In the worst-case scenario, if the CG is too far forward or to the rear and falls outside of CG limits , the aircraft may not have enough elevator to keep the plane in controlled flight. In an extreme case, this out of CG condition can have tragic results. The video below is a prime example. Calculating weight and balance is not particularly difficult. All the hard work has already been done for you by the manufacturer.
The empty weights, arms, and moments are already defined for you. In this example, we have an airplane with two rows of seats, 88 gallons of usable fuel, and two baggage areas, each of which includes the distance from the Datum Arm. Multiply the weight by the Arm to determine the Moment.
When you have done so for every location, divide the Total Moment by the Total Weight. This is your calculated CG. For example, if you have a large person in the backseat, you can have them switch places with the front seat passenger. If you have a heavy bag in the rearmost baggage compartment, you can move it to the forward compartment or even to the back seat if you have space.
For example, if you replace some of the avionics and have the seats re-upholstered, the weight will likely have changed, even if only a little. The video below is a good overview of the process. Weight and balance are critical to the safe operation of an aircraft. Making these calculations is a critical step for a pilot to ensure the safety of the flight.
As a lifelong lover of anything with wings, I decided to share my journey in educating myself about aviation. Here you will find answers to many of the questions asked by those new to flying. There are meaningful distinctions between what is safe and necessary when discussing whether or not it is legal to land a plane on a road.
When you decide that you want to learn to fly, understanding your goals is critical to helping you choose a flight school that's perfect for your needs. Skip to content. Wait, Don't Go Yet! Before you leave, read about our Top 19 Safety Tips for Pilots. Weight and Useful Load Weight by itself is an important factor in aviation.
Center of Gravity CG The center of gravity is the point at which the weight of a body is considered to act. Arm The arm is simply the horizontal distance from the Reference Datum to a given point.
Moment The Moment is the amount of torque or force applied based on the distance from an object. Ballast In an aircraft, the Ballast is any weight that can be added or removed in order to bring the CG into an acceptable range of balance. Bottom line is air needs to flow over the wing in order for this to happen.
If it moves too slowly, not enough lift is generated; moreover, engines and wings are less efficient when the air density is less dense. This means that humidity, temperature, and fuel amount must all become part of the picture.
It might not always be possible to place a person in each seat and completely fill the cargo hold. Pilots adjust for the amount of bags and what might be in them whiles taking in consideration situation like winter weather which often means heavier baggage as passengers cram in warm coats, sweatpants, and boots.
She has worked in the aviation industry in various roles for 24 years. As a United States Air Force retired veteran, she has a unique appreciation for the aviation industry. Her passion is motivating, training, coaching and serving others to reach their best potential.
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Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. Center of Gravity Every craft that moves through air, space, and water is affected by gravity. Aircraft Design While aircraft weight and balance are important, it is not as trivial on large airplanes built for stability, such as airliners than it is for small custom aircraft constructed for performance. With a few simple calculations you can determine different loading scenarios for your airplane.
You will want to compute sample loadings that result in these CG locations:. Depending on your airplane, you may want to add other scenarios. And to weigh your airplane, you need to obtain the proper scales. Some builders use bathroom scales, but given the importance of accurate weight and balance information to the safety of every flight you make in the airplane, borrow or rent platform scales that have been calibrated for accuracy.
Certainly the safety of you and your passengers is worth the rental charge. A typical scale used for aircraft. In a hangar, where wind cannot blow on the aircraft and cause fluctuations in weight, weigh your airplane in its empty condition.
You should weigh your airplane in its ready-to-fly configuration, meaning all the cowlings, doors, canopies, etc. Before you put the airplane on the scales, assemble all of the equipment you will need. This includes chocks, jacks, leveling equipment, plumb bobs, chalk lines, measuring tapes, etc. If needed, build ramps that will allow you to roll your airplane onto the scales. Make sure you weigh the airplane chocks before you weigh the airplane.
When on the scales make sure the airplane is in a level-flight attitude so all components will be at their correct distance from the datum, which results in the most accurate information. Use the leveling procedure recommended by the designer. Then record the weights indicated by the three scales nosewheel or tailwheel, left main, and right main —and then subtract the weight of the respective wheel chocks.
The easiest and most accurate way to accomplish this is to use a plumb bob and chalk line. Use a plumb bob to transfer the locations of the reference datum and the other components to the chalk line.
A good way to make sure you record all the required weights and measurements is to create a form like Table 1 or 2. To make life even easier, create the tables using a spreadsheet program, such as Microsoft Excel, so it will do the math for you. All you have to do is plug in the numbers for the variable weights like passengers and baggage. Table 2 uses hypothetical numbers for the RV-8, and after you compute the moment for each wheel, you total up the weight and moment columns.
The weights of these essential components will bring the CG inside the envelope. Try relocating some weighty components, such as the battery. For example, if your airplane is too nose-heavy and the battery is under the cowling, move the battery aft. How far?
Depending on your airplane, in some loading conditions you might need some temporary ballast to move the CG where it belongs inside the envelope.
The best solution is to add or subtract weight in the baggage compartment or to change the seating positions of passengers of different weights if possible. Compute the various loading conditions that you may encounter with your airplane and have them ready for the FAA inspector when he or she inspects your airplane.
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