What is a weight and balance loading chart and how does it work?

A weight and balance loading chart is an FAA-approved graph or table, specific to an aircraft's Pilot's Operating Handbook or Airplane Flight Manual, that allows you to determine whether the loaded center of gravity falls within the approved envelope without performing lengthy moment arithmetic by hand. You plot each occupant, fuel load, and baggage weight on its corresponding scale or loading graph to read off the moment contribution, then combine the values on a CG envelope graph to confirm the point falls within limits. This graphical method is described in the Pilot's Handbook of Aeronautical Knowledge as an acceptable and efficient alternative to the full computational method.

How do you use a loading graph to check weight and balance before a flight?

Start by entering the weight of each load item — pilot, passengers, fuel, and baggage — on the appropriate loading graph for that station, reading across to find the corresponding moment index value for each item. Add all weights to verify the total does not exceed the aircraft's maximum certificated gross weight, and add all moment index values to get a total moment index. Finally, plot the total weight against the total moment index on the CG moment envelope graph; if the point falls inside the shaded or bounded area, the aircraft is within approved CG limits as outlined in the Pilot's Handbook of Aeronautical Knowledge chapter on weight and balance.

What's the difference between a loading chart and a CG envelope graph in weight and balance?

A loading chart (or loading graph) is used first — it converts the weight at each individual station into a moment or moment index value, one load item at a time, using station-specific curves. The CG envelope graph is used second — it plots the aircraft's total weight against the combined total moment or moment index to show whether the overall loaded condition is safe. Together, the two tools replace the manual process of multiplying each weight by its arm and summing moments, as explained in the Pilot's Handbook of Aeronautical Knowledge, making the verification faster and less prone to arithmetic errors.

Using Weight and Balance Loading Charts and Graphs

Every aircraft is certified to operate within a carefully defined range of weights and center-of-gravity (CG) positions. Fly outside those limits and the aircraft may become uncontrollable or structurally overstressed — consequences that are equally unacceptable whether you are a pilot or an aviation maintenance technician (AMT) signing off a weight-and-balance record. Fortunately, aircraft manufacturers and FAA-approved data provide loading charts and graphs that simplify the arithmetic dramatically. Instead of computing every moment from scratch, a technician or pilot can read values directly from a graph and check them against an envelope.

This article walks through the purpose, construction, and proper use of weight-and-balance loading charts and graphs as described in the FAA Weight and Balance Handbook (FAA-H-8083-1). Mastering these tools is essential both for the AMT General knowledge test and for day-to-day maintenance and return-to-service work.

Fundamental Concepts Behind the Charts

Before using any graph, you need to be fluent with four terms. Weight is the force of gravity on any object, measured in pounds. Arm is the horizontal distance, in inches, from the aircraft's datum — a reference plane chosen by the manufacturer — to the item being considered. Arms forward of the datum are negative; arms aft are positive (though some manufacturers use all-positive numbering). Moment is simply weight multiplied by arm (W × A), expressed in pound-inches or, more commonly in light aircraft, pound-inches divided by 1,000 (to keep numbers manageable). Center of gravity (CG) is the point at which the aircraft would balance, found by dividing total moment by total weight.

A loading chart or graph replaces the step of individually multiplying each item's weight by its arm. Instead, the manufacturer pre-calculates moments for typical load stations — the pilot seat, rear seats, baggage compartment, and fuel tanks — and presents them graphically. The user reads the moment directly for any given weight at that station, then adds all moments together and checks the sum against the CG envelope.

Types of Loading Charts and Graphs

Loading Charts (Table Format)

A loading chart is essentially a pre-computed table. For each load station, the chart lists weights in the left column and the corresponding moments (often in pound-inches ÷ 1,000) in the right column. To use it, you find the row matching the actual weight loaded at that station and record the moment. After repeating this for every station, you sum the weights and sum the moments, then divide total moment by total weight to find CG. You then compare that CG position against the forward and aft limits listed in the aircraft's approved flight manual or maintenance records.

Loading Graphs (Graphical Format)

A loading graph plots weight on one axis (typically the vertical axis) and moment on the other (horizontal axis). Each load station — pilot/front seat, passenger rear seat, fuel, baggage — is represented by its own diagonal line or curve on the same graph. To find the moment for a given station, locate the weight on the vertical axis, move horizontally to the line for that station, then drop straight down to read the moment on the horizontal axis. This single graphical step replaces the multiplication. Like the table method, all moments are then summed, total weight is summed, and the result is cross-checked against the approved envelope.

The CG Envelope Graph

The CG envelope is a separate — sometimes combined — graph with gross weight on the vertical axis and CG position (in inches from datum, or sometimes total moment) on the horizontal axis. A closed polygon (the envelope) marks the region of approved combinations. Once you have calculated total weight and total CG (or total moment), you plot that point on the envelope. If the point falls inside the polygon, the loading is acceptable. If it falls outside — too far forward, too far aft, or over maximum gross weight — the loading must be adjusted before flight or before the aircraft is returned to service.

Some manufacturers combine the loading graph and the CG envelope into a single chart to reduce the number of steps. In that design, you read moment index values from the loading graph, sum them, and plot total weight versus total moment index directly on the envelope — all on one page.

Step-by-Step Procedure for Using a Loading Graph

Identify the aircraft's basic empty weight and moment. These values come from the most recent weight-and-balance record in the aircraft maintenance records — not from the flight manual alone, because actual equipment changes (avionics additions, seat removals, etc.) alter the empty weight.
List every load item. This includes the pilot, each passenger, usable fuel, and all baggage or cargo. Do not forget to account for oil if it is not already included in the empty weight (most modern aircraft include full oil in the empty weight, but verify).
Use the loading graph to find the moment for each item. Locate the weight on the vertical axis, trace horizontally to the correct station line, and read down to the moment axis.
Sum all weights and all moments separately. Keep your arithmetic neat — errors here are the most common source of incorrect CG computations.
Plot the result on the CG envelope. Mark the point defined by total weight (vertical axis) and total moment or CG position (horizontal axis). Confirm the point lies within the approved polygon.
Document the computation. For maintenance purposes, the weight-and-balance calculation must be recorded whenever equipment changes are made that affect the empty weight or CG.

Why Loading Charts Matter for AMTs

An AMT's responsibility extends beyond structural repair and system maintenance. Any modification, equipment addition, or equipment removal that changes the aircraft's empty weight or CG must be accompanied by a revised weight-and-balance record. If an avionics shop installs a new GPS unit at a station well aft of the datum, the empty CG shifts aft. If it is aft of the limit with a light fuel load and a rear-seat passenger, the aircraft could be returned to service in an unsafe configuration. The AMT who performs or supervises such work must recompute the empty weight CG and update the aircraft records accordingly.

Additionally, during an annual inspection or 100-hour inspection, the technician should verify that the current weight-and-balance record reflects the actual configuration of the aircraft. Unauthorized equipment changes discovered during an inspection must be resolved before the aircraft can be approved for return to service.

Key Numbers and Rules

Maximum gross weight is a hard limit — no loading configuration may exceed it regardless of where the CG falls.
Forward CG limit is primarily a controllability boundary; exceeding it can make the aircraft nose-heavy and may prevent rotation or flare due to insufficient elevator authority.
Aft CG limit is a stability boundary; loading behind it reduces or eliminates the aircraft's natural tendency to return to level flight and can make spin recovery difficult.
Moments are often divided by 1,000 (or another constant) in light-aircraft charts to keep numbers small and readable — always confirm which units the specific chart uses before computing.
Usable vs. unusable fuel: Only usable fuel is counted as a load; unusable fuel is already included in the aircraft's empty weight and moment.
Zero fuel weight: Some larger aircraft have a maximum zero-fuel weight limit; exceeding it (even if total gross weight is within limits) can overstress the wing root.
The datum location is defined by the manufacturer and noted in the Type Certificate Data Sheet (TCDS). All arms are measured from this reference.

Common Test Traps

Using the wrong empty weight. The FAA test often provides two weight figures — one from the flight manual and one from the current maintenance record. Always use the most recent weight-and-balance record; equipment changes since manufacture may have altered the actual empty weight significantly.
Confusing moment index with moment. Some charts divide moment by 100 or 1,000 to create a "moment index." Mixing raw moment values with index values will produce a wildly incorrect CG calculation.
Forgetting that a point inside the envelope at takeoff weight might fall outside at landing weight. As fuel burns off, both weight and CG shift. A loading that starts legal may drift aft of limits mid-flight, particularly in aircraft with fuel tanks located near the aft CG limit.
Ignoring unusable fuel. Students sometimes subtract all fuel weight from the empty weight calculation. Unusable fuel is already embedded in the published empty weight and must not be double-counted or subtracted.
Assuming the flight manual weight-and-balance data is current. If an avionics upgrade, interior re-configuration, or STC modification has been incorporated, the actual aircraft weight and CG will differ from the original flight manual values. The maintenance record is the authoritative source.

Weight and balance work rewards careful, methodical arithmetic. Loading charts and graphs exist to make that arithmetic faster and more intuitive, but they demand that you use the right chart for the right aircraft, verify your source documents, and always confirm that your final plotted point sits comfortably inside the approved envelope — not just touching the boundary, but with a reasonable margin for the inevitable small uncertainties in measured weights and arms.