1-1 CHAPTER 1. GENERAL
1.1 Purpose of This Advisory Circular (AC).
1.1.1 This AC provides operators with guidance on how to develop and receive approval for a Weight and Balance (W&B) control program for aircraft operated under Title 14 of the Code of Federal Regulations (14 CFR) part 91 subpart K (part 91K), and parts 121, 125, and 135.
1.1.2 This AC presents recommendations for an acceptable means, but not the only means, to develop and receive approval for a W&B control program, and includes guidance for using average and estimated weights in accordance with part 121, § 121.153(b) and other applicable sections of parts 91K, 121, 125, and 135. This AC contains guidance that is not legally binding in its own right and will not be relied upon by the Department of Transportation (DOT) or the Federal Aviation Administration (FAA) as a separate basis for affirmative enforcement action or other administrative penalty. Moreover, conformity with this guidance document (as distinct from existing statutes and regulations) is voluntary only, and nonconformity will not affect rights and obligations under existing statutes and regulations.
Note: Per part 125, § 125.91(b), no person may operate an airplane in a part 125 operation unless the current empty weight and center of gravity (CG) are calculated from the values established by an actual weighing of the airplane within the preceding 36 calendar-months.
1.1.3 If an operator adopts the suggestions contained in this AC, the operator must ensure that, when appropriate, it replaces discretionary language such as “should” and “may” with mandatory language in relevant manuals, operations specifications (OpSpecs), or management specifications (MSpecs).
1.1.4 Each W&B program for a part 121 operator should include risk management processes (RMP) and safety attributes from the current edition of AC 120-92, Safety Management Systems for Aviation Service Providers. If the operator has an approved Safety Risk Management (SRM) process, the change will run through the operator’s program as designed.
1.2 Who Should Use This AC?
1.2.1 This document provides guidance to operators that are either required to have an approved W&B control program under parts 121 and 125 or that choose to use actual or average aircraft, passenger, or baggage weights when operating under part 91K or part 135. The guidance in this AC is useful for anyone involved in developing or revising a W&B control program.
Note: Operators using an approved carry-on baggage program should refer to the current edition of AC 121-29, Carry-On Baggage, for more information regarding carry-on baggage.
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1.2.2 As shown in Table 1-1, Aircraft Cabin Size, the FAA has divided aircraft into three categories for this AC to provide guidance appropriate to the size of the aircraft.
Table 1-1. Aircraft Cabin Size For this AC, an aircraft originally certificated with— Is considered— 71 or more passenger seats A large cabin aircraft 30 to 70 passenger seats A medium cabin aircraft 5 to 29 passenger seats A small cabin aircraft Note: Aircraft with fewer than five passenger seats must use actual passenger and baggage weights.
1.3 Where You Can Find This AC. You can find this AC on the FAA’s website at http://www.faa.gov/regulations_policies/advisory_circulars.
1.4 What This AC Cancels. AC 120-27E, Aircraft Weight and Balance Control, dated June 10, 2005, is cancelled.
1.5 How is This AC Organized? This AC has four main chapters and six appendices.
Chapter 2 addresses aircraft weighing and loading schedules. Chapter 3 describes different methods to determine the weight of passengers and bags. Chapter 4 addresses the operator’s reporting systems and the FAA’s initial and continuing approval and oversight of an operator’s W&B control program. Finally, Appendices A through F contain technical information such as definitions, sources of data used in the AC, a sample loading envelope, an additional curtailment for passenger weight variation, suggestions to improve accuracy, and a checklist for operators.
1.6 What Should an Operator Consider While Reading This AC?
1.6.1 Accurately calculating an aircraft’s weight and CG before flight is essential to comply with the certification limits established for the aircraft. These limits include both weight and CG limits. The operator must comply with §§ 91.9, 121.141, 125.75, and 135.23, as applicable, and all operating limitations as specified in the Airplane Flight Manual (AFM) or Rotorcraft Flight Manual (RFM) Weight and Balance Manuals (WBM) and related supplements, and Supplemental Type Certificates (STC). The objective is to calculate the takeoff weight and CG of an aircraft as accurately as possible. Typically, an operator calculates takeoff weight by adding the Basic Empty Weight (BEW) of the aircraft, the weight of the passengers, cargo payload, and the weight of fuel.
1.6.2 When using average weights for passengers and bags, the operator must be vigilant to ensure that the W&B control program reflects the reality of actual aircraft loading (considering operation, markets served, and passenger mix and frequency of flights of particular routes). The FAA will periodically review the guidance in this AC and update it if regulatory requirements change. Ultimately, the operator is responsible for determining whether the procedures described in this AC are appropriate for use in its type(s) of operation.
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1.6.3 Weight should be a consistent measure in either pounds or kilograms. If both pounds and kilograms are used, procedures must include a method of conversion to ensure accurate weights and measures are used in the calculation of aircraft W&B.
1.7 Who Can Use Standard Average Weights?
1.7.1 Standard Average Weights. Use of standard average weights is limited to operators of multiengine turbine-powered aircraft that have a passenger-seat configuration of five or more passenger seats who hold a Letter of Authorization (LOA), OpSpecs, or MSpecs, as applicable, and were certificated under 14 CFR part 25, 29, or part 23 normal category; or the operator and manufacturer are able to prove that the aircraft can meet the performance requirements prescribed by part 23 normal category aircraft. Single-engine and multiengine turbine helicopter air ambulance (HAA) operators may also use standard average weights for emergency medical service (EMS) operations, provided they have received an LOA.
1.7.2 Use of Standard Average Weights. The FAA’s recommendations and advice on the safe use of standard average weights are contained in this document. In the FAA’s view, it would be unsafe for an aircraft operator to use standard average weights in any of the following aircraft:
1. All single-engine piston-powered aircraft.
2. All multiengine piston-powered aircraft.
3. All turbine-powered single-engine aircraft.
Note: All multiengine turbine-powered aircraft certificated under part 23, except for normal category aircraft, may only use an actual weight. Normal category aircraft per part 23, § 23.2005 may use standard average weights and should see paragraph 3.1.1.6 for further guidance.
1.8 AC Feedback Form. For your convenience, the AC Feedback Form is the last page of this AC. Note any deficiencies found, clarifications needed, or suggested improvements regarding the contents of this AC on the Feedback Form.
2-1 CHAPTER 2. AIRCRAFT WEIGHTS AND LOADING SCHEDULES
2.1 Establishing Aircraft Weight.
2.1.1 How Does an Operator Establish the Initial Weight of an Aircraft? Prior to being placed into service, each aircraft is weighed and the empty weight and center of gravity (CG) location are established. New aircraft are normally weighed at the factory and are eligible to be placed into operation without reweighing as long as the W&B records were adjusted for any alterations and modifications to the aircraft. Some modifications to aircraft, however, warrant reweighing. See paragraph 2.1.4.3 for a discussion of when it might be unsafe to fail to reweigh an aircraft after it has undergone modification(s). Aircraft that transfer from one operator to another that has an approved program do not need to be reweighed prior to use by the receiving operator unless: (1) more than 36 calendar-months have elapsed since last individual or fleet weighing or (2) some other modification to the aircraft warrants that the aircraft be weighed (e.g., paragraph 2.1.4.3).
Aircraft transferred, purchased, or leased from an operator without an approved W&B program and that have been unmodified or only minimally modified can be placed into service without being reweighed if the last weighing was accomplished by an acceptable method within the last 12 calendar-months and a W&B change record was maintained by the operator. Examples of such an acceptable method are methods consistent with the manufacturer’s instructions or that adhere to the current edition of Advisory Circular (AC) 43.13-1, Acceptable Methods, Techniques, and Practices—Aircraft Inspection and Repair.
2.1.2 How Does an Operator Document Changes to an Aircraft’s W&B? The W&B system should include methods, such as a log, ledger, or other equivalent electronic means, by which the operator will maintain a complete, current, and continuous record of the Basic Empty Weight (BEW) and CG of each aircraft. Alterations and changes affecting the W&B of the aircraft should be recorded in this log. Changes in the amount of weight or in the location of weight in or on the aircraft should be recorded whenever the weight change is at or exceeds the weights listed in Table 2-1, Incremental Weight Changes That Should Be Recorded in a Weight and Balance Change Record.
Table 2-1. Incremental Weight Changes That Should Be Recorded in a Weight and Balance Change Record In the weight change record of a— An operator should record any weight changes of— Large cabin aircraft +/- 10 lb or greater Medium cabin aircraft +/- 5 lb or greater Small cabin aircraft +/- 1 lb or greater
2.1.3 How Does the Operator Maintain the BEW? The loading schedule may utilize the individual weight of the aircraft in computing operational W&B or the operator may choose to establish fleet empty weights for a fleet or group of aircraft.
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2.1.3.1 Reestablishment of BEW. The BEW and CG position of each aircraft should be reestablished at the reweighing periods discussed in paragraph 2.1.4. In addition, it should be reestablished through calculation whenever the cumulative change to the W&B log is more than plus or minus one-half of 1 percent (0.5 percent) of the maximum landing weight or whenever the cumulative change in the CG position exceeds one-half of 1 percent
(0.5 percent) of the mean aerodynamic chord (MAC). In the case of helicopters and airplanes that do not have a MAC-based CG envelope
(e.g., canard-equipped airplane), whenever the cumulative change in the CG position exceeds one-half of 1 percent (0.5 percent) of the total CG range, the W&B should be reestablished.
Note: When reestablishing the aircraft BEW between reweighing periods, the weight changes may be computed provided the weight and CG location of the modifications are known; otherwise the aircraft must be reweighed.
2.1.3.2 Fleet Operating Empty Weights (FOEW). An operator may choose to use one weight for a fleet or group of aircraft if the weight and CG of each aircraft is within the limits stated above in paragraph 2.1.3.1 for establishment of BEW. When the cumulative changes to an aircraft W&B log exceed the weight or CG limits for the established fleet weight, the empty weight for that aircraft should be reestablished. This may be done by moving the aircraft to another group or by reestablishing new FOEWs.
2.1.4 How Often are Aircraft Weighed?
2.1.4.1 Individual Aircraft Weighing Program. Aircraft are normally weighed at intervals of 36 calendar-months. An operator may extend this weighing period for a particular model aircraft when pertinent records of actual routine weighing during the preceding period of operation show that W&B records accurately reflect aircraft weights and CG positions are within the cumulative limits specified for establishment of BEW (see paragraph 2.1.3.1). Under an individual aircraft weighing program, an increase should not be granted that would permit any aircraft to exceed 48 calendar-months since its last weighing, including when an aircraft is transferred from one operator to another. In the case of helicopters, increases should not exceed the time that is equivalent to the aircraft overhaul period.
Note: Per § 125.91(b), no person may operate an airplane in a part 125 operation unless the current empty weight and CG are calculated from the values established by an actual weighing of the airplane within the preceding 36 calendar-months.
2.1.4.2 Fleet Weighing. An operator may choose to weigh only a portion of the fleet every 36 months and apply the weight and moment change determined by these sample weighings to the remainder of the fleet. For each aircraft
2-3 weighed, the new aircraft empty weight and moment is determined by the weighing and entered in the aircraft weight log. The difference between this new aircraft weight and moment and the previous aircraft weight and moment shown in the log is the weight and moment change. The average of the weight and moment changes for the aircraft weighed as part of this fleet weighing is then entered as an adjustment to the aircraft weight logs for each of the aircraft in the fleet that were not weighed.
2.1.4.2.1 A fleet is composed of a number of aircraft of the same type. (For example, B747-200s in a passenger configuration and B747-200 freighters should be considered different fleets. Likewise, B757-200s and B757-300s should be considered different fleets.) The primary purpose of defining a fleet is to determine how many aircraft should be weighed in each weighing cycle.
A fleet may be further divided into groups to establish FOEWs.
Table 2-2. Number of Aircraft to Weigh in a Fleet For fleets of— An operator must weigh (at minimum)— 1 to 3 aircraft All aircraft 4 to 9 aircraft 3 aircraft, plus at least 50 percent of the number of aircraft greater than 3 More than 9 aircraft 6 aircraft, plus at least 10 percent of the number of aircraft greater than 9
2.1.4.2.2 In choosing the aircraft to be weighed, the aircraft in the fleet having the most hours flown since last weighing should be selected.
2.1.4.2.3 An operator should establish a time limit such that all aircraft in a fleet are eventually weighed. Based on the length of time that a fleet of aircraft typically remains in service with an operator, the time limit should not exceed 18 years (six 3-year weighing cycles). It is not intended that an operator be required to weigh any remaining aircraft in the event that business conditions result in retirement of a fleet before all aircraft have been weighed.
2.1.4.3 Weighing Aircraft—Modifications. For most aircraft modifications, a mathematical calculation of the W&B change is practical. For some modifications, such as interior reconfigurations, the large number of parts removed, replaced, and installed may make an accurate determination of the W&B change by computation impractical.
2.1.4.3.1 When the accuracy of the calculation is questionable, the weight and moment change estimate should be verified by reweighing the aircraft. The operator should weigh two or more aircraft to confirm the computed weight change estimate. The operator may choose to weigh the aircraft before and after the modification, or just after the modification. If the weighings are inconsistent with the computed weight change estimate, then additional aircraft should be weighed as prescribed in Table 2-2, based on the size of the fleet.
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2.1.4.3.2 The operator may choose not to calculate the weight change but to reestablish the aircraft W&B by reweighing the aircraft prior to subsequent revenue operation. An operator using an individual aircraft weighing program would weigh each aircraft modified, and an operator using a fleet weighing program would weigh the number of aircraft as prescribed in Table 2-2, based on the size of the fleet.
2.1.5 What Procedures Should Be Used to Weigh an Aircraft?
2.1.5.1 An operator should take precautions to ensure that it weighs an aircraft as accurately as possible. These precautions include checking to ensure that all required items are aboard the aircraft and the quantity of all fluids aboard the aircraft is considered. An operator should weigh the aircraft in still air.
2.1.5.2 An operator should establish and follow instructions for weighing the aircraft that are consistent with the recommendations of the aircraft manufacturer and scale manufacturer. The operator should ensure that all scales are certified and calibrated by the manufacturer or a certified laboratory, such as a civil department of weights and measures, or the operator may calibrate the scale under an approved calibration program. The operator should also ensure that the scale is calibrated within the manufacturer’s recommended time, or time periods, as specified in the operator’s approved calibration program.
Note: If manufacturer’s data is not available, the operator is responsible for developing appropriate weighing instructions for its particular aircraft.
2.2 Aircraft Loading Schedules.
2.2.1 What is a Loading Schedule?
2.2.1.1 The loading schedule is used to document compliance with the certificated W&B limitations contained in the manufacturer’s Airplane Flight Manual (AFM) or Rotorcraft Flight Manual (RFM), Type Certificate Data Sheet (TCDS), and Weight and Balance Manual (WBM).
2.2.1.2 The loading schedule is developed by the operator based on its specific loading calculation procedures and provides the operational limits for use with the operator’s W&B program approved under this AC. These approved operational limits are typically more restrictive and may not exceed the manufacturer’s certificated limits. This is because the loading schedule is generally designed to check only specific conditions (e.g., takeoff and zero fuel) known prior to takeoff, and must account for variations in W&B in flight. Loading the aircraft so that the calculated W&B is within the approved operational limits will maintain the actual W&B within the certificated limits throughout the flight.
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2.2.1.3 Development of a loading schedule represents a trade-off between ease of use and loading flexibility. A schedule can provide more loading flexibility by requiring more detailed inputs, or it can be made easier to use by adjusting the operational limits to account for the uncertainty caused by the less detailed inputs.
2.2.1.4 Several types of loading schedules are commonly used, including computer programs as well as “paper” schedules, which can be graphical, such as an alignment (“chase around chart”) system, slide rule, or numerical, such as an adjusted weight or index system.
2.2.1.5 It is often more convenient to compute the balance effects of combined loads and to display the results by using “balance units” or “index units.” This is done by adding the respective moments (weight times arm) of each item.
Graphing the moments’ results in a “fan grid” where lines of constant balance arms (BA) or percent MAC are closer together at lower weights and further apart at higher weights. Direct graphical or numerical addition of the balance effects are possible using these moment values.
2.2.1.6 To make the magnitude of the numbers more manageable, moments can be converted to an index unit. For example:
N ote: Where datum is the reference BA that will plot as a vertical line on the fan grid, M and K are constants that are selected by the operator.
M is used to scale the index values, and K is used to set the index value of the reference BA.
2.2.2 How Should an Operator Determine the Weight of Each Fluid Used Aboard the Aircraft?
An operator should use one of the following:
1. The actual weight of each fluid,
2. A standard volume conversion for each fluid, or
3. A volume conversion that includes a correction factor for temperature.
2.3 Constructing a Loading Envelope.
2.3.1 What Should an Operator Consider when Constructing a Loading Envelope? Each operator complying with this AC must construct a loading envelope applicable to each aircraft being operated. The envelope will include all relevant W&B limitations. It will be used to ensure that the aircraft is always operated within appropriate W&B limitations, and will include provisions to account for the loading of passengers, fuel, and cargo; the in-flight movement of passengers, aircraft components, and other loaded items; and the usage or transfer of fuel and other consumables. The operator must be able to
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