TOTAL WEIGHT INDEX LIMIT
ENVELOPE INDEX TABLE 9000 9500 10000: : 10000 Weight Index Index Min. Max.
MAXIMUM WEIGHT LIMIT 9100 8167 9350 8500 .9500 9200 9150 8212 8257 9402 9453 9250 8302 9504 8000₴ 9000 9300 8347 9556 A INDEX - MOMENT/100 9350 8392 9607 7500 8500 9400 8437 9659 9450 8481 9710 9500 8526 9761 7000 8000 9550 8571 9813 LIMI 9600 8616 9864 6500 7500 9650 9700 8661 8706 9915 9967 7000 9750 8751 10018 6000 9800 8796 10070 9850 8840 10121 88 90 92 94 96 98 100 102 104 9900 8885 10172 9950 8930 10224 CENTER OF GRAVITY - INCHES AFT OF DATUM 10000 8975 10275 FIGURE 41. Total weight index limits.
reduction factor for all moments in the calculations.
Sufficient accuracy is obtained by rounding off index numbers to the nearest tenth.
Example 25.
Assume you are a pilot planning a flight in an air-taxi aircraft. Your load consists of yourself, your copilot, 11 passengers, 300 pounds of fuel in each of the main tanks, 120 pounds of fuel in each of the auxiliary tanks, 75 pounds of oil, 100 pounds of baggage in the nose compartment, and 200 pounds of baggage in the rear compartment.
The sample manifest form in figure 37 has been completed to show the useful load and empty weight items. Use the loading tables and total weight index limit table shown in figures 38 through 41 to determine if the aircraft is properly loaded for takeoff. The intersection of the dotted weight and moment/100 lines in figure 41 shows that limits are not being exceeded.
TWIN-ENGINE CARGO AIRCRAFT Small twin-engine aircraft can be used effectively 46 for carrying cargo into airports where operations would not be practical with transport aircraft. Cargo which is particularly suitable for twin-engine aircraft are high-value items or items which must reach local destinations quickly. The scheduled transportation of mail to small cities and. towns is an example of the type service these aircraft provide.
Light twin-engine aircraft can be designed for more effective cargo operations if some special loading and handling features are employed. Large size cargo doors are a great help when bulky packages are to be loaded. Without the use of large doors, the cargo space may be restricted because big packages cannot be maneuvered through the passenger type doors. Provisions for securing the cargo to the aircraft structure are also needed. Normally, tiedown rings are attached to the floor and to structural members of the side walls for this purpose.
Many of the high-density twin-engine aircraft can be quickly converted from passenger to cargo use by removing the seats from the main cabin area (fig.
42). In some cases, cargo is carried in the passenger seats and secured by the regular seat belt. It is also
FUSELAGE STATIONS 50 60 80 90 100 110 120 130 140 150 160
CARGO TIE-DOWN METHOD CARGO
- PASSENGER AREA - - CARGO AREA "A" AREA "B" 60 100 140 160 FICURE 42. Cabin tiedown diagram.
possible that only one or two passenger seats will be removed, resulting in a mixture of cargo and passengers in the main cabin. Measures must be taken in this case to protect the passengers from possible cargo movement.
The following are recommended for the loading of cargo in other than approved cargo compartments or bins:
a. If passengers are carried, the cargo must be carried forward of the foremost passenger.
b. The cargo should be properly secured by a safety belt or other tiedown device to prevent it from becoming a hazard by shifting.
c. The cargo must not impose any load on seats or the floor structure that exceeds the load limitations for these components.
d. The location of the cargo must not restrict access to or use of any required emergency or regular exit by any passenger, or access to an emergency exit by a pilot if a regular exit is not accessible to the pilot.
e. The location of the cargo must not obscure any passenger's view of any required sign, unless an auxiliary sign or other approved means for proper instruction or notification is provided.
Cabin cargo is in danger of shifting if the deck angle (floor attitude) is not level as during the rotation and initial climb at takeoff. Unrestrained cargo will shift rearward in this event and cause a tailheavy condition which may lead to a dangerous takeoff stall. Cabin cargo is also subjected to inertia forces resulting from turbulence, acceleration, deceleration, vibration, and hard landings. These inertia forces act more strongly in some directions than in others and tend to shift the cargo unless it is properly restrained. A forward force is the one most likely to act on cargo. This force may result from a sudden application of brakes, landing on a soft sod runway, or a crash landing. That is why cargo should be located forward of all passengers in a mixed-load configuration. Cargo must also be secured from moving aft, from side to side (laterally), or up and down (vertically).
Cargo may be secured by means of tiedown devices such as straps, ropes, or nets. These devices, when properly used, will restrain the cargo from moving in any direction. Tiedown fittings should be adequate in number and strength to restrain a cargo of any allowable weight and size. Floor structure, particularly where the tiedown fittings are anchored, must be strong enough to resist any anticipated load without distortion. Cargo floor loading limits are usually expressed as maximum weight in pounds per square foot. If a cargo item is loaded in a seat, the pilot would be wise to limit its weight to that of an average passenger. A tiedown or safety belt should 47
FIGURE 43. Securing cargo in seat.
restrain its movement in the seat (fig. 43). A single cargo item on the cabin floor should be secured in a manner similar to that shown in figure 44. Its center of gravity may be determined by the method shown in figure 45.
The following general precautions should be observed when actually loading the cargo:
1. In a tailwheel aircraft, cylindrical items on their sides should be chocked until lashed down.
2. Liquid containers should be placed with their outlets at the top.
FIGURE 44. Securing cargo to floor.
48 FIGURE 45. Determining c.g. by means of a roller.
3. Lightweight items should be stacked on heavier items, or stacked separately.
4. Shoring or planking must be used when the contact area is likely to exceed the floorstrength limitations.
Many cargo loads carried in air-taxi aircraft will consist of a variety of boxes, crates, sacks, drums, etc. This type of composite cargo may be secured with the type devices shown in figures 46 and 47.
Sufficient restraint should be used to prevent shifting because of high deck angle or inertia forces. In FIcURE 46. Securing composite cargo with straps.
FIGURE 47. Securing composite cargo with net.
COMMUTER TAXI AIRLINE INC.
PASSENGER AND CARGO MANIFEST
PASSENGER - CARGO LIST WEIGHT SEAT- INDEX COMPT 670 B CARGO DESCRIPTION 600 500 D ENTERED HERE 500
PASSENGER - CARGO - MAIN CABIN TOTAL
FUEL BAGGAGE COMPT NOSE WEIGHT TANK INDEX BAGGAGE COMPT 200 REAR 200 R-MAIN PILOT - COPILOT 340 200 L-MAIN OIL 75 400 R-AUX FUEL TOTAL 400 L-AUX EMPTY WEIGHT 5655 5271.0
NOSE TAKEOFF WEIGHT TOTAL TAKEOFF LIMITS 10,000 AIRCRAFT NI23QC I HEREBY CERTIFY THAT THE ABOVE FLIGHT 46 TAKEOFF WEIGHT AND INDEX IS WITHIN LIMITS AS SPECIFIED IN THE
ROUTE MKC-DEN FLIGHT OPERATIONS MANUAL
DATE PILOT IN COMMAND FIGURE 48. Cargo manifest.
arranging composite loads, cargo items should not be arranged so the load is topheavy. If possible, the height of the load should not exceed its length.
Particular care should be taken to secure this type load against slipping out from under the tiedown device. If the individual items of this type cargo are comparatively light, a net type tiedown device is adequate. Heavy items will require ropes or straps.
Cargo should be placed as near to the c.g. of the airplane as possible, roughly at the 30% chord point; but limitations of particular areas should be observed to prevent overloading the structure. Care must also be taken not to block access to an exit in the rear of the cabin or to cut off an aisle needed for ments by this arm (2070.0÷80 = 25.9 1b.) .
By use of either method we can see that the movement of 40 lb. (two ea. 20-lb. cartons) would be required to reduce the index by at least
20.7. A new passenger and cargo manifest should now be executed to prove that the c.g. is within limits with the proposed new load distribution.
Of course, it would be possible to shift a greater number of cartons than the minimum to be on the safe side. In any case, care must be taken to remain within the compartment maximum weight limit, the floor loading limit, and the minimum and maximum index limits.
inflight inspection of the main cabin cargo. HELICOPTER WEIGHT AND BALANCE Example 26.
This problem is an example of the use of a manifest form to determine the weight and balance condition of a cargo flight. The airplane is the same one used in example 25 with the seats removed from the main cabin. Notice that the empty weight and moments have been changed due to the removal of the seats. This change must be carefully noted according to the manufacturer's recommendations. The sample manifest form in figure 48 has been completed to show the useful load and empty weight The weight and balance principles and procedures which have been described in connection with airplanes apply generally to helicopters. Each model helicopter is certificated for a specific maximum gross weight. However, it is not safe to operate at this maximum weight under all conditions. Combinations of high altitude, high temperature, and high humidity determine the density altitude at a particular location. This, in turn, critically affects the hovering, takeoff, climb, autorotation, and landing performance of a helicopter. Additional factors to be considered are wind, obstacles, type of surface, and Using the loading tables and total weight index space available for takeoff and landing. Just because table shown in figures 38 through 41 to determine a helicopter can take off with a heavy load does not the loading condition of the aircraft, you should ob- mean that flight with that load will be safe. A tain a moment of 10038.7 index units. It is apparent heavily loaded helicopter has less ability to withwhen the index limit table is checked that the cargo stand shocks and additional airloads caused by is loaded too far to the rear. The aircraft is not safe turbulence. The greater the weight, the less the or legal to fly in this loaded condition. The maxi- margin of safety for the supporting structures such mum index limit (rear c.g. limit) has been exceeded as the main rotor, fuselage, and landing gear.
by 20.7 index units (2070.0 lb.-in.). If the cargo in Most helicopters have a much more restricted c.g.
compartment E consists of cartons, each weighing range than do airplanes. In some cases this range is 20 pounds, how many cartons must be moved to compartment A to bring the index within the maxi- less than 3 inches. The exact location and length of the c.g. range is specified for each helicopter and usually extends a short distance fore and aft of the The baggage or cargo table can be used to help determine how much cargo must be shifted. At least two methods are available:
1. Select the cargo weight which would make a difference of at least 20.7 index units when compartments A and E are compared. (40 lb. =64.0-32.0=32.0 index units)
2. Determine the difference in arms between compartments A and E (Sta. 160-Sta.
80=80 in.). Divide the excessive momain rotor mast or the centroid of a dual rotor sys.
tem. Ideally, the helicopter should have such perfect balance that the fuselage remains horizontal while in a hover and the only cyclic adjustment required should be that made necessary by the wind. The fuselage acts as a pendulum suspended from the rotor. Any change in the c.g. changes the angle at which it hangs from this point of support. Many recently designed helicopters have loading compartments and fuel tanks located at or near the balance point. If the helicopter is not loaded properly and the c.g. is not very near the balance point, the fuse.
c.c.rI FIGURE 19. Effect of c.g. on helicopter attitude in hover.
lage does not hang horizontal in a hover. If the c.g.
is too far aft, the nose tilts up and excessive forward cyclic is required to maintain a stationary hover.
Conversely, if the c.g. is too far forward, the nose tilts down and excessive aft cyclic is required (fig.
49). In extreme out-of-balance conditions, full forc or aft cyclic may be insufficient to maintain control.
Similar lateral balance problems may be encountered if external loads are carried.
Upon delivery by the manufacturer, the empty weight, empty weight c.g., and the useful load are noted on the weight and balance data sheet in the helicopter flight manual. If, after delivery, additional fixed equipment is added or removed, or if a major repair or alteration is made which may affect the empty weight, empty weight c.g., or useful load.
the weight and balance data must be revised. All weight and balance changes should be entered in the appropriate aircraft record. The helicopter flight manual includes directions for solving loading problems. The procedures are similar to those already described for airplanes. For further information, read the FAA Basic Helicopter Handbook, AC 61-13A.
Chapter 7
CONTROL OF LOADING-LARGE AIRCRAFT The principles of weight and balance which have been discussed in previous chapters apply to large aircraft used by the air carriers and commercial operators as well as to small aircraft used by general aviation pilots and operators. The general concept of weights, arms, and moments apply regardless of aircraft size. The location of the c.g. can always be found by dividing total moments by total weight.
Large aircraft have the same dangerous flight characteristics as small aircraft when weight and balance limits are exceeded. It is not safe to assume that a large aircraft, because of its apparent abundance of engine power and spacious passenger and cargo compartments, cannot be loaded in an adverse manner. Any aircraft can be overloaded or loaded out of balance if weight and balance control procedures are not followed.
Aircraft which have a large number of passenger seats potentially possess great flexibility of loading configurations. From a utilization standpoint, such flexibility is desirable; but unless due consideration is given to weight and balance control, such an aircraft may easily be loaded in a nose-heavy or tailheavy condition.
Large aircraft, particularly those operated by air carriers, are flown and maintained by a large number of people. No one pilot or mechanic may be 52 fully and personally familiar with the loading or weight and balance condition of a particular aircraft. A properly documented weight and balance control system which is understood by flight, maintenance, and dispatch personnel is necessary for safe and orderly flight operations.
Weight control has a direct relationship to the profit or loss made by air carrier and commercial operator aircraft. When extra fuel is required for long trips or to allow for delays, the payload (passengers, baggage, cargo) must. be proportionately reduced to prevent exceeding maximum weight limits. When trips are short and the payload is high, there are frequent changes of passenger and cargo load. Under these conditions, a quick, accurate method must be available to keep account of the aircraft weight and balance condition.
WEIGHT AND BALANCE CONTROL
PROCEDURES The operator should develop a method and procedure by which it can be shown that the aircraft is properly loaded and will not exceed authorized weight and balance limitations during operation.
The large aircraft operator should also account for all probable loading conditions which may be experienced in service and devise a loading schedule
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.