“Aircraft Weight and Balance – Why Standard Weights Matter”

To fly safely, aircraft must be balanced and loaded correctly

Fortunately, we don’t have to

Because we use standard weight when calculating aircraft weight and balance

Today we will tell you how to calculate aircraft loads, explain the general concept, and discuss the factors that affect aircraft weight and balance

Let’s dive right in

Standard Weights for Aircraft Weights and Scales – Quick Reference Chart

The weight of various items carried on board the aircraft can be easily calculated using standard weights

Below you will find a quick reference chart detailing the standard weights used in aviation

You can use the following to calculate the weight of liquids carried on the plane: –

How to calculate aircraft weight using the chart above

Calculating liquid weight is really simple

All we need to do is multiply the total number of gallons on board the plane by the weight, taking into account the temperature

So, using the chart above, let’s assume we loaded 50 gallons of avgas onto our plane

Total Fuel Weight = Volume (in USG) x Weight Factor

Total weight of fuel = 50 x 601

Total fuel weight = 300lbs

Simple, right?

Why different liquids weight different amounts?

Different liquids weigh different amounts depending on their density

don’t worry

Generally speaking, each liquid has a different number of molecules based on a given volume

The more molecules, the more the liquid weighs

To put it in technical terms, heavier liquids have a higher density

This is called specific gravity

You might be surprised to learn that a given volume of gas, oil, and even alcohol and milk, weighs less than the same volume of water

don’t believe us?

Use the chart above using our calculation formula for ten gallons of water and compare it to ten gallons of oil!

Why do standard weights include temperature data?

The eagles among us may notice that there are two columns, which give different values ​​depending on temperature

When calculating aircraft mass and balance, we are primarily interested in weight, not volume

‘Volume’ is the total area of ​​a liquid taken up in space

Remember how we said liquids weigh different amounts depending on their density?

Well, that density (the number of molecules in a given volume of liquid) changes depending on the temperature of that liquid

As a general rule, you need to remember this

The volume of most liquids changes with temperature

Density = Mass / Volume

Density = Mass / Volume

If the volume goes up, it means that the mass is divided by a larger number, which makes the density less

While you may not think this is important, a relatively minor temperature change can make all the difference

This is especially true when lifting large volumes of liquid

Effects of weight and balance on aircraft behavior – 10 things to consider

Standard weights are critical to safe flight

Also, according to Title 14 of the Code of Federal Regulations, you must familiarize yourself with the gross weight of the aircraft

There are many things that are significantly affected by the weight of the plane, so getting to grips with mass and balance is really key

Here are several areas affected by aircraft weight and balance: –

Every plane will be designed with certain weight limits in mind

The weight on the gear and the forces generated while maneuvering are based on well-defined tolerances

Increased weight leads to increased stress on the aircraft

Too much weight will lead to too much stress, which is not good!

Fuel Efficiency and Range

If you have read our article on flight strength, you will already know that to maintain level flight, lifting must overcome weight

More weight means more lift

We need to create more thrust using the aircraft engine to overcome drag

So it is safe to say that a heavier aircraft will be less fuel efficient and have a shorter range!

There is a point when the wing stops producing lift and becomes less efficient

The speed at which the aircraft departs is influenced by the weight

The heavier the plane, the sooner we arrive at the departure

So it is very important to know how much the plane weighs

The plane is maneuvered around the center of gravity

This is the pivot point of the plane

The farther a force is applied from a pivot point, the greater its effect

The center of gravity is directly affected by where the mass is located on the plane

By moving and changing the center of gravity, we can ensure that we get the best handling characteristics

As we have already stated, the lift must exceed the weight for an airplane to fly

As lift is a function of airspeed, it would be fair to say that we need to fly faster to gain air when taking off if we have increased weight

Airplane brakes work by converting kinetic energy (a clever term for the plane’s forward speed) into heat energy (through friction)

The more weight, the greater the kinetic energy

Too much weight and the plane will not be able to stop in time

Include the need to increase air speed due to increased weight, and you may find that the required landing distance exceeds the actual landing distance!

Heavier aircraft percentage means that the aircraft’s cruise altitude will be lower

The maximum ceiling of the aircraft decreases with an increase in weight

The rate of climb is determined by the difference between the lift produced and the weight

With heavier weights, the difference is reduced

In areas with high terrain, you might find that you need to ensure the minimum rate of climb, so pay attention to the weight of the aircraft

The turning radius is a function of the aircraft’s speed

Greater weight means greater speed

And, higher speed means an increased turning radius

Aircraft stability

In extreme cases, excessive weight can cause the aircraft to behave unpredictably

However, if the weight is not within the defined limits, this can quickly change and create dangerous situations

Standard weights in aviation – Why do we use them?

It might be a little obvious, but everything on board an airplane, whether big or small, adds up

While some items may weigh only fractions of a pound, they can contribute significantly to the aircraft’s weight when added together

Imagine adding everything on a plane every time you fly?

To make life simpler, aviation regulatory organizations allow pilots to use standard weights

Most standard weights in aviation use well-defined averages

Here is a quick list of some standard weights defined by the FAA:-

If you know the actual weights of the things on the table, it is mandatory that you must use them

Standard Aircraft Weight – Frequently used terms

Standard aircraft weights can be a little daunting, and you’ll come across a lot of technical-sounding terms during your aviation studies

Here at Pilot Institute, we like to keep things simple

Here’s a quick list of common terms you’ll encounter when discussing standard weight and mass and balance in private aviation

Center of gravity

The point on the plane at which all weight acts

You can consider this ‘pivot’ around which the plane maneuvers

An arbitrary ‘line’ is used as a reference point for weight and balance measurements

When looking at an aircraft load sheet, constant reference will be made to the ‘datum’

This is normally defined by the aircraft operator, and you will usually be able to find out where the data is in the aircraft flight manual (AFM)

You will often see a small triangular symbol on load sheets and aircraft trim tables

Dry Operating Weight (DOW)

As the name suggests, the dry operating weight of the aircraft is the total weight, including all operational equipment, but no liquids

It includes your weight (as the pilot)

And, yes, the DOW includes you as the pilot

Have you ever tried to divide, add or subtract large numbers?

1 million divided by 500,000, while simple, takes some thinking

As above, aircraft manufacturers will often specify an ‘index’

Simply put, this is a large constant divisor (normally in multiples of 100 or 1000) used when calculating aircraft weight and balance to make math easy

Max Landing Weight (MLW)

This is the structural limit of the aircraft on landing

It includes everything that will be on the plane

Maximum Take Off Weight (MTOW)

This is the maximum allowable weight of the aircraft on take-off

While generally, it is a structural limitation, it can also change depending on runway length, minimum climb gradient, and the payload you carry on board

You will often find that you have to take less fuel with a full load of passengers and bags, or vice versa

Maximum Zero Fuel Weight (MZFW)

This is the structural limit of the aircraft, including everything except the fuel

This term uses a straight line drawn through the wing to express the center of gravity

A moment arm is a fancy aviation term to describe a pivot and lever

The pivot is usually the center of gravity

The more force from the pivot, the greater its effect

All the different moments are added or subtracted from each other and balanced on the plane to give a total moment

Standard weight

Standard weights are used to make life simple when calculating aircraft mass

They are normally applied to items such as gas, oil, other liquids, occupants, and bags

Specific gravity is the correction factor applied to a given volume of liquid on the plane

It is usually a decimal number used to determine how much the gas or oil weighs


Payload is added to the dry operating weight of the aircraft to give the takeoff weight

Want an easy way to remember what’s included

If it is burned, paid for, or paid to be on the plane, it normally counts as a payload

How to calculate weight and balance using standard weights?

Now that you are familiar with some terms let’s take a quick look at how weight and balance are calculated aboard private jets

In short, we need to know two things when it comes to aircraft weight:-

We can work on the effects on the plane if we know these things

To see what we mean, look at the simplified chart below

Item Weight (lbs) Arm Length (in inches) Moment ArmAircraft DOW17003559,500Fuel (30 gallons)1804720 (1400)Oil (1 gallon)75362702 x bags (30lbs each)60-5-3007,1940760,1940

You will normally see tables detailing the weight of any additional equipment (including fuel, oil, passengers, and bags)

They will also give you the area where it sits on the plane relative to the plane data

Just like on a see-saw, adding different items in different places will change the way the plane swings

By moving either the distance from the data or the weight (or both), we can ensure the correctness of the plane in trimming and balancing

The box on the lower right of the table gives a significant total moment arm

Aircraft manufacturers will dictate a range of acceptable values ​​that we must stay within in order for the aircraft to balance

If we load 350 lbs of AVGAS (assuming the standard weight is around 582 gallons), how close would that put us to the limit?

If you put it in the table above, you will notice that it comes very close!

So we know that if nothing else changes, it is the max gas we could take

The standard convention is that any number with a (-) is in front of the data

Any positive number is behind the datum, towards the tail of the plane

By summing these arms, we can determine if the aircraft is balanced within acceptable limits

Where can I learn more about aircraft weight and balance?

Weight and balance is a very big topic, and a lot of thought goes into calculating the weight of the aircraft long before you enter the cabin

Manufacturers weigh the aircraft using various calibrated scales and some very complex math to arrive at the common values ​​you will see in the AFM

The Federal Aviation Administration has an excellent guide to aircraft mass and balance that is well worth reading

Standard weights are used for items that are commonly carried on board aircraft, making mass and balance calculations simpler

Gas and oil traders vary in mass depending on temperature and quality, so it pays to know some of the standard conversion factors

The weight of the aircraft is important in how an aircraft performs

If you want to learn more about aircraft mass and balance, why not check out our flight courses, where it is covered as part of our program

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