Par 10-14 Page 10-10 SECTION 2. WEIGHING PROCEDURES
10-14. GENERAL. Weighing procedures may vary with the aircraft and the type of weighing equipment employed. The weighing procedures contained in the manufacturer’s maintenance manual should be followed for each particular aircraft.
10-15. PROCEDURES. Accepted procedures when weighing an aircraft are:
a. Remove excessive dirt, grease, moisture, etc., from the aircraft before weighing.
b. Weigh the aircraft inside a closed building to prevent error in scale reading due to wind.
c. Determine the EWCG by placing the aircraft in a level flight attitude.
d. Have all items of equipment that are included in the certificated empty weight report installed in the aircraft when weighing. These items of equipment are a part of the current W&B report.
e. The scales should have a current calibration before weighing begins. Zero and use the scales in accordance with the scale manufacturer’s instructions. Platform scales and suitable support for the aircraft, if necessary, are usually placed under the wheels of a landplane, the keel of a seaplane float, or the skis of a skiplane. Other structural locations capable of supporting the aircraft, such as jack pads, may be used. Clearly indicate these points and the alternate equipment used in the W&B report.
f. Drain the fuel system until the quantity indicator reads zero or until the tanks are empty with the aircraft in level flight attitude, unless otherwise noted in the TCDS or Aircraft Specifications. The amount of fuel remaining in the tank, lines, and engine is termed residual fuel and is to be included in the empty weight. In special cases, the aircraft may be weighed with full fuel in tanks provided a definite means of determining the exact weight of the fuel is available.
g. The oil system should be filled to the quantity noted in the TCDS or Aircraft Specifications.
NOTE: On Civil Aeronautics Regulations (CAR 3) Certified Aircraft, the weight of the oil was subtracted mathematically to get the empty weight. In 14 CFR part 23 aircraft, the weight of the oil is included in the empty weight.
When weighed with full oil, actual empty weight equals the actual recorded weight less the weight of the oil in the oil tank (oil weight = oil capacity in gallons x 7.5 lb.). Indicate on all W&B reports whether weights include full oil or oil drained. (See Figure 10-9.)
FIGURE 10-9. EMPTY WEIGHT AND EMPTY WEIGHT CENTER OF GRAVITY
WHEN AIRCRAFT IS WEIGHED WITH OIL DATUM
• EMPTY WEIGHT C.G.
AT - 49" OIL TANK 9 QTS_ WEIGHT OF AIRCRAFT WITH OIL IS 1186 LBS. C.G. AS WEIGHED WITH OIL IS +9.7"
EMPTY WEIGHT AND EMPTY WEIGHT CENTER OF GRAVITY (When aircraft is weighed with oil) GIVEN:
Aircraft as weighed with full oil - 1186 Ibs.
Center of gravity " - 9.7" Full oil capacity 9 qts. -- 17 1bs.
SOLVING:
Weight # X Arm" = Moment "# Aircraft as weighed + 1186 + 9.7 + 11504 Less oil 17 - 49.0 + 833 Total + 1169(A) + 12337(B) Empty Weight (A) = 1169 pounds Empty Weight Center of Gravity B = 12337 = + 10.6" 1169
h. Do not set brakes while taking scale reading.
I. Note any tare reading when the aircraft is removed from the scales.
• 10-16. REPAIRS AND ALTERATIONS. These are the major sources of weight changes, and it is the responsibility of the aircraft mechanic making any repairs or alteration to know the weight and location of these changes, and to compute the new CG and record the new empty weight and EWCG data in the AFM.
• 10-17. ANNUAL OR 100-HOUR INSPECTION. After conducting an annual or 100-hour inspection, the aircraft mechanic must ensure the W&B data in the aircraft records is current and accurate.
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Par 10-18 Page 10-12
10-18. W&B COMPUTATIONS. It is often necessary after completing an extensive alteration to establish by computation that the authorized weight and CG limits as shown in the TCDS and Aircraft Specifications are not exceeded. Subparagraph b(2) explains the significance of algebraic signs used in balance computations.
a. The TCDS or Aircraft Specifications contain the following information relating to the subject:
(1) CG range.
(2) EWCG range when applicable.
(3) Leveling means.
(4) Datum.
(5) Maximum weights.
(6) Number of seats and arm.
(7) Maximum baggage and arm.
(8) Fuel capacity and arm.
(9) Oil capacity and arm.
(10) Equipment items and arm.
b. The TCDS do not list the basic required equipment prescribed by the applicable airworthiness regulations for certification. Refer to the manufacturer’s equipment list for such information.
(1) Unit weight for W&B purposes.
Gasoline 6 lb. per U.S. gal.
Turbine Fuel 6.7 lb. per U.S. gal.
Lubricating oil 7.5 lb. per U.S. gal.
Crew and passengers 170 lb. per person.
(2) It is important to retain the proper algebraic sign (+ or -) through all balance computations. For the sake of uniformity in these computations, visualize the aircraft with the nose to the left. In this position, any arm to the left (forward) of the datum is “minus” and any arm to the right (rearward) of the datum is “plus.” Any item of weight added to the aircraft either side of the datum is plus weight, any weight item removed is a minus weight. When multiplying weights by arms, the answer is plus if the signs are the same, and minus if the signs are different.
The following combinations are possible:
Par 10-18 Page 10-13 Items added forward of the datum:
( + ) weight x (-) arm = (-) moment.
Items added to the rear of the datum:
( + ) weight x ( + ) arm = ( + ) moment.
Items removed forward of the datum:
(-) weight x (-) arm = ( + ) moment.
Items removed rear of the datum:
(-) weight x ( + ) arm = (-) moment.
(3) The total weight of the airplane is equal to the weight of the empty aircraft plus the weight of the items added minus the weight of the items removed.
(4) The total moment of the aircraft is the algebraic sum of the empty weight moment of the aircraft and all of the individual moments of the items added and/or removed.
10-19. W&B EXTREME CONDITIONS. The W&B extreme conditions represent the maximum forward and rearward CG position for the aircraft. Include the W&B data information showing that the CG of the aircraft (usually in the fully loaded condition) falls between the extreme conditions.
a. Forward W&B Check. When a forward W&B check is made, establish that neither the maximum weight nor the forward CG limit listed in the TCDS and Aircraft Specifications are exceeded. To make this check, the following information is needed:
(1) The weights, arms, and moment of the empty aircraft.
(2) The maximum weights, arms, and moments of the items of useful load that are located ahead of the forward CG limit.
(3) The minimum weights, arms, and moments of the items of useful load that are located aft of the forward CG limit. A typical example of the computation necessary to make this check, using this data, is shown in Figure 10-10.
b. Rearward W&B Check. When a rearward W&B check is made, establish that neither the maximum weight nor the rearward CG limit listed in the TCDS and Aircraft Specifications are exceeded. To make this check, the following information is needed:
(1) The weight, arms, and moments of the empty aircraft.
(2) The maximum weights, arms, and moments of the items of useful load that are located aft of the rearward CG limit.
(3) The minimum weights, arms, and moments of the items of useful load that are located ahead of the rearward CG limit. A typical example of the computation necessary to make this check, using this data, is shown in Figure 10-11.
FIGURE 10-10. EXAMPLE OF CHECK OF MOST FORWARD WEIGHT AND
BALANCE EXTREME
- DATUM
- NO BAGGAGE
NO PASSENGERS
FULL OIL -MINIMUM FUEL -PILOT ONLY FORWARD C.G. LIMIT TO CHECK: MOST FORWARD WEIGHT AND BALANCE EXTREME.
GIVEN:
Actual empty weight of the aircraft - 1169# Empty weight center of gravity- -+ 10.6" *Maximum weight- --2100# *Forward C.G.. limit - + 8.5" *Oil capacity. 9 qts. - - 17# at -49" *Pilot in farthest forward seat equipped with controls (unless otherwise placarded) -- - 170# at +16" *Since the fuel tank is located to the rear of the forward C.G. limit, munimum fuel should be included.
METO HP = 165 = 13.75 gal. x 64. -- 83# at +22" 12 12 * Information should be obtained from the aircraft specification.
Note: Any items or passengers must be used if they are located ahead of the forward C.G. limit.
Full fuel must be used if the tank is located ahead of the forward C.G. limit.
CHECK OF FORWARD WEIGHT AND BALANCE EXTREME Weight (#) x Arm (*) = Moment (*#) Aircraft empty + 1169 + 10.6 + 12391 + 17 - 49 833 Pilot + 170 + 16 + 2720 Fuel + 83 + 22 + 1826 Total + 1439 (TW) + 16104 (TM) Divide the TM (total moment) by the TW (total weight) to obtain the forward weight and balance extreme.
IM = 16104 = + 11.2" TW 1439 Since the forward C.G. limit and the maximum weight are not exceeded, the forward weight and balance extreme condition is satisfactory.
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FIGURE 10-11. EXAMPLE OF CHECK OF MOST REARWARD WEIGHT AND
BALANCE EXTREME -DATUM
- MAXIMUM BAGGAGE
- MAXIMUM PASSENGERS FULL OIL→ MAXIMUM FUEL PILOT ONLY REARWARD C.G. LIMIT TO CHECK: MOST REARWARD WEIGHT AND BALANCE EXTREME.
GIVEN:
Actual empty weight of the aircraft • 1169# Empty weight center of gravity- • 10.6" *Maximum weight -- 2100# *Rearward C.G.. limit- • 21.97 *Oil capacity. 9 qts. - - 17# at -49" *Baggage, placarded do not exceed 100 1bs - • 100# at +75.5" *Two passengers in rear seat, 170# x 2 - 340# at +48" *Pilot in most rearward seat equipped with controls (unless otherwise placarded) - 170# at +16" *Since the fuel tank is located aft of the rearward C.G. limit full fuel must be used 240# at +22" * Information should be obtained from the aircraft specification.
Note: If fuel tanks are located ahead of the rearward C.G. limit minimum fuel should be used.
CHECK OF REARWARD WEIGHT AND BALANCE EXTREME Weight (#) x Arm (*) = Moment (*#) Aircraft empty + 1169 + 10.6 + 12391 Oil 17 - 49 833 Pilot (1) + 170 + 16 + 2720 Passenger (2) + 340 + 48 16320 Fuel (40 gals.) + 240 + 22 + 5280 Baggage + 100 + 75.5 + 7550 Total + 2036 (IW) + 43428 (TM) Divide the TM (total moment) by the TW (total weight) to obtain the rearward weight and balance extreme.
IM = 43428 = + 21.3" TW 2036 Since the rearward C.G. limit and the maximum weight are not exceeded, the rearward weight and balance extreme condition is satisfactory.
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10-20. LOADING CONDITIONS AND/OR PLACARDS. If the following items have not been covered in the W&B extreme condition checks and are not covered by suitable placards in the aircraft, additional computations are necessary. These computations should indicate the permissible distribution of fuel, passengers, and baggage that may be carried in the aircraft at any one time without exceeding either the maximum weight or CG range. The conditions to check are:
a. With full fuel, determine the number of passengers and baggage permissible.
b. With maximum passengers, determine the fuel and baggage permissible.
c. With maximum baggage, determine the fuel and the number and location of passengers.
d. Examples of the computations for the above items are given in Figures 10-12, 10-13, and 10-14 respectively. The above cases are mainly applicable to the lighter type personal aircraft. In the case of the larger type transport aircraft, a variety of loading conditions is possible and it is necessary to have a loading schedule.
FIGURE 10-12. LOADING CONDITIONS: DETERMINATION OF THE NUMBER OF
PASSENGERS AND BAGGAGE PERMISSIBLE WITH FULL FUEL
EXAMPLE OF THE DETERMINATION OF THE NUMBER OF PASSENGERS AND BAGGAGE
PERMISSIBLE WITH FULL FUEL Actual empty weight of the aircraft 1169# Empty weight center of gravity - 10.6" Maxımum weight- - 2100# Datum is leading edge of the wing Forward center of gravity limit -- 8.5" Rearward center of gravity limit- 21.9" Oil capacity, 9 qts.; show full capacity 17# at -49" Baggage, maximum 100# at +75.5" Two passengers in rear seat, 170# x 2 - 340# at +48" Pilot in most rearward seat equipped with controls (unless otherwise placarded) - 170# at +16" Full fuel, 40 gals. x 6# -- 240# at +22" Weight (#) x Arm (*) = Moment (*#) Aircraft empty + 1169 + 10.6 + 12391 Oil + 17 - 49 833 Full Fuel + 240 + 22 + 5280 Passengers 2 rear + 340* + 48 +16320 Pilot + 170 + 16 + 2720 Baggage + 100 + 75.5 + 7550 Total + 2036 (IW) + 43428 (IM) Divide the TM (total moment) by the TW (total weight) to obtain the loaded center of gravity.
TM = 43428 = + 21.3" TW 2036 The above computations show that with full fuel, 100 pounds of baggage and two passengers in the rear seat may be carried in this aircraft without exceeding either the maximum weight or the approved C. G. range.
This condition may be entered in the loading schedule as follows:
GALLONS OF FUEL NUMBER OF PASSENGERS POUNDS OF BAGGAGE Full 2 Rear 100 * Only two passengers are listed to prevent the maximum weight of 2100 Ibs. from being exceeded.
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FIGURE 10-13. LOADING CONDITIONS: DETERMINATION OF THE FUEL AND
BAGGAGE PERMISSIBLE WITH MAXIMUM PASSENGERS
EXAMPLE OF THE DETERMINATION OF THE POUNDS OF FUEL AND BAGGAGE PERMISSIBLE
WITH MAXIMUM PASSENGERS Weight (#) X Arm (*) = Moment (*#) Aircraft empty + 1169 + 10.6 + 12391 Oil 17 - 49 833 Pilot + 170 + 16 + 2720 Passenger (1) front + 170 + 16 + 2720 Passenger (2) rear + 340 + 48 +16320 Fuel (39 gals.) + 234 + 22 + 5148 Baggage Total + 2100 + 38466 Divide the TM (total moment) by the TW (total weight) to obtain the loaded center of gravity.
TM = 38466 = + 18.6" TW 2100 The above computations show that with the maximum number of passengers, 39 gallons of fuel and zero pounds of baggage may be carried in this aircraft without exceeding either the maximum weight or the approved C. G. range.
This condition may be entered in the loading schedule as follows:
GALLONS OF FUEL NUMBER OF PASSENGERS POUNDS OF BAGGAGE *Full *2 Rear * 100 39 1(F) 2(R) None * Conditions as entered from Figure 10-12 (F) Front seat (R) Rear seat Par 10-20 Page 10-18
FIGURE 10-14. LOADING CONDITIONS: DETERMINATION OF THE FUEL AND
THE NUMBER AND LOCATION OF PASSENGERS PERMISSIBLE WITH
MAXIMUM BAGGAGE
EXAMPLE OF THE DETERMINATION OF THE FUEL AND THE NUMBER AND LOCATION OF
PASSENGERS PERMISSIBLE WITH MAXIMUM BAGGAGE Weight (#) x Arm (*) = Moment (*#) Aircraft empty + 1169 + 10.6 + 12391 Oil 17 - 49 833 Pilot + 170 + 16 + 2720 Passenger (1) rear + 170 + 48 + 8160 Passenger (1) front + 170 + 16 + 2720 Fuel (40 gals.) + 240 + 22 + 5280 Baggage + 100 + 75.5 + 7550 Total + 2036 + 37988 Divide the TM (total moment) by the TW (total weight) to obtain the loaded center of gravity.
TM = 37988 - = + 18.7 TW 20366 The above computations show that with maximun baggage, full fuel and 2 passengers (1 in the front seat and 1 in the rear seat) may be carried in this aircraft without exceeding either the maximum weight or the approved C. G. range.
This condition may be entered in the loading schedule as follows:
GALLONS OF FUEL NUMBER OF PASSENGERS POUNDS OF BAGGAGE *Full *2 Rear * 100 ** 39 *1(F) 2(R) **None Full 1(F) 1(R) Full * Conditions as entered from Figure 10-12 ** Conditions as entered from Figure 10-13 (F) Front seat (R) Rear seat
10-21. EQUIPMENT LIST. A list of the equipment included in the certificated empty weight may be found in either the approved AFM or the W&B report. Enter into the W&B report all required, optional, and special equipment installed in the aircraft at time of weighing and/or subsequent equipment changes.
a. Required equipment items are listed in the pertinent Aircraft Specifications.
b. Optional equipment items are listed in the pertinent Aircraft Specifications and may be installed in the aircraft at the option of the owner.
Par 10-20 Page 10-19
c. Special equipment is any item not corresponding exactly to the descriptive information in the Aircraft Specifications. This includes items such as emergency locator transmitter (ELT), tail or logo lights, instruments, ashtrays, radios, navigation lights, and carpets.
d. Required and optional equipment may be shown on the equipment list with reference to the pertinent item number listed in the applicable specifications only when they are identical to that number item with reference to description, weight, and arm given in the specifications.
Show all special equipment items with reference to the item by name, make, model, weight, and arm. When the arm for such an item is not available, determine by actual measurement.
10-22. EQUIPMENT CHANGE. The person making an equipment change is obligated to make an entry on the equipment list indicating items added, removed, or relocated with the date accomplished, and identify himself by name and certificate number in the aircraft records.
Examples of items so affected are the installation of extra fuel tanks, seats, and baggage compartments.
a. Figure 10-15 illustrates the effect on balance when equipment items are added within the acceptable CG limits and fore and aft of the established CG limits.
FIGURE 10-15. EFFECTS OF THE ADDITION OF EQUIPMENT ITEMS ON
BALANCE
WEIGHTS FORWARD C.G. LIMIT - REARWARD C.G. LIMIT Weights added anywhere between the C.G. limits will not upset the balance of the aircrait.
-WEIGHT FORWARD C.G. LIMIT- -REARWARD C.G. LIMIT Any weights added ahead of the forward C.G. limit would tend to upset the balance around the forward balance limit.
WEIGHT FORWARD C.G. LIMIT -REARWARD C.G. LIMIT Any weights added aft of the rearward C.G. limit would tend to upset the balance around the rearward balance limit.
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b. Moment computations for typical equipment changes are given in Figure 10-16 and are also included in the sample W&B sheet in Figure 10-18.
10-23. SAMPLE W&B REPORT. Suggested methods of tabulating the various data and computations for determining the CG, both in the empty weight condition and the fully loaded condition, are given in Figures 10-17 and 10-18, respectively, and represent a suggested means of recording this information. The data presented in Figure 10-17 have previously been computed in Figures 10-10 and 10-11 for the extreme load conditions and Figure 10-16 for equipment change, and represents suggested means of recording this information.
FIGURE 10-16. EXAMPLE OF MOMENT AND WEIGHT CHANGES RESULTING
FROM EQUIPMENT CHANGES Forward Rearward Moments (counterclockwise) + Moments (clockwise) Wheel pants added (+6# at -1") Battery added (+29# at +13") Battery removed -24# at -29") Landing light removed (-1# at +4") DATUM- Weight (#) × Arm (") = Moment ("#) ADDED Item 204 wheel pants + 6 - 1 - 6 Item 302b Battery + 29 + 13 +377
REMOVED Item 302a Battery - 24 -29 +696 Item 303 Landing light - 1 + 4 4 This condition is shown properly entered on a sample weight and balance report on Figure 10-18 under Equipment Change.
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