot and front loading graph (fig. 35) is typical of those found in passenger .. 320 35.0 11,200 general aviation aircraft owner's manuals. This Fuel .... 241 48.0 11,568 graph, in effect, multiplies weight by arm giving Rear passengers. 300 72.0 21,600 moment, then divides the moment by a reduction Baggage •..• 60 92.0 5,520 factor, giving an index number. Weight values ap- Total 2,276... ............... pear along the left side of the graph. The moment/ NoTE.-Observe that the oil tank for this aircraft is located forward of the datum. Care must be taken to subtract the negative oil moment when totaling the moment column.
6. Adding the weights produces a total of 2,276 lb., and adding the moments produces a total of 101,178 lb.-in. The c.g.
is calculated by dividing the total moment by the total weight:
101,178 = 44.5 in. aft of datum 2,276
7. The total weight of 2,276 lb. does not ex ceed the maximum weight of 2,400 lb., and the computed c.g. of 44.5 falls within the allowable c.g. range of 35.6 to 45.8 in. aft of datum.
1,000 or index numbers are along the bottom. In this example, each line representing a load item is labeled. To determine the moment of any load item, find the weight along the left margin, then project a line right to a point of intersection with the appropriate load item line. For example, the index number of a pilot weighing 170 lb. is 6.1. The c.g.
moment envelope (fig. 36) allows the pilot to bypass the computation of a c.g. number. It gives an acceptable range of index numbers for any aircraft weight from minimum to maximum. If the lines from total weight and total moment intersect within the envelope, the aircraft is within weight and balance limits. In solving the sample problem, follow this procedure:
360 320 PASSENGER 280 240 LOAD WEIGHT (LBS) PILOT & FRONT 200 FUEL PASSENGERS
REAR A BAGGAGE MOMENT/1000 (LB INS) 10 12 14 16 18 20 22 24 26 28 FIGURE 35. Loading graph.
2400 2300 2200 LOADED AIRCRAFT WEIGHT (LBS) -NORMAL CATEGORY
21.00 2000 1900 CATECORY LOADED AIRCRAFT MOMENT/1000 (LB INS) 1500 50 55 60 65 70 75 80 85 90 95 100 105 110 115 FIGURE 36. C.G. moment envelope.
Example 24. Sample Loading Problem
1. Determine the aircraft empty weight and the ltem Weight Moment/1,000 empty weight index from the weight and 1. Empty aircraft weight .1,340 51.6 balance report. 2. Oil 3. Pilot and front passenger 320 15 - 0.3 112
2. Construct a table such as the one that follows. 4. Fuel 241 11.6 In the left column, enter the actual weights of 5. Rear seat passengers 300 21.6 the empty aircraft, oil, pilot and front seat 6. Baggage 60 5.5 passenger, fuel, rear seat passenger, and bag- 7. Total aircraft weight •2,276 101.2 gage. In the right column, enter the aircraft empty weight index (moment/1,000).
3. From the loading graph, fig. 35, determine the index number (moment/1,000) of each useful load weight item and enter it in the table.
4. Add the weight and moment columns and write in the totals.
5. Refer to the c.g. moment envelope, fig. 36, and find the point of intersection of a line projected right from total weight (2,276 Ibs.) and of a line projected up from total moment/1,000 (101.2).
6. The point of intersection falls within the envelope, therefore, the weight and c.g. are within limits.
LIGHT TWIN-ENGINE AIRCRAFT Modern light twin-engine aircraft are larger than most single-engine aircraft; accordingly, their useful load is almost always greater than that found in the smaller aircraft. In these aircraft, it is possible to have many different loading combinations. Their large baggage compartments may be full or empty, and there may be wide variations in the number of seats being occupied. These variations are to be expected and are normal for the types of operations for which the aircraft are used. However, the c.g.
is bound to range backward and forward as the loads are varied; therefore, weight and balance control is essential.
If a variety of loads can be placed aboard an aircraft in a number of locations, the pilot must be 40
especially aware of duties regarding weight and balance control. Pilots should use a reliable weight and balance system, preferably the type recommended by the manufacturer, to assure that the weight and balance is within limits for each fight.
They should insist that passengers are assigned to the correct seat from a weight distribution standpoint. They should also be sure that passenger baggage or miscellaneous cargo is properly loaded.
The weight and balance systems used on light twin-engine aircraft are essentially the same as those used for single-engine aircraft. Weights, arms, and moments are the basic factors, and the final c.g.
computation must fall within the allowable c.g.
limits. Many twin-engine aircraft make use of the loading graph and moment envelope system (figs.
35 and 36). Other models make use of index tables similar to those explained earlier for single-engine aircraft (fig. 24).
Some light twin-engine aircraft have weight and balance control systems which make use of a special weight and balance plotter. The typical plotter is made of plastic material similar to an aeronautical computer. It consists of several movable parts which can be adjusted over a plotting board on which is printed a c.g. envelope. The reverse side of the typical plotter contains general loading recommendations for the particular aircraft. The recommendations may suggest that occupants be loaded progressively from front to rear. In other words, the forward and center seats should be occupied before passengers are assigned to the rear seats. A pencil line plot can be made directly on the envelope imprinted on the working side of the plotting board.
This plot can be erased and recalculated anew for each flight. The plotter is to be used only for the aircraft for which it was designed. This weight and balance control system is very similar to one used on air carrier aircraft as explained on page 60 and illustrated by figure 57.
A typical weight and balance plotter should contain this reminder: iIt is the responsibility of the owner and pilot to ascertain that the aircraft always remains within the allowable weight versus c.g. envelope while in flight." This note should serve as a precaution to the pilot to be sure to check the weight and balance condition before takeoff and to be sure that any shift in passenger seating locations does not adversely affect the location of the aircraft center of gravity.
HIGH-DENSITY-SEATING AIRCRAFT Many light twin-engine aircraft are being used for transportation of passengers, cargo, or mail in the form of commuter or air-taxi service to supplement the scheduled and unscheduled air carriers. An increasing number of twin-engine aircraft are being used to carry mail on a scheduled basis. Many commuter and air-taxi operators carry passengers to and from small cities to make connections with trunk carriers at airports in large cities. The aircraft used for this purpose are in some cases fitted with a large number of seats in relation to fuselage size and are called high-density-seating aircraft. The aircraft may contain seats for eight to 15 passengers and some of the larger types may seat over 25 passengers. The loading problems are relatively more complex than for aircraft which carry only six passengers. The complexity of the loading situation approaches that encountered in air carrier operations. Weight and balance limits for high-density-seating aircraft must be respected. The passenger, cargo, or mail load on high-density-seating aircraft may vary considerably from flight to flight. Some trips may be made with a full load and others with a minimum load. Some of the high-density-seating aircraft have special weight and balance problems because they have been modified and modernized from older aircraft which originally did not have a great number of seats. Some of these modified aircraft are very sensitive as far as loading toward the rear limit is concerned. The recommended weight and balance checking procedures for modified aircraft must be carefully followed and operators should be sure to make a thorough analysis of weight and balance records to assure currency.
An operator's manual, when required for highdensity-seating aircraft, should contain procedures for assuring compliance with weight and balance limits, including periodic reweighing of the aircraft.
The weight and balance procedures contained in the
1. Be based on sound principles, using standardized terminology, and be compatible with the type (s) of aircraft operated.
2. When followed, assure that the aircraft is properly loaded and will not exceed authorized weight and balance limitations during operation.
3. Provide for blocking off seats or compartments when necessary to remain within c.g. limits.
Effective means should be provided to assure that those seats and compartments are not occupied during operations specified.
4. Provide crewmembers, cargo handlers, and other personnel concerned complete information regarding distribution of passengers, fuel, and other items, and should give com- 41
COMMUTER TAXI AIRLINE INC.
PASSENGER AND CARGO MANIFEST
PASSENGER - CARGO LIST WEIGHT SEAT- INDEX COMPT 180 170 2 140 PASSENGER NAMES 150 200 5 ENTERED HERE 160 6 210 7 130 8 120 9 140 10 130 11
PASSENGER - CARGO - MAIN CABIN TOTAL FUEL BAGGAGE COMPT 100 NOSE WEIGHT TANK INDEX BAGGAGE COMPT 200 REAR 300 R-MAIN PILOT - COPILOT 330 300 L-MAIN OIL 85 120 R-AUX FUEL TOTAL 120 L-AUX EMPTY WEIGHT 6,150 5842.5
NOSE TAKEOFF WEIGHT TOTAL TAKEOFF LIMITS 10,000 AIRCRAFT N 123 QC I HEREBY CERTIFY THAT THE ABOVE FLIGHT 45 TAKEOFF WEIGHT AND INDEX IS WITHIN LIMITS AS SPECIFIED IN THE ROUTE окс-Мка FLIGHT OPERATIONS MANUAL
DATE PILOT IN COMMAND FIGURE 37. Passenger manifest.
OCCUPANTS - MOMENTS/100 Pilot & Seats Seats Seats Seats Seats Seat Weight Co-Pilot 162 364 566 768 9 6 10 11 100 50.0 70.0 90.0 110.0 130.0 150.0 170.0 110 55.0 77.0 99.0 121.0 143.0 165.0 187.0 120 60.0 84.0 108.0 132.0 156.0 180.0 204.0 130 65.0 91.0 117.0 143.0 169.0 195.0 221.0 140 70.0 98.0 126.0 154.0 182.0 210.0 238.0 150 75.0 105.0 135.0 165.0 195.0 225.0 255.0 160 80.0 112.0 144.0 176.0 208.0 240.0 272.0 170 85.0 119.0 153.0 187.0 221.0 255.0 289.0 180 90.0 126.0 162.0 198.0 234.0 270.0 306.0 190 95.0 133.0 171.0 209.0 247.0 285.0 323.0 200 100.0 140.0 180.0 220.0 260.0 300.0 340.0 180 PILOT & COPILOT SEATS 1 & 2 1 60 55&6 WEICHT SEATS 7 & 8 • SEATS 9 & 10 SEAT 11
• 100 80 GRAPHIC PRESENTATION OF OCCUPANTS TABLE 60 40 20 FINDEX MOMENT/100 50 100 150 200 250 300 350 FIGURE 38. Occupants loading moments.
BAGGAGE OR CARGO MOMENTS/100 Nose Compt. Compt. Compt. Compt. Compt. Rear Weight Baggage B C D E Baggage 20 4.0 16.0 20.0 24.0 28.0 32.0 38.0 40 8.0 32.0 40.0 48.0 56.0 64.0 76.0 60 12.0 48.0 60.0 72.0 84.0 96.0 114.0 80 16.0 64.0 80.0 96.0 112.0 128.0 152.0 100 20.0 80.0 100.0 120.0 140.0 160.0 190.0 120 24.0 96.0 120.0 144.0 168.0 192.0 228.0 140 112.0 140.0 168.0 196.0 224.0 266.0 160 128.0 160.0 192.0 224.0 256.0 304.0 180 144.0 180.0 216.0 252.0 288.0 342.0 200 160.0 200.0 240.0 280.0 320.0 380.0 300 240.0 300.0 360.0 420.0 480.0 400 320.0 400.0 480.0 560.0 640.0 500 400.0 500.0 600.0 700.0 800.0 STA 20 STA 80 STA 100 STA 120 STA 140 STA 160 STA 190
B D E REAR 500 LB 750 LB 800 LB 500 LB 500 LB 200 LB
MAX MAX MAX MAX MAX MAX NOSE 120 LB MAX
MAIN CABIN FLOOR LOADING LIMIT 150 LBS SQ FT FIGURE 39. Baggage and cargo loading moments.
plete information regarding the distribution and security of cargo to prevent the shifting of weight in flight.
5. Provide other information relative to maximum weights, capacities, and other pertinent limitations affecting the weight and balance of the aircraft.
Pilots of these high-density-seating aircraft must be aware of the effect of passenger and cargo location on c.g., and they must have a personal knowledge of the means of correcting an out-of-limits condition. They often have no one to assist them with loading problems; they act as pilot, dispatcher, and loading agent in many cases.
44 In commuter or air taxi operations, pilots are confronted with the problem of frequent trips with varying loads. They need to have a positive, accurate, and fast way to compute the weight and balance. They must have reliable empty weight and c.g. information readily available for use. This information must be updated to account for all the modifications performed on the aircraft.
A load manifest, when required for air-taxi or commercial operations, should contain the following information concerning the aircraft loading at takeoff time:
1. The weight of the aircraft, fuel and oil, cargo (including mail and baggage), and passengers;
FUEL - MOMENTS/100 Weight Nose Main Aux. Weight Nose Main Aux.
30 6.0 27.0 36.0 330 66.0 297.0 396.0 60 12.0 54.0 72.0 360 72.0 324.0 432.0 90 18.0 81.0 108.0 390 78.0 351.0 468.0 120 24.0 108.0 144.0 420 84.0 378.0 504.0 150 30.0 135.0 180.0 450 90.0 405.0 540.0 180 36.0 162.0 216.0 480 96.0 432.0 576.0 210 42.0 189.0 252.0 510 102.0 459.0 612.0 240 48.0 216.0 288.0 540 108.0 486.0 648.0 270 54.0 243.0 324.0 570 114.0 513.0 684.0 300 60.0 270.0 360.0 600 120.0 540.0 720.0 OIL - MOMENTS/100 Gallon Weight Moment 2 17 1.5 4 34 3.1 6 51 4.6 8 68 6.1 10 85 7.7 FIcURE 40. Fuel and oil loading moments.
2. The maximum allowable weight for that Aight;
3. The total weight computed under approved procedures;
4. Evidence that the aircraft is loaded according to an approved schedule that insures that the c.g. is within approved limits.
The execution of a load manifest is always a highly recommended procedure from the standpoint of making a uniform preflight check of the weight and balance condition. A typical load manifest may be a simple form similar to that illustrated in figure
37. This form provides a record of passengers and of all useful loads for the particular flight. The major advantage of such a form is that the pilot has a standardized means of calculating and recording the weight and balance condition of the aircraft for each flight. If care is taken to carry forward or make proper record of the empty weight and c.g., the pilot can be spared the task of a search through aircraft records for this vital information. The form may also be used as a record of passenger identification as may be needed for administrative purposes.
One typical weight and balance control system for high-density-seating aircraft is based upon the utilization of useful load index tables and a total weight index limit envelope or table. With these tables (higs. 30-41), it is possible to determine it weight and balance is within limits even in a situation where the passenger, cargo, or fuel loads change fairly rapidly. The tables can be read for intermediate weights by interpolation of values. To simplify and speed up calculations, use the nearest listed weight, but be conservative when checking against particular limits. The system is generally similar to those discussed on smaller aircraft. The pilot adds the weight and moments (index) of the empty aircraft and the useful load items. Then, checks are made against the published limits-in this case the index limit envelope or table. Care must be taken to use the empty weight and moments or index from the latest weight and balance report. The pilot must be sure to use the same 45