Accurate calculator for pilot flight planning, ensuring Center of Gravity (CG) safety compliance.
Aircraft Loading Configuration
Weight of standard aircraft.
Please enter a valid weight.
Distance from datum.
Total weight of front seat occupants.
Total weight of rear seat occupants.
1 Gallon Avgas = 6 lbs.
Center of Gravity (CG)
0.00 in
Aft of Datum
Status: Within Limits
Total Gross Weight
0 lbs
Total Moment
0
Fuel Weight
0 lbs
Station
Weight (lbs)
Arm (in)
Moment (in-lb)
Formula: Moment = Weight × Arm | CG = Total Moment ÷ Total Weight
CG Envelope Visualization
Blue area represents the safe flight envelope. Red dot is your current loading.
What is Calculating Weight and Balance Aviation?
Calculating weight and balance aviation refers to the critical process of determining the total mass of an aircraft and the location of its Center of Gravity (CG) relative to a specific reference point called the datum. Unlike driving a car, where weight distribution has a minor effect on handling, an aircraft's stability and performance are governed by strict physics limitations.
Every aircraft has a maximum gross weight and a specific Center of Gravity envelope defined by the manufacturer. If the plane is too heavy, it may not generate enough lift to take off. If the CG is too far forward or too far aft, the pilot may lose control of the pitch axis, leading to potentially catastrophic stalls or an inability to flare during landing.
This calculation is mandatory for every flight. It is used by student pilots, commercial airline dispatchers, and private aviators to ensure the aircraft remains within the certified flight envelope throughout the journey, accounting for fuel burn and payload.
Calculating Weight and Balance Aviation: Formula and Explanation
The mathematics behind calculating weight and balance aviation relies on the principle of moments. A "moment" is a rotational force calculated by multiplying a weight by its distance from the datum.
The Core Formula
Moment = Weight × Arm Center of Gravity (CG) = Total Moment ÷ Total Weight
Variables Definition
Variable
Meaning
Unit
Typical Range (Small GA Plane)
Weight
The force of gravity on the object (load)
lbs (pounds)
10 – 2,550 lbs
Arm
Horizontal distance from the reference datum
inches
30 – 100+ inches
Moment
The rotational tendency of the weight
in-lbs
50,000 – 150,000+
Datum
Imaginary vertical plane (reference point)
N/A
Usually firewall or propeller tip
Practical Examples of Weight and Balance
Example 1: The Solo Training Flight
A student pilot is preparing for a solo cross-country. We are calculating weight and balance aviation for a Cessna 172 type aircraft.
Basic Empty Weight: 1650 lbs @ 39.5″ Arm = 65,175 Moment
Pilot: 180 lbs @ 37.0″ Arm = 6,660 Moment
Fuel: 40 Gallons (240 lbs) @ 48.0″ Arm = 11,520 Moment
Total Weight: 2,070 lbs
Total Moment: 83,355 in-lbs
Resulting CG: 83,355 / 2,070 = 40.27 inches.
Interpretation: The aircraft is well under max gross weight (2,550 lbs) and the CG is centrally located. This is a very stable configuration.
Example 2: Overloading the Baggage Compartment
A pilot attempts to carry heavy equipment in the rear. This scenario highlights the danger of aft CG.
Basic Empty Weight: 1650 lbs @ 39.5″ Arm
Pilot & Pax: 400 lbs @ 37.0″ Arm
Rear Pax: 350 lbs @ 73.0″ Arm
Baggage: 120 lbs @ 95.0″ Arm (Heavy!)
Fuel: 30 Gallons (180 lbs) @ 48.0″ Arm
Total Weight: 2,700 lbs (Exceeds 2,550 limit)
Calculated CG: Shifts dangerously aft.
Financial & Safety Impact: Operating in this state is illegal and voids insurance coverage. The plane may become unrecoverable from a stall. The pilot must remove weight or shift it forward.
How to Use This Calculator
Enter Basic Empty Weight (BEW): Input the weight and arm found in your specific aircraft's POH (Pilot's Operating Handbook).
Add Occupants: Enter the weight of the pilot and front passenger. If carrying rear passengers, input their combined weight.
Input Fuel: Enter the fuel in gallons. The calculator automatically converts avgas (6 lbs/gal) to weight.
Check Baggage: Add any cargo weight in the baggage area.
Review the Chart: Look at the visual graph. The red dot MUST be inside the blue polygon.
Analyze Results: Check the "Status" indicator. If it is red/unsafe, reduce fuel or baggage weight.
Key Factors Affecting Weight and Balance Results
When calculating weight and balance aviation, several dynamic factors influence the outcome beyond simple addition:
Fuel Burn: As you fly, you burn fuel. This reduces total weight but also shifts the CG. If the fuel tank arm is different from the CG, the aircraft's stability changes mid-flight.
Density Altitude: While not a weight factor, high density altitude reduces the lift capability. A plane loaded to max gross weight at sea level may not be able to take off at a high-altitude airport on a hot day.
Retractable Gear: On complex aircraft, the moment of the landing gear changes as it retracts, shifting the CG slightly.
Zero Fuel Weight: Some aircraft have a structural limitation on how much weight can be carried in the fuselage vs. the wings to prevent structural bending.
Modification Changes: Installing new avionics or a new propeller changes the Basic Empty Weight and Arm, requiring an updated weight and balance amendment in the logs.
Fluid Densities: While Avgas is ~6 lbs/gal, Jet A is ~6.7 lbs/gal. Using the wrong density conversion when calculating weight and balance aviation can lead to dangerous errors.
Frequently Asked Questions (FAQ)
Why is calculating weight and balance aviation legally required?
It is required by FAA regulations (FAR 91.9) to ensure the aircraft is operated within its approved limitations. Flying outside these limits makes the aircraft unairworthy.
What happens if the CG is too far aft?
An aft CG makes the aircraft tail-heavy. This reduces longitudinal stability, makes stall recovery difficult or impossible, and increases cruise speed due to less tail downforce required.
What happens if the CG is too far forward?
A forward CG makes the aircraft nose-heavy. This increases stability but requires more back pressure to flare for landing, potentially leading to hard landings or nose-wheel damage. It also increases drag and fuel consumption.
How often must I recalculate weight and balance?
You must calculate it for every flight where the loading configuration changes. A standard calculation can be reused if the load (passengers, bags, fuel) is identical.
Does fuel weight change with temperature?
Yes, slightly. Fuel expands in heat, becoming less dense. However, pilots typically use the standard 6 lbs/gal for Avgas for safety margins unless precision is critical.
Can I use this calculator for any aircraft?
No. This calculator assumes a generic envelope similar to a Cessna 172. You must use the specific data and envelope charts from your aircraft's Pilot Operating Handbook (POH).
What is "Useful Load"?
Useful load is the difference between Max Gross Weight and Basic Empty Weight. It represents the weight available for pilot, passengers, fuel, and baggage.
How do I fix an overweight condition?
To return to safe limits, you must remove payload. Usually, this means draining fuel, removing baggage, or flying with fewer passengers.
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