2-6 demonstrate that the aircraft is being operated within its certificated W&B limitations using reasonable assumptions that are clearly stated.
2.3.2 What Information from the Aircraft Manufacturer Should an Operator Use? The construction of the loading envelope will begin with the W&B limitations provided by the aircraft manufacturer in the WBM, TCDS, or similar approved document as required by part 91, § 91.9 and §§ 121.141, 125.75, 125.91, and 135.23(b). These limitations will include, at minimum, the following items, as applicable:
1. Maximum zero fuel weight.
2. Maximum takeoff weight.
3. Maximum taxi weight.
4. Takeoff and landing CG limitations.
5. In-flight CG limitations.
6. Maximum floor loadings—including both running and per square foot limitations.
7. Maximum compartment weights.
8. Fuselage shear limitations.
9. Any other limitations provided by the manufacturer.
2.3.3 What Should the Operator Consider When Curtailing the Manufacturer’s Loading Envelope?
2.3.3.1 The operator should curtail the manufacturer’s loading limitations to account for loading variations and in-flight movement that are encountered in normal operations. For example, if passengers are expected to move about the cabin in flight, the operator must curtail the manufacturer’s CG envelope by an amount necessary to ensure that movement of passengers does not take the aircraft outside its certified envelope. If the aircraft is loaded within the new, curtailed envelope, it will always be operated within the manufacturer’s envelope, even though some of the loading parameters, such as passenger seating location, are not precisely known.
2.3.3.2 In some cases, an aircraft may have more than one loading envelope for preflight planning and loading. Each envelope must have the appropriate curtailments applied for those variables that are expected to be relevant for that envelope. For example, an aircraft might have separate takeoff, in-flight, and landing envelopes. Passengers are expected to remain seated in the cabin during takeoff or landing. Therefore, the takeoff and landing envelope does not need to be curtailed for passenger movement.
2.3.3.3 Upon determination of the curtailed version of each envelope, the most restrictive points (for each condition the operator’s program will check) generated by an “overlay” of the envelopes will form the aircraft “operational
2-7 envelopes.” Operators must adhere to the limitations relevant to such envelopes. By restricting operation to these operational envelopes, compliance with the manufacturer’s certified envelope will be ensured in all phases of flight, based upon the assumptions within the curtailment process. An operator may choose to not combine the envelopes but observe each envelope independently. However, due to calculation complexity, this is typically only possible through automation of the W&B calculation.
2.3.3.4 An operator could make an allowance for curtailment of the aircraft loading envelope to account for minor errors in bag counts and documentation, provided the operator provides valid survey data to ensure the accuracy of the baggage weight. The survey data should show the average variance an operator experiences in bag counts and include calculations for these variances to demonstrate that no limitations were exceeded. The operator should include the average variance in their loading schedule developed in paragraph 2.3.3.3.
Note: For acceptable methods used in surveying weights, see paragraph 3.3.
2.3.3.5 The specific amount of weight added to the Basic Operating Weight (BOW) would be based on the operator conducting a survey of their bag count and documentation errors and providing the appropriate amount of curtailment to ensure the aircraft remains within the CG envelope. This could be in the form of a minor tolerance specific to their approved program, rather than a broadly applicable allowance for all operators.
2.3.4 What are Some Examples of Common Curtailments to the Manufacturer’s Loading Envelope? The following paragraphs provide examples of common loading curtailments.
Appendix C, Sample Operational Loading Envelope, also provides an example of how operators may calculate these curtailments. Operators must include curtailments appropriate to the operations being conducted. Each of the items mentioned below is a single curtailment factor. The total curtailment of the manufacturer’s envelope is computed by combining the curtailments resulting from each of these factors.
2.3.4.1 Passenger Distribution. The operator must account for the seating of passengers in the cabin. The loading envelope does not need to be curtailed if the actual seating location of each passenger is known. If assigned seating is used to determine passenger location, the operator must implement procedures to ensure that the assignment of passenger seating is incorporated into the loading procedure. Operator procedures should take into account the possibility that passengers may not sit in their assigned seat and how this may affect CG during takeoff and landing.
2.3.4.1.1 If the actual seating location of each passenger is not known, the operator may assume that all passengers are seated uniformly throughout the cabin or a specified subsection of the cabin. If this assumption is made, the operator
2-8 must curtail the loading envelope to account for the fact that the passenger loading may not be uniform. The curtailment may make reasonable assumptions about the manner in which people distribute themselves throughout the cabin. For example, the operator may assume that window seats are occupied first, followed by aisle seats, followed by the remaining seats (window-aisle-remaining seating). Both forward and rear loading conditions should be considered. That is, the passengers may fill up the window, aisle, and remaining seats from the front of the aircraft to the back, or the back to the front.
2.3.4.1.2 If necessary, the operator may divide the passenger cabin into subsections or “zones” and manage the loading of each zone individually. It can be assumed that passengers will be sitting uniformly throughout each zone, as long as the curtailments described in the previous paragraph are put in place.
2.3.4.1.3 All such assumptions should be adequately documented.
2.3.4.2 Fuel. The operator’s curtailed loading envelope must account for the effects of fuel. The following are examples of several types of fuel-related curtailments:
2.3.4.2.1 Fuel Density. A certain fuel density may be assumed and a curtailment included accounting for the possibility of different fuel density values. Fuel density curtailments only pertain to differences in fuel moment caused by varying fuel volumes, not to differences in total fuel weight. The fuel gauges in most transport category aircraft measure weight, not volume. Therefore, the indicated weight of the fuel load can be assumed accurate.
2.3.4.2.2 Fuel Movement. The movement or transfer of fuel in flight.
2.3.4.2.3 Fuel Usage In Flight. The burning of fuel may cause the CG of the fuel load to change. The effect of fuel burning down to the required reserve fuel or to an acceptable fuel amount established by the operator should be accounted for.
A curtailment may be included to ensure that this change does not cause the CG of the aircraft to move outside of the acceptable envelope.
2.3.4.3 Fluids. The operator’s curtailed CG envelope must account for the effects of galley and lavatory fluids. These factors include such things as:
1. Use of potable water in flight.
2. Movement of water or lavatory fluids.
2.3.4.4 In-Flight Movement of Passenger and Crew. The operational envelope must account for the in-flight movement of passengers, crew, and equipment.
This may be done by including a curtailment equal to the moment change caused by the motion being considered. It may be assumed that all passengers, crew, and equipment are secured when the aircraft is in the takeoff or landing
2-9 configuration. Standard operational procedures may be taken into account.
Examples of items that can move during flight are:
2.3.4.4.1 Flight Deck Crewmembers Moving to the Lavatory. Flight deck crewmembers may move to the most forward lavatory in accordance with the security procedures prescribed for crews leaving the cockpit. An offsetting credit may be taken if another crewmember moves to the flight deck during a lavatory trip.
2.3.4.4.2 Flight Attendants (F/A) Moving Throughout the Cabin. Operators should take their standard operating procedures into account. If procedures do not dictate otherwise, it should be assumed that the F/As can travel anywhere within the compartment to which they are assigned.
2.3.4.4.3 Service Carts Moving Throughout the Cabin. Operators should consider their standard operating procedures. If procedures do not dictate otherwise, it should be assumed that the service carts can travel anywhere within the compartment to which they are assigned. If multiple carts are in a given compartment and no restrictions are placed on their movement, then the maximum number of carts, moving the maximum distance, must be considered. The weight of the number of F/As assigned to each cart must also be considered. The assumed weight of each cart may be the maximum anticipated cartload or the maximum design load, as appropriate for the operator’s procedures.
2.3.4.4.4 Passengers Moving Throughout the Cabin. Allowances should be made for the possibility that passengers may move about the cabin in flight. The most common would be movement to the lavatory, described below. If a lounge or other passenger gathering area is provided, the operator should assume that passengers move there from the centroid of the passenger cabin(s). The maximum capacity of the lounge should be taken into account.
2.3.4.4.5 Passengers Moving to the Lavatory. Operators should account for the CG change caused by passengers moving to the lavatory. Operators should develop reasonable scenarios for the movement of passengers in their cabins and consider the CG shifts that can be expected to occur. Generally, operators may assume that passengers move to the lavatories closest to their seats. In aircraft with a single lavatory, operators should consider movement from the “most adverse” seat. Operators may make assumptions that reflect operator lavatory and seating policies. For example, operators may assume that coach passengers may only use the lavatories in the coach cabin, if that is the operator’s normal policy.
2.3.4.5 Movement of Flaps and Landing Gear. If the manufacturer has not already done so, the operator must account for the movement of landing gear, flaps, wing leading edge devices, or any other moveable components of the
2-10 aircraft. Devices deployed only while in contact with the ground, such as ground spoilers or thrust reversers, may be excluded from such curtailments.
2.3.4.6 Baggage and Freight. It can be assumed that baggage and freight may be loaded at the centroid of each baggage compartment. Operators do not need to include a curtailment if procedures are used to ensure the cargo is loaded uniformly and physically restrained (secured) to prevent the contents from becoming a hazard by shifting between zones or compartments.
2.4 Onboard W&B Systems.
2.4.1 How Does an Onboard W&B System Compare to a Conventional Weight Buildup Method?
2.4.1.1 An operator may use an onboard W&B system to measure an aircraft’s W&B as a primary means to dispatch an aircraft, provided the FAA has certified the system and approved the system for use in an operator’s W&B control program. This paragraph discusses the differences an operator should consider when using an onboard W&B system compared to a conventional weight buildup method. This paragraph addresses only the operational considerations related to the use of an FAA-approved onboard W&B system.
2.4.1.2 Like operators using a conventional weight buildup method to calculate W&B, an operator using an onboard W&B system as a primary W&B control system should curtail the manufacturer’s loading envelope to ensure the aircraft does not exceed the manufacturer’s certificated weight and CG limits.
However, an operator using an onboard W&B system would not need to curtail the loading envelope for assumptions about passenger and bag weight or distribution.
2.4.1.3 Because an onboard W&B system measures the actual weight and CG location of an aircraft, an operator may not need to include certain curtailments to the loading envelope to account for variables such as passenger seating variation or variation in passenger weight. However, an operator should curtail the loading envelope for any system tolerances that may result in CG errors. Using an onboard W&B system does not relieve an operator from the requirement to complete and maintain a load manifest.
2.4.2 What Measures Should an Operator Take to Obtain Operational Approval for an Onboard W&B System?
2.4.2.1 System Calibration. An operator should develop procedures to calibrate its onboard W&B system equipment periodically in accordance with the manufacturer’s instructions. An operator may calibrate its system with operational items or fuel aboard the aircraft to test the system at a representative operational weight. However, an operator may not use an onboard W&B system in place of procedures described in paragraph 2.1 for weighing the aircraft to establish BEW or CG location.
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2.4.2.2 Demonstration of System Accuracy. As part of the approval process, an operator should demonstrate that the onboard W&B system maintains its certificated accuracy. An operator should only have to conduct this demonstration once for each type aircraft with a similarly installed onboard W&B system. For the demonstration, the operator should use the accuracy demonstration test provided in the maintenance manual portion of the Supplemental Type Certificate (STC) or type certificate (TC) of the onboard W&B system.
2.4.3 What Operational Considerations Should an Operator Take into Account when Using an Onboard W&B System?
2.4.3.1 Certification Limits. An operator using an onboard W&B system as its primary means of calculating W&B should have procedures in place to ensure that the system is operated within the limits established during the system’s certification process.
2.4.3.2 Environmental Considerations. An operator using an onboard W&B system should ensure that it uses the system within the environmental limits established by the manufacturer. Environmental conditions that may affect the performance of an onboard W&B system include temperature, barometric pressure, wind, ramp slope, rain, snow, ice, frost, dew, and deicing fluid.
2.4.3.3 Aircraft Considerations. An operator using an onboard W&B system should ensure the weight and CG measured by the system are not affected by the aircraft configuration, such as the movement of flaps, stabilizers, doors, stairways or jetways, or any connections to ground service equipment. Other factors that an operator should consider include engine thrust, oleo strut extension, and aircraft taxi movement.
2.4.3.4 Takeoff Trim Settings. If the aircraft manufacturer provides trim settings for takeoff based on the aircraft’s CG location, an operator using an onboard W&B system should ensure that the onboard W&B system provides flightcrew members with adequate information to determine the appropriate trim setting.
2.4.3.5 Operational Envelope. The operational envelope for onboard W&B systems should be developed using the same procedures described in other parts of this AC, with the exception that the operational envelope does not need to be curtailed for passenger random seating and passenger weight variance. Also, note that the fuel load is subtracted from the measured takeoff weight to determine the zero fuel weight and CG, instead of being added to the zero fuel weight as part of the load buildup. In addition, an operator should curtail the CG envelope for any system CG tolerance.
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2.4.3.6 Complying with Compartment or Unit Load Device (ULD) Load Limits.
When using an onboard W&B system, an operator should develop in its W&B control program a method to ensure that it does not exceed the floor, linear or running loading limits specified for a compartment or ULD. If an operator develops appropriate procedures, an operator may request approval to exclude bag counts from its load manifest. The following are two examples of acceptable means to demonstrate compliance with compartment load limits.
2.4.3.6.1 An operator may assign a standard average weight to bags. Operators should see paragraphs 3.3 and 3.4 for baggage. Based on that standard average weight, the operator may place a placard in each compartment stating the maximum number of bags permitted. An operator may also create a table that lists the total weight associated with a given number of bags to ensure the operator does not exceed the load limit of a compartment or ULD.
2.4.3.6.2 By conducting sample loadings, an operator may demonstrate that the average density of the bags it places in a compartment or ULD would not allow it to exceed the compartment or ULD load limits inadvertently.
2.4.4 May an Operator Use the Information in this AC to Develop a Backup System? An operator using an onboard W&B system as its primary means of measuring W&B may use the guidance in this AC to develop a backup system based on a conventional weight buildup provided that the backup system has been approved by the Certificate Management Office (CMO)/Flight Standards District Office (FSDO). Should the primary onboard W&B system become inoperative, the operator should have provisions for deferring the inoperative equipment until repairs can be made prior to further operations.
The FAA may grant relief for an onboard W&B system through the minimum equipment list (MEL). An operator using an onboard W&B system should not use the backup system unless:
1. The onboard system is inoperative;
2. The onboard system has been deferred in accordance with the aircraft MEL; and
3. The operator has been approved to use average weights or conventional weight buildup.
3-1 CHAPTER 3. METHODS TO DETERMINE THE WEIGHT OF PASSENGERS
3.1 Choosing the Appropriate Method.
3.1.1 What Should an Operator Consider when Choosing the Appropriate Method?
3.1.1.1 Using Average Weights. For many years, operators of transport category aircraft have used average weights for passengers and bags to calculate an aircraft’s W&B, in accordance with standards and recommended practices.
This method eliminates many potential sources of error associated with accounting for a large number of relatively lightweights. However, differences between the actual weight of passengers and bags and the average weight of passengers and bags can occur when using average weights.
3.1.1.2 Using Standard Average Passenger Weights. Statistical probability dictates that the smaller the sample size (i.e., cabin size), the more the average of the sample will deviate from the average of the larger universe. Because of this, the use of standard average passenger weights in W&B programs for small and medium cabin aircraft should be examined in greater detail.
3.1.1.3 Determining Passenger and Bag Weight. Three methods are available to operators to determine passenger and bag weight. These methods include standard average weights, as described in paragraph 3.2; average weights based on survey results, as described in paragraph 3.3; and actual weights, as described in paragraph 3.4. An operator should review the following discussion and consult Table 3-1, Example of Standard Average Passenger Weights, to determine which methods are appropriate to its type of operation.
Operators should see paragraphs 3.3 and 3.4 for determining baggage weights.
3.1.1.4 Large Cabin Aircraft. Operators of large cabin aircraft may use the standard average weights for passengers. If an operator determines the standard average weights are not representative of its operation for certain route or regions, the operator should conduct a survey as detailed in paragraph 3.3 to establish more appropriate average weights for its operation. Operators of large cabin aircraft should conduct a baggage survey as detailed in paragraph 3.3 to establish standard average baggage weights for their operation. Large cabin operators also have the option of using actual baggage weights as described in paragraph 3.4. Operators should have procedures along with controls for identifying situations that would require the use of nonstandard weight groups or actual weights.
3.1.1.5 Medium Cabin Aircraft.
3.1.1.5.1 Evaluation Criteria for Medium Cabin Aircraft. Operators should evaluate medium cabin aircraft to determine whether to treat the aircraft as a large or small cabin aircraft. For the FAA to recommend that medium cabin aircraft be treated as a large cabin aircraft, the aircraft must meet either:
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1. Loadability criteria, or
2. The loading schedule criteria.
3.1.1.5.2 Evaluation Criteria for Small Cabin Aircraft. If the aircraft does not meet either the loadability or loading schedule criteria, then the FAA does not recommend that the operator use large cabin aircraft procedures. Instead, the aircraft should be subject to the small cabin aircraft methods outlined in paragraph 3.1.1.6.
3.1.1.5.3 Loadability Criteria.
• The center of gravity (CG) of the Basic Empty Weight (BEW) is within the manufacturer’s loading envelope.
• The CG of the zero fuel weight is within the manufacturer’s loading envelope when loaded with a full load of passengers and all cargo compartments are filled with a density of 10 pounds per cubic foot.
3.1.1.5.4 Loading Schedule Criteria.
• The operator must use a loading schedule based upon zones.
• The aircraft cabin may have no more than four rows of seats per zone with not less than four zones.
3.1.1.6 Small Cabin Aircraft. Operators of small cabin aircraft may request approval to use any one of the following methods when calculating the aircraft W&B.
1. Actual passenger and bag weights, or
2. Standard average passenger and standard average by surveying bag weights prescribed for large cabin aircraft or average weights based on an FAA-accepted survey if:
• The aircraft was certificated under part 23 normal category, part 25, or part 29 (or is able to prove the aircraft has equivalent part 23 normal category or part 29 performance data); and
• When using the Window-Aisle-Remaining (Zone) Method, the operator applies the additional curtailments as prescribed in Appendix D, Additional Curtailment to CG Envelopes for Passenger Weight Variations in Small Cabin Aircraft.
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3.2 Standard Average Weights.
3.2.1 What Standard Average Passenger Weights Should an Operator Use?
3.2.1.1 The standard average passenger weights are based on data from U.S. Government health agency surveys. An operator may use the example table in Table 3-1 in association with the Centers for Disease Control (CDC) weights to establish their standard average weights. The first column in Table 3-1 are CDC/National Health and Nutrition Examination Survey (NHANES) weights without summer or winter clothing weights. For more background information on the source of these weights, refer to Appendix B, Source of Standard Average Weights.
3.2.1.2 The operator will use the third column labeled “Standard Average Weight” in Table 3-1 to enter in their standard average weight per passenger based on seasonal clothing variance. The standard average weight is calculated by adding the CDC/NHANES weights in the first column and the clothing weights located the middle column. The clothing weights are 5 pounds for summer clothing, and 10 pounds for winter clothing. Where no gender is given, the standard average passenger weights are based on the assumption that 50 percent of passengers are male and 50 percent of passengers are female.
Table 3-1. Example of Standard Average Passenger Weights
CDC/NHANES Weights Average Clothing Weight Standard Average Weight Summer Weights Summer Weights lbs Average passenger weight (5 lbs) lbs lbs Average male passenger weight (5 lbs) lbs lbs Average female passenger weight (5 lbs) lbs lbs Child weight (2 years to less than 13 years of age) (5 lbs) lbs
Winter Weights Winter Weights lbs Average passenger weight (10 lbs) lbs lbs Average male passenger weight (10 lbs) lbs lbs Average female passenger weight (10 lbs) lbs lbs Child weight (2 years to less than 13 years of age) (10 lbs) lbs
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3.2.1.3 An operator may use summer weights from May 1 to October 31, and winter weights from November 1 to April 30. However, these dates may not be appropriate for all routes or operators. For routes with no seasonal variation, an operator may use the average weights appropriate to the climate. Use of year-round average weights for operators with seasonal variation should avoid using an average weight that falls between the summer and winter average weights. Operators with seasonal variation that elect to use a year-round average weight should use the winter average weight. The FAA must approve use of seasonal dates, other than those listed above.
3.2.1.4 The standard average weights listed in Table 3-1 will not take into consideration a carry-on bag program. Operators should see paragraphs 3.3 and 3.4 for baggage weights.
Note: The weight of children under the age of 2 must be accounted for by using the current edition of CDC Anthropometric Reference Data for Children and Adults. The carrier may either: 1) use the mean of both male and female weights under the age of 2; or 2) provide the Administrator with survey data to support how many children under the age of 2 should be calculated along with the adult passenger weights.
3.2.1.5 The standard average passenger weights established by the operator will be provided to the FAA for review and approval, and entered into the operator’s operations specifications (OpSpecs), management specifications (MSpecs), or Letter of Authorization (LOA), as applicable.
3.2.2 What Are the Standard Average Weights for Crewmembers?
3.2.2.1 An operator may choose to use one of the following for crewmember weights:
CDC/NHANES weights for F/As and Civil Aerospace Medical Institute (CAMI) first- and second-class medical certificate weights to establish their standard crewmember weights. The operator also has the option to conduct a survey as described in paragraph 3.3, or use actual weights as described in paragraph 3.4 to establish average crewmember weights appropriate for its operation.
3-5 Table 3-2. Standard Crewmember Weights Crewmember CAMI Medical Certificate Average Weights CDC/ NHANES Average Weight Uniform Weights Crewmember Average Weights with Uniform Crewmember Average Weight with Uniform & Bags Male flightcrew member lbs lbs lbs lbs lbs Female flightcrew member lbs lbs lbs lbs lbs Flight attendant NA lbs lbs lbs lbs Male flight attendant NA lbs lbs lbs lbs Female flight attendant NA lbs lbs lbs lbs Crewmember Bag Weights
Crewmember roller bag lbs Pilot flight bag lbs Flight attendant kit lbs
3.2.2.2 The operator should use Table 3-2, Standard Crewmember Weights to establish their standard crewmember weights. The operator must either use survey weights or actual weights for crewmember uniforms, bags, pilot flight bags, and F/A kit(s) as described in paragraphs 3.3 and 3.4. The operator will add CDC/NHANES weights to the table as described in paragraph 3.2.1, and Appendix B.
3.2.2.3 If the operator opts to use first- and second-class medical weights provided by CAMI, the operator must use the most current Aerospace Medical Certification Statistical Handbook report. The first-and second-class medical mean weight from the report should be placed in the second column titled “CAMI Medical Certificate Average Weights” of Table 3-2. (For additional information on CAMI, see Appendix B.)
3.2.2.4 The F/A weights with bags assume that each F/A has one crewmember roller bag and one F/A kit.
3.2.2.5 An operator may include the weight of crewmembers in an aircraft’s BEW or add the weight to the load manifest prepared for each flight.