Part of the RC Airplane Setup & Preflight Center
The center of gravity (CG) is the point where an airplane balances from front to back. I check it before every maiden and again anytime I change something that can move the airplane’s weight. Get it right and the airplane has a much better chance of being stable and predictable. Get it wrong—especially tail-heavy—and you may spend the whole flight trying to catch up with it.
Why CG matters
A nose-heavy airplane will usually feel stable, but it may need more elevator, fly faster, and be harder to flare. A tail-heavy airplane is the one that can get away from you in a hurry. It may become overly sensitive, unstable, and difficult or impossible to recover. I would rather make a first flight a little nose-heavy than guess too far aft. If you are not sure where to start, use the forward end of the manufacturer’s recommended range.
Find the specified balance point
Start with the balance point in the manual or on the plans. It may be measured back from the wing’s leading edge at the fuselage, or it may be marked directly on the wing. A percentage rule can be useful when there is no other information, but do not use one in place of a tested manufacturer’s value.
How to balance the airplane
- Set up the model just as it will fly, including the propeller, spinner, landing gear, receiver battery, and accessories.
- Put the flight battery in the position where it will be secured for flight.
- Mark the recommended CG position on both sides of the wing.
- Support the airplane at those marks with fingertips, a balancing stand, or padded points.
- Hold the model in the attitude specified by the manufacturer and see whether the nose or tail drops.
For a large or heavy model, use a proper balancing stand or sling and have someone help you.
Correcting the balance
Before I add ballast, I look for equipment that can be moved. On an electric model, sliding the flight battery is usually the easiest adjustment. Once you find the right position, mark it and make sure the battery cannot move in flight. If you do need ballast, attach it permanently and place it as far forward or aft as practical so you can use less weight. A loose chunk of balance weight is worse than having the balance wrong to begin with.
Lateral balance
Support the model at the spinner and tail—or use the method in the manual—and see whether the same wing keeps dropping. Before adding weight to a wingtip, look for the real cause: unequal batteries, retracts, repairs, or accessories can all throw off the lateral balance.
Recheck after changes
Check the balance again after a repair, a battery change, a new engine or motor, added paint, landing-gear changes, or moved equipment. It also helps to mark the battery position inside the model so you can put it back in the same place every time.
Adding floats is a reason to measure the balance again with the complete installation fitted. Water inside a float can also change weight and lateral balance. See floatplane CG and handling changes before the first water flight.
CG and the maiden flight
- Use the forward part of the recommended range.
- Keep control throws conservative.
- Choose calm weather and a large flying area.
- Have an experienced pilot inspect and fly the model if possible.
- Make small adjustments between flights rather than large changes.
Do not try to fix an incorrect CG with a pile of trim or transmitter mixing. Get the airplane mechanically balanced first, then fine-tune it within the approved range.
Continue with pre-flight checks and our guide to preventing common crashes. If handling is already abnormal, compare the pitch-sensitive, sluggish-pitch, stall and wing-drop, and constant-roll diagnostics before moving equipment.
Putting the entire setup together? Center of gravity is one part of a flight-ready airplane. Use the RC Airplane Setup & Preflight Center to work through the mechanical, radio, power-system, and final checks in order.
Trying to diagnose the way the airplane flies? Compare the signs in Nose-Heavy vs. Tail-Heavy RC Airplane before moving equipment or adding ballast.