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Notice

Announcement of FAA Advisory Circular (AC) 120-27D, Aircraft Weight and Balance Control

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Information about this document as published in the Federal Register.

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AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of availability of AC, and request for comments.

SUMMARY:

This notice announces the availability of and requests comments on AC 120-27D, which provides guidance on the requirements for maintaining an aircraft weight and balance control program.

DATES:

Submit comments on or before September 17, 2004.

ADDRESSES:

Send all maintenance-related comments on AC 120-27D to Mr. Darcy D. Reed, Aircraft Maintenance Division, Air Carrier Maintenance Branch (AFS-330), Federal Aviation Administration, 800 Independence Ave., SW., Washington, DC 20591; facsimile (202) 267-5115; e-mail Darcy.D.Reed@faa.gov. Send all operations-related comments on AC 120-27D to Mr. Dennis Pratte, Air Transportation Division, Air Carrier Operations Branch (AFS-220), Federal Aviation Administration, 800 Independence Ave., SW., Washington, DC 20591; facsimile (202) 267-5229; e-mail Dennis.Pratte@faa.gov.

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FOR FURTHER INFORMATION CONTACT:

Mr. Darcy D. Reed, AFS-330, at the address, facsimile, or e-mail listed above, or by telephone at (202) 267-9948; or Mr. Dennis Pratte, AFS-220, at the address, facsimile, or e-mail listed above, or by telephone at (202) 267-5488.

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SUPPLEMENTARY INFORMATION:

Comments Invited

AC 120-27D is available on the FAA's Regulatory Guidance Library Web site at http://www.airweb.faa.gov/​rgl, under the Advisory Circulars link. Interested persons are invited to comment on the AC by submitting written data, views, or suggestions, as they may desire. Please identify AC 120-27D, Aircraft Weight and Balance Control, and submit comments, either hardcopy or electronic, to the appropriate address listed above. Comments may be inspected at the above address between 9 a.m. and 4 p.m. weekdays, except Federal holidays.

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Issued in Washington, DC, on August 11, 2004.

John M. Allen,

Deputy Director, Flight Standards Service.

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Table of Contents

Chapter 1. Introduction

100. What is the purpose of this advisory circular (AC)?

101. How is this AC organized?Start Printed Page 51509

102. What documents does this AC cancel?

103. What should an operator consider while reading this AC?

104. Who should use this AC?

Table 1-1. Aircraft Cabin Size

105. Who can use standard average or segmented weights?

Chapter 2. Aircraft Weights and Loading Schedules

Section 1. Establishing Aircraft Weight

200. How does an operator establish the initial weight of an aircraft?

201. How does an operator document changes to an aircraft's weight and balance?

Table 2-1. Incremental Weight Changes that Should Be Recorded in a Weight and Balance Change Record

202. How does the operator maintain the OEW?

203. How often are aircraft weighed?

Table 2-2. Number of Aircraft to Weigh in a Fleet

204. What procedures should be used to weigh aircraft?

Section 2. Aircraft Loading Schedules

205. What is a loading schedule?

206. How should an operator determine the weight of each fluid used aboard the aircraft?

Section 3. Constructing a Loading Envelope

207. What should an operator consider when constructing a loading envelope?

208. What information from the aircraft manufacturer should an operator use?

209. What should the operator consider when curtailing the manufacturer's loading envelope?

210. What are some examples of common curtailments to the manufacturer's loading envelope?

Section 4. Automated Weight and Balance Systems

211. How does an onboard weight and balance system compare to a conventional weight buildup method?

212. What measures should an operator take to obtain operational approval for an onboard weight and balance system?

213. What operational considerations should an operator take into account when using an onboard weight and balance system?

214. May an operator use the information in this AC to develop a backup system?

215. What operational considerations should an operator take into account when using a computerized weight and balance system?

Chapter 3. Methods to Determine the Weight of Passengers and Bags

Section 1. Choosing the Appropriate Method

300. What should an operator consider when choosing the appropriate method?

Section 2. Standard Average Weights

301. What standard average passenger weights should an operator with an approved carry-on bag program use?

Table 3-1. Standard Average Passenger Weights

302. What standard average weights should an operator use for carry-on bags and personal items?

303. What standard average weights should an operator use for checked bags?

304. What standard average weight should an operator of large cabin aircraft use for bags checked plane-side?

305. What standard average weights should an operator of small and medium cabin aircraft use, if it has a “no-carry-on bag program?”

Table 3-2. Average Passenger Weights for Operators with a No-Carry-on Bag Program

306. What are the standard average weights for crewmembers?

Table 3-3. Standard Crewmember Weights

307. What weights may be used for company materials and mail?

308. What are the standard average weights for special passenger groups that do not fit an operator's standard average weight profile?

Section 3. Average Weights Based on Survey Results

309. What should an operator consider when designing a survey?

310. What sample sizes should an operator use?

Table 3-4. Minimum Sample Sizes

311. When conducting a survey, can an operator collect a smaller sample size than that published in Table 3-4?

312. What sampling method should an operator use?

313. What should an operator consider when developing a survey plan and submitting it to the FAA?

314. What general survey procedures should an operator use?

315. What information might an operator gain from conducting a count survey?

316. When should an operator conduct another survey to revalidate the data from an earlier survey?

Section 4. Segmented Passenger Weights

317. What should an operator consider when using segmented weights?

Table 3-5. Segmented Weights for Adult Passengers (in Pounds; Summer)

318. How are loading envelope curtailment and bag weight affected by an operator's use of segmented weights?

319. What might be an example of an operator using the segmented weights in Table 3-5?

Section 5. Actual Weight Programs

320. If the operator decides to use an actual weights program, how might it determine the actual weight of passengers?

321. If the operator decides to use an actual weight program, how should it determine the actual weights of personal items and bags?

322. What approach should an operator use to record actual weights?

Chapter 4. Operator Reporting Systems and FAA Oversight

Section 1. Pilot and Agent Reporting Systems

400. What are the pilots' and operators' responsibilities in reporting aircraft loading and manifest preparation discrepancies?

Section 2. FAA Oversight

401. Which FAA inspectors are responsible for overseeing an operator's weight and balance program?

402. Which portions of OpSpecs or MSpecs are relevant to an operator's weight and balance program?

403. When will the FAA revise the standard average weights in this AC?

Appendix 1. Definitions

Appendix 2. Source of Standard Average Weights in This AC

1. Standard average passenger weights.

2. Standard average bag weights.

Table 2-1. Bag Survey Results

Appendix 3. Sample Operational Loading Envelope

1. Introduction.

2. Assumptions for this example.

Figure 3-1. Sample Aircraft Interior Seating Diagram

3. Curtailments for passenger seating variation.

Table 3-1. Calculation of Zone 1 Centroid

Table 3-2. Calculation of Zone 2 Centroid

Table 3-3. Calculation of Zone 3 Centroid

Table 3-4. Moments Resulting from the Zone Centroid Assumption for Zone 1

Table 3-5. Moments Resulting from the Window-Aisle-Remaining Assumption for Zone 1

Table 3-6. Comparison of Moments for Zone 1

Table 3-7. Moments Resulting from the Zone Centroid Assumption for Zone 2

Table 3-8. Moments Resulting from the Window-Aisle-Remaining Assumption for Zone 2

Table 3-9. Comparison of Moments for Zone 2

Table 3-10. Moments Resulting from the Zone Centroid Assumption for Zone 3

Table 3-11. Moments Resulting from the Window-Aisle-Remaining Assumption for Zone 3

Table 3-12. Comparison of Moments for Zone 3

4. Other curtailments to the manufacturer's loading envelope.

5. Operational loading envelope diagrams.

Figure 3-2. Operational Loading Envelope with a Curtailment for Variations in Passenger Seating

Figure 3-3. Operational Loading Envelope Using Actual Seating Location of Passengers

Appendix 4. Additional Curtailments to CG Envelopes to Account for Variations to Passenger Weights

Table 4-1. Row Factor

Table 4-2. Sample Curtailment Due to Variations in Passenger Weight and Male/Female Ratio Using Window-Aisle Method

Appendix 5. Options to Improve Accuracy

Figure 5-1. Sample Aircraft Interior Seating Diagram

Figure 5-2. Sample Passenger Seating Moment

Figure 5-3. Sample Passenger Seating Moment

Figure 5-4. Sample Passenger Seating Moment

Appendix 6. Sample CG Envelope Development

Figure 6-1. Operational CG Envelope—3 Passenger Cabin Zones

Figure 6-2. Operational CG Envelope—Actual Passenger Seating

Appendix 7. Checklist

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Chapter 1. Introduction

100. What Is the Purpose of This Advisory Circular (AC)?

a. This AC provides operators with guidance on how to develop and receive approval for a weight and balance control program for aircraft operated under Title 14 of the Code of Federal Regulations (14 CFR) part 91, subpart K of part 91, and parts 121, 125, and 135.

b. This AC presents recommendations for an acceptable means, but not the only means, to develop and receive approval for a weight and balance control program, and includes guidance for using average and estimated weights in accordance with part 121, section 121.153(b) and other applicable parts of subpart K of part 91 and parts 121, 125, and 135.

Note:

Per part 125, section 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 actual weighing of the airplane within the preceding 36 calendar-months.

c. 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).

101. How Is This AC Organized?

This AC has four main chapters and seven appendixes. Chapter 1 contains general information about this AC and background. 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 Federal Aviation Administration's (FAA) role in developing and approving an operator's weight and balance control program. Finally, appendixes 1 through 7 contain technical information such as definitions, the source of data used in the AC, a sample loading envelope, an example of curtailments to the loading envelope, suggestions to improve accuracy, sample CG envelope development, and checklists for operators.

102. What Documents Does This AC Cancel?

This AC cancels—

a. AC 120-27C, Aircraft Weight and Balance Control, dated November 7, 1995; and

b. Joint Handbook Bulletin for Airworthiness (HBAW) 95-14 and Air Transportation (HBAT) 95-15, Adherence to Advisory Circular 120-27C, “Aircraft Weight and Balance Control,” dated November 17, 1995.

103. What Should an Operator Consider While Reading This AC?

a. 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. By complying with these limits and operating under the procedures established by the manufacturer, an operator is able to meet the weight and balance requirements specified in the aircraft flight manual (AFM). Typically, an operator calculates takeoff weight by adding the operational empty weight (OEW) of the aircraft, the weight of the passenger and cargo payload, and the weight of fuel. The objective is to calculate the takeoff weight and CG of an aircraft as accurately as possible.

b. When using average weights for passengers and bags, the operator must be vigilant to ensure that the weight and balance control program reflects the reality of aircraft loading. The FAA will periodically review the guidance in this AC and update this AC if average weights of the traveling public should change or if regulatory requirements for carry-on bags or personal items should change. Ultimately, the operator is responsible for determining if the procedures described in this AC are appropriate for use in its type of operation.

104. Who Should Use This AC?

a. This document provides guidance to operators that are either required to have an approved weight and balance control program under parts 121 and 125, or choose to use average aircraft, passenger or baggage weights when operating under subpart K of part 91 or part 135. The guidance in this AC is useful for anyone involved in developing or implementing a weight and balance control program.

b. As shown in Table 1-1, 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 type-certificated with—Is considered—
71 or more passenger seatsA large-cabin aircraft.
30 to 70 passenger seatsA medium-cabin aircraft.
5 to 29 passenger seatsA small-cabin aircraft.
0 to 4 passenger seatsNot eligible.

105. Who Can Use Standard Average or Segmented Weights?

a. Standard Average Weights. Use of standard average weights is limited to operators of multiengine turbine-powered aircraft originally type-certificated for five (5) 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 commuter category or the operator and manufacturer is able to prove that the aircraft can meet the performance requirements of subpart B of part 25. Single-engine and multiengine turbine Emergency Medical Service Helicopter (EMS/H) operators may use standard average weights for EMS operations, provided they have received an LOA.

b. Segmented Weights. Use of segmented weights is limited to those aircraft that meet the requirements of paragraph 105(a) or that are multiengine turbine-powered aircraft originally type-certificated for five (5) or more passenger seats and that do not meet the performance requirements of subpart B of part 25. Segmented passenger weights are listed in Chapter 3, Table 3-5.

Chapter 2. Aircraft Weights and Loading Schedules

Section 1. Establishing Aircraft Weight

200. How Does an Operator Establish the Initial Weight of an Aircraft?

Prior to being placed into service, each aircraft should be weighed and the empty weight and CG location established. New aircraft are normally weighed at the factory and are eligible to be placed into operation without reweighing if the weight and balance records were adjusted for alterations and modifications to the aircraft and if the cumulative change to the weight and balance log is not more than plus or minus one-half of one percent (0.5 percent) of the maximum landing weight or the cumulative change in the CG position exceeds one-half of one percent (0.5 percent) of the mean aerodynamic chord. Aircraft transferred from one operator that has an approved weight and balance program, to another operator with an approved program, need not be weighed prior to use by the Start Printed Page 51511receiving operator unless more than 36 calendar-months have elapsed since last individual or fleet weighing, or unless some other modification to the aircraft warrants that the aircraft be weighed (e.g., paragraph 203(c)). Aircraft transferred, purchased, or leased from an operator without an approved weight and balance 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 a method established through an operator's approved weight and balance control program within the last 12 calendar-months and a weight and balance change record was maintained by the operator. See paragraph 203(c) for a discussion of when it may be potentially unsafe to fail to reweigh an aircraft after it has been modified.

201. How Does an Operator Document Changes to an Aircraft's Weight and Balance?

The weight and balance 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 weight and CG of each aircraft. Alterations and changes affecting either the weight and/or balance of the aircraft should be recorded in this log. Changes to an aircraft that result in a weight being added to the aircraft, weight being removed from the aircraft, or weight being relocated in or on the aircraft should be recorded in such a 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.

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.

202. How Does the Operator Maintain the OEW?

The loading schedule may utilize the individual weight of the aircraft in computing operational weight and balance or the operator may choose to establish fleet empty weights for a fleet or group of aircraft.

a. Establishment of OEW. The OEW and CG position of each aircraft should be reestablished at the reweighing periods discussed in paragraph 203. In addition, it should be reestablished whenever the cumulative change to the Weight and Balance 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 weight and balance should be reestablished.

b. 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 for establishment of OEW. When the cumulative changes to an aircraft Weight and Balance 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 reestablishing new FOEWs.

203. How Often Are Aircraft Weighed?

a. Individual Aircraft Weighing Program. Aircraft are normally weighed at intervals of 36 calendar-months. An operator may, however, extend this weighing period for a particular model aircraft when pertinent records of actual routine weighing during the preceding period of operation show that weight and balance records maintained are sufficiently accurate to indicate that aircraft weights and CG positions are within the cumulative limits specified for establishment of OEW, (see paragraph 202). Such applications should be substantiated in each instance with at least two aircraft weighed. Under an individual aircraft weighing program, an increase should not be granted which would permit any aircraft to exceed 48 calendar-months since the last weighing, including when an aircraft is transferred from one operator to another. In the case of helicopters, increases should not exceed a time that is equivalent to the aircraft overhaul period.

Note:

Per part 125, section 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 actual weighing of the airplane within the preceding 36 calendar-months.

b. Fleet Weighing. An operator may choose to weigh only a portion of the fleet and apply the unaccounted weight and moment change determined by this sample to the remainder of the fleet.

(1) A fleet is composed of a number of aircraft of the same model (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 aircraftAll aircraft.
4 to 9 aircraft3 aircraft, plus at least 50 percent of the number of aircraft greater than 3.
More than 9 aircraft6 aircraft, plus at least 10 percent of the number of aircraft greater than 9.

(2) In choosing the aircraft to be weighed, the aircraft in the fleet having the most hours flown since last weighing should be selected.

(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.

c. Weighing Aircraft—Modifications. For most aircraft modifications, computing the weight and balance changes is practical. For some modifications, such as interior reconfigurations, the large number of parts removed, replaced, and installed make an accurate determination of the weight and balance change by computation impractical. It would be potentially unsafe to fail to reestablish the aircraft weight and balance, by actually reweighing the aircraft, in situations where the cumulative net change in the weight and balance log exceeds:

(1) In the case of airplanes, plus or minus one-half of 1 percent (0.5 Start Printed Page 51512percent) 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 MAC.

(2) 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.

Note:

In the situations specified in paragraphs 203c(1) and (2), the operator should weigh two or more aircraft in a fleet, as required in Table 2-2, to get consistent results. The operator may choose to weigh the aircraft before and after the modification, or just after the modification.

204. What Procedures Should Be Used to Weigh Aircraft?

a. 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 aircraft in an enclosed building because scale readings stabilize faster in the absence of drafts from open doors.

b. 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 period, or time periods, as specified in the operator's approved calibration program.

Section 2. Aircraft Loading Schedules

205. What is a Loading Schedule?

a. The loading schedule is used to document compliance with the certificated weight and balance limitations contained in the manufacturer's AFM and weight and balance manual.

b. 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 weight and balance program approved under this AC. These approved operational limits are typically more restrictive but do 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 weight and balance in flight. It must also account for factors selected to be excluded, for ease of use, from the calculation process. Loading the aircraft so that the calculated weight and balance is within the approved limits will maintain the actual weight and balance within the certificated limits throughout the flight.

c. 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 further limiting the operational limits to account for the uncertainty caused by the less detailed inputs.

d. Several types of loading schedules are commonly-used, including computer programs as well as “paper” schedules, which can be either graphical, such as an alignment (“chase around chart”) system, slide rule, or numerical, such as an adjusted weight or index system.

e. 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 % 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.

f. To make the magnitude of the numbers more manageable, moments can be converted to an index unit. For example:

Note:

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.

206. How Should an Operator Determine the Weight of Each Fluid Used Aboard the Aircraft?

An operator should use one of the following:

a. The actual weight of each fluid,

b. A standard volume conversion for each fluid, or

c. A volume conversion that includes a correction factor for temperature.

Section 3. Constructing a Loading Envelope

207. 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 weight and balance limitations. It will be used to ensure that the aircraft is always operated within appropriate weight and balance 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 demonstrate that the aircraft is being operated within its certificated weight and balance limitations using reasonable assumptions that are clearly stated.

208. What Information From the Aircraft Manufacturer Should an Operator Use?

The construction of the loading envelope will begin with the weight and balance limitations provided by the aircraft manufacturer in the weight and balance manual, type certificate data sheet, or similar approved document. These limitations will include, at minimum, the following items, as applicable:

a. Maximum zero-fuel weight.

b. Maximum takeoff weight.

c. Maximum taxi weight.

d. Takeoff and landing CG limitations.

e. In-flight CG limitations.

f. Maximum floor loadings-including both running and per square foot limitations.

g. Maximum compartment weights.

h. Cabin shear limitations.

i. Any other limitations provided by the manufacturer.

209. What Should the Operator Consider When Curtailing the Manufacturer's Loading Envelope?

a. 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 Start Printed Page 51513passenger seating location, are not precisely known.

b. 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 take-off or landing. Therefore, the takeoff and landing envelope need not be curtailed for passenger movement.

c. 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 envelopes. These envelopes must be observed. 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. Optionally, 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 weight and balance calculation.

210. What Are Some Examples of Common Curtailments to the Manufacturer's Loading Envelope?

The following subparagraphs provide examples of common loading curtailments. They are only examples. Operators using an approved weight and balance control program 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.

a. Passengers. The operator must account for the seating of passengers in the cabin. The loading envelope need not 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. It is recommended that the operator take into account the possibility that some passengers may not sit in their assigned seats.

(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 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) 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.

(3) All such assumptions should be adequately documented.

b. 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:

(1) Fuel density. A certain fuel density may be assumed and a curtailment included to account 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 to be accurate.

(2) Fuel movement. The movement or transfer of fuel in flight.

(3) Fuel usage in flight. The burning of fuel may cause the CG of the fuel load to change. 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.

c. 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.

d. 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 configuration. Standard operational procedures may be taken into account. Examples of items that can move during flight are:

(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 such lavatory trip.

(2) Flight attendants moving throughout the cabin.

(3) Service carts 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 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 flight attendants assigned to each cart must also be considered. The assumed weight of each cart may be the maximum anticipated cart-load or the maximum design load, as appropriate to the operator's procedures.

(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.

(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, it may be assumed that passengers to move to the lavatories closest to their seats. In aircraft with a single lavatory, movement from the “most adverse” seat must be taken into account. Assumptions may be made which reflect operator lavatory and seating policies. For example, it may be assumed that coach passengers may only use the lavatories in the coach Start Printed Page 51514cabin, if that is the operator's normal policy.

e. 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 aircraft. Devices deployed only while in contact with the ground, such as ground spoilers or thrust reversers, may be excluded from such curtailments.

f. 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 which ensure that the cargo is loaded uniformly throughout each compartment.

Section 4. Automated Weight and Balance Systems

211. How does an onboard weight and balance system compare to a conventional weight buildup method?

a. An operator may use an onboard weight and balance system to calculate an aircraft's weight and balance, provided the FAA has approved the system for use in an operator's weight and balance control program. This section discusses the differences an operator should consider when using an onboard weight and balance system compared to a conventional weight buildup method. This section addresses only the operational considerations related to the use of an FAA-authorized onboard weight and balance system.

b. Like operators using a conventional weight buildup method to calculate weight and balance, an operator using an onboard weight and balance system as a primary weight and balance 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 weight and balance system would not need to curtail the loading envelope for assumptions about passenger and bag weight or distribution.

c. Because an onboard weight and balance 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 or weight errors. Using an onboard weight and balance system does not relieve an operator from the requirement to complete and maintain a load manifest.

212. What measures should an operator take to obtain operational approval for an onboard weight and balance system?

a. System calibration. An operator should develop procedures to calibrate its onboard weight and balance 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 weight and balance system in place of procedures described in Section 1 of this chapter for weighing the aircraft to establish OEW or CG location.

b. Demonstration of system accuracy. As part of the operational approval process, an operator should demonstrate that its onboard weight and balance system maintains its certificated system accuracy between calibration periods. An operator should not have to conduct this demonstration more than once for installing a specific system on one type of aircraft. For the demonstration, the operator should use an aircraft in normal operational service, or in operations that represent the expected environmental and operational conditions in which the aircraft will operate.

213. What operational considerations should an operator take into account when using an onboard weight and balance system?

a. Certification limits. An operator using an onboard weight and balance system as its primary means of calculating weight and balance should have procedures in place to ensure that the system is operated within the limits established during the system's certification process.

b. Environmental considerations. An operator using an onboard weight and balance 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 weight and balance system include temperature, barometric pressure, wind, ramp slope, rain, snow, ice, frost, dew, deicing fluid, etc.

c. Aircraft considerations. An operator using an onboard weight and balance 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.

d. Takeoff trim settings. If the aircraft manufacturer provides trim settings for takeoff based on the aircraft's CG location, an operator using an onboard weight and balance system should ensure that the onboard weight and balance system provides flight crewmembers with adequate information to determine the appropriate trim setting.

e. Operational envelope. The operational envelope for onboard weight and balance systems shall be developed using the same procedures described in other parts of this AC, with the exception that the operational envelope need not 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 must curtail the CG envelope for any system CG tolerance and the weight must be curtailed for any system tolerance above 1 percent.

f. Complying with compartment or unit load device (ULD) load limits. When using an onboard weight and balance system, an operator should develop in its weight and balance control program a method to ensure that it does not exceed the load 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.

(1) An operator may assign a standard average weight to bags. 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) 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.Start Printed Page 51515

214. May an operator use the information in this AC to develop a backup system?

An operator using an onboard weight and balance system as its primary means of calculating weight and balance may use the guidance in this AC to develop a backup system based on a conventional weight buildup. If an operator develops and receives approval for a backup system, the FAA may grant the operator relief to include an onboard weight and balance system in the operator's minimum equipment list.

215. What operational considerations should an operator take into account when using a computerized weight and balance system?

a. An operator may use an installed computerized weight and balance system to calculate the load schedule for the aircraft's weight and balance for primary dispatch, provided that the system received certification and operational approval for use in an operator's approved weight and balance control program. The system consists of a computer program that runs on installed Electronic Flight Bag computing devices or the Aircraft Communication Addressing and Reporting System, and can be downloaded to ground operations via electronic links. The system displays the load sheet to the pilot or flight operations for primary dispatch.

b. Like operators using a conventional weight buildup method to calculate weight and balance, an operator may use the computerized weight and balance system to provide the FAA approved loading schedules. The operator who uses the computerized weight and balance system as part of its approved weight and balance program should meet all provisions pertinent to the operator's approved weight and balance program as described in this AC.

Chapter 3. Methods to Determine the Weight of Passengers and Bags

Section 1. Choosing the Appropriate Method

300. What should an operator consider when choosing the appropriate method?

a. For many years, operators of transport category aircraft have used average weights for passengers and bags to calculate an aircraft's weight and balance, in accordance with standards and recommended practices. This method eliminates many potential sources of error associated with accounting for a large number of relatively light weights. However, differences between the actual weight of passengers and bags and the average weight of passengers and bags can occur when using average weights.

b. 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 weight and balance programs for small and medium cabin aircraft should be examined in greater detail.

c. The next four sections describe four methods available to operators to determine passenger and bag weight. They are standard average weights in Section 2; average weights based on survey results in Section 3; segmented weights in Section 4; and actual weights in Section 5. An operator should review the following discussion and consult Table 3-1 to determine which method or methods are appropriate to its type of operation.

d. Large Cabin Aircraft. Operators of large cabin aircraft may use the standard average weights for passengers and bags. If an operator determines that the standard average weights are not representative of its operation for some route or regions, it is encouraged to conduct a survey as detailed in Section 3 of this chapter, to establish more appropriate average weights for its operation. Operators should have procedures for identifying situations that would require the use of nonstandard or actual weights.

e. Medium Cabin Aircraft. Medium cabin aircraft should be evaluated to determine if the aircraft should be treated more like large or small cabin aircraft. To determine if a medium cabin aircraft can be treated as a large cabin aircraft, the aircraft must meet either both of the loadability criteria or the loading schedule criteria or else be subject to the small cabin weights and curtailments:

Loadability Criteria:

  • The CG of the OEW is within the manufacturer's loading envelope, and
  • 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.

Or

Loading Schedule Criteria:

  • The operator must use a loading schedule based upon zones. The aircraft cabin may have no more than four rows per zone with not less than four zones.

f. Small Cabin Aircraft. Operators of small cabin aircraft may request approval to use any one of the following methods when calculating the aircraft weight and balance.

(1) The operator may use actual passenger and bag weights, or

(2) The operator may use the segmented passenger weights listed in Table 3-5 and average bag weights listed in Section 2 of this chapter, or

(3) The operator may use the standard average passenger and bag weights prescribed for large cabin aircraft, or average weights based on an FAA-accepted survey, if—

(a) The aircraft was certificated under part 23 commuter category, part 25, or part 29 (or is able to prove an aircraft has equivalent part 25 or 29 performance data), and

(b) The operator curtails the aircraft CG envelope as prescribed in Appendixes 3 and 4 of this AC.

Section 2. Standard Average Weights

301. What standard average passenger weights should an operator with an approved carry-on bag program use?

a. The standard average passenger weights provided in Table 3-1 were established based on data from U.S. Government health agency surveys. For more background information on the source of these weights, refer to Appendix 2.

b. The standard average passenger weights in Table 3-1 include 5 pounds for summer clothing, 10 pounds for winter clothing, and a 16-pound allowance for personal items and carry-on bags. 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.

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c. 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. Use of seasonal dates, other than those listed above, will be entered as nonstandard text and approved through the operator's OpSpec, MSpec, or LOA, as applicable.

d. The standard average weights listed in Table 3-1 are based on the assumption that the operator has a carry-on bag program. Operators using a no-carry-on bag program should refer to paragraph 305 of this section.

Note:

The weight of children under the age of 2 has been factored into the standard average and segmented adult passenger weights.

302. What standard average weights should an operator use for carry-on bags and personal items?

a. An operator using standard average passenger weights should include the weight of carry-on bags and personal items in the passenger's weight. The standard average passenger weights in Table 3-1 include a 16-pound allowance for personal items and carry-on bags, based on the assumption that—

(1) One-third of passengers carry one personal item and one carry-on bag.

(2) One-third of passengers carry one personal item or carry-on bag.

(3) One-third of passengers carry neither a personal item nor a carry-on bag.

(4) The average weight allowance of a personal item or a carry-on bag is 16 pounds.

b. If an operator believes the 16-pound allowance for personal items and carry-on bags is not appropriate for its operations or receives notification from the FAA that the assumptions provided in paragraph 302a are not consistent with the operator's approved program, the operator should conduct a survey to determine what percentage of passengers carry personal items or carry-on bags aboard the aircraft. An example of how to adjust the personal item and carry-on bag allowance, based on the results of a survey, is in Section 3. An operator should not use an allowance of less than 16 pounds for personal items and carry-on bags unless the operator conducts a survey or unless the operator has a no-carry-on bag program.

303. What standard average weights should an operator use for checked bags?

An operator that chooses to use standard average weights for checked bags should use a standard average weight of at least 30 pounds. An operator that requests approval to use a standard average weight of less than 30 pounds for checked bags should have current, valid survey data to support a lesser weight. An operator also may conduct a study to establish different standard average bag weights for portions of its operation to account for regional, seasonal, demographic, aircraft, or route variation. For example, an operator could establish different standard average bag weights for domestic and international routes.

a. Heavy bags. Heavy bags are considered any bag that weighs more than 50 pounds but less than 100 pounds. An operator should account for a heavy bag by using one of the following weights:

(1) A standard average weight of 60 pounds,

(2) An average weight based on the results of a survey of heavy bags, or

(3) The actual weight of the heavy bag.

Note:

An operator that uses “double-counting” to treat a heavy bag as if it were two checked bags for weight purposes should ensure the load manifest represents the actual number of bags for counting purposes. An operator should have a system in place to ensure that heavy bags are identified, although operators may not be required to weigh heavy bags on a scale.

b. Non-luggage bags. A non-luggage bag is any bag that does not meet the normal criteria for luggage. Examples include golf bags, fishing equipment packages, wheelchairs and strollers in their shipping configuration, windsurfing kits, boxed bicycles, etc. For non-luggage bags, operators may use any appropriate combination of actual weights, average weights based on survey results, or standard average bag weights. Operators that wish to establish an average weight for a particular type of non-luggage bag, such as a golf bag, must conduct a survey in accordance with the procedures established in Section 3 of this chapter. Operators also should establish a method to calculate the effect on CG of a large non-luggage bag, such as a surfboard, that may occupy more than one compartment on the aircraft.

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304. What standard average weight should an operator of large cabin aircraft use for bags checked plane-side?

Operators with a carry-on bag program that use standard average weights should account for the weight of each carry-on bag checked plane-side as 30 pounds. An operator may request approval to use a weight other than 30 pounds if the operator has current, valid survey data to support a different average weight for plane-side-loaded bags.

305. What standard average weights should an operator of small and medium cabin aircraft use, if it has a “no-carry-on bag program?'

Note:

A no-carry-on bag program is limited to small and medium cabin aircraft. A no-carry-on bag program is a term of art created for this AC. Associated with this program are certain standard average weight credits and reductions. Nothing in this AC prevents an operator of large cabin aircraft from having a no-carry-on bag “policy;” however, the acceptable standard bag weights for such checked baggage for large cabin aircraft are outlined in paragraphs 303 and 304 above. Furthermore, the passenger weight credit associated with a no-carry-on-bag program is limited to the small and medium cabin aircraft.

a. An operator with a no-carry-on bag program may allow passengers to carry only personal items aboard the aircraft. Because these passengers do not have carry-on bags, an operator may use standard average passenger weights that are 6 pounds lighter than those for an operator with an approved carry-on bag program. See Table 3-2.

b. An operator that has a no-carry-on bag program may account for a plane-side loaded bag as 20 pounds. To receive authorization to use 20 pounds as the average weight for a plane-side loaded bag, an operator should demonstrate that sufficient controls exist to ensure that passengers do not bring carry-on bags aboard the aircraft. An operator also should demonstrate that sufficient controls exist to ensure the personal items brought aboard the aircraft can fit completely under a passenger seat or in an approved stowage compartment.

c. If an operator discovers that a plane-side loaded bag should have been treated as a checked bag, the operator should account for that bag at the standard average weight of 30 pounds for a checked bag.

306. What are the standard average weights for crewmembers?

a. An operator may choose to use the standard crewmember weights shown in Table 3-3 or conduct a survey to establish average crewmember weights appropriate for its operation.

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b. The flight crewmember weights in Table 3-3 were derived from weights listed on all first- and second-class medical certificates. The flight crewmember weight with bags assumes that each flight crewmember has one crewmember roller bag and one pilot flight bag.

c. The flight attendant weights in Table 3-3 were derived from National Health and Nutrition Examination Survey (NHANES) data. (For additional information on NHANES, see Appendix 2.) The flight attendant weights with bags assume that each flight attendant has one crewmember roller bag and one flight attendant kit.

d. An operator may include the weight of crewmembers in an aircraft's OEW or add the weight to the load manifest prepared for each flight.

307. What weights may be used for company materials and mail?

a. Company Material. An operator should use actual weights for company material and aircraft parts carried aboard an aircraft.

b. Mail. An operator should use the weights provided with manifested mail shipments to account for the weight of the mail. If an operator has to separate a shipment of mail, the operator may make actual estimates about the weight of the individual pieces, provided the sum of the estimated weights is equal to the actual manifested weight of the entire shipment.

308. What are the standard average weights for special passenger groups that do not fit an operator's standard average weight profile?

a. Sports Teams.

(1) Actual passenger weights should be used for nonstandard weight groups (sports teams, etc.) unless average weights have been established for such groups by conducting a survey in accordance with the procedures established in Section 3 of this chapter. When such groups form only a part of the total passenger load, actual weights, or established average weights for the nonstandard group, may be used for such exception groups and average weights used for the balance of the passenger load. In such instances, a notation should be made in the load manifest indicating the number of persons in the special group and identifying the group; e.g., football squad, etc.

(2) Roster weights may be used for determining the actual passenger weight.

(3) A standard allowance of 16 pounds per person may be used to account for carry-on and personal items as provided in the operator's approved carry-on bag program.

(4) If the carry-on bags are representative of the operator's profile but do not meet the number of bags authorized per person, the operator may count bags and use a 16 pounds per bag allocation.

(5) Actual weights must be used in cases where the carry-on bags are not representative of the operator's profile.

b. Groups that are predominantly male or female should use the standard average weights for males or females provided in Table 3-1.

c. Military Groups. The Department of Defense (DOD) requires actual passenger and cargo weights be used in computing the aircraft weight and balance for all DOD charter missions. This requirement is specified in DOD Commercial Air Carrier Quality and Safety requirements (reference 32 CFR part 861, section 861.4(e)(3)(ix), as revised). FAA-approved air carrier weight and balance control programs may be used to account for carry-on/personal items for mixed loads of military and their dependents (such as channel missions). For combat-equipped troop charters, the Air Mobility Command (AMC) will provide guidance to account for the additional weight. If aircraft operators perceive that the weights provided are understated, they should seek confirmation of the actual weights and should make reasonable upward estimations and adjustments to those passenger and/or bag weights.

Section 3. Average Weights Based on Survey Results

309. What should an operator consider when designing a survey?

a. This section provides operators with an acceptable survey method to use in determining average weights for a weight and balance control program. This section also describes how an operator can conduct a survey to count personal items and carry-on bags to determine an appropriate allowance for those items to include in passenger weight. In addition, an operator may use the methods described in this section to conduct a survey to determine the percentage of male and female passengers, to calculate an average passenger weight.

b. Surveys conducted correctly allow an operator to draw reliable inferences about large populations based on relatively small sample sizes. In designing a survey, an operator should consider—

(1) The sample size required to achieve the desired reliability,

(2) The sample selection process, and

(3) The type of survey (average weights or a count of items).

310. What sample sizes should an operator use?

Several factors must be considered when determining an adequate sample size. The more varied the population, the larger the sample size required to obtain a reliable estimate. Paragraph 311 provides a formula to derive the absolute minimum sample size to achieve a 95-percent confidence level. Table 3-4 has been provided for those operators that wish to use calculations other than those listed in paragraph 311. Table 3-4 provides the operator with an acceptable number of samples that may be collected to obtain a 95-percent confidence level and lists the tolerable error associated with each category.

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311. When conducting a survey, can an operator collect a smaller sample size than that published in Table 3-4?

If the operator has chosen to use a sample size that is smaller than that provided in Table 3-4, the operator should collect a sufficient number of samples to satisfy the following formulas:

Where:

s is the standard deviation

n is the number of points surveyed

xj is the individual survey weights

x̄ is the sample average

Where:

e is the tolerable error

312. What sampling method should an operator use?

a. An operator conducting a survey must employ random sampling techniques. Random sampling means that every member of a group has an equal chance of being selected for inclusion in the sample. If an operator conducts a survey that does not employ random sampling, the characteristics of the selected sample may not be indicative of the larger group as a whole. Because of this, any conclusions drawn from such a survey may not be valid.

b. The following are two examples of random sampling methods that an operator may find appropriate for the type of survey conducted. An operator may also consult a basic textbook on statistics to determine if another random sampling method is more appropriate.

(1) Simple random selection. An operator should assign a sequential number to each item in a group (such as passengers waiting on a line or bag claim tickets). Then the operator randomly selects numbers and includes the item corresponding with the number in the sample. The operator repeats this process until it has obtained the minimum sample size.

(2) Systematic random selection. An operator should randomly select an item in sequence to begin the process of obtaining samples. The operator should then use a predetermined, systematic process to select the remaining samples following the first sample. For example, an operator selects the third person in line to participate in the survey. The operator then selects every fifth person after that to participate in the survey. The operator continues selecting items to include in the sample until it has obtained the minimum sample size.

c. Regardless of the sampling method used, an operator has the option of surveying each passenger and bag aboard the aircraft and should always give a passenger the right to decline to participate in any passenger or bag weight survey. If a passenger declines to participate, the operator should select the next passenger based on the operator's random selection method rather than select the next passenger in a line. If a passenger declines to participate, an operator should not attempt to estimate data for inclusion in the survey.

313. What should an operator consider when developing a survey plan and submitting it to the FAA?

a. Developing a survey plan. Before conducting a survey, an operator should develop a survey plan. The plan should describe the dates, times, and locations the survey will take place. In developing a survey plan, the operator should consider its type of operation, hours of operation, markets served, and frequency of flights on particular routes. An operator should avoid conducting surveys on holidays unless it has a valid reason to request the particular date.

b. Submitting the survey plan to the FAA. It is recommended that an operator submit its survey plan to the FAA at least 2 weeks before the survey is expected to begin. Before the survey begins, the operator's principal inspectors (PI) will review the plan and work with the operator to develop a mutually acceptable plan. During the survey, the PI will oversee the survey process to validate the execution of the survey plan. After the survey is complete, the PI will review the survey results and issue the appropriate OpSpecs or MSpecs. Once a survey begins, the operator should continue the survey until complete, even if the initial survey data indicates that the average weights are lighter or heavier than expected.

314. What general survey procedures should an operator use?

a. Survey locations. An operator should accomplish a survey at one or more airports that represent at least 15 percent of an operator's daily departures. To provide connecting passengers with an equal chance of being selected in the survey, an operator should conduct its survey within the secure area of the airport. An operator should select locations to conduct its survey that would provide a sample that is random and representative of its operations. For example, an operator should not conduct a survey at a gate used by shuttle operations unless the operator is conducting a survey specific to that route or the operator only conducts shuttle operations.

b. Weighing passengers. An operator that chooses to weigh passengers as part of a survey should take care to protect the privacy of passengers. The scale Start Printed Page 51520readout should remain hidden from public view. An operator should ensure that any passenger weight data collected remains confidential.

c. Weighing bags. When weighing bags on a particular flight, an operator should take care to ensure that it is properly accounting for all items taken aboard the aircraft.

d. Rounding sample results. If the operator uses rounding in the weight and balance calculations, it is recommended that the operator round passenger weights to the nearest pound and bag weights to the nearest half-pound. An operator should ensure that rounding is done consistently in all calculations.

e. Surveys for particular routes. An operator may conduct a survey for a particular route if the operator believes that the average weights on that route may differ from those in the rest of its operations. To establish a standard average passenger weight along the route, an operator may survey passengers at only one location. However, an operator should conduct surveys of personal items and bags at the departure and arrival locations, unless the operator can verify there is no significant difference in the weight and number of bags in either direction along the route.

315. What information might an operator gain from conducting a count survey?

a. An operator may conduct a survey to count certain items without determining the weight of those items. For example, an operator may determine that the standard average weights for male and female passengers are appropriate for its operations, but on some routes the passengers are predominantly male or female. In this case, an operator may conduct a survey to determine the percentage of male and female passengers. The operator could use the results of the survey to justify a weight other than the standard weights, which assume a 50-percent male and 50-percent female mix of passengers. Similarly, an operator may conduct a survey to determine the number of personal items and carry-on bags passengers carry aboard aircraft to determine if the allowance of 16 pounds per passenger is appropriate to its operations.

b. For example, an operator conducts a survey on a particular route (or multiple routes if amending the program average weight) to count the percentage of passengers carrying personal items and carry-on bags. The operator finds that—

(1) Fifty percent of passengers carry one carry-on bag and one personal item.

(2) Thirty percent of passengers carry one carry-on bag or one personal item.

(3) Twenty percent of passengers carry neither a carry-on bag nor a personal item.

(4) The survey results show that the average passenger carries approximately 21 pounds of personal items and carry-on bags rather than the standard allowance of 16 pounds. In such a case, it would be irresponsible for the operator to fail to increase the standard average weights for that route(s) by 5 pounds per passenger.

Note:

The calculation below determines the appropriate allowance for personal items and carry-on bags.

0.50 “ (16 pounds + 16 pounds)] + [0.30 “ (16 pounds)] + [0.20 “(0 pounds)] = 20.8 pounds

316. When should an operator conduct another survey to revalidate the data from an earlier survey?

In order to use survey-derived average weights, an operator must revalidate such survey data every 36 calendar-months or revert to the standard average weights, provided the new survey average weight results are within 2 percent of the standard average weights listed in this AC.

Section 4. Segmented Passenger Weights

317. What should an operator consider when using segmented weights?

a. The concept of segmented weights involves adding a portion of the standard deviation to an average weight to increase the confidence that the actual weight will not exceed the average weight. Like the standard average weights in Section 2, the segmented weights in Table 3-5 were derived from average weights and standard deviations found based on NHANES data, assuming a 95-percent confidence interval and 1-percent tolerable error.

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b. An operator may make the following adjustments to the table above:

(1) An operator may subtract 6 pounds from the passenger weight outlined above if it has a no-carry-on bag program or does not allow any carry-on baggage into the cabin of the aircraft.

(2) An operator should add 5 pounds to the weights above during the winter season.

c. An operator may interpolate between columns on the chart if the operator's assumed ratio of male passengers to female passengers does not exactly match the values given.

d. To account for a child's weight, for children ages 2 years to less than 13 years of age, the standard average child weight located in Table 3-1 may be used. Weights of children under the age of 2 have been factored into the segmented adult passenger weight.

318. How are loading envelope curtailment and bag weight affected by an operator's use of segmented weights?

a. Loading envelope curtailment. An operator using segmented passenger weights should consider curtailing its operational loading envelope using the methods described in Appendix 4.

b. Bag weights. An operator using segmented weights may use actual weights for bags or the standard average bag weights provided in Section 2. An operator using segmented passenger weights may not use survey-derived average bag weights.

319. What might be an example of an operator using the segmented weights in Table 3-5?

An operator of a 30 passenger-seat aircraft conducts a survey to count the percentage of male and female passengers on its flights and determines that 50 percent of its passengers are male and 50 percent are female. If the operator has an approved carry-on bag program, the operator should use 204 pounds in the summer and 209 pounds in the winter. If the operator has a no-carry-on bag program, the operator should use 198 pounds in the summer and 203 pounds in the winter and account for all plane-side loaded bags as 20 pounds each.

Section 5. Actual Weight Programs

320. If the operator decides to use an actual weights program, how might it determine the actual weight of passengers?

An operator may determine the actual weight of passengers by—

a. Weighing each passenger on a scale before boarding the aircraft (types of weight scales and scale tolerances will be defined in the operator's approved weight and balance control program); or

b. Asking each passenger his or her weight. An operator should add to this asked (volunteered) weight at least 10 pounds to account for clothing. An operator may increase this allowance for clothing on certain routes or during certain seasons, if appropriate.

Note:

If an operator believes that the weight volunteered by a passenger is understated, the operator should make a reasonable estimate of the passenger's actual weight and add 10 pounds.

321. If the operator decides to use an actual weight program, how should it determine the actual weights of personal items and bags?

To determine the actual weight of a personal item, carry-on bag, checked bag, plane-side loaded bag, or a heavy bag, an operator should weigh the item on a scale.

322. What approach should an operator use to record actual weights?

An operator using actual weights should record all weights used in the load buildup.

Chapter 4. Operator Reporting Systems and FAA Oversight

Section 1. Pilot and Agent Reporting Systems

400. What are the pilots' and operators' responsibilities in reporting aircraft loading and manifest preparation discrepancies?

Each operator should develop a reporting system and encourage employees to report any discrepancies in aircraft loading or manifest preparation. These discrepancies may include errors in documentation or calculation, or issues with aircraft performance and handling qualities that indicate the aircraft weight or balance is not accurate. Operators should attempt to determine the cause of each discrepancy and take appropriate corrective action. This would include a load audit on affected flights or conducting a passenger or bag weight survey in accordance with this AC if trends indicate it is warranted.

Section 2. FAA Oversight

401. Which FAA inspectors are responsible for overseeing an operator's weight and balance program?

The FAA has divided the responsibility of overseeing an operator's weight and balance control program between the operator's principal operations inspector (POI) and principal maintenance inspector (PMI). An operator that wishes to change aspects of its weight and balance control program, including average weights, should submit all applicable supporting data to the POI and PMI, as applicable, for approval. If the FAA approves the changes, the FAA will issue revised OpSpecs, MSpecs, or LOA, as appropriate.

402. Which portions of OpSpecs or MSpecs are relevant to an operator's weight and balance program?

a. This AC details methods to develop a weight and balance control program with greater accuracy and increased flexibility. By changing its OpSpecs or MSpecs, an operator may alter the weights used in its weight and balance control program to include appropriate combinations of standard average weights, average weights based on survey results, or actual weights.

b. Parts A and E of OpSpecs or MSpecs authorize an operator's weight and balance control program. These parts will address—

(1) Average passenger and bag weights;

(2) Situations when the use of average weights is inappropriate;

(3) The treatment of charter flights or special groups, if applicable;

(4) The type of loading schedule and instructions for its use;

(5) Aircraft weighing schedules; and

(6) Other procedures that the operator may require to assure control of weight and balance.

c. Paragraph E096 of the OpSpecs or MSpecs is issued to an operator with an approved aircraft fleet actual or average weight program. The FAA issues this paragraph after reviewing and approving an operator's weight and balance control program in its entirety.

d. Paragraph A011 of the OpSpecs or MSpecs is issued to an operator with an approved carry-on bag program. This paragraph provides details about the operator's approved carry-on bag program and states whether the operator has a carry-on bag program or a no-carry-on bag program. The FAA will issue this paragraph after reviewing the operator's carry-on baggage program in its entirety.

e. If an operator chooses to use standard average weights as outlined in this AC, the FAA will document that decision by issuing one or more of the following OpSpecs or MSpecs paragraphs. If an operator proposes to use different average weights (weights other than the standard average or segmented weights) and the FAA concurs with the statistically valid data provided by the operator to support Start Printed Page 51522such average weight differences, then those differences will be documented in the following OpSpecs or MSpecs. Although these paragraphs authorize an operator to use average and/or segmented weights, an operator may use actual weights at any time once issued these paragraphs.

(1) Paragraph A097—Small Cabin Aircraft Passenger and Baggage Weight Program.

(2) Paragraph A098—Medium Cabin Aircraft Passenger and Baggage Weight Program.

(3) Paragraph A099—Large Cabin Aircraft Passenger and Baggage Weight Program.

Note:

If an operator does not provide the FAA with adequate information to justify the issuance of one of the above paragraphs that documents the use of standard average, survey-derived average, and/or segmented weights, the FAA may issue paragraph A096, requiring the operator to use actual weights for a specific aircraft or aircraft fleet.

f. If an operator chooses to develop a weight and balance control program using only actual weights for all the aircraft it operates, the FAA may issue OpSpec/MSpec paragraph A096. The FAA will not issue paragraphs A097, A098, or A099 to operators with a weight and balance control program that uses only actual weights. The FAA will only issue paragraphs A096, A097, A098, and/or A099 after reviewing the operator's actual or average weight program.

g. An operator that receives approval to use nonstandard average weights should document and make available, upon request, the data and methodology used to derive those weights. An operator's documentation should be sufficiently comprehensive to allow the FAA to reproduce the same results during an audit. An operator should retain this documentation for as long as the operator uses the nonstandard average weights in its weight and balance control program.

h. If an operator chooses to conduct a survey, the operator will use the results of the survey to establish a revised average weight and must curtail the loading envelope as necessary. However, if the survey results indicate the average weights are within 2 percent of the standard average weights outlined in this AC, the operator may elect to adopt the standard average weights only after submitting the survey results to the FAA and receiving approval through its OpSpecs, MSpecs, or LOA.

i. For operators using an onboard weight and balance system to determine the weight and balance of the aircraft, the FAA will issue OpSpecs or MSpecs paragraph A096. Paragraph A096 documents the use of actual weights and the use of its onboard weight and balance system. For an operator that chooses to use standard average weights as a backup system, the FAA will issue paragraphs A097, A098, or A099, as appropriate. By authorizing the use of average weights, the operator may elect to use actual weights derived from its onboard weight and balance system, and may use average weights as an alternative should the system be inoperative.

j. For operators of all-cargo aircraft, the FAA will issue OpSpecs or MSpecs paragraph A096. Paragraph A096 documents the use of actual weights, with the exception of flightcrew and flightcrew bag weights. These weights may be accounted for using the standard average weights described in Chapter 3, Table 3-3.

403. When will the FAA revise the standard average weights in this AC?

The FAA will periodically review the standard average passenger weights listed in this AC, after the release of a new NHANES. If the FAA finds that the data from NHANES indicates a weight change of more than 2 percent, the FAA will revise this AC to update the standard average weights.

Start Signature

James J. Ballough,

Director, Flight Standards Service.

End Signature

Appendix 1. Definitions

1. Basic empty weight. The aircraft empty weight, adjusted for variations in standard items.

2. Cargo. As used in this advisory circular (AC), cargo refers to everything carried in the cargo compartments of the aircraft. This includes bags, mail, freight, express, and company material. It also includes live animals, dangerous goods, and hazardous materials as subcategories of the above.

3. Carry-on bag. A bag that the operator allows the passenger to carry onboard. It should be of a size and shape that will allow it to be stowed under the passenger seat or in a storage compartment. The operator establishes the exact dimensional limits based on the particular aircraft stowage limits.

4. Certificated weight and CG limits. Weight and center of gravity (CG) limits are established at the time of aircraft certification. They are specified in the applicable aircraft flight manual (AFM).

5. Checked bags. Checked bags are those bags placed in the cargo compartment of the aircraft. This includes bags that are too large to be placed in the cabin of the aircraft or those bags that are required to be carried in the cargo compartment by regulation, security program, or company policy. For bags checked plane-side, see the definition for plane-side loaded bags.

6. Curtailment. Creating an operational loading envelope that is more restrictive than the manufacturers' CG envelope, to assure the aircraft will be operated within limits during all phases of flight. Curtailment typically accounts for, but is not limited to, in-flight movement, gear and flap movement, cargo variation, fuel density, fuel burn-off, and seating variation.

7. Fleet empty weight. Average operational empty weight (OEW) used for a fleet or group of aircraft of the same model and configuration.

8. Freight. Cargo carried for hire in the cargo compartment that is not mail or passenger bags.

9. Heavy bags. For this AC, heavy bags are considered any bag that weighs more than 50 pounds but less than 100 pounds. Bags that are 100 pounds or more are considered freight.

10. Large cabin aircraft. Aircraft with a maximum type-certificated seating capacity of 71 or more passenger seats.

11. Loading envelope. Weight and CG envelope used in a loading schedule. Loading the aircraft within the loading envelope will maintain the aircraft weight and CG within the manufacturer's type-certificated limits throughout the flight.

12. Loading schedule. Method for calculating and documenting aircraft weight and balance prior to taxiing, to ensure the aircraft will remain within all required weight and balance limitations throughout the flight.

13. Manufacturer's empty weight. Weight of structure, powerplant, furnishings, systems, and other items of equipment that are an integral part of a particular aircraft configuration. (It is essentially a “dry” weight, including only those fluids contained in closed systems.)

14. Maximum landing weight. The maximum weight at which the aircraft may normally be landed.

15. Maximum takeoff weight. The maximum allowable aircraft weight at the start of the takeoff run.

16. Maximum taxi weight. The maximum allowable aircraft weight for taxiing.

17. Maximum zero-fuel weight. The maximum permissible weight of an aircraft with no disposable fuel and oil.

18. Medium cabin aircraft. Aircraft with a maximum type-certificated seating capacity between 70 and 30 passenger seats, inclusive.

19. Moment. A force that causes or tries to cause an object to rotate.

20. Onboard weight and balance system. A system that weighs an aircraft and payload, then computes the CG using equipment onboard the aircraft.

21. Operational empty weight (OEW). Basic empty weight or fleet empty weight plus operational items.

22. Operational items. Personnel, equipment, and supplies necessary for a particular operation but not included in basic empty weight. These items may vary for a particular aircraft and may include, but are not limited to, the following:

a. Crewmembers, supernumeraries, and bags;

b. Manuals and navigation equipment;

c. Passenger service equipment, including pillows, blankets, and magazines;

d. Removable service equipment for cabin, galley, and bar;Start Printed Page 51523

e. Food and beverage, including liquor;

f. Usable fluids, other than those in useful load;

g. Required emergency equipment for all flights;

h. Life rafts, life vests, and emergency transmitters;

i. Aircraft unit load devices;

j. Potable water;

k. Drainable unusable fuel;

l. Spare parts normally carried aboard and not accounted for as cargo; and

m. All other equipment considered standard by the operator.

23. Passenger assist/comfort animals and devices. These include, but are not limited to, canes, crutches, walkers, wheelchairs, medically-required animal comfort companions, or animals required to assist the vision impaired.

24. Passenger weight. Passenger weight is the actual weight or the approved average weight of the passenger.

a. An adult is defined as an individual 13 years or older.

b. A child is defined as an individual aged 2 to less than 13 years of age.

c. Infants are children who have not yet reached their second birthday and are considered part of the adult standard average and segmented passenger weight.

25. Personal item. Items the operator may allow a passenger to carry aboard, in addition to a carry-on bag. Typically, an operator may allow one personal item such as a purse, briefcase, computer and case, camera and case, diaper bag, or an item of similar size. Other items, such as coats, umbrellas, reading material, food for immediate consumption, infant restraining device, and passenger assist/comfort animals and devices, are allowed to be carried on the aircraft and are not counted against the personal item allowance.

26. Plane-side loaded bag. Any bag or item that is placed at the door or steps of an aircraft and subsequently placed in the aircraft cargo compartment or cargo bin.

27. Reference Balance Arm (BA). The horizontal distance from the reference datum to the CG of an item.

28. Segmented Weights. Passenger weights derived by adding a portion of the standard deviation to an average weight to increase the confidence that the actual weight will not exceed the average weight.

29. Small cabin aircraft. Aircraft with a maximum type-certificated seating capacity between 5 and 29 passenger seats, inclusive.

30. Standard basic empty weight. Manufacturer's empty weight plus standard items.

31. Standard items. Equipment and fluids not considered an integral part of a particular aircraft and not a variation for the same type of aircraft. These items may include, but are not limited to, the following:

a. Unusable fuel and other unusable fluids;

b. Engine oil;

c. Toilet fluid and chemical;

d. Fire extinguishers, pyrotechnics, and emergency oxygen equipment;

e. Structure in galley, buffet, and bar; and

f. Supplementary electronic equipment.

32. Useful Load. Difference between takeoff weight and OEW. It includes payload, usable fuel, and other usable fluids not included as operational items.

Appendix 2. Source of Standard Average Weights in This AC

1. Standard average passenger weights.

a. The Federal Aviation Administration (FAA) examined data from several large-scale, national health studies conducted by U.S. Government health agencies. The FAA found that the National Health and Nutrition Examination Survey (NHANES), conducted by the Centers for Disease Control (CDC), provided the most comprehensive and appropriate data. The data in NHANES cover a broad spectrum of the general population, are based on a large sample size, and are not restricted geographically to a particular area.

b. The CDC collects NHANES data annually by conducting an actual scale weighing of approximately 9,000 subjects in a clinical setting. The standard deviation of the sample was 47 pounds. The CDC last published results from NHANES in 2000. Additional information on NHANES can be found at the following Web sites:

(1) General information. http://www.cdc.gov/​nchs/​nhanes.htm.

(2) Analytic and reporting guidelines. http://www.cdc.gov/​nchs/​data/​nhanes/​nhanes3/​nh3gui.pdf.

(3) Data files for 1999-2000 survey. http://www.cdc.gov/​nchs/​about/​major/​nhanes/​NHANES99_​00.htm.

c. The FAA used most recent NHANES data set from surveys conducted in 1999 and 2000 to calculate the standard average passenger weights used in this advisory circular (AC). From this data set, the FAA separated out a separate data set of individuals who had not yet reached their 13th birthday to determine average child weight. From the remaining adult data set, the FAA removed all weight data that indicated the subject was clothed during the weighing and removed all data points more than two standard deviations from the mean. The FAA then calculated the average weights for males and females in the remaining data set.

2. Standard average bag weights.

To determine standard average weights for different types of bags, the FAA closely examined previous surveys conducted by operators, including several surveys conducted in response to FAA Notice 8400.40, Weight and Balance Control Programs for 10 to 19 Seat Airplanes Operated Under 14 CFR 121. The results of those surveys are summarized in Table 2-1.

Appendix 3. Sample Operational Loading Envelope

1. Introduction.

The following is an example of how to develop an operational loading envelope. For this example, a hypothetical 19-seat commuter category aircraft is used. Although this example uses inches to measure fuselage station, an operator may choose to use an index system for convenience.

2. Assumptions for this example.

a. Passenger weight. Because the aircraft is certificated under the commuter category of Title 14 of the Code of Federal Regulations (14 CFR) part 23 and because it is originally type-certificated for 5 or more passenger seats, it would be appropriate to use the average weights listed in Chapter 3, Section 2. For this example, it is assumed that the operator does not have a carry-on bag program. Therefore, the operator should use a standard average passenger weight of 189 pounds in winter and 184 pounds in summer. For this example, a standard average passenger weight of 189 pounds is used. The operator also assumes that passengers are distributed throughout the cabin in accordance with the window-aisle-remaining method. Note that because this aircraft has only two window seats per row, the operator may reasonably assume that passengers begin seating themselves in the front of the cabin and select the most forward seat available.

b. Bag weights. For this example, the operator assumes that a checked bag weighs 30 pounds and a plane-side loaded bag weighs 20 pounds.

c. Interior seating. For this example, consider a commuter category 19-seat aircraft with the interior seating diagram shown in Figure 3-1.

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3. Curtailments for passenger seating variation.

a. Establishing zones. The operator elects to separate the passenger cabin into three zones. Zone 1 will contain rows 1 to 3, zone 2 will contain rows 4 to 6, and zone 3 will contain rows 7 to 9.

b. Determining the centroid of each zone. When using cabin zones, an operator assumes that all passengers are sitting at the centroid of their zone. To find the centroid of each zone—

(1) Multiply the number of seats in each row of the zone by the location of the row,

(2) Add each number calculated in step 1, and

(3) Divide the number in step 2 by the total number of seats in the zone.

Note:

For this sample aircraft, see Tables 3-1 through 3-3 below.

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c. Comparing loading assumptions. To determine the appropriate amount of curtailment, the operator should compare aircraft loading based on the window-aisle-remaining assumption with aircraft loaded based on the assumption that passengers are sitting at the centroid of their respective zones. An operator may determine the appropriate curtailment by comparing the moments resulting from these assumptions and identifying the loading scenarios that result in the most forward or aft center of gravity (CG) location. See Tables 3-4 through 3-12 below.

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(1) Curtailment calculation for zone 1.

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(2) Curtailment calculation for zone 2.

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(3) Curtailment calculation for zone 3.

(4) Determining the most adverse loading. It is important that an operator examine the above results for each zone and determine which loading scenario results in the greatest difference in moments. For zones 1 and 2, having two, three, or four passengers in the zone results in the largest difference between the moments. For zone 3, having four passengers in the zone results in the largest difference. In this case, the operator should curtail the manufacturer's loading envelope forward and aft by the sum of these moments, 36,666 inch-pounds, to account for the potential variation in passenger seating. In this example, the 36,666 inch-pounds is the sum of 11,340 from Table 3-6; 10,962 from Table 3-9; and 14,364 from Table 3-12.

(5) Using actual seating location. Alternatively, an operator may reasonably avoid the above curtailment calculations by determining the actual seating location of Start Printed Page 51529each passenger in the cabin. By eliminating potential variation in passenger seating, an operator would not need to make assumptions about passenger seating and would not need to curtail the loading envelope accordingly. An operator choosing to use actual seating location should have procedures in place to ensure that passengers sit in their assigned location.

4. Other curtailments to the manufacturer's loading envelope.

a. Variation in passenger weight. Because the operator in this example elects to use standard average weights on a small-cabin aircraft, an additional curtailment for potential variation in passenger weight is required. The operator should curtail the manufacturer's loading envelope by 23,791 inch-pounds forward and aft to account for the variation in passenger weight. A full explanation of this calculation is contained in Appendix 4.

b. Variation in fuel density. Because the loading of fuel does not significantly change the CG of the aircraft, the operator would not need to provide a curtailment for variation in fuel density.

c. Fuel movement in flight. For this sample aircraft, the manufacturer has considered the movement of fuel in flight. Therefore, the operator does not need to include additional curtailments in the operational loading envelope.

d. Fluids. The sample aircraft does not have a lavatory or catering.

e. Bags and freight. The sample aircraft has an aft bag compartment split into two sections. If the operator has procedures in place to restrict the movement of bags between the two sections, no additional curtailment to the envelope is required.

f. In-flight movement of passengers and crewmembers. Because there are no flight attendants and the aircraft is not equipped with a lavatory, it is reasonable to assume that passengers or crewmembers will not move about the cabin in flight.

g. Movement of flaps and landing gear. The manufacturer of the sample aircraft has considered the movement of flaps and landing gear in the development of its loading envelope. The operator does not need to include any additional curtailments in its operational loading envelope for the movement of those items.

h. Fuel consumption. To ensure the sample aircraft remains within the manufacturer's CG limits as fuel is consumed, the operator should curtail the aft CG at weights less than the zero-fuel weight by 8,900 inch-pounds. In this example, the 8,900 inch-pounds is the fuel burn deviation that would bring the aircraft outside the aft CG limit during the course of flight.

5. Operational loading envelope diagrams.

a. Figure 3-2 below shows the operator's curtailments to the manufacturer's loading envelope, based on the assumptions made about variations in passenger seating and weight, as well as fuel consumption.

b. To expand the operational loading envelope, an operator could choose to use the actual seating location of passengers in the cabin and eliminate the curtailment for variations in passenger seating. Figure 3-3 below shows the expansion of the operational loading envelope.

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Appendix 4. Additional Curtailments to CG Envelopes To Account for Variations to Passenger Weights

a. The use of average weights for small cabin aircraft requires consideration of an additional curtailment to the center of gravity (CG) envelope for passenger weight variations and male/female passenger ratio. This curtailment is in addition to the standard curtailments discussed in Chapter 2.

(1) Passenger weight variation is determined by multiplying the standard deviation (from the source of the average passenger weight used) by the row factor from Table 4-1. The following table ensures a 95-percent confidence level of passenger weight variation, using the window-aisle-remaining seating method.

Start Printed Page 51531

(2) Protect against the possibility of an all-male flight by subtracting the difference between the male and average passenger weight.

(3) The sum of these two provides an additional weight to be used for CG curtailment, similar to the way in which passenger seating variation is calculated.

b. If the operator chooses to use the passenger cabin zone concept (as described in Appendix 3) and apply this concept to account for variation in passenger weight, then the row factor in Table 4-1 corresponding to the number of rows in each zone should be used. For the purposes of this curtailment, the zone can be no smaller than two rows, if row count is used for passenger seating calculations. Therefore, if an operator chooses to use row count, the operator must use the row factor for two rows.

c. Calculation of the curtailment passenger weight variation is decided by multiplying the standard deviation by the correction factor and adding the difference between male and female passenger weight. For example, assuming a 47 pound standard deviation, the difference between the average passenger weight and an all-male weight is 10 pounds (from 1999-2000 National Health and Nutrition Examination Survey (NHANES) data), and a sample aircraft with 9 rows in a 2-abreast configuration. The additional weight to be curtailed is determined as:

Weight for Additional Curtailment = (47 × 1.70) + (10) = 90 lbs

d. For the example, the additional curtailment should be accomplished by assuming passenger loading at 90 pounds using the program method for passenger seating variation (e.g., window-aisle-remaining). Using the window-aisle-remaining method, the additional curtailment in the example is determined to be 62,310 inch-pounds forward and aft. Table 4-2 displays the calculations used in this example.

Note:

The following definitions describe the parameters used in the sample:

  • Seat Centroid: Location of passenger weight at seat.
  • Seat Moment: Additional passenger weight × seat centroid.
  • Total Weight: Sum of additional passenger weights (running total).
  • Total Moment: Sum of additional passenger moments.
  • Moment Deviation: Difference between total moment and moment generated by assuming additional passenger weight is located at the cabin centroid (323.8 in).
Start Printed Page 51532

Appendix 5. Options To Improve Accuracy

A number of options are available that enable operators to deviate from standard assumed weights and may also provide relief from constraints required when assumed averages are used. These options include:

(1) Surveys. Surveys may be accomplished for passenger weights (to include carry-on bags), checked baggage weights, male/female ratios and fuel densities. These surveys may be conducted for entire operator route systems, or by specific market or region. Surveys practices and data reduction must conform to the requirements defined in this advisory circular (AC). Use of surveys may allow an operator to use passenger and baggage weights less than the standard specified in this AC. Also, a survey may find that the assumed male/female ratio is incorrect and appropriate adjustments must be made. For example, let's assume the following results from an approved passenger and baggage survey.

Male passenger weight (M) = 183.3 pounds

Female passenger weight (F) = 135.8 pounds

Difference between male and average passenger weights = 24.0 pounds

Standard deviation of total sample (Sigma) = 47.6 pounds

Male/female ratio (Pax Ratio) = 50.6 percent

Checked baggage weight = 29.2 pounds

Baggage checked plane-side = 21.3 pounds

Carry-on and personal items weight (CO Wt) = 10.4 pounds

Carry-on and personal items per passenger ratio (CO Ratio) = 0.82 pounds

Survey conducted in summer months

The resulting assumed passenger weight for loading is expressed as:

Passenger Weight = M × Pax Ratio + F × (1 − Pax Ratio) + CO Wt × CO Ratio

And is determined as:

Summer Passenger Weight = 0.506 × 183.3 + (1 − 0.506) × 135.8 + 10.4 × 0.82 = 169 lb

Winter Passenger Weight = 169 + 5 = 174 lb

Survey results would also be used to determine the additional curtailment for variations to passenger weight. Assuming a 19-seat aircraft in 2-abreast configuration in our example, the additional weight to be curtailed would be:

Additional Weight for Curtailment = (47.6 × 1.70) + 24 = 104.9 lb

Also in our example, the assumed checked baggage weight is 30 pounds. Plane-side loaded bags would be assumed to weigh 20 pounds. (These weights are the standard average weights provided for a no-carry-on baggage program as described in Chapter 3, Section 2).

(2) Actual Weights. It is permissible to use actual weights in lieu of standard average, segmented, or survey-derived average weights (if applicable). Parameters that may use actual weights include passenger weights, checked baggage weights, carry-on bag weights, crew weights, and fuel density/weight.

(3) Passenger Cabin Zones and Row Count. Passenger cabins may be split up into zones provided an acceptable procedure for determination of passenger seating is included (e.g., use of seat assignments or crew counts seated passengers by zone). If zones are used, it may be reasonable for the operator to reduce the center of gravity (CG) passenger seating curtailment suggested in this AC by accommodating variations within each individual zone separately and totaling the results. Passenger row count allows the operator to eliminate the seating variation by accounting for where the passenger is actually seated.

An example of use of passenger zones follows.

Assume an aircraft interior as displayed in Figure 5-1.

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Assume that for weight and balance purposes, it is desirable to break the cabin up into three passenger zones. The passenger zones will be determined as zone 1 (rows 1-3), zone 2 (rows 4-6), and zone 3 (rows 7-9). Use of the window-aisle-remaining method will be used in each zone to provide a total curtailment to the CG envelope. (For this sample aircraft, window-aisle-remaining method simply becomes forward and aft end loading). For each zone, a zone centroid must be calculated by counting the total number of seats and averaging their location.

Zone 1 centroid = (2 × 198.0 + 2 × 228.0 + 2 × 258.0) / (2 + 2 + 2) = 228.0 in.

Zone 2 centroid = (2 × 289.0 + 2 × 318.0 + 2 × 347.0) / (2 + 2 + 2) = 318.0 in.

Zone 3 centroid = (2 × 377.0 + 2 × 407.0 + 3 × 436.0) / (2 + 2 + 3) = 410.9 in.

Assuming the standard winter passenger weight of 195 pounds is used for the curtailment, the calculation of total moment is required for comparison to moment assuming each passenger is seated at the centroid of each passenger zone. The total moment is found by summing the individual moments calculated at each occupied seat in the window-aisle-remaining progression.

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The curtailment for passenger seating variation is determined by adding the largest delta moments from each of the passenger zones. In our example, the curtailment to the forward CG limit for passenger seating variation is −37,719 inch-pounds (−11,700 + −11,310 + − 4,709). Similarly, curtailment to the aft limit of the CG envelope using window-aisle-remaining method loading from the most aft seat row moving forward (in each zone) would result in an adjustment of 37,719 inch-pounds. Figures 5-2 through 5-4 graphically show the curtailments for each passenger zone through use of forward and aft end loading using our example.

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(4) Actual M/F Counts. Loading systems may use separate male and female assumed passenger weights for each operation. If the operator's weight and balance program is approved for use of male/female weights, then the operator must count the number of male passengers and female passengers separately. The male and female weights used may be from the development of standard passenger weight as described in this AC or they may be determined through an operator-developed survey as also described in this AC. Use of male/female weights may be for entire operations or for a particular route and/or region of flying.

An example of how male/female ratios can be applied to weight and balance systems follows.

Assuming the operator is using the survey results as described in subparagraph (1) above, the assumed male and female passenger weights, including average carry-on baggage, are computed as:

Male passenger weight (summer) = 183.3 + 10.4 × 0.82 = 192 lb

Male passenger weight (winter) = 192 + 5 = 197 lb

Female passenger weight (summer) = 135.8 + 10.4 × 0.82 = 144 lb

Female passenger weight (winter) = 144 + 5 = 149 lb

The weight and balance manifest would provide for identification of male/female identification and the passenger weights would be summed accordingly. For instance, 7 male and 11 female passengers would result in a total passenger weight of (7 × 192) + (11 × 144) = 2,928 pounds.

(5) Adolescent (Child) Weights. In most circumstances, an operator may consider any passenger less than 13 years of age, who is occupying a seat, to weigh less than an adult passenger as described in this AC. The standard adolescent child weights can be found in Table 3-1 of Chapter 3.

(6) Standard Weights With Approved No-Carry-on Baggage Program.

Summer Passenger Weight = 184 lb

Winter Passenger Weight = 189 lb

Checked Baggage Weight = 30 lb each

Baggage Checked Plane-side = 20 lb each

Inclusion in the no-carry-on baggage program does not preclude use of actual or surveyed weights for passengers, carry-on/personal items, checked baggage, or baggage checked plane-side.

(7) Automation. Automation may also be used to provide a more accurate weight and balance program. Examples of automation include use of seat assignments for the determination of passenger moment and historical seating to determine passenger moment.

Appendix 6. Sample CG Envelope Development

Outlined below is an example of the development of a center of gravity (CG) envelope construction for a 19-seat commuter category aircraft. The sample system uses a CG diagram displayed in inches. Operators' systems may use a variety of methods to display CG diagram, including an Index system detailed in Chapter 2, Section 2 and in Appendix 3.

Sample Development of Weight and Balance System for 19-Seat Aircraft

a. CG Envelope Construction. The certified CG envelope provided by the manufacturer must be examined for the following curtailments.

(1) Variations to Passenger Seating (Outlined in Chapter 2). In this example, the window-aisle-remaining method was used considering a passenger weight of 189 pounds and using 3 passenger zones, where zone 1 is defined as rows 1-3, zone 2 is defined as rows 4-6, and zone 3 is defined as rows 7-9. (189 lb/pax is used since the operator will be using a no-carry-on baggage program as detailed later on in this sample exercise). The resulting curtailment for use of 3 passenger zones is 36,600 inch-pounds forward and aft.

(2) Variations to Passenger Weight (Outlined in Appendix 4). Since the sample Start Printed Page 51538aircraft falls into the group of aircraft requiring full evaluation of small cabin aircraft rules, application of a curtailment due to variations to passenger weight is required.

(a) Use of Passenger Zone Concept for Curtailment. Considering three cabin zones with each zone containing three rows in a 2-abreast configuration, the required row factor (see Appendix 4, Table 4-1) is 2.41. The row factor is multiplied by the standard deviation and the difference between average male and average female weights is added to provide the additional weight consideration. In our example, the standard deviation is calculated from the National Health and Nutrition Examination Survey (NHANES) data as 47 pounds, and the difference between average all-male and average passenger weights is 10 pounds. The resulting additional weight for curtailment is 47 × 2.41 + 10 = 123 pounds. This additional weight is applied per the window-aisle-remaining concept for each cabin zone independently and the results are summed to determine the amount of curtailment. In this case, the curtailment is found to be 23,791 inch-pounds forward and aft.

(b) Use of Row Count for Curtailment. When using row count, the required row factor is 2.96. The row factor is multiplied by the standard deviation and the difference between average male and average female weights is added to provide the additional weight consideration. In our example, the standard deviation is calculated from the NHANES data as 47 pounds, and the difference between average all-male and average passenger weights is 10 pounds. The resulting additional weight for curtailment is 47 × 2.96 + 10 = 149 pounds. This additional weight is applied as if a 2-row passenger zone concept is used for passenger seating. The resulting curtailment is determined to be 16,657 inch-pounds forward and aft.

(3) Variations to Fuel Density. Since the loading of fuel does not significantly shift the CG for the aircraft, it is not necessary to correct for variations in fuel density (i.e., the correction is negligible).

(4) Fuel Movement in Flight. Fuel movement has been considered by the manufacturer in the development of the certified envelope, making an additional curtailment unnecessary.

(5) Fluids. The sample aircraft does not have a lavatory and there is no catering.

(6) Baggage and Freight. The sample aircraft provides a baggage web in the aft baggage compartment, splitting the compartment into forward and aft sections. In our example, we assume the operator is making full use of this web and the movement of baggage is restricted. No curtailment is necessary.

(7) In Flight Movement of Passengers and Crew. Since there are no flight attendants and no lavatories on the sample aircraft, it is reasonable to assume that the passengers will remain in their seats for the duration of the flight. Therefore, it is not necessary to curtail the limits for passenger and crew in-flight movement.

(8) Movement of Flaps and Landing Gear. In the case of the sample aircraft, the manufacturer has included consideration of flap and landing gear movement in the development of the certified envelope. No additional curtailment is necessary.

(9) Fuel consumption. The fuel vector for the sample aircraft provides a small aft movement that requires a −8,900 inch-pounds curtailment to the aft zero fuel weight limits to ensure the aircraft does not exceed the aft limit as fuel is burned. This equates to a −0.8 inch curtailment at an estimated operational empty weight of 11,000 pounds with a linear transition to a −0.6 inch curtailment at MZFW of 16,155 pounds. In this example, the 8,900 inch-pounds is the fuel burn deviation that would bring the aircraft outside the aft CG limit during the course of flight.

b. Three operational curtailments to the sample aircraft CG envelope are required. These are for variations to passenger seating and passenger weight, and fuel burn-off. Figure 6-1 displays the operational CG envelope highlighting the required curtailments.

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c. Assuming the operator wishes to widen the envelope, use of actual passenger seating (row count) may be used to eliminate the curtailment required for variations to passenger seating. Figure 6-2 displays a CG envelope that makes use of actual passenger seating.

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d. No-Carry-On Baggage Program. This example assumes a no-carry-on bag program. This allows consideration of reduced passenger weight to 184 pounds (summer) and 189 pounds (winter). Carry-on bags checked at the gate or “plane-side loaded” will be counted as 20 pounds/bag. Bags checked at the ticket counter will remain at 30 pounds/bag.

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BILLING CODE 4910-13-P

BILLING CODE 4910-13-C

BILLING CODE 4910-13-P

[FR Doc. 04-18905 Filed 8-18-04; 8:45 am]

BILLING CODE 4910-13-C