DATUM (LEADING EDGE OF
COMPUTED WING ROOT SECTION)
• C.G.
COMPUTED• LEFT SCALE 620 LBS., TARE 5LBS.
RIGHT SCALE 609 LBS., TARE 5 LBS.
WEIGHING POINT D, MEASURED (Q NOSE WHEEL)
WEIGHING POINT
L, MEASURED (Q MAIN WHEEL) TO FIND: EMPTY WEIGHT AND EMPTY WEIGHT CENTER OF GRAVITY Datum is the leading edge of the wing (from aircraft specification) (D) Actual measured horizontal distance from the main wheel weighing point (Q main wheel) to the Datum -.
(L) Actual measured horizontal distance from " 34.0" the front wheel weighing point (Q front wheel) to the main wheel weighing point -
- 67.8" SOLVING: EMPTY WEIGHT Weighing Scale Tare Net Point Reading Weight Right 609 5 604 Left 620 5 615 Front 464 10 454 Empty Weight (W 1673 SOLVING: EMPTY WEIGHT CENTER OF GRAVITY Formula: C.G. = D - F X L = 3" + 454 × 67.8 =34"-18.3"=15.7" 1673 Reference for formula, Figure 10-4.
FIGURE 10-6. Empty weight and empty weight center of gravity - nosewheel type aircraft.
Par 10-2 Page 10-464
Par 10-2 Page 10-465
FIGURE 10-7. Operating center of gravity range.
scales under the landing gear tires, a vertical line passing through the centerline of the axle will locate the point on the scale at which th e weight is concentrated.
This point is called the “weighing point.” Other structural locations capable of supporting the aircraft, such as jack pads on the main spar, may also be used if the aircraft weight is resting on the jack pads. Indicate these points clearly in the weight and balance report when used instead of the landing gear. Typical locations of the weighing points are shown in figure 10-8.
Zero Fuel Weight. The maximum permissible weight of a loaded aircraft (passengers, crew, cargo, etc.) less its fuel is zero fuel weight. All weights in excess of maximum zero fuel weight must consist of usable fuel.
Minimum Fuel. The minimum fuel for balance purposes is 1/12 gallon per maximumexcept-take-off horsepower (METO). Minimum fuel is the maximum amount of fuel which can be used in weight and balance computations when low fuel might adversely affect the most critical balance conditions. To determine the weight of fuel in pounds divide the METO horsepower by two.
Full Oil. The full oil is the quantity of oil shown in the Aircraft Specifications or TCDS as oil capacity. Use full oil as the quantity of oil when making the loaded weight and balance computations.
Tare. The weight of chocks, blocks, stands, etc., used when weighing aircraft is called tare and is included in the scale readings. Tare is deducted from the scale reading at each respective we ighing point when tare is involved, to obtain the actual aircraft weight.
Par 10-2 Page 10-466 (and 10-10)
FIGURE 10-8. Weighing point centerline.
10-3.10-13. [RESERVED.]
Par 10-14 Page 10-467
SECTION 2 WEIGHING PROCEDURES
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.
PROCEDURES. Accepted procedures when weighing an aircraft are:
Remove excessive dirt, grease, moisture, etc., from the aircraft before weighing.
Weigh the aircraft inside a cl osed building to prevent error in scale reading due to wind.
Determine the c.g. by placing the aircraft in a level flight attitude.
Have all items of equipment that are included in the certificated empty weight inst alled in the aircraft when weighing. These items of equipment are a part of the current weight and balance report.
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 weight and balance report.
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.
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 math ematically to get the empty weight. In 14 CFR, part 23 aircraft, the weight of the oil was included in the empty weight.
Do not set brakes while taking scale reading.
Note any tare reading when the aircraft is removed from the scales.
WEIGHT AND BALANCE COMPUTATIONS. It is often necessary after completing an extensive alteration to establish by computation that the authorized weight and c.g. limits as shown in the TCDS and Aircraft Specifications are not exceeded. Paragraph b(2) explains the significance of algebraic signs used in balance computations.
Par 10-14 Page 10-468
EMPTY WEIGHT AND EMPTY WEIGHT CENTER OF GRAVITY (when aircraft is weighed with oil)
GIVEN:
Aircraft as weighed with full oil ------------------------------------------------------------1186 lbs.
Center of gravity ------------------------------------------------------------------------------9.7” Full oil capacity 9 qts.------------------------------------------------------------------------17 lbs.
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” A 1169
FIGURE 10-9. Empty weight and empty weight center of gravity when aircraft is weighed with oil.
The TCDS or Aircraft Specifications contain the following information relating to the subject:
• Center of gravity range.
• Empty weight c.g. range when applicable.
• Leveling means.
• Datum.
• Maximum weights.
• Number of seats and arm.
• Maximum baggage and arm.
• Fuel capacity and arm.
• Oil capacity and arm.
• Equipment items and arm.
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.
Par 10-16 Page 10-469 Unit weight for weight and balance purposes.
Gasoline ----------- 6 pounds per U.S. gal.
Turbine Fuel ------ 6.7 pounds per U.S. gal.
Lubricating oil ---- 7.5 pounds per U.S. gal.
Crew and passengers ----- 170 pounds per person.
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:
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.
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.
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.
WEIGHT AND BALANCE EXTREME CONDITIONS. The weight and balance extreme conditions represent the maximum forward and rearward c.g. position for the aircraft. Include the weight and balance data information showing that the c.g. of the aircraft (usually in the fully loaded condition) falls between the extreme conditions.
Forward Weight and Balance Check. When a forward weight and balance check is made, establish that neither the maximum weight nor the forward c.g.
limit listed in the TCDS and Aircraft Specifications are exceeded. To make th is check, the following information is needed:
The weights, arms, and moment of the empty aircraft.
The maximum weights, arms, and moments of the items of useful load that are located ahead of the forward c.g. limit.
The minimum weights, arms, and moments of the items of useful load that are located aft of the forward c.g. limit. A typical example of the computation necessary to make this check, using this data, is shown in figure 10-10.
Rearward Weight and Balance Check. When a rearward weight and balance check is made, establish that neither the maximum wei ght nor the rearward c.g.
limit listed in the TCDS and Aircraft Specifications are exceeded. To make th is check, the following information is needed:
The weight, arms, and moments of the empty aircraft.
The maximum weights, arms, and moments of the items of useful load that are located aft of the rearward c.g. limit.
Par 10-16 Page 10-470
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, minimum fuel should be included.
METO HP = 165 = 13.75 gal. x 6# ----------------------------------------------------------------------- 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 Oil + 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.
TM = 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.
FIGURE 10-10. Example of check of most forward weight and balance extreme.
Par 10-17 Page 10-471 The minimum weights, arms, and moments of the items of useful load that are located ahead of the rearward c.g. limit. A typical example of the computation necessary to make this check, using this data, is shown in figure 10-11.
LOADING CONDITIONS AND/OR PLACARDS. If the following items have not been covered in the weight and balance extreme condition checks and are not covered by suitable placards in the aircraft, a dditional 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
c.g. range. The conditions to check are:
With full fuel, determine the number of passengers and baggage permissible.
With maximum passengers, determine the fuel and baggage permissible.
With maximum baggage, determine the fuel and the number and location of passengers.
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.
EQUIPMENT LIST. A list of the equipment included in the certificated empty weight may be found in either the approved aircraft flight manual or the weight and balance report. Enter into the weight and balance report all required, optional, and special equipment installed in the aircraft at time of weighing and/or subsequent equipment changes.
Required equipment items are listed in the pertinent Aircraft Specifications.
Optional equipment items are listed in the pertinent Aircraft Specifications and may be installed in the aircraft at the option of the owner.
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.
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.
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. Figure 10-15 illustrates the effect on balance when equipment items are added within the acceptable c.g. limits and fore and aft of the established c.g. limits.
Par 10-17 Page 10-472
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 -------------------------------------------------------------------------------------- 21.9” *Oil capacity, 9 qts.----------------------------------------------------------------------------------------- 17# at -49” *Baggage, placarded do not exceed 100 lbs------------------------------------------------------------- 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 (TW) + 43428 (TM) Divide the TM (total moment) by the TW (total weight) to obtain the rearward weight and balance extreme.
TM = 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.
FIGURE 10-11. Example of check of most rearward weight and balance extreme.
Par 10-20 Page 10-473
EXAMPLE OF THE DETERMINATION OF THE NUMBER OF PASSENGERS AND BAGGAGE
PERMISSIBLE WITH FULL FUEL
GIVEN:
Actual empty weight of the aircraft----------------------------------------------------------------------- 1169# Empty weight center of gravity --------------------------------------------------------------------------- 10.6” Maximum 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 (TW) + 43428 (TM)
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 w ith 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 lbs. from being exceeded.
FIGURE 10-12. Loading conditions: determination of the number of passengers and baggage permissible with full fuel.
Par 10-20 Page 10-474
EXAMPLE OF THE DETERMINATION OF TH E 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 w ith the maximum number of passengers, 39 gallons of fuel and zero pounds of baggage ma y 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
FIGURE 10-13. Loading conditions: determination of the fuel and baggage permissible with maximum passengers.
Par 10-20 Page 10-475
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 maximum 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
FIGURE 10-14. Loading conditions: determination of the fuel and the number and location of passengers permissible with maximum baggage.