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
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