Aircraft Weight and Balance: What a Pilot Needs to Know
Aircraft weight and balance is the process of confirming, before every flight, that an aircraft is loaded below its maximum weight limits and that its center of gravity (CG) stays within the manufacturer’s approved range. Getting it wrong changes how the airplane climbs, handles, and stops, and carrying current weight and balance data on board is a legal requirement. Below are the key terms, the weight limits that matter, how much common aircraft weigh, and how pilots keep the CG within limits.
Key Takeaways
- Weight and balance means keeping an aircraft under its weight limits and its center of gravity within the approved range.
- Gross weight is the basic empty weight plus the useful load (passengers, cargo, and fuel). It must stay below both the maximum takeoff weight and the maximum landing weight.
- The center of gravity is found by dividing total moment by total weight, and it must fall inside the aircraft’s CG range.
- A CG too far forward makes the nose heavy; a CG too far aft makes the aircraft unstable and harder to recover from a stall.
- Aircraft weights vary widely: a Cessna 172 weighs about 1,700 lb empty, while a Boeing 737-800 weighs about 91,300 lb empty.
- Weight and balance data must be on board for every flight (14 CFR 91.9).
Weight and Balance Terms at a Glance
| Term | What it Means |
|---|---|
| Standard empty weight | The airframe, engine, fixed equipment, unusable fuel, and full operating fluids, with no optional equipment. |
| Basic empty weight (BEW) | Standard empty weight plus any optional or special equipment installed. |
| Useful load | Maximum gross weight minus basic empty weight; the weight available for crew, passengers, baggage, cargo, and usable fuel. |
| Payload | The weight of passengers, baggage, and cargo (fuel not included). |
| Gross weight | Basic empty weight plus the useful load actually carried on a given flight. |
| Maximum takeoff weight (MTOW) | The maximum weight the manufacturer certifies for takeoff. A fixed structural limit that does not change with temperature, altitude, or runway length. |
| Maximum ramp (taxi) weight | The maximum weight for ground operations, including fuel burned during start, taxi, and run-up. |
| Zero fuel weight (ZFW) | Total weight with no usable fuel on board. |
| Maximum landing weight (MLW) | The maximum certified weight for landing. A fixed limit, usually lower than MTOW. |
| Arm | The horizontal distance, in inches, from the reference datum to an item. |
| Moment | Weight multiplied by arm (measured in pound-inches). |
| Center of gravity (CG) | The point where the aircraft would balance; found by dividing total moment by total weight. |
| CG range / limits | The forward and aft boundaries the CG must stay within, set by the manufacturer. |
How Aircraft Weight is Measured
Before discussing how the weight of an aircraft is calculated, there are some terms pilots need to know to help their understanding: basic empty weight, gross weight, maximum takeoff weight, and maximum landing weight.
These terms are useful for getting a sense of the various factors that are taken into account when considering an aircraft’s weight.
The first term, basic empty weight (BEW), is the total weight of the aircraft itself, any optional equipment that is onboard, unusable fuel stored onboard, and full operating fluids. Operating fluids include those that are required for planes to work properly, such as coolant and engine oils.
The second term, gross weight, is how much the aircraft will actually weigh during the flight. This is calculated by taking the BEW and adding the weight of passengers, crew, cargo, and fuel.
The third term, maximum takeoff weight (MTOW), refers to the maximum weight at which an aircraft is certified to take off. This is a fixed value and does not change, regardless of temperature, altitude, or runway length.
The final term, maximum landing weight (MLW), is the maximum weight that an aircraft is certified to land. Like MTOW, it is a fixed certified limit set by the manufacturer, and it is usually lower than MTOW because landing puts more stress on the airframe than takeoff.
Two more terms round out the picture. Useful load is the weight available for people, cargo, and fuel, found by subtracting the basic empty weight from the maximum gross weight. Payload is the passengers, baggage, and cargo, not counting fuel.
With these terms in mind, a flight’s gross weight is the basic empty weight plus the useful load (passengers, crew, cargo, and fuel). This gross weight must stay below both the MTOW and the MLW. If the gross weight surpasses either of these limits, then an aircraft cannot legally take off or land.
How Much Does an Airplane Weigh?
An airplane can weigh approximately 1,700 pounds when empty for a light training aircraft or more than 900,000 pounds when a large passenger jet is fully loaded for takeoff. The exact answer depends on the aircraft model and whether airplane weight refers to empty weight or maximum takeoff weight.
Empty weight generally includes the aircraft structure, engines, installed equipment, unusable fuel, and required operating fluids. It does not include the usable fuel, passengers, baggage, or cargo added for a particular flight. Maximum takeoff weight represents the highest certified weight at which the aircraft may begin its takeoff roll.
The difference between these figures can be substantial. A Cessna 172 weighs about 1,700 pounds empty and has a maximum takeoff weight of approximately 2,550 pounds. At the other end of the range, a Boeing 747-400 may weigh around 407,000 pounds empty but reach approximately 910,000 pounds at its maximum takeoff weight. Business jets and other commercial airliners fall between these examples.
The table below compares representative empty and maximum takeoff weights for several aircraft categories. Figures are rounded because weights can vary by model, configuration, installed equipment, and operating specifications.
| Aircraft | Typical Empty Weight | Typical Max Takeoff Weight |
|---|---|---|
| Light single-engine trainer (Cessna 172) | ~1,700 lb | ~2,550 lb |
| Light business jet (Embraer Phenom 300) | ~11,800 lb | ~18,000 lb |
| Narrow-body airliner (Boeing 737-800) | ~91,300 lb | ~174,200 lb |
| Wide-body airliner (Boeing 777-300ER) | ~370,000 lb | ~775,000 lb |
| Jumbo jet (Boeing 747-400) | ~407,000 lb | ~910,000 lb |
An aircraft’s actual weight for a flight typically falls between its empty weight and the applicable maximum limit. Because the number changes with the amount of fuel, baggage, cargo, and people on board, pilots must complete an airplane weight and balance calculation using the conditions for each flight.
How Aircraft Weight Affects Performance
Knowing how an aircraft’s weight affects its performance is equally important to assessing its weight. An aircraft’s ability to fly requires operating within certain parameters, including specific weight and balance. If either of these are out of the acceptable range, it can affect an aircraft’s performance and its safe operation. This is why an aircraft’s weight and balance are vital considerations.
According to the Federal Aviation Administration (FAA), aircraft affected by excess weight will encounter performance issues, which include but are not limited to: requiring longer runways and higher speeds for takeoff, reduced maneuverability, and an increase in fuel consumption.
Runways provide the necessary space for planes to reach takeoff speeds and to safely decelerate when landing. If a runway is too short, planes may not be able to take off or could face safety risks during landing due to insufficient room to slow down. Heavier planes are slower therefore require more runway space to reach the appropriate takeoff speed. Runways typically range between 1,000 feet long at small airports to 18,000 feet at larger airports, so it is important for pilots to determine if the runway at their airport is long enough to support the weight of their aircraft.
An aircraft’s ability to maneuver is reduced as its weight increases. If an aircraft is overloaded, pilots may have a more difficult time operating it than lightweight aircraft. Aircraft weight increases can result in reduced angles and rates of climb, lower maximum altitudes, lower cruising speeds, and higher stalling speeds, all of which are factors that lie within maneuverability.
The heavier an aircraft is, the more fuel it will consume to cover the same distance as a plane with a lighter weight. This is due to the fact that the plane’s engine has to work harder to maintain lift, the force that keeps airplanes in the air.
Some aircraft are better equipped than others to handle heavier loads, such as newer aircraft with higher fuel efficiency than older models.
For these reasons, flying a heavy aircraft as opposed to a lighter version of the same aircraft may feel like flying an entirely different machine.
Safety Considerations
If an aircraft’s weight exceeds the MTOW or MLW, then its safety is compromised. An aircraft weighing more than its MTOW may not be able to gain enough altitude before the end of the runway, which may result in a dangerous event. On the other hand, an aircraft weighing more than its MLW may hit the runway too fast, also causing disaster. In addition to these issues, an overweight aircraft may suffer structural damage during in-flight maneuvers, which can cause damage to the fuselage or wings, posing safety risks for those on board.
“When I teach weight and balance, I emphasize that it is not simply a calculation we complete before a flight. It is an important part of the pilot’s overall risk management and preflight decision making process. I encourage students to use actual passenger, baggage, and loading information whenever it is available rather than relying on assumptions, because even relatively small differences can affect center of gravity, aircraft performance, and the safety margins available to the pilot. My goal as a Check Airman at Phoenix East Aviation is to help students develop disciplined habits early in their training so that evaluating weight, balance, and aircraft performance becomes a consistent part of every flight they conduct.”
– Esteban Lasso, Instructor at Phoenix East Aviation
Maintaining Records
It is vital that records are kept to document the weight and balance of an aircraft for every flight. For commercial airlines, this is not the responsibility of the pilot, but the airframe and powerplant (A&P) mechanic. The A&P Mechanic is solely responsible for making sure the weight and balance records are kept current. However, the pilot is responsible for checking these records and ensuring the aircraft is at a safe weight before every flight. If a pilot is flying solely for recreation, they should be maintaining their own weight and balance records.
Center of Gravity Limits
An aircraft’s center of gravity is just as important as its weight. The center of gravity limits are the boundaries that an aircraft’s center of gravity must remain within while in flight. There are both longitudinal and lateral center of gravity limits. As the center of gravity of the aircraft can change during flight, due to such things as fuel consumption and cargo shifts, a pilot must pay careful attention to ensure that the center of gravity never leaves its boundaries. Should this happen, the consequences can be disastrous. For example, if the center of gravity goes too far forward, the plane will become nose-heavy, which can make it difficult to raise the nose. This can cause a crash during landing.
The CG is worked out using two simple terms. The arm is the horizontal distance, in inches, from a fixed reference point called the datum to each item on board. The moment is that item’s weight multiplied by its arm. Add up every moment, divide by the total weight, and the result is the center of gravity, which must fall within the forward and aft limits published for the aircraft.
Additional FAA Regulations and Requirements
There are certain Federal Aviation Administration (FAA) regulations and requirements that must be kept in mind when operating an aircraft. These include:
- All weight and balance data must be on board the airplane.
- Data must be entered accurately if software is used for calculating weight and balance.
- Aircraft are required to be under MTOW and MLW.
- An aircraft’s center of gravity is required to be within the center of gravity limits at all times. If the CG position changes by more than 0.5% of the total CG range, the weight and balance must be reestablished.
- Pilots must be able to perform weight and balance calculations at any moment if required.
These regulations are intended to ensure all aircraft are operated safely. Pilots must always comply with these regulations.
Frequently Asked Questions
What is the maximum weight of an aircraft?
The maximum weight depends on the aircraft’s certified limits. Maximum takeoff weight is the highest weight permitted at the start of the takeoff roll, while maximum landing weight is the highest permitted for landing and may be lower.
What is useful load on an aircraft?
Useful load is the difference between an aircraft’s maximum allowable gross weight and its basic empty weight. It represents the weight available for the pilot, passengers, baggage, cargo, and usable fuel.
How do you calculate an aircraft’s center of gravity?
Calculate the center of gravity by dividing the aircraft’s total moment by its total weight. Each item’s moment is found by multiplying its weight by its arm, or distance from the reference datum. The resulting CG must remain within the manufacturer’s approved limits.
Do you need to check weight and balance before every flight?
Yes, pilots must determine that the aircraft is properly loaded and safe to operate before each flight. Changes in fuel, passengers, baggage, or cargo can affect both the total weight and center of gravity, even when the aircraft flew within limits previously.
Why is aircraft weight and balance important?
Weight and balance in aviation directly affects an aircraft’s takeoff distance, climb performance, stall speed, handling, fuel consumption, and landing performance. Excess weight or a center of gravity outside the approved range can make the aircraft difficult or unsafe to control.
Conclusion
Weight and balance comes down to two preflight checks: confirming the aircraft is under its weight limits and that the center of gravity sits within the approved range. Run it before every flight with actual weights, and the flight stays predictable from takeoff to landing. At Phoenix East Aviation, students learn to make this part of their preflight routine from day one. Contact our Admissions team at info2@pea.com to learn more about our flight training programs.
References:
